diff --git a/.github/ISSUE_TEMPLATE.md b/.github/ISSUE_TEMPLATE.md deleted file mode 100644 index 0178465..0000000 --- a/.github/ISSUE_TEMPLATE.md +++ /dev/null @@ -1,23 +0,0 @@ -## What to expect when you file an issue here - -This is the repo for an in-progress rework of The Rust Programming Language book -available at http://rust-lang.github.io/book/. - -If you are filing an issue about the existing book available at -https://doc.rust-lang.org/book/, please note that we are now concentrating on -the new version of the book. - -We would still love feedback on the existing book as well as the new book, just -know that one of a few things may happen with your issue: - -- If we have not gotten to that topic in the new book, we may leave a note for - ourselves about this issue to address when we get there. -- We may have already addressed this issue in a rewritten version of the topic - relating to this issue, so we might close it. -- If this issue still applies to the new book, we will fix it. - -If you have time before filing this issue, please take a look at the new book -to see if this issue has been addressed and include that information in the -issue. - -Thank you for reading, you may now delete this text! diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md deleted file mode 100644 index e366c2a..0000000 --- a/.github/PULL_REQUEST_TEMPLATE.md +++ /dev/null @@ -1,14 +0,0 @@ -## What to expect when you open a PR here - -We are currently working with No Starch Press to bring this book to print. -Chapters go through a number of stages in the editing process, and once they've -gotten to the layout stage, they're effectively frozen. - -For chapters that have gotten to the layout stage, we will likely only be -accepting changes that correct factual errors or major problems and not, for -example, minor wording changes. - -Scroll all the way to the right on https://github.com/rust-lang/book/projects/1 -to see which chapters have been frozen. - -Thank you for reading, you may now delete this text! diff --git a/.travis.yml b/.travis.yml deleted file mode 100644 index b26b252..0000000 --- a/.travis.yml +++ /dev/null @@ -1,27 +0,0 @@ -sudo: false -language: rust -cache: cargo -rust: - - nightly - - beta - - stable -branches: - only: - - master -addons: - apt: - packages: - - aspell - - aspell-en -before_script: - - (cargo install mdbook --git https://github.com/azerupi/mdBook.git --force || true) -script: - - bash spellcheck.sh list - - PATH=$PATH:/home/travis/.cargo/bin mdbook test - - PATH=$PATH:/home/travis/.cargo/bin mdbook build - - cargo run --bin lfp src -after_success: - - test $TRAVIS_PULL_REQUEST == "false" && test $TRAVIS_BRANCH == "master" && bash deploy.sh -env: - global: - secure: 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 diff --git a/Cargo.lock b/Cargo.lock deleted file mode 100644 index 5cd51aa..0000000 --- a/Cargo.lock +++ /dev/null @@ -1,142 +0,0 @@ -[root] -name = "rust-book" -version = "0.0.1" -dependencies = [ - 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-[[bin]] -name = "concat_chapters" -path = "tools/src/bin/concat_chapters.rs" - -[[bin]] -name = "lfp" -path = "tools/src/bin/lfp.rs" - -[[bin]] -name = "link2print" -path = "tools/src/bin/link2print.rs" - -[[bin]] -name = "remove_links" -path = "tools/src/bin/remove_links.rs" - -[dependencies] -walkdir = "0.1.5" -docopt = "0.6.82" -rustc-serialize = "0.3.19" -regex = "0.1.73" -lazy_static = "0.2.1" diff --git a/book.json b/book.json deleted file mode 100644 index 4153925..0000000 --- a/book.json +++ /dev/null @@ -1,5 +0,0 @@ -{ - "title": "Rust 程序设计语言", - "author": "The Rust Project Developers", - "translator": "Aaklo Xu" -} diff --git a/deploy.sh b/deploy.sh index a297bbb..02e2f9e 100644 --- a/deploy.sh +++ b/deploy.sh @@ -7,8 +7,8 @@ rev=$(git rev-parse --short HEAD) cd book git init -git config user.name "Aaklo Xu" -git config user.email "aakloxu@gmail.com" +git config user.name "Aaran Xu" +git config user.email "aaranxu@outlook.com" git remote add upstream "git@github.com:rust-lang-cn/book-cn.git" git fetch upstream diff --git a/dictionary.txt b/dictionary.txt deleted file mode 100644 index c1cf32e..0000000 --- a/dictionary.txt +++ /dev/null @@ -1,281 +0,0 @@ -personal_ws-1.1 en 0 utf-8 -abcabcabc -abcd -abcdefghijklmnopqrstuvwxyz -adaptor -adaptors -Addr -aliasability -alignof -Amir -APIs -aren -args -backtrace -backtraces -BACKTRACE -Backtraces -benchmarking -bitand -BitAnd -bitor -BitOr -bitwise -Bitwise -bitxor -BitXor -Bjarne -Boehm -bool -boolean -booleans -Bors -BuildHasher -Cagain -callsite -CamelCase -cargodoc -ChangeColor -ChangeColorMessage -chXX -chYY -config -Config -const -constant's -copyeditor -couldn -cratesio -cryptographically -CStr -CString -ctrl -Ctrl -deallocated -deallocating -debuginfo -deps -deref -Deref -dereference -Dereference -dereferencing -DerefMut -destructure -destructuring -Destructuring -didn -Dobrý -doccargo -doccratesio -doesn -Edsger -else's -emoji -encodings -enum -Enum -enums -enum's -Enums -ErrorKind -Executables -extern -FFFF -figcaption -filename -Filename -filesystem -Filesystem -FnMut -FnOnce -formatter -FromIterator -GitHub -gitignore -grapheme -Grapheme -greprs -growable -hardcoded -hardcoding -hasher -hashmap -HashMap -Hashmaps -Haskell -hasn -helloworld -Hmmm -Hoare -Hola -homogenous -html -IEEE -impl -indices -init -instantiation -internet -IntoIterator -InvalidDigit -ioerror -iokind -ioresult -iostdin -IpAddr -IpAddrKind -irst -isize -iter -iterator's -JavaScript -lang -latin -libc -libcore -librarys -libreoffice -libstd -lifecycle -login -loopback -lval -mathematic -metadata -Metadata -metaprogramming -mibbit -Mibbit -mkdir -modifiability -monomorphization -Monomorphization -monomorphized -MoveMessage -Mutex -namespace -namespaced -namespaces -namespacing -newfound -newtype -nocapture -nomicon -Nomicon -NotFound -null's -OCaml -offsetof -online -OptionalFloatingPointNumber -OptionalNumber -OsStr -OsString -overread -parameterize -ParseIntError -PartialEq -PartialOrd -powi -preprocessing -Preprocessing -preprocessor -PrimaryColor -println -priv -proc -pthreads -QuitMessage -RAII -randcrate -READMEs -rect -redeclaring -Refactoring -refactor -refactoring -RefCell -repr -ripgrep -runtime -Rustacean -Rustaceans -rustc -rustdoc -rustup -SecondaryColor -semver -SemVer -shouldn -sizeof -someproject -someusername -SPDX -spdx -SpreadsheetCell -sqrt -stackoverflow -stderr -stdin -Stdin -stdlib -stdout -steveklabnik's -Stroustrup -struct -Struct -structs -struct's -Structs -subcommand -subcommands -subdirectories -subdirectory -submodule -submodules -Submodules -suboptimal -subtree -subtyping -Supertraits -That'd -test's -timeline -TODO -toml -TOML -tradeoff -tradeoffs -TrafficLight -trpl -tuple -tuples -typeof -UFCS -unary -Unary -Uninstalling -uninstall -unoptimized -UnsafeCell -unsized -unsynchronized -username -USERPROFILE -usize -UsState -utils -variable's -vers -Versioning -wasn -whitespace -wildcards -workspace -workspaces -Workspaces -wouldn -writeln -WriteMessage -yyyy diff --git a/doc-to-md.sh b/doc-to-md.sh deleted file mode 100755 index 5103c84..0000000 --- a/doc-to-md.sh +++ /dev/null @@ -1,20 +0,0 @@ -#!/bin/bash - -set -eu - -# Get all the docx files in the tmp dir, -ls tmp/*.docx | \ -# Extract just the filename so we can reuse it easily. -xargs -n 1 basename -s .docx | \ -while IFS= read -r filename; do - # Make a directory to put the XML in - mkdir -p "tmp/$filename" - # Unzip the docx to get at the xml - unzip -o "tmp/$filename.docx" -d "tmp/$filename" - # Convert to markdown with XSL - xsltproc tools/docx-to-md.xsl "tmp/$filename/word/document.xml" | \ - # Hard wrap at 80 chars at word bourdaries - fold -w 80 -s | \ - # Remove trailing whitespace & save in the nostarch dir for comparison - sed -e "s/ *$//" > "nostarch/$filename.md" -done diff --git a/dot/trpl04-01.dot b/dot/trpl04-01.dot index 24f6964..331d591 100644 --- a/dot/trpl04-01.dot +++ b/dot/trpl04-01.dot @@ -1,5 +1,6 @@ digraph { rankdir=LR; + overlap=false; dpi=300.0; node [shape="plaintext"]; diff --git a/dot/trpl04-02.dot b/dot/trpl04-02.dot index d785760..e46d2ed 100644 --- a/dot/trpl04-02.dot +++ b/dot/trpl04-02.dot @@ -1,5 +1,6 @@ digraph { rankdir=LR; + overlap=false; dpi=300.0; node [shape="plaintext"]; diff --git a/dot/trpl04-03.dot b/dot/trpl04-03.dot index 2ddc335..16c0b28 100644 --- a/dot/trpl04-03.dot +++ b/dot/trpl04-03.dot @@ -1,5 +1,6 @@ digraph { rankdir=LR; + overlap=false; dpi=300.0; node [shape="plaintext"]; diff --git a/dot/trpl04-04.dot b/dot/trpl04-04.dot index 87b1303..1c95c23 100644 --- a/dot/trpl04-04.dot +++ b/dot/trpl04-04.dot @@ -1,5 +1,6 @@ digraph { rankdir=LR; + overlap=false; dpi=300.0; node [shape="plaintext"]; diff --git a/dot/trpl04-05.dot b/dot/trpl04-05.dot index 55aa221..ca1f7e0 100644 --- a/dot/trpl04-05.dot +++ b/dot/trpl04-05.dot @@ -1,5 +1,6 @@ digraph { rankdir=LR; + overlap=false; dpi=300.0; node [shape="plaintext"]; diff --git a/dot/trpl04-06.dot b/dot/trpl04-06.dot index a81d208..a23f179 100644 --- a/dot/trpl04-06.dot +++ b/dot/trpl04-06.dot @@ -1,5 +1,6 @@ digraph { rankdir=LR; + overlap=false; dpi=300.0; node [shape="plaintext"]; diff --git a/dot/trpl15-01.dot b/dot/trpl15-01.dot new file mode 100644 index 0000000..e8b95f9 --- /dev/null +++ b/dot/trpl15-01.dot @@ -0,0 +1,24 @@ +digraph { + rankdir=LR; + overlap=false; + dpi=300.0; + node [shape="plaintext"]; + + table0[label=< + + +
Cons
i32 + + +
Cons
i32 + + +
Cons
i32 + + +
Cons
i32 + + +
Cons
i32
>]; +} + diff --git a/dot/trpl15-02.dot b/dot/trpl15-02.dot new file mode 100644 index 0000000..f7dfd22 --- /dev/null +++ b/dot/trpl15-02.dot @@ -0,0 +1,18 @@ +digraph { + rankdir=LR; + overlap=false; + dpi=300.0; + node [shape="plaintext"]; + + table0[label=< + + + +
Cons
i32 + + + +
Box
usize
+
>]; +} + diff --git a/dot/trpl15-03.dot b/dot/trpl15-03.dot new file mode 100644 index 0000000..16f0268 --- /dev/null +++ b/dot/trpl15-03.dot @@ -0,0 +1,51 @@ +digraph { + rankdir=LR; + overlap=false; + dpi=300.0; + node [shape="plaintext"]; + + table4[label=< + +
b
>]; + + table5[label=< + +
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>]; + + + table0[label=< + +
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>]; + + table1[label=< + +
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>]; + + + table6[label=< + +
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>]; + + table7[label=< + +
4
>]; + + + edge[tailclip="false"]; + table0:ptr0:c -> table1:pte0; + table1:ptr1:c -> table2:pte1; + table2:ptr2:c -> table3:pte2; + table4:ptr4:c -> table5:pte4; + table5:ptr5:c -> table1:pte0; + table6:ptr6:c -> table7:pte6; + table7:ptr7:c -> table1:pte0; +} + diff --git a/dot/trpl15-04.dot b/dot/trpl15-04.dot new file mode 100644 index 0000000..562543c --- /dev/null +++ b/dot/trpl15-04.dot @@ -0,0 +1,16 @@ +digraph { + node[shape=record]; + rankdir=LR; + + l1[label="{ 5| }"]; + l2[label="{ 10| }"]; + + {node[shape=point height=0] invisible_start invisible_end} + + a -> l1:n; + b -> l2:n; + invisible_start:n -> l1[arrowtail=none]; + invisible_start:s -> invisible_end:s[dir=none]; + l1:next:c -> l2:data; + l2:next:c -> invisible_end:n[arrowhead=none]; +} diff --git a/listings/ch02-guessing-game-tutorial/listing-02-01/Cargo.lock b/listings/ch02-guessing-game-tutorial/listing-02-01/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch02-guessing-game-tutorial/listing-02-01/Cargo.toml b/listings/ch02-guessing-game-tutorial/listing-02-01/Cargo.toml new file mode 100644 index 0000000..e3091e7 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-01/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs b/listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs new file mode 100644 index 0000000..b822b89 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs @@ -0,0 +1,31 @@ +// ANCHOR: all +// ANCHOR: io +use std::io; +// ANCHOR_END: io + +// ANCHOR: main +fn main() { + // ANCHOR_END: main + // ANCHOR: print + println!("Guess the number!"); + + println!("Please input your guess."); + // ANCHOR_END: print + + // ANCHOR: string + let mut guess = String::new(); + // ANCHOR_END: string + + // ANCHOR: read + io::stdin() + .read_line(&mut guess) + // ANCHOR_END: read + // ANCHOR: expect + .expect("Failed to read line"); + // ANCHOR_END: expect + + // ANCHOR: print_guess + println!("You guessed: {}", guess); + // ANCHOR_END: print_guess +} +// ANCHOR: all diff --git a/listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.lock b/listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.toml b/listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-02/src/main.rs b/listings/ch02-guessing-game-tutorial/listing-02-02/src/main.rs new file mode 100644 index 0000000..60fb2a8 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-02/src/main.rs @@ -0,0 +1,15 @@ +use std::io; + +fn main() { + println!("Guess the number!"); + + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + println!("You guessed: {}", guess); +} diff --git a/listings/ch02-guessing-game-tutorial/listing-02-03/Cargo.lock b/listings/ch02-guessing-game-tutorial/listing-02-03/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-03/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-03/Cargo.toml b/listings/ch02-guessing-game-tutorial/listing-02-03/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-03/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-03/src/main.rs b/listings/ch02-guessing-game-tutorial/listing-02-03/src/main.rs new file mode 100644 index 0000000..de35846 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-03/src/main.rs @@ -0,0 +1,28 @@ +// ANCHOR: all +use std::io; +// ANCHOR: ch07-04 +use rand::Rng; + +fn main() { + // ANCHOR_END: ch07-04 + println!("Guess the number!"); + + // ANCHOR: ch07-04 + let secret_number = rand::thread_rng().gen_range(1..101); + // ANCHOR_END: ch07-04 + + println!("The secret number is: {}", secret_number); + + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + println!("You guessed: {}", guess); + // ANCHOR: ch07-04 +} +// ANCHOR_END: ch07-04 +// ANCHOR_END: all diff --git a/listings/ch02-guessing-game-tutorial/listing-02-04/Cargo.lock b/listings/ch02-guessing-game-tutorial/listing-02-04/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-04/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-04/Cargo.toml b/listings/ch02-guessing-game-tutorial/listing-02-04/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-04/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-04/output.txt b/listings/ch02-guessing-game-tutorial/listing-02-04/output.txt new file mode 100644 index 0000000..6ee46be --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-04/output.txt @@ -0,0 +1,24 @@ +$ cargo build + Compiling libc v0.2.86 + Compiling getrandom v0.2.2 + Compiling cfg-if v1.0.0 + Compiling ppv-lite86 v0.2.10 + Compiling rand_core v0.6.2 + Compiling rand_chacha v0.3.0 + Compiling rand v0.8.3 + Compiling guessing_game v0.1.0 (file:///projects/guessing_game) +error[E0308]: mismatched types + --> src/main.rs:22:21 + | +22 | match guess.cmp(&secret_number) { + | ^^^^^^^^^^^^^^ expected struct `String`, found integer + | + = note: expected reference `&String` + found reference `&{integer}` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `guessing_game` + +To learn more, run the command again with --verbose. diff --git a/listings/ch02-guessing-game-tutorial/listing-02-04/src/main.rs b/listings/ch02-guessing-game-tutorial/listing-02-04/src/main.rs new file mode 100644 index 0000000..349bc27 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-04/src/main.rs @@ -0,0 +1,32 @@ +// ANCHOR: here +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + // --snip-- + // ANCHOR_END: here + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + println!("The secret number is: {}", secret_number); + + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + // ANCHOR: here + + println!("You guessed: {}", guess); + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => println!("You win!"), + } +} +// ANCHOR_END: here diff --git a/listings/ch02-guessing-game-tutorial/listing-02-05/Cargo.lock b/listings/ch02-guessing-game-tutorial/listing-02-05/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-05/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-05/Cargo.toml b/listings/ch02-guessing-game-tutorial/listing-02-05/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-05/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-05/src/main.rs b/listings/ch02-guessing-game-tutorial/listing-02-05/src/main.rs new file mode 100644 index 0000000..41a4cdd --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-05/src/main.rs @@ -0,0 +1,45 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + println!("The secret number is: {}", secret_number); + + loop { + println!("Please input your guess."); + + let mut guess = String::new(); + + // ANCHOR: here + // --snip-- + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + // ANCHOR: ch19 + let guess: u32 = match guess.trim().parse() { + Ok(num) => num, + Err(_) => continue, + }; + // ANCHOR_END: ch19 + + println!("You guessed: {}", guess); + + // --snip-- + // ANCHOR_END: here + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => { + println!("You win!"); + break; + } + } + } +} diff --git a/listings/ch02-guessing-game-tutorial/listing-02-06/Cargo.lock b/listings/ch02-guessing-game-tutorial/listing-02-06/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-06/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-06/Cargo.toml b/listings/ch02-guessing-game-tutorial/listing-02-06/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-06/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/listing-02-06/src/main.rs b/listings/ch02-guessing-game-tutorial/listing-02-06/src/main.rs new file mode 100644 index 0000000..30859c7 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/listing-02-06/src/main.rs @@ -0,0 +1,35 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + loop { + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + let guess: u32 = match guess.trim().parse() { + Ok(num) => num, + Err(_) => continue, + }; + + println!("You guessed: {}", guess); + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => { + println!("You win!"); + break; + } + } + } +} diff --git a/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.lock b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.toml b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.toml new file mode 100644 index 0000000..e3091e7 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/output.txt b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/output.txt new file mode 100644 index 0000000..2724c14 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished dev [unoptimized + debuginfo] target(s) in 1.50s + Running `target/debug/guessing_game` +Hello, world! diff --git a/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/src/main.rs b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/src/main.rs new file mode 100644 index 0000000..e7a11a9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + println!("Hello, world!"); +} diff --git a/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/Cargo.lock b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/Cargo.toml b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/Cargo.toml new file mode 100644 index 0000000..e3091e7 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/output.txt b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/output.txt new file mode 100644 index 0000000..c56c889 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/output.txt @@ -0,0 +1,14 @@ +$ cargo build + Compiling guessing_game v0.1.0 (file:///projects/guessing_game) +warning: unused `Result` that must be used + --> src/main.rs:10:5 + | +10 | io::stdin().read_line(&mut guess); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: `#[warn(unused_must_use)]` on by default + = note: this `Result` may be an `Err` variant, which should be handled + +warning: 1 warning emitted + + Finished dev [unoptimized + debuginfo] target(s) in 0.59s diff --git a/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/src/main.rs b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/src/main.rs new file mode 100644 index 0000000..aaf90bd --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/src/main.rs @@ -0,0 +1,13 @@ +use std::io; + +fn main() { + println!("Guess the number!"); + + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin().read_line(&mut guess); + + println!("You guessed: {}", guess); +} diff --git a/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/Cargo.lock b/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/Cargo.toml b/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/src/main.rs b/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/src/main.rs new file mode 100644 index 0000000..0b21d95 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/src/main.rs @@ -0,0 +1,33 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + println!("The secret number is: {}", secret_number); + + println!("Please input your guess."); + + // ANCHOR: here + // --snip-- + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + let guess: u32 = guess.trim().parse().expect("Please type a number!"); + + println!("You guessed: {}", guess); + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => println!("You win!"), + } + // ANCHOR_END: here +} diff --git a/listings/ch02-guessing-game-tutorial/no-listing-04-looping/Cargo.lock b/listings/ch02-guessing-game-tutorial/no-listing-04-looping/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-04-looping/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/no-listing-04-looping/Cargo.toml b/listings/ch02-guessing-game-tutorial/no-listing-04-looping/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-04-looping/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/no-listing-04-looping/src/main.rs b/listings/ch02-guessing-game-tutorial/no-listing-04-looping/src/main.rs new file mode 100644 index 0000000..61a5dc0 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-04-looping/src/main.rs @@ -0,0 +1,40 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + // ANCHOR: here + // --snip-- + + println!("The secret number is: {}", secret_number); + + loop { + println!("Please input your guess."); + + // --snip-- + + // ANCHOR_END: here + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + let guess: u32 = guess.trim().parse().expect("Please type a number!"); + + println!("You guessed: {}", guess); + + // ANCHOR: here + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => println!("You win!"), + } + } +} +// ANCHOR_END: here diff --git a/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/Cargo.lock b/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/Cargo.toml b/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/src/main.rs b/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/src/main.rs new file mode 100644 index 0000000..3f8e8b7 --- /dev/null +++ b/listings/ch02-guessing-game-tutorial/no-listing-05-quitting/src/main.rs @@ -0,0 +1,38 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + println!("The secret number is: {}", secret_number); + + loop { + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + let guess: u32 = guess.trim().parse().expect("Please type a number!"); + + println!("You guessed: {}", guess); + + // ANCHOR: here + // --snip-- + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => { + println!("You win!"); + break; + } + } + } +} +// ANCHOR_END: here diff --git a/listings/ch03-common-programming-concepts/listing-03-01/Cargo.lock b/listings/ch03-common-programming-concepts/listing-03-01/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/listing-03-01/Cargo.toml b/listings/ch03-common-programming-concepts/listing-03-01/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/listing-03-01/src/main.rs b/listings/ch03-common-programming-concepts/listing-03-01/src/main.rs new file mode 100644 index 0000000..b492d38 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-01/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + let y = 6; +} diff --git a/listings/ch03-common-programming-concepts/listing-03-02/Cargo.lock b/listings/ch03-common-programming-concepts/listing-03-02/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/listing-03-02/Cargo.toml b/listings/ch03-common-programming-concepts/listing-03-02/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/listing-03-02/output.txt b/listings/ch03-common-programming-concepts/listing-03-02/output.txt new file mode 100644 index 0000000..3eb8d10 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-02/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling branches v0.1.0 (file:///projects/branches) + Finished dev [unoptimized + debuginfo] target(s) in 0.30s + Running `target/debug/branches` +The value of number is: 5 diff --git a/listings/ch03-common-programming-concepts/listing-03-02/src/main.rs b/listings/ch03-common-programming-concepts/listing-03-02/src/main.rs new file mode 100644 index 0000000..0b8ee95 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-02/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + let condition = true; + let number = if condition { 5 } else { 6 }; + + println!("The value of number is: {}", number); +} diff --git a/listings/ch03-common-programming-concepts/listing-03-03/Cargo.lock b/listings/ch03-common-programming-concepts/listing-03-03/Cargo.lock new file mode 100644 index 0000000..9942b36 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "loops" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/listing-03-03/Cargo.toml b/listings/ch03-common-programming-concepts/listing-03-03/Cargo.toml new file mode 100644 index 0000000..b5ed848 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "loops" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/listing-03-03/src/main.rs b/listings/ch03-common-programming-concepts/listing-03-03/src/main.rs new file mode 100644 index 0000000..651ed68 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-03/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + let mut number = 3; + + while number != 0 { + println!("{}!", number); + + number -= 1; + } + + println!("LIFTOFF!!!"); +} diff --git a/listings/ch03-common-programming-concepts/listing-03-04/Cargo.lock b/listings/ch03-common-programming-concepts/listing-03-04/Cargo.lock new file mode 100644 index 0000000..9942b36 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "loops" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/listing-03-04/Cargo.toml b/listings/ch03-common-programming-concepts/listing-03-04/Cargo.toml new file mode 100644 index 0000000..b5ed848 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "loops" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/listing-03-04/output.txt b/listings/ch03-common-programming-concepts/listing-03-04/output.txt new file mode 100644 index 0000000..35c0f80 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-04/output.txt @@ -0,0 +1,9 @@ +$ cargo run + Compiling loops v0.1.0 (file:///projects/loops) + Finished dev [unoptimized + debuginfo] target(s) in 0.32s + Running `target/debug/loops` +the value is: 10 +the value is: 20 +the value is: 30 +the value is: 40 +the value is: 50 diff --git a/listings/ch03-common-programming-concepts/listing-03-04/src/main.rs b/listings/ch03-common-programming-concepts/listing-03-04/src/main.rs new file mode 100644 index 0000000..38fd301 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-04/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + let a = [10, 20, 30, 40, 50]; + let mut index = 0; + + while index < 5 { + println!("the value is: {}", a[index]); + + index += 1; + } +} diff --git a/listings/ch03-common-programming-concepts/listing-03-05/Cargo.lock b/listings/ch03-common-programming-concepts/listing-03-05/Cargo.lock new file mode 100644 index 0000000..9942b36 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "loops" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/listing-03-05/Cargo.toml b/listings/ch03-common-programming-concepts/listing-03-05/Cargo.toml new file mode 100644 index 0000000..b5ed848 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "loops" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/listing-03-05/src/main.rs b/listings/ch03-common-programming-concepts/listing-03-05/src/main.rs new file mode 100644 index 0000000..6e3cca6 --- /dev/null +++ b/listings/ch03-common-programming-concepts/listing-03-05/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let a = [10, 20, 30, 40, 50]; + + for element in a.iter() { + println!("the value is: {}", element); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/Cargo.lock new file mode 100644 index 0000000..2d62cbe --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "variables" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/Cargo.toml new file mode 100644 index 0000000..7915d39 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "variables" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/output.txt b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/output.txt new file mode 100644 index 0000000..7c2ec5b --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling variables v0.1.0 (file:///projects/variables) +error[E0384]: cannot assign twice to immutable variable `x` + --> src/main.rs:4:5 + | +2 | let x = 5; + | - + | | + | first assignment to `x` + | help: make this binding mutable: `mut x` +3 | println!("The value of x is: {}", x); +4 | x = 6; + | ^^^^^ cannot assign twice to immutable variable + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0384`. +error: could not compile `variables` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/src/main.rs new file mode 100644 index 0000000..a6c7ac0 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-01-variables-are-immutable/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + let x = 5; + println!("The value of x is: {}", x); + x = 6; + println!("The value of x is: {}", x); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/Cargo.lock new file mode 100644 index 0000000..2d62cbe --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "variables" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/Cargo.toml new file mode 100644 index 0000000..7915d39 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "variables" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/output.txt b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/output.txt new file mode 100644 index 0000000..8ed6598 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling variables v0.1.0 (file:///projects/variables) + Finished dev [unoptimized + debuginfo] target(s) in 0.30s + Running `target/debug/variables` +The value of x is: 5 +The value of x is: 6 diff --git a/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/src/main.rs new file mode 100644 index 0000000..c4e4a19 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-02-adding-mut/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + let mut x = 5; + println!("The value of x is: {}", x); + x = 6; + println!("The value of x is: {}", x); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-03-shadowing/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/Cargo.lock new file mode 100644 index 0000000..2d62cbe --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "variables" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-03-shadowing/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/Cargo.toml new file mode 100644 index 0000000..7915d39 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "variables" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-03-shadowing/output.txt b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/output.txt new file mode 100644 index 0000000..64ac2bf --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling variables v0.1.0 (file:///projects/variables) + Finished dev [unoptimized + debuginfo] target(s) in 0.31s + Running `target/debug/variables` +The value of x is: 12 diff --git a/listings/ch03-common-programming-concepts/no-listing-03-shadowing/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/src/main.rs new file mode 100644 index 0000000..d325180 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-03-shadowing/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let x = 5; + + let x = x + 1; + + let x = x * 2; + + println!("The value of x is: {}", x); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/Cargo.lock new file mode 100644 index 0000000..2d62cbe --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "variables" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/Cargo.toml new file mode 100644 index 0000000..7915d39 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "variables" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/src/main.rs new file mode 100644 index 0000000..42589f5 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-04-shadowing-can-change-types/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let spaces = " "; + let spaces = spaces.len(); + // ANCHOR_END: here +} diff --git a/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/Cargo.lock new file mode 100644 index 0000000..2d62cbe --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "variables" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/Cargo.toml new file mode 100644 index 0000000..7915d39 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "variables" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/output.txt b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/output.txt new file mode 100644 index 0000000..166b079 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/output.txt @@ -0,0 +1,14 @@ +$ cargo run + Compiling variables v0.1.0 (file:///projects/variables) +error[E0308]: mismatched types + --> src/main.rs:3:14 + | +3 | spaces = spaces.len(); + | ^^^^^^^^^^^^ expected `&str`, found `usize` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `variables` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/src/main.rs new file mode 100644 index 0000000..f52635d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-05-mut-cant-change-types/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let mut spaces = " "; + spaces = spaces.len(); + // ANCHOR_END: here +} diff --git a/listings/ch03-common-programming-concepts/no-listing-06-floating-point/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-06-floating-point/Cargo.lock new file mode 100644 index 0000000..3b40559 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-06-floating-point/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "floating-point" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-06-floating-point/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-06-floating-point/Cargo.toml new file mode 100644 index 0000000..81e80c2 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-06-floating-point/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "floating-point" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-06-floating-point/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-06-floating-point/src/main.rs new file mode 100644 index 0000000..6f4f0fe --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-06-floating-point/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + let x = 2.0; // f64 + + let y: f32 = 3.0; // f32 +} diff --git a/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/Cargo.lock new file mode 100644 index 0000000..94a12b2 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "numeric-operations" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/Cargo.toml new file mode 100644 index 0000000..00601dd --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "numeric-operations" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/src/main.rs new file mode 100644 index 0000000..0a784bb --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-07-numeric-operations/src/main.rs @@ -0,0 +1,16 @@ +fn main() { + // addition + let sum = 5 + 10; + + // subtraction + let difference = 95.5 - 4.3; + + // multiplication + let product = 4 * 30; + + // division + let quotient = 56.7 / 32.2; + + // remainder + let remainder = 43 % 5; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-08-boolean/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-08-boolean/Cargo.lock new file mode 100644 index 0000000..5d5728e --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-08-boolean/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "boolean" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-08-boolean/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-08-boolean/Cargo.toml new file mode 100644 index 0000000..783df3d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-08-boolean/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "boolean" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-08-boolean/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-08-boolean/src/main.rs new file mode 100644 index 0000000..2c56e62 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-08-boolean/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + let t = true; + + let f: bool = false; // with explicit type annotation +} diff --git a/listings/ch03-common-programming-concepts/no-listing-09-char/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-09-char/Cargo.lock new file mode 100644 index 0000000..bb58446 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-09-char/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "char" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-09-char/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-09-char/Cargo.toml new file mode 100644 index 0000000..cfde83b --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-09-char/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "char" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-09-char/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-09-char/src/main.rs new file mode 100644 index 0000000..4b8d9d9 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-09-char/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + let c = 'z'; + let z = 'ℤ'; + let heart_eyed_cat = '😻'; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-10-tuples/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-10-tuples/Cargo.lock new file mode 100644 index 0000000..f57f076 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-10-tuples/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "tuples" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-10-tuples/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-10-tuples/Cargo.toml new file mode 100644 index 0000000..8d6c2d5 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-10-tuples/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "tuples" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-10-tuples/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-10-tuples/src/main.rs new file mode 100644 index 0000000..b7b51fb --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-10-tuples/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + let tup: (i32, f64, u8) = (500, 6.4, 1); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/Cargo.lock new file mode 100644 index 0000000..f57f076 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "tuples" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/Cargo.toml new file mode 100644 index 0000000..8d6c2d5 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "tuples" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/src/main.rs new file mode 100644 index 0000000..35dcb44 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-11-destructuring-tuples/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let tup = (500, 6.4, 1); + + let (x, y, z) = tup; + + println!("The value of y is: {}", y); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/Cargo.lock new file mode 100644 index 0000000..f57f076 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "tuples" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/Cargo.toml new file mode 100644 index 0000000..8d6c2d5 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "tuples" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/src/main.rs new file mode 100644 index 0000000..1b1e646 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-12-tuple-indexing/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let x: (i32, f64, u8) = (500, 6.4, 1); + + let five_hundred = x.0; + + let six_point_four = x.1; + + let one = x.2; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-13-arrays/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-13-arrays/Cargo.lock new file mode 100644 index 0000000..68e3c59 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-13-arrays/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "arrays" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-13-arrays/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-13-arrays/Cargo.toml new file mode 100644 index 0000000..ec97b7d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-13-arrays/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "arrays" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-13-arrays/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-13-arrays/src/main.rs new file mode 100644 index 0000000..d475901 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-13-arrays/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + let a = [1, 2, 3, 4, 5]; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/Cargo.lock new file mode 100644 index 0000000..68e3c59 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "arrays" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/Cargo.toml new file mode 100644 index 0000000..ec97b7d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "arrays" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/src/main.rs new file mode 100644 index 0000000..d33e317 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-14-array-indexing/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + let a = [1, 2, 3, 4, 5]; + + let first = a[0]; + let second = a[1]; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/Cargo.lock new file mode 100644 index 0000000..68e3c59 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "arrays" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/Cargo.toml new file mode 100644 index 0000000..ec97b7d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "arrays" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/src/main.rs new file mode 100644 index 0000000..5e51216 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-15-invalid-array-access/src/main.rs @@ -0,0 +1,25 @@ +use std::io; + +fn main() { + let a = [1, 2, 3, 4, 5]; + + println!("Please enter an array index."); + + let mut index = String::new(); + + io::stdin() + .read_line(&mut index) + .expect("Failed to read line"); + + let index: usize = index + .trim() + .parse() + .expect("Index entered was not a number"); + + let element = a[index]; + + println!( + "The value of the element at index {} is: {}", + index, element + ); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-16-functions/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-16-functions/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-16-functions/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-16-functions/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-16-functions/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-16-functions/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-16-functions/output.txt b/listings/ch03-common-programming-concepts/no-listing-16-functions/output.txt new file mode 100644 index 0000000..723fad3 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-16-functions/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling functions v0.1.0 (file:///projects/functions) + Finished dev [unoptimized + debuginfo] target(s) in 0.28s + Running `target/debug/functions` +Hello, world! +Another function. diff --git a/listings/ch03-common-programming-concepts/no-listing-16-functions/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-16-functions/src/main.rs new file mode 100644 index 0000000..38be856 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-16-functions/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + println!("Hello, world!"); + + another_function(); +} + +fn another_function() { + println!("Another function."); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/output.txt b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/output.txt new file mode 100644 index 0000000..546bbc0 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling functions v0.1.0 (file:///projects/functions) + Finished dev [unoptimized + debuginfo] target(s) in 1.21s + Running `target/debug/functions` +The value of x is: 5 diff --git a/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/src/main.rs new file mode 100644 index 0000000..029446c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + another_function(5); +} + +fn another_function(x: i32) { + println!("The value of x is: {}", x); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/output.txt b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/output.txt new file mode 100644 index 0000000..d651191 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling functions v0.1.0 (file:///projects/functions) + Finished dev [unoptimized + debuginfo] target(s) in 0.31s + Running `target/debug/functions` +The value of x is: 5 +The value of y is: 6 diff --git a/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/src/main.rs new file mode 100644 index 0000000..fe476db --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + another_function(5, 6); +} + +fn another_function(x: i32, y: i32) { + println!("The value of x is: {}", x); + println!("The value of y is: {}", y); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/Cargo.lock new file mode 100644 index 0000000..89a654d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/output.txt b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/output.txt new file mode 100644 index 0000000..7409e85 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/output.txt @@ -0,0 +1,33 @@ +$ cargo run + Compiling functions v0.1.0 (file:///projects/functions) +error[E0658]: `let` expressions in this position are experimental + --> src/main.rs:2:14 + | +2 | let x = (let y = 6); + | ^^^^^^^^^ + | + = note: see issue #53667 for more information + = help: you can write `matches!(, )` instead of `let = ` + +error: expected expression, found statement (`let`) + --> src/main.rs:2:14 + | +2 | let x = (let y = 6); + | ^^^^^^^^^ + | + = note: variable declaration using `let` is a statement + +warning: unnecessary parentheses around assigned value + --> src/main.rs:2:13 + | +2 | let x = (let y = 6); + | ^^^^^^^^^^^ help: remove these parentheses + | + = note: `#[warn(unused_parens)]` on by default + +error: aborting due to 2 previous errors; 1 warning emitted + +For more information about this error, try `rustc --explain E0658`. +error: could not compile `functions` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/rustfmt-ignore b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/rustfmt-ignore new file mode 100644 index 0000000..06a976d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/rustfmt-ignore @@ -0,0 +1 @@ +This listing deliberately doesn't parse so rustfmt fails. diff --git a/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/src/main.rs new file mode 100644 index 0000000..988f965 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + let x = (let y = 6); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/src/main.rs new file mode 100644 index 0000000..baa853e --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + let x = 5; + + let y = { + let x = 3; + x + 1 + }; + + println!("The value of y is: {}", y); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/output.txt b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/output.txt new file mode 100644 index 0000000..a457e33 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling functions v0.1.0 (file:///projects/functions) + Finished dev [unoptimized + debuginfo] target(s) in 0.30s + Running `target/debug/functions` +The value of x is: 5 diff --git a/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/src/main.rs new file mode 100644 index 0000000..5303b10 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-21-function-return-values/src/main.rs @@ -0,0 +1,9 @@ +fn five() -> i32 { + 5 +} + +fn main() { + let x = five(); + + println!("The value of x is: {}", x); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/src/main.rs new file mode 100644 index 0000000..b4c8443 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let x = plus_one(5); + + println!("The value of x is: {}", x); +} + +fn plus_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/Cargo.lock new file mode 100644 index 0000000..88287d1 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/Cargo.toml new file mode 100644 index 0000000..291680c --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/output.txt b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/output.txt new file mode 100644 index 0000000..6657c63 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/output.txt @@ -0,0 +1,18 @@ +$ cargo run + Compiling functions v0.1.0 (file:///projects/functions) +error[E0308]: mismatched types + --> src/main.rs:7:24 + | +7 | fn plus_one(x: i32) -> i32 { + | -------- ^^^ expected `i32`, found `()` + | | + | implicitly returns `()` as its body has no tail or `return` expression +8 | x + 1; + | - help: consider removing this semicolon + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `functions` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/src/main.rs new file mode 100644 index 0000000..c9c4edc --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let x = plus_one(5); + + println!("The value of x is: {}", x); +} + +fn plus_one(x: i32) -> i32 { + x + 1; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/Cargo.lock new file mode 100644 index 0000000..a289136 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "comments" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/Cargo.toml new file mode 100644 index 0000000..c53d875 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "comments" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/src/main.rs new file mode 100644 index 0000000..535f4b9 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-24-comments-end-of-line/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + let lucky_number = 7; // I’m feeling lucky today +} diff --git a/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/Cargo.lock new file mode 100644 index 0000000..a289136 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "comments" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/Cargo.toml new file mode 100644 index 0000000..c53d875 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "comments" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/src/main.rs new file mode 100644 index 0000000..81cd935 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-25-comments-above-line/src/main.rs @@ -0,0 +1,4 @@ +fn main() { + // I’m feeling lucky today + let lucky_number = 7; +} diff --git a/listings/ch03-common-programming-concepts/no-listing-26-if-true/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-26-if-true/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-26-if-true/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-26-if-true/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-26-if-true/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-26-if-true/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-26-if-true/output.txt b/listings/ch03-common-programming-concepts/no-listing-26-if-true/output.txt new file mode 100644 index 0000000..3d8c7dc --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-26-if-true/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling branches v0.1.0 (file:///projects/branches) + Finished dev [unoptimized + debuginfo] target(s) in 0.31s + Running `target/debug/branches` +condition was true diff --git a/listings/ch03-common-programming-concepts/no-listing-26-if-true/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-26-if-true/src/main.rs new file mode 100644 index 0000000..e64a42a --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-26-if-true/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let number = 3; + + if number < 5 { + println!("condition was true"); + } else { + println!("condition was false"); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-27-if-false/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-27-if-false/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-27-if-false/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-27-if-false/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-27-if-false/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-27-if-false/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-27-if-false/output.txt b/listings/ch03-common-programming-concepts/no-listing-27-if-false/output.txt new file mode 100644 index 0000000..e40da96 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-27-if-false/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling branches v0.1.0 (file:///projects/branches) + Finished dev [unoptimized + debuginfo] target(s) in 0.31s + Running `target/debug/branches` +condition was false diff --git a/listings/ch03-common-programming-concepts/no-listing-27-if-false/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-27-if-false/src/main.rs new file mode 100644 index 0000000..f7d76cf --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-27-if-false/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let number = 7; + // ANCHOR_END: here + + if number < 5 { + println!("condition was true"); + } else { + println!("condition was false"); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/output.txt b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/output.txt new file mode 100644 index 0000000..5ddb737 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/output.txt @@ -0,0 +1,14 @@ +$ cargo run + Compiling branches v0.1.0 (file:///projects/branches) +error[E0308]: mismatched types + --> src/main.rs:4:8 + | +4 | if number { + | ^^^^^^ expected `bool`, found integer + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `branches` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/src/main.rs new file mode 100644 index 0000000..bc4af76 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let number = 3; + + if number { + println!("number was three"); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/src/main.rs new file mode 100644 index 0000000..704650f --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let number = 3; + + if number != 0 { + println!("number was something other than zero"); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-30-else-if/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-30-else-if/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-30-else-if/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-30-else-if/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-30-else-if/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-30-else-if/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-30-else-if/output.txt b/listings/ch03-common-programming-concepts/no-listing-30-else-if/output.txt new file mode 100644 index 0000000..b218941 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-30-else-if/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling branches v0.1.0 (file:///projects/branches) + Finished dev [unoptimized + debuginfo] target(s) in 0.31s + Running `target/debug/branches` +number is divisible by 3 diff --git a/listings/ch03-common-programming-concepts/no-listing-30-else-if/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-30-else-if/src/main.rs new file mode 100644 index 0000000..d0ef9b2 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-30-else-if/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + let number = 6; + + if number % 4 == 0 { + println!("number is divisible by 4"); + } else if number % 3 == 0 { + println!("number is divisible by 3"); + } else if number % 2 == 0 { + println!("number is divisible by 2"); + } else { + println!("number is not divisible by 4, 3, or 2"); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/Cargo.lock new file mode 100644 index 0000000..4ca0c2d --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "branches" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/Cargo.toml new file mode 100644 index 0000000..8ddf691 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "branches" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/output.txt b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/output.txt new file mode 100644 index 0000000..90934b6 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling branches v0.1.0 (file:///projects/branches) +error[E0308]: `if` and `else` have incompatible types + --> src/main.rs:4:44 + | +4 | let number = if condition { 5 } else { "six" }; + | - ^^^^^ expected integer, found `&str` + | | + | expected because of this + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `branches` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/src/main.rs new file mode 100644 index 0000000..440b286 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let condition = true; + + let number = if condition { 5 } else { "six" }; + + println!("The value of number is: {}", number); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-32-loop/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-32-loop/Cargo.lock new file mode 100644 index 0000000..9942b36 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-32-loop/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "loops" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-32-loop/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-32-loop/Cargo.toml new file mode 100644 index 0000000..b5ed848 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-32-loop/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "loops" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-32-loop/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-32-loop/src/main.rs new file mode 100644 index 0000000..f1692e4 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-32-loop/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + loop { + println!("again!"); + } +} diff --git a/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/Cargo.lock new file mode 100644 index 0000000..9942b36 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "loops" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/Cargo.toml new file mode 100644 index 0000000..b5ed848 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "loops" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/src/main.rs new file mode 100644 index 0000000..6ffdab5 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + let mut counter = 0; + + let result = loop { + counter += 1; + + if counter == 10 { + break counter * 2; + } + }; + + println!("The result is {}", result); +} diff --git a/listings/ch03-common-programming-concepts/no-listing-34-for-range/Cargo.lock b/listings/ch03-common-programming-concepts/no-listing-34-for-range/Cargo.lock new file mode 100644 index 0000000..9942b36 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-34-for-range/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "loops" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/no-listing-34-for-range/Cargo.toml b/listings/ch03-common-programming-concepts/no-listing-34-for-range/Cargo.toml new file mode 100644 index 0000000..b5ed848 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-34-for-range/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "loops" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/no-listing-34-for-range/src/main.rs b/listings/ch03-common-programming-concepts/no-listing-34-for-range/src/main.rs new file mode 100644 index 0000000..e7286a8 --- /dev/null +++ b/listings/ch03-common-programming-concepts/no-listing-34-for-range/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + for number in (1..4).rev() { + println!("{}!", number); + } + println!("LIFTOFF!!!"); +} diff --git a/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/Cargo.lock b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/Cargo.lock new file mode 100644 index 0000000..b5664bc --- /dev/null +++ b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "no_type_annotations" +version = "0.1.0" + diff --git a/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/Cargo.toml b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/Cargo.toml new file mode 100644 index 0000000..964f9e8 --- /dev/null +++ b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "no_type_annotations" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/output.txt b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/output.txt new file mode 100644 index 0000000..df0ed35 --- /dev/null +++ b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/output.txt @@ -0,0 +1,14 @@ +$ cargo build + Compiling no_type_annotations v0.1.0 (file:///projects/no_type_annotations) +error[E0282]: type annotations needed + --> src/main.rs:2:9 + | +2 | let guess = "42".parse().expect("Not a number!"); + | ^^^^^ consider giving `guess` a type + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0282`. +error: could not compile `no_type_annotations` + +To learn more, run the command again with --verbose. diff --git a/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/src/main.rs b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/src/main.rs new file mode 100644 index 0000000..f41c558 --- /dev/null +++ b/listings/ch03-common-programming-concepts/output-only-01-no-type-annotations/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + let guess = "42".parse().expect("Not a number!"); +} diff --git a/listings/ch04-understanding-ownership/listing-04-01/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-01/Cargo.lock new file mode 100644 index 0000000..9e4e62d --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-01/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-01/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-01/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-01/rustfmt-ignore b/listings/ch04-understanding-ownership/listing-04-01/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-01/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch04-understanding-ownership/listing-04-01/src/main.rs b/listings/ch04-understanding-ownership/listing-04-01/src/main.rs new file mode 100644 index 0000000..148ad84 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-01/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + { // s is not valid here, it’s not yet declared + let s = "hello"; // s is valid from this point forward + + // do stuff with s + } // this scope is now over, and s is no longer valid + // ANCHOR_END: here +} \ No newline at end of file diff --git a/listings/ch04-understanding-ownership/listing-04-02/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-02/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-02/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-02/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-02/src/main.rs b/listings/ch04-understanding-ownership/listing-04-02/src/main.rs new file mode 100644 index 0000000..de0f1b3 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-02/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let x = 5; + let y = x; + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/listing-04-03/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-03/Cargo.lock new file mode 100644 index 0000000..9e4e62d --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-03/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-03/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-03/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-03/rustfmt-ignore b/listings/ch04-understanding-ownership/listing-04-03/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-03/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch04-understanding-ownership/listing-04-03/src/main.rs b/listings/ch04-understanding-ownership/listing-04-03/src/main.rs new file mode 100644 index 0000000..b001cc5 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-03/src/main.rs @@ -0,0 +1,23 @@ +fn main() { + let s = String::from("hello"); // s comes into scope + + takes_ownership(s); // s's value moves into the function... + // ... and so is no longer valid here + + let x = 5; // x comes into scope + + makes_copy(x); // x would move into the function, + // but i32 is Copy, so it's okay to still + // use x afterward + +} // Here, x goes out of scope, then s. But because s's value was moved, nothing + // special happens. + +fn takes_ownership(some_string: String) { // some_string comes into scope + println!("{}", some_string); +} // Here, some_string goes out of scope and `drop` is called. The backing + // memory is freed. + +fn makes_copy(some_integer: i32) { // some_integer comes into scope + println!("{}", some_integer); +} // Here, some_integer goes out of scope. Nothing special happens. diff --git a/listings/ch04-understanding-ownership/listing-04-04/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-04/Cargo.lock new file mode 100644 index 0000000..9e4e62d --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-04/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-04/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-04/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-04/rustfmt-ignore b/listings/ch04-understanding-ownership/listing-04-04/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-04/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch04-understanding-ownership/listing-04-04/src/main.rs b/listings/ch04-understanding-ownership/listing-04-04/src/main.rs new file mode 100644 index 0000000..e3e54a8 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-04/src/main.rs @@ -0,0 +1,29 @@ +fn main() { + let s1 = gives_ownership(); // gives_ownership moves its return + // value into s1 + + let s2 = String::from("hello"); // s2 comes into scope + + let s3 = takes_and_gives_back(s2); // s2 is moved into + // takes_and_gives_back, which also + // moves its return value into s3 +} // Here, s3 goes out of scope and is dropped. s2 goes out of scope but was + // moved, so nothing happens. s1 goes out of scope and is dropped. + +fn gives_ownership() -> String { // gives_ownership will move its + // return value into the function + // that calls it + + let some_string = String::from("hello"); // some_string comes into scope + + some_string // some_string is returned and + // moves out to the calling + // function +} + +// takes_and_gives_back will take a String and return one +fn takes_and_gives_back(a_string: String) -> String { // a_string comes into + // scope + + a_string // a_string is returned and moves out to the calling function +} diff --git a/listings/ch04-understanding-ownership/listing-04-05/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-05/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-05/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-05/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-05/src/main.rs b/listings/ch04-understanding-ownership/listing-04-05/src/main.rs new file mode 100644 index 0000000..22aee14 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-05/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + let s1 = String::from("hello"); + + let (s2, len) = calculate_length(s1); + + println!("The length of '{}' is {}.", s2, len); +} + +fn calculate_length(s: String) -> (String, usize) { + let length = s.len(); // len() returns the length of a String + + (s, length) +} diff --git a/listings/ch04-understanding-ownership/listing-04-06/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-06/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-06/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-06/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-06/output.txt b/listings/ch04-understanding-ownership/listing-04-06/output.txt new file mode 100644 index 0000000..b62dbd0 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-06/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling ownership v0.1.0 (file:///projects/ownership) +error[E0596]: cannot borrow `*some_string` as mutable, as it is behind a `&` reference + --> src/main.rs:8:5 + | +7 | fn change(some_string: &String) { + | ------- help: consider changing this to be a mutable reference: `&mut String` +8 | some_string.push_str(", world"); + | ^^^^^^^^^^^ `some_string` is a `&` reference, so the data it refers to cannot be borrowed as mutable + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0596`. +error: could not compile `ownership` + +To learn more, run the command again with --verbose. diff --git a/listings/ch04-understanding-ownership/listing-04-06/src/main.rs b/listings/ch04-understanding-ownership/listing-04-06/src/main.rs new file mode 100644 index 0000000..330ffa6 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-06/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let s = String::from("hello"); + + change(&s); +} + +fn change(some_string: &String) { + some_string.push_str(", world"); +} diff --git a/listings/ch04-understanding-ownership/listing-04-07/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-07/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-07/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-07/Cargo.toml new file mode 100644 index 0000000..dddcb5a --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Carol (Nichols || Goulding) "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-07/src/main.rs b/listings/ch04-understanding-ownership/listing-04-07/src/main.rs new file mode 100644 index 0000000..3bb3c85 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-07/src/main.rs @@ -0,0 +1,21 @@ +// ANCHOR: here +fn first_word(s: &String) -> usize { + // ANCHOR: as_bytes + let bytes = s.as_bytes(); + // ANCHOR_END: as_bytes + + // ANCHOR: iter + for (i, &item) in bytes.iter().enumerate() { + // ANCHOR_END: iter + // ANCHOR: inside_for + if item == b' ' { + return i; + } + } + + s.len() + // ANCHOR_END: inside_for +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch04-understanding-ownership/listing-04-08/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-08/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-08/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-08/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-08/src/main.rs b/listings/ch04-understanding-ownership/listing-04-08/src/main.rs new file mode 100644 index 0000000..b6182fe --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-08/src/main.rs @@ -0,0 +1,24 @@ +fn first_word(s: &String) -> usize { + let bytes = s.as_bytes(); + + for (i, &item) in bytes.iter().enumerate() { + if item == b' ' { + return i; + } + } + + s.len() +} + +// ANCHOR: here +fn main() { + let mut s = String::from("hello world"); + + let word = first_word(&s); // word will get the value 5 + + s.clear(); // this empties the String, making it equal to "" + + // word still has the value 5 here, but there's no more string that + // we could meaningfully use the value 5 with. word is now totally invalid! +} +// ANCHOR_END: here diff --git a/listings/ch04-understanding-ownership/listing-04-09/Cargo.lock b/listings/ch04-understanding-ownership/listing-04-09/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/listing-04-09/Cargo.toml b/listings/ch04-understanding-ownership/listing-04-09/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/listing-04-09/src/main.rs b/listings/ch04-understanding-ownership/listing-04-09/src/main.rs new file mode 100644 index 0000000..19a9cc7 --- /dev/null +++ b/listings/ch04-understanding-ownership/listing-04-09/src/main.rs @@ -0,0 +1,31 @@ +// ANCHOR: here +fn first_word(s: &str) -> &str { + // ANCHOR_END: here + let bytes = s.as_bytes(); + + for (i, &item) in bytes.iter().enumerate() { + if item == b' ' { + return &s[0..i]; + } + } + + &s[..] +} + +// ANCHOR: usage +fn main() { + let my_string = String::from("hello world"); + + // first_word works on slices of `String`s + let word = first_word(&my_string[..]); + + let my_string_literal = "hello world"; + + // first_word works on slices of string literals + let word = first_word(&my_string_literal[..]); + + // Because string literals *are* string slices already, + // this works too, without the slice syntax! + let word = first_word(my_string_literal); +} +// ANCHOR_END: usage diff --git a/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/src/main.rs b/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/src/main.rs new file mode 100644 index 0000000..b68f0f1 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("hello"); + + s.push_str(", world!"); // push_str() appends a literal to a String + + println!("{}", s); // This will print `hello, world!` + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.lock new file mode 100644 index 0000000..9e4e62d --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-02-string-scope/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-02-string-scope/rustfmt-ignore b/listings/ch04-understanding-ownership/no-listing-02-string-scope/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-02-string-scope/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch04-understanding-ownership/no-listing-02-string-scope/src/main.rs b/listings/ch04-understanding-ownership/no-listing-02-string-scope/src/main.rs new file mode 100644 index 0000000..7e6d46f --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-02-string-scope/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + { + let s = String::from("hello"); // s is valid from this point forward + + // do stuff with s + } // this scope is now over, and s is no + // longer valid + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-03-string-move/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-03-string-move/src/main.rs b/listings/ch04-understanding-ownership/no-listing-03-string-move/src/main.rs new file mode 100644 index 0000000..a5817e7 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-03-string-move/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("hello"); + let s2 = s1; + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/output.txt b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/output.txt new file mode 100644 index 0000000..b69c878 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling ownership v0.1.0 (file:///projects/ownership) +error[E0382]: borrow of moved value: `s1` + --> src/main.rs:5:28 + | +2 | let s1 = String::from("hello"); + | -- move occurs because `s1` has type `String`, which does not implement the `Copy` trait +3 | let s2 = s1; + | -- value moved here +4 | +5 | println!("{}, world!", s1); + | ^^ value borrowed here after move + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `ownership` + +To learn more, run the command again with --verbose. diff --git a/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/src/main.rs b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/src/main.rs new file mode 100644 index 0000000..d0b9f18 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("hello"); + let s2 = s1; + + println!("{}, world!", s1); + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-05-clone/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-05-clone/src/main.rs b/listings/ch04-understanding-ownership/no-listing-05-clone/src/main.rs new file mode 100644 index 0000000..4e61cc1 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-05-clone/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("hello"); + let s2 = s1.clone(); + + println!("s1 = {}, s2 = {}", s1, s2); + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-06-copy/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-06-copy/src/main.rs b/listings/ch04-understanding-ownership/no-listing-06-copy/src/main.rs new file mode 100644 index 0000000..63a1fae --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-06-copy/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let x = 5; + let y = x; + + println!("x = {}, y = {}", x, y); + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-07-reference/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-07-reference/src/main.rs b/listings/ch04-understanding-ownership/no-listing-07-reference/src/main.rs new file mode 100644 index 0000000..fd32a5f --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-07-reference/src/main.rs @@ -0,0 +1,15 @@ +// ANCHOR: all +fn main() { + // ANCHOR: here + let s1 = String::from("hello"); + + let len = calculate_length(&s1); + // ANCHOR_END: here + + println!("The length of '{}' is {}.", s1, len); +} + +fn calculate_length(s: &String) -> usize { + s.len() +} +// ANCHOR_END: all diff --git a/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.lock new file mode 100644 index 0000000..9e4e62d --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/rustfmt-ignore b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/src/main.rs b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/src/main.rs new file mode 100644 index 0000000..6e40b8c --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/src/main.rs @@ -0,0 +1,14 @@ +fn main() { + let s1 = String::from("hello"); + + let len = calculate_length(&s1); + + println!("The length of '{}' is {}.", s1, len); +} + +// ANCHOR: here +fn calculate_length(s: &String) -> usize { // s is a reference to a String + s.len() +} // Here, s goes out of scope. But because it does not have ownership of what + // it refers to, nothing happens. +// ANCHOR_END: here diff --git a/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/src/main.rs b/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/src/main.rs new file mode 100644 index 0000000..fdf7f0a --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let mut s = String::from("hello"); + + change(&mut s); +} + +fn change(some_string: &mut String) { + some_string.push_str(", world"); +} diff --git a/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/output.txt b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/output.txt new file mode 100644 index 0000000..7e40a22 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling ownership v0.1.0 (file:///projects/ownership) +error[E0499]: cannot borrow `s` as mutable more than once at a time + --> src/main.rs:5:14 + | +4 | let r1 = &mut s; + | ------ first mutable borrow occurs here +5 | let r2 = &mut s; + | ^^^^^^ second mutable borrow occurs here +6 | +7 | println!("{}, {}", r1, r2); + | -- first borrow later used here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0499`. +error: could not compile `ownership` + +To learn more, run the command again with --verbose. diff --git a/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/src/main.rs b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/src/main.rs new file mode 100644 index 0000000..ddbf812 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("hello"); + + let r1 = &mut s; + let r2 = &mut s; + + println!("{}, {}", r1, r2); + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/src/main.rs b/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/src/main.rs new file mode 100644 index 0000000..4b1a5a3 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("hello"); + + { + let r1 = &mut s; + } // r1 goes out of scope here, so we can make a new reference with no problems. + + let r2 = &mut s; + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/output.txt b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/output.txt new file mode 100644 index 0000000..25ca954 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling ownership v0.1.0 (file:///projects/ownership) +error[E0502]: cannot borrow `s` as mutable because it is also borrowed as immutable + --> src/main.rs:6:14 + | +4 | let r1 = &s; // no problem + | -- immutable borrow occurs here +5 | let r2 = &s; // no problem +6 | let r3 = &mut s; // BIG PROBLEM + | ^^^^^^ mutable borrow occurs here +7 | +8 | println!("{}, {}, and {}", r1, r2, r3); + | -- immutable borrow later used here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0502`. +error: could not compile `ownership` + +To learn more, run the command again with --verbose. diff --git a/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/src/main.rs b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/src/main.rs new file mode 100644 index 0000000..0da04c0 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("hello"); + + let r1 = &s; // no problem + let r2 = &s; // no problem + let r3 = &mut s; // BIG PROBLEM + + println!("{}, {}, and {}", r1, r2, r3); + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/src/main.rs b/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/src/main.rs new file mode 100644 index 0000000..3b0a7da --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("hello"); + + let r1 = &s; // no problem + let r2 = &s; // no problem + println!("{} and {}", r1, r2); + // r1 and r2 are no longer used after this point + + let r3 = &mut s; // no problem + println!("{}", r3); + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/output.txt b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/output.txt new file mode 100644 index 0000000..dc23312 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling ownership v0.1.0 (file:///projects/ownership) +error[E0106]: missing lifetime specifier + --> src/main.rs:5:16 + | +5 | fn dangle() -> &String { + | ^ expected named lifetime parameter + | + = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from +help: consider using the `'static` lifetime + | +5 | fn dangle() -> &'static String { + | ^^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0106`. +error: could not compile `ownership` + +To learn more, run the command again with --verbose. diff --git a/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/src/main.rs b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/src/main.rs new file mode 100644 index 0000000..b102697 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-14-dangling-reference/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let reference_to_nothing = dangle(); +} + +fn dangle() -> &String { + let s = String::from("hello"); + + &s +} diff --git a/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/Cargo.lock new file mode 100644 index 0000000..9e4e62d --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/rustfmt-ignore b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/src/main.rs b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/src/main.rs new file mode 100644 index 0000000..9fbb372 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + let reference_to_nothing = dangle(); +} + +// ANCHOR: here +fn dangle() -> &String { // dangle returns a reference to a String + + let s = String::from("hello"); // s is a new String + + &s // we return a reference to the String, s +} // Here, s goes out of scope, and is dropped. Its memory goes away. + // Danger! +// ANCHOR_END: here diff --git a/listings/ch04-understanding-ownership/no-listing-16-no-dangle/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-16-no-dangle/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-16-no-dangle/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-16-no-dangle/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-16-no-dangle/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-16-no-dangle/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-16-no-dangle/src/main.rs b/listings/ch04-understanding-ownership/no-listing-16-no-dangle/src/main.rs new file mode 100644 index 0000000..9c20a3b --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-16-no-dangle/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + let string = no_dangle(); +} + +// ANCHOR: here +fn no_dangle() -> String { + let s = String::from("hello"); + + s +} +// ANCHOR_END: here diff --git a/listings/ch04-understanding-ownership/no-listing-17-slice/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-17-slice/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-17-slice/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-17-slice/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-17-slice/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-17-slice/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-17-slice/src/main.rs b/listings/ch04-understanding-ownership/no-listing-17-slice/src/main.rs new file mode 100644 index 0000000..44163af --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-17-slice/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let s = String::from("hello world"); + + let hello = &s[0..5]; + let world = &s[6..11]; + // ANCHOR_END: here +} diff --git a/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/src/main.rs b/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/src/main.rs new file mode 100644 index 0000000..f44a970 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-18-first-word-slice/src/main.rs @@ -0,0 +1,15 @@ +// ANCHOR: here +fn first_word(s: &String) -> &str { + let bytes = s.as_bytes(); + + for (i, &item) in bytes.iter().enumerate() { + if item == b' ' { + return &s[0..i]; + } + } + + &s[..] +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch04-understanding-ownership/no-listing-19-slice-error/Cargo.lock b/listings/ch04-understanding-ownership/no-listing-19-slice-error/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-19-slice-error/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch04-understanding-ownership/no-listing-19-slice-error/Cargo.toml b/listings/ch04-understanding-ownership/no-listing-19-slice-error/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-19-slice-error/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch04-understanding-ownership/no-listing-19-slice-error/output.txt b/listings/ch04-understanding-ownership/no-listing-19-slice-error/output.txt new file mode 100644 index 0000000..503a503 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-19-slice-error/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling ownership v0.1.0 (file:///projects/ownership) +error[E0502]: cannot borrow `s` as mutable because it is also borrowed as immutable + --> src/main.rs:18:5 + | +16 | let word = first_word(&s); + | -- immutable borrow occurs here +17 | +18 | s.clear(); // error! + | ^^^^^^^^^ mutable borrow occurs here +19 | +20 | println!("the first word is: {}", word); + | ---- immutable borrow later used here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0502`. +error: could not compile `ownership` + +To learn more, run the command again with --verbose. diff --git a/listings/ch04-understanding-ownership/no-listing-19-slice-error/src/main.rs b/listings/ch04-understanding-ownership/no-listing-19-slice-error/src/main.rs new file mode 100644 index 0000000..99e0401 --- /dev/null +++ b/listings/ch04-understanding-ownership/no-listing-19-slice-error/src/main.rs @@ -0,0 +1,23 @@ +fn first_word(s: &String) -> &str { + let bytes = s.as_bytes(); + + for (i, &item) in bytes.iter().enumerate() { + if item == b' ' { + return &s[0..i]; + } + } + + &s[..] +} + +// ANCHOR: here +fn main() { + let mut s = String::from("hello world"); + + let word = first_word(&s); + + s.clear(); // error! + + println!("the first word is: {}", word); +} +// ANCHOR_END: here diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-01/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-01/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-01/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-01/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-01/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-01/src/main.rs new file mode 100644 index 0000000..a7cff6e --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-01/src/main.rs @@ -0,0 +1,10 @@ +// ANCHOR: here +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-02/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-02/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-02/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-02/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-02/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-02/src/main.rs new file mode 100644 index 0000000..390c8ff --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-02/src/main.rs @@ -0,0 +1,17 @@ +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} + +fn main() { + // ANCHOR: here + let user1 = User { + email: String::from("someone@example.com"), + username: String::from("someusername123"), + active: true, + sign_in_count: 1, + }; + // ANCHOR_END: here +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-03/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-03/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-03/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-03/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-03/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-03/src/main.rs new file mode 100644 index 0000000..c599c9d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-03/src/main.rs @@ -0,0 +1,19 @@ +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} + +fn main() { + // ANCHOR: here + let mut user1 = User { + email: String::from("someone@example.com"), + username: String::from("someusername123"), + active: true, + sign_in_count: 1, + }; + + user1.email = String::from("anotheremail@example.com"); + // ANCHOR_END: here +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-04/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-04/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-04/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-04/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-04/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-04/src/main.rs new file mode 100644 index 0000000..f934d4c --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-04/src/main.rs @@ -0,0 +1,24 @@ +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} + +// ANCHOR: here +fn build_user(email: String, username: String) -> User { + User { + email: email, + username: username, + active: true, + sign_in_count: 1, + } +} +// ANCHOR_END: here + +fn main() { + let user1 = build_user( + String::from("someone@example.com"), + String::from("someusername123"), + ); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-05/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-05/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-05/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-05/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-05/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-05/src/main.rs new file mode 100644 index 0000000..1833aa8 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-05/src/main.rs @@ -0,0 +1,24 @@ +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} + +// ANCHOR: here +fn build_user(email: String, username: String) -> User { + User { + email, + username, + active: true, + sign_in_count: 1, + } +} +// ANCHOR_END: here + +fn main() { + let user1 = build_user( + String::from("someone@example.com"), + String::from("someusername123"), + ); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-06/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-06/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-06/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-06/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-06/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-06/src/main.rs new file mode 100644 index 0000000..6c6d83d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-06/src/main.rs @@ -0,0 +1,24 @@ +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} + +fn main() { + let user1 = User { + email: String::from("someone@example.com"), + username: String::from("someusername123"), + active: true, + sign_in_count: 1, + }; + + // ANCHOR: here + let user2 = User { + email: String::from("another@example.com"), + username: String::from("anotherusername567"), + active: user1.active, + sign_in_count: user1.sign_in_count, + }; + // ANCHOR_END: here +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-07/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-07/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-07/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-07/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-07/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-07/src/main.rs new file mode 100644 index 0000000..17cef45 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-07/src/main.rs @@ -0,0 +1,23 @@ +struct User { + username: String, + email: String, + sign_in_count: u64, + active: bool, +} + +fn main() { + let user1 = User { + email: String::from("someone@example.com"), + username: String::from("someusername123"), + active: true, + sign_in_count: 1, + }; + + // ANCHOR: here + let user2 = User { + email: String::from("another@example.com"), + username: String::from("anotherusername567"), + ..user1 + }; + // ANCHOR_END: here +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-08/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-08/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-08/output.txt b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/output.txt new file mode 100644 index 0000000..c44b582 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling rectangles v0.1.0 (file:///projects/rectangles) + Finished dev [unoptimized + debuginfo] target(s) in 0.42s + Running `target/debug/rectangles` +The area of the rectangle is 1500 square pixels. diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-08/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/src/main.rs new file mode 100644 index 0000000..f324529 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-08/src/main.rs @@ -0,0 +1,17 @@ +// ANCHOR: all +fn main() { + let width1 = 30; + let height1 = 50; + + println!( + "The area of the rectangle is {} square pixels.", + area(width1, height1) + ); +} + +// ANCHOR: here +fn area(width: u32, height: u32) -> u32 { + // ANCHOR_END: here + width * height +} +// ANCHOR_END: all diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-09/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-09/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-09/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-09/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-09/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-09/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-09/src/main.rs new file mode 100644 index 0000000..d4b77ba --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-09/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + let rect1 = (30, 50); + + println!( + "The area of the rectangle is {} square pixels.", + area(rect1) + ); +} + +fn area(dimensions: (u32, u32)) -> u32 { + dimensions.0 * dimensions.1 +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-10/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-10/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-10/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-10/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-10/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-10/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-10/src/main.rs new file mode 100644 index 0000000..62ef9ac --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-10/src/main.rs @@ -0,0 +1,20 @@ +struct Rectangle { + width: u32, + height: u32, +} + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + + println!( + "The area of the rectangle is {} square pixels.", + area(&rect1) + ); +} + +fn area(rectangle: &Rectangle) -> u32 { + rectangle.width * rectangle.height +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-11/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-11/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-11/output.txt b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/output.txt new file mode 100644 index 0000000..4a3f462 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling rectangles v0.1.0 (file:///projects/rectangles) +error[E0277]: `Rectangle` doesn't implement `std::fmt::Display` + --> src/main.rs:12:29 + | +12 | println!("rect1 is {}", rect1); + | ^^^^^ `Rectangle` cannot be formatted with the default formatter + | + = help: the trait `std::fmt::Display` is not implemented for `Rectangle` + = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead + = note: required by `std::fmt::Display::fmt` + = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info) + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `rectangles` + +To learn more, run the command again with --verbose. diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-11/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/src/main.rs new file mode 100644 index 0000000..0ff8dcc --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-11/src/main.rs @@ -0,0 +1,13 @@ +struct Rectangle { + width: u32, + height: u32, +} + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + + println!("rect1 is {}", rect1); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-12/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-12/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-12/output.txt b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/output.txt new file mode 100644 index 0000000..c37be6b --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling rectangles v0.1.0 (file:///projects/rectangles) + Finished dev [unoptimized + debuginfo] target(s) in 0.48s + Running `target/debug/rectangles` +rect1 is Rectangle { width: 30, height: 50 } diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-12/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/src/main.rs new file mode 100644 index 0000000..2ffc4b8 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-12/src/main.rs @@ -0,0 +1,14 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + + println!("rect1 is {:?}", rect1); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-13/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-13/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-13/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-13/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-13/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-13/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-13/src/main.rs new file mode 100644 index 0000000..e4f45e8 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-13/src/main.rs @@ -0,0 +1,23 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +impl Rectangle { + fn area(&self) -> u32 { + self.width * self.height + } +} + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + + println!( + "The area of the rectangle is {} square pixels.", + rect1.area() + ); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-14/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-14/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-14/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-14/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-14/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-14/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-14/src/main.rs new file mode 100644 index 0000000..843dab4 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-14/src/main.rs @@ -0,0 +1,17 @@ +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + let rect2 = Rectangle { + width: 10, + height: 40, + }; + let rect3 = Rectangle { + width: 60, + height: 45, + }; + + println!("Can rect1 hold rect2? {}", rect1.can_hold(&rect2)); + println!("Can rect1 hold rect3? {}", rect1.can_hold(&rect3)); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-15/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-15/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-15/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-15/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-15/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-15/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-15/src/main.rs new file mode 100644 index 0000000..e6a3272 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-15/src/main.rs @@ -0,0 +1,35 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +// ANCHOR: here +impl Rectangle { + fn area(&self) -> u32 { + self.width * self.height + } + + fn can_hold(&self, other: &Rectangle) -> bool { + self.width > other.width && self.height > other.height + } +} +// ANCHOR_END: here + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + let rect2 = Rectangle { + width: 10, + height: 40, + }; + let rect3 = Rectangle { + width: 60, + height: 45, + }; + + println!("Can rect1 hold rect2? {}", rect1.can_hold(&rect2)); + println!("Can rect1 hold rect3? {}", rect1.can_hold(&rect3)); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-16/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/listing-05-16/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-16/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-16/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/listing-05-16/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/listing-05-16/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/listing-05-16/src/main.rs new file mode 100644 index 0000000..a5d3f77 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/listing-05-16/src/main.rs @@ -0,0 +1,37 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +// ANCHOR: here +impl Rectangle { + fn area(&self) -> u32 { + self.width * self.height + } +} + +impl Rectangle { + fn can_hold(&self, other: &Rectangle) -> bool { + self.width > other.width && self.height > other.height + } +} +// ANCHOR_END: here + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + let rect2 = Rectangle { + width: 10, + height: 40, + }; + let rect3 = Rectangle { + width: 60, + height: 45, + }; + + println!("Can rect1 hold rect2? {}", rect1.can_hold(&rect2)); + println!("Can rect1 hold rect3? {}", rect1.can_hold(&rect3)); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/Cargo.toml new file mode 100644 index 0000000..431e5c3 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/src/main.rs new file mode 100644 index 0000000..4c92c5d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + struct Color(i32, i32, i32); + struct Point(i32, i32, i32); + + let black = Color(0, 0, 0); + let origin = Point(0, 0, 0); + // ANCHOR_END: here +} diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/Cargo.lock new file mode 100644 index 0000000..bede081 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "structs" +version = "0.1.0" + diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/Cargo.toml new file mode 100644 index 0000000..dec1c4b --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "structs" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/output.txt b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/output.txt new file mode 100644 index 0000000..9b54ddd --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/output.txt @@ -0,0 +1,33 @@ +$ cargo run + Compiling structs v0.1.0 (file:///projects/structs) +error[E0106]: missing lifetime specifier + --> src/main.rs:2:15 + | +2 | username: &str, + | ^ expected named lifetime parameter + | +help: consider introducing a named lifetime parameter + | +1 | struct User<'a> { +2 | username: &'a str, + | + +error[E0106]: missing lifetime specifier + --> src/main.rs:3:12 + | +3 | email: &str, + | ^ expected named lifetime parameter + | +help: consider introducing a named lifetime parameter + | +1 | struct User<'a> { +2 | username: &str, +3 | email: &'a str, + | + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0106`. +error: could not compile `structs` + +To learn more, run the command again with --verbose. diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/src/main.rs new file mode 100644 index 0000000..3cf6ffa --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-02-reference-in-struct/src/main.rs @@ -0,0 +1,15 @@ +struct User { + username: &str, + email: &str, + sign_in_count: u64, + active: bool, +} + +fn main() { + let user1 = User { + email: "someone@example.com", + username: "someusername123", + active: true, + sign_in_count: 1, + }; +} diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/src/main.rs new file mode 100644 index 0000000..d5b1692 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/src/main.rs @@ -0,0 +1,20 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +// ANCHOR: here +impl Rectangle { + fn square(size: u32) -> Rectangle { + Rectangle { + width: size, + height: size, + } + } +} +// ANCHOR_END: here + +fn main() { + let sq = Rectangle::square(3); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/output.txt b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/output.txt new file mode 100644 index 0000000..c78a008 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling rectangles v0.1.0 (file:///projects/rectangles) +error[E0277]: `Rectangle` doesn't implement `Debug` + --> src/main.rs:12:31 + | +12 | println!("rect1 is {:?}", rect1); + | ^^^^^ `Rectangle` cannot be formatted using `{:?}` + | + = help: the trait `Debug` is not implemented for `Rectangle` + = note: add `#[derive(Debug)]` or manually implement `Debug` + = note: required by `std::fmt::Debug::fmt` + = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info) + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `rectangles` + +To learn more, run the command again with --verbose. diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/src/main.rs new file mode 100644 index 0000000..019a357 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/src/main.rs @@ -0,0 +1,13 @@ +struct Rectangle { + width: u32, + height: u32, +} + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + + println!("rect1 is {:?}", rect1); +} diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/Cargo.lock b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/Cargo.lock new file mode 100644 index 0000000..4aabe7d --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangles" +version = "0.1.0" diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/Cargo.toml b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/Cargo.toml new file mode 100644 index 0000000..58787d2 --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangles" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/output.txt b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/output.txt new file mode 100644 index 0000000..db6deed --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/output.txt @@ -0,0 +1,8 @@ +$ cargo run + Compiling rectangles v0.1.0 (file:///projects/rectangles) + Finished dev [unoptimized + debuginfo] target(s) in 0.48s + Running `target/debug/rectangles` +rect1 is Rectangle { + width: 30, + height: 50, +} diff --git a/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/src/main.rs b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/src/main.rs new file mode 100644 index 0000000..84e32ae --- /dev/null +++ b/listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/src/main.rs @@ -0,0 +1,14 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +fn main() { + let rect1 = Rectangle { + width: 30, + height: 50, + }; + + println!("rect1 is {:#?}", rect1); +} diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-01/Cargo.lock b/listings/ch06-enums-and-pattern-matching/listing-06-01/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-01/Cargo.toml b/listings/ch06-enums-and-pattern-matching/listing-06-01/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-01/src/main.rs b/listings/ch06-enums-and-pattern-matching/listing-06-01/src/main.rs new file mode 100644 index 0000000..5b688e0 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-01/src/main.rs @@ -0,0 +1,23 @@ +fn main() { + // ANCHOR: here + enum IpAddrKind { + V4, + V6, + } + + struct IpAddr { + kind: IpAddrKind, + address: String, + } + + let home = IpAddr { + kind: IpAddrKind::V4, + address: String::from("127.0.0.1"), + }; + + let loopback = IpAddr { + kind: IpAddrKind::V6, + address: String::from("::1"), + }; + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-02/Cargo.lock b/listings/ch06-enums-and-pattern-matching/listing-06-02/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-02/Cargo.toml b/listings/ch06-enums-and-pattern-matching/listing-06-02/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-02/src/main.rs b/listings/ch06-enums-and-pattern-matching/listing-06-02/src/main.rs new file mode 100644 index 0000000..3ba7497 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-02/src/main.rs @@ -0,0 +1,10 @@ +// ANCHOR: here +enum Message { + Quit, + Move { x: i32, y: i32 }, + Write(String), + ChangeColor(i32, i32, i32), +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-03/Cargo.lock b/listings/ch06-enums-and-pattern-matching/listing-06-03/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-03/Cargo.toml b/listings/ch06-enums-and-pattern-matching/listing-06-03/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-03/src/main.rs b/listings/ch06-enums-and-pattern-matching/listing-06-03/src/main.rs new file mode 100644 index 0000000..93dce48 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-03/src/main.rs @@ -0,0 +1,19 @@ +// ANCHOR: here +enum Coin { + Penny, + Nickel, + Dime, + Quarter, +} + +fn value_in_cents(coin: Coin) -> u8 { + match coin { + Coin::Penny => 1, + Coin::Nickel => 5, + Coin::Dime => 10, + Coin::Quarter => 25, + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-04/Cargo.lock b/listings/ch06-enums-and-pattern-matching/listing-06-04/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-04/Cargo.toml b/listings/ch06-enums-and-pattern-matching/listing-06-04/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-04/src/main.rs b/listings/ch06-enums-and-pattern-matching/listing-06-04/src/main.rs new file mode 100644 index 0000000..3ba384f --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-04/src/main.rs @@ -0,0 +1,17 @@ +// ANCHOR: here +#[derive(Debug)] // so we can inspect the state in a minute +enum UsState { + Alabama, + Alaska, + // --snip-- +} + +enum Coin { + Penny, + Nickel, + Dime, + Quarter(UsState), +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-05/Cargo.lock b/listings/ch06-enums-and-pattern-matching/listing-06-05/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-05/Cargo.toml b/listings/ch06-enums-and-pattern-matching/listing-06-05/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs b/listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs new file mode 100644 index 0000000..c86190a --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs @@ -0,0 +1,18 @@ +fn main() { + // ANCHOR: here + fn plus_one(x: Option) -> Option { + match x { + // ANCHOR: first_arm + None => None, + // ANCHOR_END: first_arm + // ANCHOR: second_arm + Some(i) => Some(i + 1), + // ANCHOR_END: second_arm + } + } + + let five = Some(5); + let six = plus_one(five); + let none = plus_one(None); + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-06/Cargo.lock b/listings/ch06-enums-and-pattern-matching/listing-06-06/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-06/Cargo.toml b/listings/ch06-enums-and-pattern-matching/listing-06-06/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/listing-06-06/src/main.rs b/listings/ch06-enums-and-pattern-matching/listing-06-06/src/main.rs new file mode 100644 index 0000000..222d545 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/listing-06-06/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + let some_u8_value = Some(0u8); + match some_u8_value { + Some(3) => println!("three"), + _ => (), + } + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs new file mode 100644 index 0000000..c631e56 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs @@ -0,0 +1,22 @@ +// ANCHOR: def +enum IpAddrKind { + V4, + V6, +} +// ANCHOR_END: def + +fn main() { + // ANCHOR: instance + let four = IpAddrKind::V4; + let six = IpAddrKind::V6; + // ANCHOR_END: instance + + // ANCHOR: fn_call + route(IpAddrKind::V4); + route(IpAddrKind::V6); + // ANCHOR_END: fn_call +} + +// ANCHOR: fn +fn route(ip_kind: IpAddrKind) {} +// ANCHOR_END: fn diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/src/main.rs new file mode 100644 index 0000000..7d59b81 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + enum IpAddr { + V4(String), + V6(String), + } + + let home = IpAddr::V4(String::from("127.0.0.1")); + + let loopback = IpAddr::V6(String::from("::1")); + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/src/main.rs new file mode 100644 index 0000000..844a140 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + enum IpAddr { + V4(u8, u8, u8, u8), + V6(String), + } + + let home = IpAddr::V4(127, 0, 0, 1); + + let loopback = IpAddr::V6(String::from("::1")); + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/src/main.rs new file mode 100644 index 0000000..df451be --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/src/main.rs @@ -0,0 +1,11 @@ +// ANCHOR: here +struct QuitMessage; // unit struct +struct MoveMessage { + x: i32, + y: i32, +} +struct WriteMessage(String); // tuple struct +struct ChangeColorMessage(i32, i32, i32); // tuple struct + // ANCHOR_END: here + +fn main() {} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/src/main.rs new file mode 100644 index 0000000..66e0b6d --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/src/main.rs @@ -0,0 +1,19 @@ +fn main() { + enum Message { + Quit, + Move { x: i32, y: i32 }, + Write(String), + ChangeColor(i32, i32, i32), + } + + // ANCHOR: here + impl Message { + fn call(&self) { + // method body would be defined here + } + } + + let m = Message::Write(String::from("hello")); + m.call(); + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/src/main.rs new file mode 100644 index 0000000..9de5791 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let some_number = Some(5); + let some_string = Some("a string"); + + let absent_number: Option = None; + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/output.txt b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/output.txt new file mode 100644 index 0000000..856826c --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling enums v0.1.0 (file:///projects/enums) +error[E0277]: cannot add `Option` to `i8` + --> src/main.rs:5:17 + | +5 | let sum = x + y; + | ^ no implementation for `i8 + Option` + | + = help: the trait `Add>` is not implemented for `i8` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `enums` + +To learn more, run the command again with --verbose. diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/src/main.rs new file mode 100644 index 0000000..ec65565 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let x: i8 = 5; + let y: Option = Some(5); + + let sum = x + y; + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/src/main.rs new file mode 100644 index 0000000..3f909dc --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/src/main.rs @@ -0,0 +1,22 @@ +enum Coin { + Penny, + Nickel, + Dime, + Quarter, +} + +// ANCHOR: here +fn value_in_cents(coin: Coin) -> u8 { + match coin { + Coin::Penny => { + println!("Lucky penny!"); + 1 + } + Coin::Nickel => 5, + Coin::Dime => 10, + Coin::Quarter => 25, + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/src/main.rs new file mode 100644 index 0000000..a4d500c --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/src/main.rs @@ -0,0 +1,31 @@ +#[derive(Debug)] +enum UsState { + Alabama, + Alaska, + // --snip-- +} + +enum Coin { + Penny, + Nickel, + Dime, + Quarter(UsState), +} + +// ANCHOR: here +fn value_in_cents(coin: Coin) -> u8 { + match coin { + Coin::Penny => 1, + Coin::Nickel => 5, + Coin::Dime => 10, + Coin::Quarter(state) => { + println!("State quarter from {:?}!", state); + 25 + } + } +} +// ANCHOR_END: here + +fn main() { + value_in_cents(Coin::Quarter(UsState::Alaska)); +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/output.txt b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/output.txt new file mode 100644 index 0000000..0ab76cc --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/output.txt @@ -0,0 +1,17 @@ +$ cargo run + Compiling enums v0.1.0 (file:///projects/enums) +error[E0004]: non-exhaustive patterns: `None` not covered + --> src/main.rs:3:15 + | +3 | match x { + | ^ pattern `None` not covered + | + = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms + = note: the matched value is of type `Option` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0004`. +error: could not compile `enums` + +To learn more, run the command again with --verbose. diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/src/main.rs new file mode 100644 index 0000000..f1963d0 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + fn plus_one(x: Option) -> Option { + match x { + Some(i) => Some(i + 1), + } + } + // ANCHOR_END: here + + let five = Some(5); + let six = plus_one(five); + let none = plus_one(None); +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/src/main.rs new file mode 100644 index 0000000..6fc8ab0 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + let some_u8_value = 0u8; + match some_u8_value { + 1 => println!("one"), + 3 => println!("three"), + 5 => println!("five"), + 7 => println!("seven"), + _ => (), + } + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/src/main.rs new file mode 100644 index 0000000..a2bc0e3 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let some_u8_value = Some(0u8); + if let Some(3) = some_u8_value { + println!("three"); + } + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/src/main.rs new file mode 100644 index 0000000..12c4c0f --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/src/main.rs @@ -0,0 +1,24 @@ +#[derive(Debug)] +enum UsState { + Alabama, + Alaska, + // --snip-- +} + +enum Coin { + Penny, + Nickel, + Dime, + Quarter(UsState), +} + +fn main() { + let coin = Coin::Penny; + // ANCHOR: here + let mut count = 0; + match coin { + Coin::Quarter(state) => println!("State quarter from {:?}!", state), + _ => count += 1, + } + // ANCHOR_END: here +} diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/Cargo.lock b/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/Cargo.lock new file mode 100644 index 0000000..f62e8ac --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "enums" +version = "0.1.0" + diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/Cargo.toml b/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/Cargo.toml new file mode 100644 index 0000000..04988d1 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "enums" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/src/main.rs b/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/src/main.rs new file mode 100644 index 0000000..ba7eda2 --- /dev/null +++ b/listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/src/main.rs @@ -0,0 +1,25 @@ +#[derive(Debug)] +enum UsState { + Alabama, + Alaska, + // --snip-- +} + +enum Coin { + Penny, + Nickel, + Dime, + Quarter(UsState), +} + +fn main() { + let coin = Coin::Penny; + // ANCHOR: here + let mut count = 0; + if let Coin::Quarter(state) = coin { + println!("State quarter from {:?}!", state); + } else { + count += 1; + } + // ANCHOR_END: here +} diff --git a/listings/ch07-managing-growing-projects/listing-07-01/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-01/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-01/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-01/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-01/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-01/src/lib.rs new file mode 100644 index 0000000..591e245 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-01/src/lib.rs @@ -0,0 +1,15 @@ +mod front_of_house { + mod hosting { + fn add_to_waitlist() {} + + fn seat_at_table() {} + } + + mod serving { + fn take_order() {} + + fn serve_order() {} + + fn take_payment() {} + } +} diff --git a/listings/ch07-managing-growing-projects/listing-07-03/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-03/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-03/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-03/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-03/output.txt b/listings/ch07-managing-growing-projects/listing-07-03/output.txt new file mode 100644 index 0000000..4979d5f --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-03/output.txt @@ -0,0 +1,32 @@ +$ cargo build + Compiling restaurant v0.1.0 (file:///projects/restaurant) +error[E0603]: module `hosting` is private + --> src/lib.rs:9:28 + | +9 | crate::front_of_house::hosting::add_to_waitlist(); + | ^^^^^^^ private module + | +note: the module `hosting` is defined here + --> src/lib.rs:2:5 + | +2 | mod hosting { + | ^^^^^^^^^^^ + +error[E0603]: module `hosting` is private + --> src/lib.rs:12:21 + | +12 | front_of_house::hosting::add_to_waitlist(); + | ^^^^^^^ private module + | +note: the module `hosting` is defined here + --> src/lib.rs:2:5 + | +2 | mod hosting { + | ^^^^^^^^^^^ + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0603`. +error: could not compile `restaurant` + +To learn more, run the command again with --verbose. diff --git a/listings/ch07-managing-growing-projects/listing-07-03/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-03/src/lib.rs new file mode 100644 index 0000000..0b8a43c --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-03/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + mod hosting { + fn add_to_waitlist() {} + } +} + +pub fn eat_at_restaurant() { + // Absolute path + crate::front_of_house::hosting::add_to_waitlist(); + + // Relative path + front_of_house::hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-05/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-05/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-05/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-05/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-05/output.txt b/listings/ch07-managing-growing-projects/listing-07-05/output.txt new file mode 100644 index 0000000..22b4601 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-05/output.txt @@ -0,0 +1,32 @@ +$ cargo build + Compiling restaurant v0.1.0 (file:///projects/restaurant) +error[E0603]: function `add_to_waitlist` is private + --> src/lib.rs:9:37 + | +9 | crate::front_of_house::hosting::add_to_waitlist(); + | ^^^^^^^^^^^^^^^ private function + | +note: the function `add_to_waitlist` is defined here + --> src/lib.rs:3:9 + | +3 | fn add_to_waitlist() {} + | ^^^^^^^^^^^^^^^^^^^^ + +error[E0603]: function `add_to_waitlist` is private + --> src/lib.rs:12:30 + | +12 | front_of_house::hosting::add_to_waitlist(); + | ^^^^^^^^^^^^^^^ private function + | +note: the function `add_to_waitlist` is defined here + --> src/lib.rs:3:9 + | +3 | fn add_to_waitlist() {} + | ^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0603`. +error: could not compile `restaurant` + +To learn more, run the command again with --verbose. diff --git a/listings/ch07-managing-growing-projects/listing-07-05/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-05/src/lib.rs new file mode 100644 index 0000000..05372db --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-05/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + pub mod hosting { + fn add_to_waitlist() {} + } +} + +pub fn eat_at_restaurant() { + // Absolute path + crate::front_of_house::hosting::add_to_waitlist(); + + // Relative path + front_of_house::hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-07/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-07/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-07/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-07/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-07/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-07/src/lib.rs new file mode 100644 index 0000000..7b89ee7 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-07/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + pub mod hosting { + pub fn add_to_waitlist() {} + } +} + +pub fn eat_at_restaurant() { + // Absolute path + crate::front_of_house::hosting::add_to_waitlist(); + + // Relative path + front_of_house::hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-08/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-08/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-08/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-08/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-08/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-08/src/lib.rs new file mode 100644 index 0000000..7d4b597 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-08/src/lib.rs @@ -0,0 +1,10 @@ +fn serve_order() {} + +mod back_of_house { + fn fix_incorrect_order() { + cook_order(); + super::serve_order(); + } + + fn cook_order() {} +} diff --git a/listings/ch07-managing-growing-projects/listing-07-09/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-09/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-09/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-09/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-09/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-09/src/lib.rs new file mode 100644 index 0000000..92c4695 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-09/src/lib.rs @@ -0,0 +1,27 @@ +mod back_of_house { + pub struct Breakfast { + pub toast: String, + seasonal_fruit: String, + } + + impl Breakfast { + pub fn summer(toast: &str) -> Breakfast { + Breakfast { + toast: String::from(toast), + seasonal_fruit: String::from("peaches"), + } + } + } +} + +pub fn eat_at_restaurant() { + // Order a breakfast in the summer with Rye toast + let mut meal = back_of_house::Breakfast::summer("Rye"); + // Change our mind about what bread we'd like + meal.toast = String::from("Wheat"); + println!("I'd like {} toast please", meal.toast); + + // The next line won't compile if we uncomment it; we're not allowed + // to see or modify the seasonal fruit that comes with the meal + // meal.seasonal_fruit = String::from("blueberries"); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-10/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-10/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-10/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-10/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-10/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-10/src/lib.rs new file mode 100644 index 0000000..908f1df --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-10/src/lib.rs @@ -0,0 +1,11 @@ +mod back_of_house { + pub enum Appetizer { + Soup, + Salad, + } +} + +pub fn eat_at_restaurant() { + let order1 = back_of_house::Appetizer::Soup; + let order2 = back_of_house::Appetizer::Salad; +} diff --git a/listings/ch07-managing-growing-projects/listing-07-11/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-11/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-11/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-11/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-11/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-11/src/lib.rs new file mode 100644 index 0000000..44defd0 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-11/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + pub mod hosting { + pub fn add_to_waitlist() {} + } +} + +use crate::front_of_house::hosting; + +pub fn eat_at_restaurant() { + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-12/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-12/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-12/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-12/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-12/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-12/src/lib.rs new file mode 100644 index 0000000..671bc10 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-12/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + pub mod hosting { + pub fn add_to_waitlist() {} + } +} + +use self::front_of_house::hosting; + +pub fn eat_at_restaurant() { + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-13/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-13/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-13/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-13/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-13/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-13/src/lib.rs new file mode 100644 index 0000000..e886c24 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-13/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + pub mod hosting { + pub fn add_to_waitlist() {} + } +} + +use crate::front_of_house::hosting::add_to_waitlist; + +pub fn eat_at_restaurant() { + add_to_waitlist(); + add_to_waitlist(); + add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-14/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-14/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-14/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-14/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-14/src/main.rs b/listings/ch07-managing-growing-projects/listing-07-14/src/main.rs new file mode 100644 index 0000000..4379e7c --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-14/src/main.rs @@ -0,0 +1,6 @@ +use std::collections::HashMap; + +fn main() { + let mut map = HashMap::new(); + map.insert(1, 2); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-15/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-15/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-15/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-15/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-15/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-15/src/lib.rs new file mode 100644 index 0000000..bfac3a0 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-15/src/lib.rs @@ -0,0 +1,18 @@ +// ANCHOR: here +use std::fmt; +use std::io; + +fn function1() -> fmt::Result { + // --snip-- + // ANCHOR_END: here + Ok(()) + // ANCHOR: here +} + +fn function2() -> io::Result<()> { + // --snip-- + // ANCHOR_END: here + Ok(()) + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch07-managing-growing-projects/listing-07-16/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-16/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-16/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-16/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-16/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-16/src/lib.rs new file mode 100644 index 0000000..843490b --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-16/src/lib.rs @@ -0,0 +1,18 @@ +// ANCHOR: here +use std::fmt::Result; +use std::io::Result as IoResult; + +fn function1() -> Result { + // --snip-- + // ANCHOR_END: here + Ok(()) + // ANCHOR: here +} + +fn function2() -> IoResult<()> { + // --snip-- + // ANCHOR_END: here + Ok(()) + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch07-managing-growing-projects/listing-07-17/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-17/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-17/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-17/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-17/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-17/src/lib.rs new file mode 100644 index 0000000..835e571 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-17/src/lib.rs @@ -0,0 +1,13 @@ +mod front_of_house { + pub mod hosting { + pub fn add_to_waitlist() {} + } +} + +pub use crate::front_of_house::hosting; + +pub fn eat_at_restaurant() { + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/listing-07-18/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-18/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-18/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch07-managing-growing-projects/listing-07-18/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-18/Cargo.toml new file mode 100644 index 0000000..1e53bae --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-18/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch07-managing-growing-projects/listing-07-18/src/main.rs b/listings/ch07-managing-growing-projects/listing-07-18/src/main.rs new file mode 100644 index 0000000..6c88bc4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-18/src/main.rs @@ -0,0 +1,32 @@ +use rand::Rng; +// ANCHOR: here +// --snip-- +use std::{cmp::Ordering, io}; +// --snip-- +// ANCHOR_END: here + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + println!("The secret number is: {}", secret_number); + + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + let guess: u32 = guess.trim().parse().expect("Please type a number!"); + + println!("You guessed: {}", guess); + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => println!("You win!"), + } +} diff --git a/listings/ch07-managing-growing-projects/listing-07-19/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-19/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-19/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-19/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-19/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-19/src/lib.rs new file mode 100644 index 0000000..3fee46c --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-19/src/lib.rs @@ -0,0 +1,2 @@ +use std::io; +use std::io::Write; diff --git a/listings/ch07-managing-growing-projects/listing-07-20/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-20/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-20/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-20/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-20/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-20/src/lib.rs new file mode 100644 index 0000000..341f40a --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-20/src/lib.rs @@ -0,0 +1 @@ +use std::io::{self, Write}; diff --git a/listings/ch07-managing-growing-projects/listing-07-21-and-22/Cargo.lock b/listings/ch07-managing-growing-projects/listing-07-21-and-22/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-21-and-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/listing-07-21-and-22/Cargo.toml b/listings/ch07-managing-growing-projects/listing-07-21-and-22/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-21-and-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/listing-07-21-and-22/src/front_of_house.rs b/listings/ch07-managing-growing-projects/listing-07-21-and-22/src/front_of_house.rs new file mode 100644 index 0000000..6875dfd --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-21-and-22/src/front_of_house.rs @@ -0,0 +1,3 @@ +pub mod hosting { + pub fn add_to_waitlist() {} +} diff --git a/listings/ch07-managing-growing-projects/listing-07-21-and-22/src/lib.rs b/listings/ch07-managing-growing-projects/listing-07-21-and-22/src/lib.rs new file mode 100644 index 0000000..065b1b8 --- /dev/null +++ b/listings/ch07-managing-growing-projects/listing-07-21-and-22/src/lib.rs @@ -0,0 +1,9 @@ +mod front_of_house; + +pub use crate::front_of_house::hosting; + +pub fn eat_at_restaurant() { + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); +} diff --git a/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/Cargo.lock b/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/Cargo.toml b/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/Cargo.toml new file mode 100644 index 0000000..930a7d9 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/Cargo.toml @@ -0,0 +1,10 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/src/main.rs b/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/src/main.rs new file mode 100644 index 0000000..af1b2b4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/src/main.rs @@ -0,0 +1,31 @@ +use rand::Rng; +// ANCHOR: here +// --snip-- +use std::cmp::Ordering; +use std::io; +// --snip-- +// ANCHOR_END: here + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + println!("The secret number is: {}", secret_number); + + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + println!("You guessed: {}", guess); + + match guess.cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => println!("You win!"), + } +} diff --git a/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/Cargo.lock b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/Cargo.lock new file mode 100644 index 0000000..f25ab35 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "restaurant" +version = "0.1.0" + diff --git a/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/Cargo.toml b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/Cargo.toml new file mode 100644 index 0000000..8bdd0a4 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "restaurant" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house.rs b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house.rs new file mode 100644 index 0000000..d0a8154 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house.rs @@ -0,0 +1 @@ +pub mod hosting; diff --git a/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house/hosting.rs b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house/hosting.rs new file mode 100644 index 0000000..d65f3af --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house/hosting.rs @@ -0,0 +1 @@ +pub fn add_to_waitlist() {} diff --git a/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/lib.rs b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/lib.rs new file mode 100644 index 0000000..065b1b8 --- /dev/null +++ b/listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/lib.rs @@ -0,0 +1,9 @@ +mod front_of_house; + +pub use crate::front_of_house::hosting; + +pub fn eat_at_restaurant() { + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); + hosting::add_to_waitlist(); +} diff --git a/listings/ch08-common-collections/listing-08-01/Cargo.lock b/listings/ch08-common-collections/listing-08-01/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-01/Cargo.toml b/listings/ch08-common-collections/listing-08-01/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-01/src/main.rs b/listings/ch08-common-collections/listing-08-01/src/main.rs new file mode 100644 index 0000000..45e4558 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-01/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + // ANCHOR: here + let v: Vec = Vec::new(); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-02/Cargo.lock b/listings/ch08-common-collections/listing-08-02/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-02/Cargo.toml b/listings/ch08-common-collections/listing-08-02/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-02/src/main.rs b/listings/ch08-common-collections/listing-08-02/src/main.rs new file mode 100644 index 0000000..3b10a53 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-02/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + // ANCHOR: here + let v = vec![1, 2, 3]; + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-03/Cargo.lock b/listings/ch08-common-collections/listing-08-03/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-03/Cargo.toml b/listings/ch08-common-collections/listing-08-03/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-03/src/main.rs b/listings/ch08-common-collections/listing-08-03/src/main.rs new file mode 100644 index 0000000..147223f --- /dev/null +++ b/listings/ch08-common-collections/listing-08-03/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + let mut v = Vec::new(); + + v.push(5); + v.push(6); + v.push(7); + v.push(8); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-04/Cargo.lock b/listings/ch08-common-collections/listing-08-04/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-04/Cargo.toml b/listings/ch08-common-collections/listing-08-04/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-04/src/main.rs b/listings/ch08-common-collections/listing-08-04/src/main.rs new file mode 100644 index 0000000..abda2db --- /dev/null +++ b/listings/ch08-common-collections/listing-08-04/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + { + let v = vec![1, 2, 3, 4]; + + // do stuff with v + } // <- v goes out of scope and is freed here + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-05/Cargo.lock b/listings/ch08-common-collections/listing-08-05/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-05/Cargo.toml b/listings/ch08-common-collections/listing-08-05/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-05/src/main.rs b/listings/ch08-common-collections/listing-08-05/src/main.rs new file mode 100644 index 0000000..9bfa37a --- /dev/null +++ b/listings/ch08-common-collections/listing-08-05/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + let v = vec![1, 2, 3, 4, 5]; + + let third: &i32 = &v[2]; + println!("The third element is {}", third); + + match v.get(2) { + Some(third) => println!("The third element is {}", third), + None => println!("There is no third element."), + } + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-06/Cargo.lock b/listings/ch08-common-collections/listing-08-06/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-06/Cargo.toml b/listings/ch08-common-collections/listing-08-06/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-06/src/main.rs b/listings/ch08-common-collections/listing-08-06/src/main.rs new file mode 100644 index 0000000..783d9b1 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-06/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let v = vec![1, 2, 3, 4, 5]; + + let does_not_exist = &v[100]; + let does_not_exist = v.get(100); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-07/Cargo.lock b/listings/ch08-common-collections/listing-08-07/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-07/Cargo.toml b/listings/ch08-common-collections/listing-08-07/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-07/output.txt b/listings/ch08-common-collections/listing-08-07/output.txt new file mode 100644 index 0000000..d99310d --- /dev/null +++ b/listings/ch08-common-collections/listing-08-07/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling collections v0.1.0 (file:///projects/collections) +error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable + --> src/main.rs:6:5 + | +4 | let first = &v[0]; + | - immutable borrow occurs here +5 | +6 | v.push(6); + | ^^^^^^^^^ mutable borrow occurs here +7 | +8 | println!("The first element is: {}", first); + | ----- immutable borrow later used here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0502`. +error: could not compile `collections` + +To learn more, run the command again with --verbose. diff --git a/listings/ch08-common-collections/listing-08-07/src/main.rs b/listings/ch08-common-collections/listing-08-07/src/main.rs new file mode 100644 index 0000000..1b42274 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-07/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let mut v = vec![1, 2, 3, 4, 5]; + + let first = &v[0]; + + v.push(6); + + println!("The first element is: {}", first); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-08/Cargo.lock b/listings/ch08-common-collections/listing-08-08/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-08/Cargo.toml b/listings/ch08-common-collections/listing-08-08/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-08/src/main.rs b/listings/ch08-common-collections/listing-08-08/src/main.rs new file mode 100644 index 0000000..38b9778 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-08/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let v = vec![100, 32, 57]; + for i in &v { + println!("{}", i); + } + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-09/Cargo.lock b/listings/ch08-common-collections/listing-08-09/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-09/Cargo.toml b/listings/ch08-common-collections/listing-08-09/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-09/src/main.rs b/listings/ch08-common-collections/listing-08-09/src/main.rs new file mode 100644 index 0000000..c62ba21 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-09/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let mut v = vec![100, 32, 57]; + for i in &mut v { + *i += 50; + } + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-10/Cargo.lock b/listings/ch08-common-collections/listing-08-10/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-10/Cargo.toml b/listings/ch08-common-collections/listing-08-10/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-10/src/main.rs b/listings/ch08-common-collections/listing-08-10/src/main.rs new file mode 100644 index 0000000..c219888 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-10/src/main.rs @@ -0,0 +1,15 @@ +fn main() { + // ANCHOR: here + enum SpreadsheetCell { + Int(i32), + Float(f64), + Text(String), + } + + let row = vec![ + SpreadsheetCell::Int(3), + SpreadsheetCell::Text(String::from("blue")), + SpreadsheetCell::Float(10.12), + ]; + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-11/Cargo.lock b/listings/ch08-common-collections/listing-08-11/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-11/Cargo.toml b/listings/ch08-common-collections/listing-08-11/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-11/src/main.rs b/listings/ch08-common-collections/listing-08-11/src/main.rs new file mode 100644 index 0000000..4cf4c81 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-11/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + // ANCHOR: here + let mut s = String::new(); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-12/Cargo.lock b/listings/ch08-common-collections/listing-08-12/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-12/Cargo.toml b/listings/ch08-common-collections/listing-08-12/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-12/src/main.rs b/listings/ch08-common-collections/listing-08-12/src/main.rs new file mode 100644 index 0000000..d9e5e76 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-12/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + let data = "initial contents"; + + let s = data.to_string(); + + // the method also works on a literal directly: + let s = "initial contents".to_string(); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-13/Cargo.lock b/listings/ch08-common-collections/listing-08-13/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-13/Cargo.toml b/listings/ch08-common-collections/listing-08-13/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-13/src/main.rs b/listings/ch08-common-collections/listing-08-13/src/main.rs new file mode 100644 index 0000000..b81e374 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-13/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + // ANCHOR: here + let s = String::from("initial contents"); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-14/Cargo.lock b/listings/ch08-common-collections/listing-08-14/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-14/Cargo.toml b/listings/ch08-common-collections/listing-08-14/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-14/src/main.rs b/listings/ch08-common-collections/listing-08-14/src/main.rs new file mode 100644 index 0000000..f701fd5 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-14/src/main.rs @@ -0,0 +1,19 @@ +fn main() { + // ANCHOR: here + let hello = String::from("السلام عليكم"); + let hello = String::from("Dobrý den"); + let hello = String::from("Hello"); + let hello = String::from("שָׁלוֹם"); + let hello = String::from("नमस्ते"); + let hello = String::from("こんにちは"); + let hello = String::from("안녕하세요"); + let hello = String::from("你好"); + let hello = String::from("Olá"); + // ANCHOR: russian + let hello = String::from("Здравствуйте"); + // ANCHOR_END: russian + // ANCHOR: spanish + let hello = String::from("Hola"); + // ANCHOR_END: spanish + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-15/Cargo.lock b/listings/ch08-common-collections/listing-08-15/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-15/Cargo.toml b/listings/ch08-common-collections/listing-08-15/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-15/src/main.rs b/listings/ch08-common-collections/listing-08-15/src/main.rs new file mode 100644 index 0000000..7dec657 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-15/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("foo"); + s.push_str("bar"); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-16/Cargo.lock b/listings/ch08-common-collections/listing-08-16/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-16/Cargo.toml b/listings/ch08-common-collections/listing-08-16/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-16/src/main.rs b/listings/ch08-common-collections/listing-08-16/src/main.rs new file mode 100644 index 0000000..8938dc1 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-16/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let mut s1 = String::from("foo"); + let s2 = "bar"; + s1.push_str(s2); + println!("s2 is {}", s2); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-17/Cargo.lock b/listings/ch08-common-collections/listing-08-17/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-17/Cargo.toml b/listings/ch08-common-collections/listing-08-17/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-17/src/main.rs b/listings/ch08-common-collections/listing-08-17/src/main.rs new file mode 100644 index 0000000..0a9e8cc --- /dev/null +++ b/listings/ch08-common-collections/listing-08-17/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let mut s = String::from("lo"); + s.push('l'); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-18/Cargo.lock b/listings/ch08-common-collections/listing-08-18/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-18/Cargo.toml b/listings/ch08-common-collections/listing-08-18/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-18/src/main.rs b/listings/ch08-common-collections/listing-08-18/src/main.rs new file mode 100644 index 0000000..93939a6 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-18/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("Hello, "); + let s2 = String::from("world!"); + let s3 = s1 + &s2; // note s1 has been moved here and can no longer be used + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-19/Cargo.lock b/listings/ch08-common-collections/listing-08-19/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-19/Cargo.toml b/listings/ch08-common-collections/listing-08-19/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-19/output.txt b/listings/ch08-common-collections/listing-08-19/output.txt new file mode 100644 index 0000000..d6e45b2 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-19/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling collections v0.1.0 (file:///projects/collections) +error[E0277]: the type `String` cannot be indexed by `{integer}` + --> src/main.rs:3:13 + | +3 | let h = s1[0]; + | ^^^^^ `String` cannot be indexed by `{integer}` + | + = help: the trait `Index<{integer}>` is not implemented for `String` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `collections` + +To learn more, run the command again with --verbose. diff --git a/listings/ch08-common-collections/listing-08-19/src/main.rs b/listings/ch08-common-collections/listing-08-19/src/main.rs new file mode 100644 index 0000000..fc08e9c --- /dev/null +++ b/listings/ch08-common-collections/listing-08-19/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("hello"); + let h = s1[0]; + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-20/Cargo.lock b/listings/ch08-common-collections/listing-08-20/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-20/Cargo.toml b/listings/ch08-common-collections/listing-08-20/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-20/src/main.rs b/listings/ch08-common-collections/listing-08-20/src/main.rs new file mode 100644 index 0000000..54c2010 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-20/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let mut scores = HashMap::new(); + + scores.insert(String::from("Blue"), 10); + scores.insert(String::from("Yellow"), 50); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-21/Cargo.lock b/listings/ch08-common-collections/listing-08-21/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-21/Cargo.toml b/listings/ch08-common-collections/listing-08-21/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-21/src/main.rs b/listings/ch08-common-collections/listing-08-21/src/main.rs new file mode 100644 index 0000000..0ebd20d --- /dev/null +++ b/listings/ch08-common-collections/listing-08-21/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let teams = vec![String::from("Blue"), String::from("Yellow")]; + let initial_scores = vec![10, 50]; + + let mut scores: HashMap<_, _> = + teams.into_iter().zip(initial_scores.into_iter()).collect(); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-22/Cargo.lock b/listings/ch08-common-collections/listing-08-22/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-22/Cargo.toml b/listings/ch08-common-collections/listing-08-22/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-22/src/main.rs b/listings/ch08-common-collections/listing-08-22/src/main.rs new file mode 100644 index 0000000..2b2a73f --- /dev/null +++ b/listings/ch08-common-collections/listing-08-22/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let field_name = String::from("Favorite color"); + let field_value = String::from("Blue"); + + let mut map = HashMap::new(); + map.insert(field_name, field_value); + // field_name and field_value are invalid at this point, try using them and + // see what compiler error you get! + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-23/Cargo.lock b/listings/ch08-common-collections/listing-08-23/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-23/Cargo.toml b/listings/ch08-common-collections/listing-08-23/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-23/src/main.rs b/listings/ch08-common-collections/listing-08-23/src/main.rs new file mode 100644 index 0000000..508e33c --- /dev/null +++ b/listings/ch08-common-collections/listing-08-23/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let mut scores = HashMap::new(); + + scores.insert(String::from("Blue"), 10); + scores.insert(String::from("Yellow"), 50); + + let team_name = String::from("Blue"); + let score = scores.get(&team_name); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-24/Cargo.lock b/listings/ch08-common-collections/listing-08-24/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-24/Cargo.toml b/listings/ch08-common-collections/listing-08-24/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-24/src/main.rs b/listings/ch08-common-collections/listing-08-24/src/main.rs new file mode 100644 index 0000000..e8684cf --- /dev/null +++ b/listings/ch08-common-collections/listing-08-24/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let mut scores = HashMap::new(); + + scores.insert(String::from("Blue"), 10); + scores.insert(String::from("Blue"), 25); + + println!("{:?}", scores); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-25/Cargo.lock b/listings/ch08-common-collections/listing-08-25/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-25/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-25/Cargo.toml b/listings/ch08-common-collections/listing-08-25/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-25/src/main.rs b/listings/ch08-common-collections/listing-08-25/src/main.rs new file mode 100644 index 0000000..3ad97b5 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-25/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let mut scores = HashMap::new(); + scores.insert(String::from("Blue"), 10); + + scores.entry(String::from("Yellow")).or_insert(50); + scores.entry(String::from("Blue")).or_insert(50); + + println!("{:?}", scores); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/listing-08-26/Cargo.lock b/listings/ch08-common-collections/listing-08-26/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/listing-08-26/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/listing-08-26/Cargo.toml b/listings/ch08-common-collections/listing-08-26/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/listing-08-26/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/listing-08-26/src/main.rs b/listings/ch08-common-collections/listing-08-26/src/main.rs new file mode 100644 index 0000000..f3f6aa1 --- /dev/null +++ b/listings/ch08-common-collections/listing-08-26/src/main.rs @@ -0,0 +1,16 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let text = "hello world wonderful world"; + + let mut map = HashMap::new(); + + for word in text.split_whitespace() { + let count = map.entry(word).or_insert(0); + *count += 1; + } + + println!("{:?}", map); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/Cargo.lock b/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/Cargo.toml b/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/src/main.rs b/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/src/main.rs new file mode 100644 index 0000000..4995650 --- /dev/null +++ b/listings/ch08-common-collections/no-listing-01-concat-multiple-strings/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("tic"); + let s2 = String::from("tac"); + let s3 = String::from("toe"); + + let s = s1 + "-" + &s2 + "-" + &s3; + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/no-listing-02-format/Cargo.lock b/listings/ch08-common-collections/no-listing-02-format/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/no-listing-02-format/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/no-listing-02-format/Cargo.toml b/listings/ch08-common-collections/no-listing-02-format/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/no-listing-02-format/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/no-listing-02-format/src/main.rs b/listings/ch08-common-collections/no-listing-02-format/src/main.rs new file mode 100644 index 0000000..4a38e63 --- /dev/null +++ b/listings/ch08-common-collections/no-listing-02-format/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + let s1 = String::from("tic"); + let s2 = String::from("tac"); + let s3 = String::from("toe"); + + let s = format!("{}-{}-{}", s1, s2, s3); + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/Cargo.lock b/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/Cargo.toml b/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/src/main.rs b/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/src/main.rs new file mode 100644 index 0000000..2e7dc02 --- /dev/null +++ b/listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/src/main.rs @@ -0,0 +1,14 @@ +fn main() { + // ANCHOR: here + use std::collections::HashMap; + + let mut scores = HashMap::new(); + + scores.insert(String::from("Blue"), 10); + scores.insert(String::from("Yellow"), 50); + + for (key, value) in &scores { + println!("{}: {}", key, value); + } + // ANCHOR_END: here +} diff --git a/listings/ch08-common-collections/output-only-01-not-char-boundary/Cargo.lock b/listings/ch08-common-collections/output-only-01-not-char-boundary/Cargo.lock new file mode 100644 index 0000000..d3daeff --- /dev/null +++ b/listings/ch08-common-collections/output-only-01-not-char-boundary/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "collections" +version = "0.1.0" + diff --git a/listings/ch08-common-collections/output-only-01-not-char-boundary/Cargo.toml b/listings/ch08-common-collections/output-only-01-not-char-boundary/Cargo.toml new file mode 100644 index 0000000..b36871b --- /dev/null +++ b/listings/ch08-common-collections/output-only-01-not-char-boundary/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "collections" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch08-common-collections/output-only-01-not-char-boundary/output.txt b/listings/ch08-common-collections/output-only-01-not-char-boundary/output.txt new file mode 100644 index 0000000..35db879 --- /dev/null +++ b/listings/ch08-common-collections/output-only-01-not-char-boundary/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling collections v0.1.0 (file:///projects/collections) + Finished dev [unoptimized + debuginfo] target(s) in 0.43s + Running `target/debug/collections` +thread 'main' panicked at 'byte index 1 is not a char boundary; it is inside 'З' (bytes 0..2) of `Здравствуйте`', src/main.rs:4:14 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace diff --git a/listings/ch08-common-collections/output-only-01-not-char-boundary/src/main.rs b/listings/ch08-common-collections/output-only-01-not-char-boundary/src/main.rs new file mode 100644 index 0000000..9283ff5 --- /dev/null +++ b/listings/ch08-common-collections/output-only-01-not-char-boundary/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + let hello = "Здравствуйте"; + + let s = &hello[0..1]; +} diff --git a/listings/ch09-error-handling/listing-09-01/Cargo.lock b/listings/ch09-error-handling/listing-09-01/Cargo.lock new file mode 100644 index 0000000..4fe030f --- /dev/null +++ b/listings/ch09-error-handling/listing-09-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "panic" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-01/Cargo.toml b/listings/ch09-error-handling/listing-09-01/Cargo.toml new file mode 100644 index 0000000..310342c --- /dev/null +++ b/listings/ch09-error-handling/listing-09-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "panic" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-01/output.txt b/listings/ch09-error-handling/listing-09-01/output.txt new file mode 100644 index 0000000..89aebb9 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-01/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling panic v0.1.0 (file:///projects/panic) + Finished dev [unoptimized + debuginfo] target(s) in 0.27s + Running `target/debug/panic` +thread 'main' panicked at 'index out of bounds: the len is 3 but the index is 99', src/main.rs:4:5 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace diff --git a/listings/ch09-error-handling/listing-09-01/src/main.rs b/listings/ch09-error-handling/listing-09-01/src/main.rs new file mode 100644 index 0000000..70194ab --- /dev/null +++ b/listings/ch09-error-handling/listing-09-01/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + let v = vec![1, 2, 3]; + + v[99]; +} diff --git a/listings/ch09-error-handling/listing-09-03/Cargo.lock b/listings/ch09-error-handling/listing-09-03/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-03/Cargo.toml b/listings/ch09-error-handling/listing-09-03/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-03/src/main.rs b/listings/ch09-error-handling/listing-09-03/src/main.rs new file mode 100644 index 0000000..0dfd10b --- /dev/null +++ b/listings/ch09-error-handling/listing-09-03/src/main.rs @@ -0,0 +1,5 @@ +use std::fs::File; + +fn main() { + let f = File::open("hello.txt"); +} diff --git a/listings/ch09-error-handling/listing-09-04/Cargo.lock b/listings/ch09-error-handling/listing-09-04/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-04/Cargo.toml b/listings/ch09-error-handling/listing-09-04/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-04/output.txt b/listings/ch09-error-handling/listing-09-04/output.txt new file mode 100644 index 0000000..f776a59 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-04/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling error-handling v0.1.0 (file:///projects/error-handling) + Finished dev [unoptimized + debuginfo] target(s) in 0.73s + Running `target/debug/error-handling` +thread 'main' panicked at 'Problem opening the file: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/main.rs:8:23 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace diff --git a/listings/ch09-error-handling/listing-09-04/src/main.rs b/listings/ch09-error-handling/listing-09-04/src/main.rs new file mode 100644 index 0000000..070fc33 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-04/src/main.rs @@ -0,0 +1,10 @@ +use std::fs::File; + +fn main() { + let f = File::open("hello.txt"); + + let f = match f { + Ok(file) => file, + Err(error) => panic!("Problem opening the file: {:?}", error), + }; +} diff --git a/listings/ch09-error-handling/listing-09-05/Cargo.lock b/listings/ch09-error-handling/listing-09-05/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-05/Cargo.toml b/listings/ch09-error-handling/listing-09-05/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-05/src/main.rs b/listings/ch09-error-handling/listing-09-05/src/main.rs new file mode 100644 index 0000000..8c4f773 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-05/src/main.rs @@ -0,0 +1,19 @@ +use std::fs::File; +use std::io::ErrorKind; + +fn main() { + let f = File::open("hello.txt"); + + let f = match f { + Ok(file) => file, + Err(error) => match error.kind() { + ErrorKind::NotFound => match File::create("hello.txt") { + Ok(fc) => fc, + Err(e) => panic!("Problem creating the file: {:?}", e), + }, + other_error => { + panic!("Problem opening the file: {:?}", other_error) + } + }, + }; +} diff --git a/listings/ch09-error-handling/listing-09-06/Cargo.lock b/listings/ch09-error-handling/listing-09-06/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-06/Cargo.toml b/listings/ch09-error-handling/listing-09-06/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-06/src/main.rs b/listings/ch09-error-handling/listing-09-06/src/main.rs new file mode 100644 index 0000000..437d858 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-06/src/main.rs @@ -0,0 +1,25 @@ +// ANCHOR: here +use std::fs::File; +use std::io; +use std::io::Read; + +fn read_username_from_file() -> Result { + let f = File::open("hello.txt"); + + let mut f = match f { + Ok(file) => file, + Err(e) => return Err(e), + }; + + let mut s = String::new(); + + match f.read_to_string(&mut s) { + Ok(_) => Ok(s), + Err(e) => Err(e), + } +} +// ANCHOR_END: here + +fn main() { + let username = read_username_from_file().expect("Unable to get username"); +} diff --git a/listings/ch09-error-handling/listing-09-07/Cargo.lock b/listings/ch09-error-handling/listing-09-07/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-07/Cargo.toml b/listings/ch09-error-handling/listing-09-07/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-07/src/main.rs b/listings/ch09-error-handling/listing-09-07/src/main.rs new file mode 100644 index 0000000..b9f6172 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-07/src/main.rs @@ -0,0 +1,16 @@ +// ANCHOR: here +use std::fs::File; +use std::io; +use std::io::Read; + +fn read_username_from_file() -> Result { + let mut f = File::open("hello.txt")?; + let mut s = String::new(); + f.read_to_string(&mut s)?; + Ok(s) +} +// ANCHOR_END: here + +fn main() { + let username = read_username_from_file().expect("Unable to get username"); +} diff --git a/listings/ch09-error-handling/listing-09-08/Cargo.lock b/listings/ch09-error-handling/listing-09-08/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-08/Cargo.toml b/listings/ch09-error-handling/listing-09-08/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-08/src/main.rs b/listings/ch09-error-handling/listing-09-08/src/main.rs new file mode 100644 index 0000000..f36e4d0 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-08/src/main.rs @@ -0,0 +1,17 @@ +// ANCHOR: here +use std::fs::File; +use std::io; +use std::io::Read; + +fn read_username_from_file() -> Result { + let mut s = String::new(); + + File::open("hello.txt")?.read_to_string(&mut s)?; + + Ok(s) +} +// ANCHOR_END: here + +fn main() { + let username = read_username_from_file().expect("Unable to get username"); +} diff --git a/listings/ch09-error-handling/listing-09-09/Cargo.lock b/listings/ch09-error-handling/listing-09-09/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/listing-09-09/Cargo.toml b/listings/ch09-error-handling/listing-09-09/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/listing-09-09/src/main.rs b/listings/ch09-error-handling/listing-09-09/src/main.rs new file mode 100644 index 0000000..4597dc2 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-09/src/main.rs @@ -0,0 +1,12 @@ +// ANCHOR: here +use std::fs; +use std::io; + +fn read_username_from_file() -> Result { + fs::read_to_string("hello.txt") +} +// ANCHOR_END: here + +fn main() { + let username = read_username_from_file().expect("Unable to get username"); +} diff --git a/listings/ch09-error-handling/listing-09-10/Cargo.lock b/listings/ch09-error-handling/listing-09-10/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-10/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch09-error-handling/listing-09-10/Cargo.toml b/listings/ch09-error-handling/listing-09-10/Cargo.toml new file mode 100644 index 0000000..1e53bae --- /dev/null +++ b/listings/ch09-error-handling/listing-09-10/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch09-error-handling/listing-09-10/src/main.rs b/listings/ch09-error-handling/listing-09-10/src/main.rs new file mode 100644 index 0000000..3375279 --- /dev/null +++ b/listings/ch09-error-handling/listing-09-10/src/main.rs @@ -0,0 +1,55 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +// ANCHOR: here +pub struct Guess { + value: i32, +} + +impl Guess { + pub fn new(value: i32) -> Guess { + if value < 1 || value > 100 { + panic!("Guess value must be between 1 and 100, got {}.", value); + } + + Guess { value } + } + + pub fn value(&self) -> i32 { + self.value + } +} +// ANCHOR_END: here + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + loop { + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + let guess: i32 = match guess.trim().parse() { + Ok(num) => num, + Err(_) => continue, + }; + + let guess = Guess::new(guess); + + match guess.value().cmp(&secret_number) { + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => { + println!("You win!"); + break; + } + } + } +} diff --git a/listings/ch09-error-handling/no-listing-01-panic/Cargo.lock b/listings/ch09-error-handling/no-listing-01-panic/Cargo.lock new file mode 100644 index 0000000..4fe030f --- /dev/null +++ b/listings/ch09-error-handling/no-listing-01-panic/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "panic" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-01-panic/Cargo.toml b/listings/ch09-error-handling/no-listing-01-panic/Cargo.toml new file mode 100644 index 0000000..310342c --- /dev/null +++ b/listings/ch09-error-handling/no-listing-01-panic/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "panic" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-01-panic/output.txt b/listings/ch09-error-handling/no-listing-01-panic/output.txt new file mode 100644 index 0000000..b25ed85 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-01-panic/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling panic v0.1.0 (file:///projects/panic) + Finished dev [unoptimized + debuginfo] target(s) in 0.25s + Running `target/debug/panic` +thread 'main' panicked at 'crash and burn', src/main.rs:2:5 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace diff --git a/listings/ch09-error-handling/no-listing-01-panic/src/main.rs b/listings/ch09-error-handling/no-listing-01-panic/src/main.rs new file mode 100644 index 0000000..32a4c24 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-01-panic/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + panic!("crash and burn"); +} diff --git a/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/Cargo.lock b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/Cargo.toml b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/output.txt b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/output.txt new file mode 100644 index 0000000..6436fe6 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling error-handling v0.1.0 (file:///projects/error-handling) +error[E0308]: mismatched types + --> src/main.rs:4:18 + | +4 | let f: u32 = File::open("hello.txt"); + | --- ^^^^^^^^^^^^^^^^^^^^^^^ expected `u32`, found enum `Result` + | | + | expected due to this + | + = note: expected type `u32` + found enum `Result` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `error-handling` + +To learn more, run the command again with --verbose. diff --git a/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/src/main.rs b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/src/main.rs new file mode 100644 index 0000000..a637f5f --- /dev/null +++ b/listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/src/main.rs @@ -0,0 +1,7 @@ +use std::fs::File; + +fn main() { + // ANCHOR: here + let f: u32 = File::open("hello.txt"); + // ANCHOR_END: here +} diff --git a/listings/ch09-error-handling/no-listing-03-closures/Cargo.lock b/listings/ch09-error-handling/no-listing-03-closures/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-03-closures/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-03-closures/Cargo.toml b/listings/ch09-error-handling/no-listing-03-closures/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-03-closures/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-03-closures/src/main.rs b/listings/ch09-error-handling/no-listing-03-closures/src/main.rs new file mode 100644 index 0000000..c6682cd --- /dev/null +++ b/listings/ch09-error-handling/no-listing-03-closures/src/main.rs @@ -0,0 +1,14 @@ +use std::fs::File; +use std::io::ErrorKind; + +fn main() { + let f = File::open("hello.txt").unwrap_or_else(|error| { + if error.kind() == ErrorKind::NotFound { + File::create("hello.txt").unwrap_or_else(|error| { + panic!("Problem creating the file: {:?}", error); + }) + } else { + panic!("Problem opening the file: {:?}", error); + } + }); +} diff --git a/listings/ch09-error-handling/no-listing-04-unwrap/Cargo.lock b/listings/ch09-error-handling/no-listing-04-unwrap/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-04-unwrap/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-04-unwrap/Cargo.toml b/listings/ch09-error-handling/no-listing-04-unwrap/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-04-unwrap/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-04-unwrap/src/main.rs b/listings/ch09-error-handling/no-listing-04-unwrap/src/main.rs new file mode 100644 index 0000000..7b6b13a --- /dev/null +++ b/listings/ch09-error-handling/no-listing-04-unwrap/src/main.rs @@ -0,0 +1,5 @@ +use std::fs::File; + +fn main() { + let f = File::open("hello.txt").unwrap(); +} diff --git a/listings/ch09-error-handling/no-listing-05-expect/Cargo.lock b/listings/ch09-error-handling/no-listing-05-expect/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-05-expect/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-05-expect/Cargo.toml b/listings/ch09-error-handling/no-listing-05-expect/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-05-expect/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-05-expect/src/main.rs b/listings/ch09-error-handling/no-listing-05-expect/src/main.rs new file mode 100644 index 0000000..cab643b --- /dev/null +++ b/listings/ch09-error-handling/no-listing-05-expect/src/main.rs @@ -0,0 +1,5 @@ +use std::fs::File; + +fn main() { + let f = File::open("hello.txt").expect("Failed to open hello.txt"); +} diff --git a/listings/ch09-error-handling/no-listing-06-question-mark-in-main/Cargo.lock b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-06-question-mark-in-main/Cargo.toml b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-06-question-mark-in-main/output.txt b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/output.txt new file mode 100644 index 0000000..76ff859 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling error-handling v0.1.0 (file:///projects/error-handling) +error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `Try`) + --> src/main.rs:4:13 + | +3 | / fn main() { +4 | | let f = File::open("hello.txt")?; + | | ^^^^^^^^^^^^^^^^^^^^^^^^ cannot use the `?` operator in a function that returns `()` +5 | | } + | |_- this function should return `Result` or `Option` to accept `?` + | + = help: the trait `Try` is not implemented for `()` + = note: required by `from_error` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `error-handling` + +To learn more, run the command again with --verbose. diff --git a/listings/ch09-error-handling/no-listing-06-question-mark-in-main/src/main.rs b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/src/main.rs new file mode 100644 index 0000000..8608dc1 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-06-question-mark-in-main/src/main.rs @@ -0,0 +1,5 @@ +use std::fs::File; + +fn main() { + let f = File::open("hello.txt")?; +} diff --git a/listings/ch09-error-handling/no-listing-07-main-returning-result/Cargo.lock b/listings/ch09-error-handling/no-listing-07-main-returning-result/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-07-main-returning-result/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-07-main-returning-result/Cargo.toml b/listings/ch09-error-handling/no-listing-07-main-returning-result/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-07-main-returning-result/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-07-main-returning-result/src/main.rs b/listings/ch09-error-handling/no-listing-07-main-returning-result/src/main.rs new file mode 100644 index 0000000..7f16b8e --- /dev/null +++ b/listings/ch09-error-handling/no-listing-07-main-returning-result/src/main.rs @@ -0,0 +1,8 @@ +use std::error::Error; +use std::fs::File; + +fn main() -> Result<(), Box> { + let f = File::open("hello.txt")?; + + Ok(()) +} diff --git a/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/Cargo.lock b/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/Cargo.lock new file mode 100644 index 0000000..1fa96b7 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "error-handling" +version = "0.1.0" + diff --git a/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/Cargo.toml b/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/Cargo.toml new file mode 100644 index 0000000..2a48dae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "error-handling" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/src/main.rs b/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/src/main.rs new file mode 100644 index 0000000..e829724 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + use std::net::IpAddr; + + let home: IpAddr = "127.0.0.1".parse().unwrap(); + // ANCHOR_END: here +} diff --git a/listings/ch09-error-handling/no-listing-09-guess-out-of-range/Cargo.lock b/listings/ch09-error-handling/no-listing-09-guess-out-of-range/Cargo.lock new file mode 100644 index 0000000..0a2f222 --- /dev/null +++ b/listings/ch09-error-handling/no-listing-09-guess-out-of-range/Cargo.lock @@ -0,0 +1,83 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "guessing_game" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch09-error-handling/no-listing-09-guess-out-of-range/Cargo.toml b/listings/ch09-error-handling/no-listing-09-guess-out-of-range/Cargo.toml new file mode 100644 index 0000000..1e53bae --- /dev/null +++ b/listings/ch09-error-handling/no-listing-09-guess-out-of-range/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch09-error-handling/no-listing-09-guess-out-of-range/src/main.rs b/listings/ch09-error-handling/no-listing-09-guess-out-of-range/src/main.rs new file mode 100644 index 0000000..cbe8fbc --- /dev/null +++ b/listings/ch09-error-handling/no-listing-09-guess-out-of-range/src/main.rs @@ -0,0 +1,47 @@ +use rand::Rng; +use std::cmp::Ordering; +use std::io; + +fn main() { + println!("Guess the number!"); + + let secret_number = rand::thread_rng().gen_range(1..101); + + // ANCHOR: here + loop { + // --snip-- + + // ANCHOR_END: here + println!("Please input your guess."); + + let mut guess = String::new(); + + io::stdin() + .read_line(&mut guess) + .expect("Failed to read line"); + + // ANCHOR: here + let guess: i32 = match guess.trim().parse() { + Ok(num) => num, + Err(_) => continue, + }; + + if guess < 1 || guess > 100 { + println!("The secret number will be between 1 and 100."); + continue; + } + + match guess.cmp(&secret_number) { + // --snip-- + // ANCHOR_END: here + Ordering::Less => println!("Too small!"), + Ordering::Greater => println!("Too big!"), + Ordering::Equal => { + println!("You win!"); + break; + } + } + // ANCHOR: here + } + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/src/main.rs new file mode 100644 index 0000000..d2ba23b --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/src/main.rs @@ -0,0 +1,18 @@ +// ANCHOR: here +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let mut largest = number_list[0]; + + for number in number_list { + if number > largest { + largest = number; + } + } + + println!("The largest number is {}", largest); + // ANCHOR_END: here + assert_eq!(largest, 100); + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/src/main.rs new file mode 100644 index 0000000..9138dfc --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/src/main.rs @@ -0,0 +1,25 @@ +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let mut largest = number_list[0]; + + for number in number_list { + if number > largest { + largest = number; + } + } + + println!("The largest number is {}", largest); + + let number_list = vec![102, 34, 6000, 89, 54, 2, 43, 8]; + + let mut largest = number_list[0]; + + for number in number_list { + if number > largest { + largest = number; + } + } + + println!("The largest number is {}", largest); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/src/main.rs new file mode 100644 index 0000000..7704ff3 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/src/main.rs @@ -0,0 +1,31 @@ +// ANCHOR: here +fn largest(list: &[i32]) -> i32 { + let mut largest = list[0]; + + for &item in list { + if item > largest { + largest = item; + } + } + + largest +} + +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let result = largest(&number_list); + println!("The largest number is {}", result); + // ANCHOR_END: here + assert_eq!(result, 100); + // ANCHOR: here + + let number_list = vec![102, 34, 6000, 89, 54, 2, 43, 8]; + + let result = largest(&number_list); + println!("The largest number is {}", result); + // ANCHOR_END: here + assert_eq!(result, 6000); + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/src/main.rs new file mode 100644 index 0000000..6b483ec --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/src/main.rs @@ -0,0 +1,43 @@ +// ANCHOR: here +fn largest_i32(list: &[i32]) -> i32 { + let mut largest = list[0]; + + for &item in list { + if item > largest { + largest = item; + } + } + + largest +} + +fn largest_char(list: &[char]) -> char { + let mut largest = list[0]; + + for &item in list { + if item > largest { + largest = item; + } + } + + largest +} + +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let result = largest_i32(&number_list); + println!("The largest number is {}", result); + // ANCHOR_END: here + assert_eq!(result, 100); + // ANCHOR: here + + let char_list = vec!['y', 'm', 'a', 'q']; + + let result = largest_char(&char_list); + println!("The largest char is {}", result); + // ANCHOR_END: here + assert_eq!(result, 'y'); + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/output.txt new file mode 100644 index 0000000..9b6e53e --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/output.txt @@ -0,0 +1,21 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0369]: binary operation `>` cannot be applied to type `T` + --> src/main.rs:5:17 + | +5 | if item > largest { + | ---- ^ ------- T + | | + | T + | +help: consider restricting type parameter `T` + | +1 | fn largest(list: &[T]) -> T { + | ^^^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0369`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/src/main.rs new file mode 100644 index 0000000..e731157 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/src/main.rs @@ -0,0 +1,23 @@ +fn largest(list: &[T]) -> T { + let mut largest = list[0]; + + for &item in list { + if item > largest { + largest = item; + } + } + + largest +} + +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let result = largest(&number_list); + println!("The largest number is {}", result); + + let char_list = vec!['y', 'm', 'a', 'q']; + + let result = largest(&char_list); + println!("The largest char is {}", result); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/src/main.rs new file mode 100644 index 0000000..4252593 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/src/main.rs @@ -0,0 +1,9 @@ +struct Point { + x: T, + y: T, +} + +fn main() { + let integer = Point { x: 5, y: 10 }; + let float = Point { x: 1.0, y: 4.0 }; +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/output.txt new file mode 100644 index 0000000..5f32bdc --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/output.txt @@ -0,0 +1,14 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0308]: mismatched types + --> src/main.rs:7:38 + | +7 | let wont_work = Point { x: 5, y: 4.0 }; + | ^^^ expected integer, found floating-point number + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/src/main.rs new file mode 100644 index 0000000..7883db1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/src/main.rs @@ -0,0 +1,8 @@ +struct Point { + x: T, + y: T, +} + +fn main() { + let wont_work = Point { x: 5, y: 4.0 }; +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/src/main.rs new file mode 100644 index 0000000..615b78c --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/src/main.rs @@ -0,0 +1,10 @@ +struct Point { + x: T, + y: U, +} + +fn main() { + let both_integer = Point { x: 5, y: 10 }; + let both_float = Point { x: 1.0, y: 4.0 }; + let integer_and_float = Point { x: 5, y: 4.0 }; +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/src/main.rs new file mode 100644 index 0000000..288b64e --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/src/main.rs @@ -0,0 +1,16 @@ +struct Point { + x: T, + y: T, +} + +impl Point { + fn x(&self) -> &T { + &self.x + } +} + +fn main() { + let p = Point { x: 5, y: 10 }; + + println!("p.x = {}", p.x()); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/src/main.rs new file mode 100644 index 0000000..4c5b01b --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/src/main.rs @@ -0,0 +1,24 @@ +struct Point { + x: T, + y: T, +} + +impl Point { + fn x(&self) -> &T { + &self.x + } +} + +// ANCHOR: here +impl Point { + fn distance_from_origin(&self) -> f32 { + (self.x.powi(2) + self.y.powi(2)).sqrt() + } +} +// ANCHOR_END: here + +fn main() { + let p = Point { x: 5, y: 10 }; + + println!("p.x = {}", p.x()); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/src/main.rs new file mode 100644 index 0000000..4a08d1a --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/src/main.rs @@ -0,0 +1,22 @@ +struct Point { + x: T, + y: U, +} + +impl Point { + fn mixup(self, other: Point) -> Point { + Point { + x: self.x, + y: other.y, + } + } +} + +fn main() { + let p1 = Point { x: 5, y: 10.4 }; + let p2 = Point { x: "Hello", y: 'c' }; + + let p3 = p1.mixup(p2); + + println!("p3.x = {}, p3.y = {}", p3.x, p3.y); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/src/lib.rs new file mode 100644 index 0000000..cfaedb0 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/src/lib.rs @@ -0,0 +1,3 @@ +pub trait Summary { + fn summarize(&self) -> String; +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/src/lib.rs new file mode 100644 index 0000000..c4c8332 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/src/lib.rs @@ -0,0 +1,31 @@ +pub trait Summary { + fn summarize(&self) -> String; +} + +// ANCHOR: here +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle { + fn summarize(&self) -> String { + format!("{}, by {} ({})", self.headline, self.author, self.location) + } +} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/src/lib.rs new file mode 100644 index 0000000..fb59b84 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/src/lib.rs @@ -0,0 +1,29 @@ +// ANCHOR: here +pub trait Summary { + fn summarize(&self) -> String { + String::from("(Read more...)") + } +} +// ANCHOR_END: here + +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle {} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/src/main.rs new file mode 100644 index 0000000..7aa6a3b --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/src/main.rs @@ -0,0 +1,23 @@ +fn largest(list: &[T]) -> T { + let mut largest = list[0]; + + for &item in list { + if item > largest { + largest = item; + } + } + + largest +} + +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let result = largest(&number_list); + println!("The largest number is {}", result); + + let char_list = vec!['y', 'm', 'a', 'q']; + + let result = largest(&char_list); + println!("The largest char is {}", result); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/src/lib.rs new file mode 100644 index 0000000..669cc5f --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/src/lib.rs @@ -0,0 +1,22 @@ +use std::fmt::Display; + +struct Pair { + x: T, + y: T, +} + +impl Pair { + fn new(x: T, y: T) -> Self { + Self { x, y } + } +} + +impl Pair { + fn cmp_display(&self) { + if self.x >= self.y { + println!("The largest member is x = {}", self.x); + } else { + println!("The largest member is y = {}", self.y); + } + } +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/output.txt new file mode 100644 index 0000000..c79e59c --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0597]: `x` does not live long enough + --> src/main.rs:7:17 + | +7 | r = &x; + | ^^ borrowed value does not live long enough +8 | } + | - `x` dropped here while still borrowed +9 | +10 | println!("r: {}", r); + | - borrow later used here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0597`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/src/main.rs new file mode 100644 index 0000000..16adb6a --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/src/main.rs @@ -0,0 +1,14 @@ +fn main() { + // ANCHOR: here + { + let r; + + { + let x = 5; + r = &x; + } + + println!("r: {}", r); + } + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/Cargo.lock new file mode 100644 index 0000000..6388bb2 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/rustfmt-ignore b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/src/main.rs new file mode 100644 index 0000000..65dbf37 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/src/main.rs @@ -0,0 +1,14 @@ +fn main() { + // ANCHOR: here + { + let r; // ---------+-- 'a + // | + { // | + let x = 5; // -+-- 'b | + r = &x; // | | + } // -+ | + // | + println!("r: {}", r); // | + } // ---------+ + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/Cargo.lock new file mode 100644 index 0000000..6388bb2 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/rustfmt-ignore b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/rustfmt-ignore new file mode 100644 index 0000000..9a53c71 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/rustfmt-ignore @@ -0,0 +1,3 @@ +We have some weird comments pointing out borrowing scopes that we don't want to change; +unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to +manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028 diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/src/main.rs new file mode 100644 index 0000000..94e70f0 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + { + let x = 5; // ----------+-- 'b + // | + let r = &x; // --+-- 'a | + // | | + println!("r: {}", r); // | | + // --+ | + } // ----------+ + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/src/main.rs new file mode 100644 index 0000000..0f076a7 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let string1 = String::from("abcd"); + let string2 = "xyz"; + + let result = longest(string1.as_str(), string2); + println!("The longest string is {}", result); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/output.txt new file mode 100644 index 0000000..aa38ce0 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0106]: missing lifetime specifier + --> src/main.rs:9:33 + | +9 | fn longest(x: &str, y: &str) -> &str { + | ---- ---- ^ expected named lifetime parameter + | + = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `x` or `y` +help: consider introducing a named lifetime parameter + | +9 | fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { + | ^^^^ ^^^^^^^ ^^^^^^^ ^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0106`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/src/main.rs new file mode 100644 index 0000000..6af8c9f --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/src/main.rs @@ -0,0 +1,17 @@ +fn main() { + let string1 = String::from("abcd"); + let string2 = "xyz"; + + let result = longest(string1.as_str(), string2); + println!("The longest string is {}", result); +} + +// ANCHOR: here +fn longest(x: &str, y: &str) -> &str { + if x.len() > y.len() { + x + } else { + y + } +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/src/main.rs new file mode 100644 index 0000000..09c3a0d --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/src/main.rs @@ -0,0 +1,17 @@ +fn main() { + let string1 = String::from("abcd"); + let string2 = "xyz"; + + let result = longest(string1.as_str(), string2); + println!("The longest string is {}", result); +} + +// ANCHOR: here +fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { + if x.len() > y.len() { + x + } else { + y + } +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/src/main.rs new file mode 100644 index 0000000..836ec72 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/src/main.rs @@ -0,0 +1,19 @@ +// ANCHOR: here +fn main() { + let string1 = String::from("long string is long"); + + { + let string2 = String::from("xyz"); + let result = longest(string1.as_str(), string2.as_str()); + println!("The longest string is {}", result); + } +} +// ANCHOR_END: here + +fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { + if x.len() > y.len() { + x + } else { + y + } +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/output.txt new file mode 100644 index 0000000..05ffdc7 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/output.txt @@ -0,0 +1,18 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0597]: `string2` does not live long enough + --> src/main.rs:6:44 + | +6 | result = longest(string1.as_str(), string2.as_str()); + | ^^^^^^^ borrowed value does not live long enough +7 | } + | - `string2` dropped here while still borrowed +8 | println!("The longest string is {}", result); + | ------ borrow later used here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0597`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/src/main.rs new file mode 100644 index 0000000..2a6fa58 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/src/main.rs @@ -0,0 +1,19 @@ +// ANCHOR: here +fn main() { + let string1 = String::from("long string is long"); + let result; + { + let string2 = String::from("xyz"); + result = longest(string1.as_str(), string2.as_str()); + } + println!("The longest string is {}", result); +} +// ANCHOR_END: here + +fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { + if x.len() > y.len() { + x + } else { + y + } +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/src/main.rs new file mode 100644 index 0000000..2937b19 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/src/main.rs @@ -0,0 +1,11 @@ +struct ImportantExcerpt<'a> { + part: &'a str, +} + +fn main() { + let novel = String::from("Call me Ishmael. Some years ago..."); + let first_sentence = novel.split('.').next().expect("Could not find a '.'"); + let i = ImportantExcerpt { + part: first_sentence, + }; +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/Cargo.lock new file mode 100644 index 0000000..2aa4918 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/Cargo.toml new file mode 100644 index 0000000..686de93 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "ownership" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/src/main.rs new file mode 100644 index 0000000..431a261 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/src/main.rs @@ -0,0 +1,29 @@ +// ANCHOR: here +fn first_word(s: &str) -> &str { + let bytes = s.as_bytes(); + + for (i, &item) in bytes.iter().enumerate() { + if item == b' ' { + return &s[0..i]; + } + } + + &s[..] +} +// ANCHOR_END: here + +fn main() { + let my_string = String::from("hello world"); + + // first_word works on slices of `String`s + let word = first_word(&my_string[..]); + + let my_string_literal = "hello world"; + + // first_word works on slices of string literals + let word = first_word(&my_string_literal[..]); + + // Because string literals *are* string slices already, + // this works too, without the slice syntax! + let word = first_word(my_string_literal); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/lib.rs new file mode 100644 index 0000000..fa644ca --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/lib.rs @@ -0,0 +1,29 @@ +pub trait Summary { + fn summarize(&self) -> String; +} + +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle { + fn summarize(&self) -> String { + format!("{}, by {} ({})", self.headline, self.author, self.location) + } +} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/main.rs new file mode 100644 index 0000000..466dc4d --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/main.rs @@ -0,0 +1,16 @@ +use chapter10::{self, Summary, Tweet}; + +fn main() { + // ANCHOR: here + let tweet = Tweet { + username: String::from("horse_ebooks"), + content: String::from( + "of course, as you probably already know, people", + ), + reply: false, + retweet: false, + }; + + println!("1 new tweet: {}", tweet.summarize()); + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/lib.rs new file mode 100644 index 0000000..b6f93a6 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/lib.rs @@ -0,0 +1,27 @@ +pub trait Summary { + fn summarize(&self) -> String { + String::from("(Read more...)") + } +} + +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle {} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/main.rs new file mode 100644 index 0000000..44c9c64 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/main.rs @@ -0,0 +1,17 @@ +use chapter10::{self, NewsArticle, Summary}; + +fn main() { + // ANCHOR: here + let article = NewsArticle { + headline: String::from("Penguins win the Stanley Cup Championship!"), + location: String::from("Pittsburgh, PA, USA"), + author: String::from("Iceburgh"), + content: String::from( + "The Pittsburgh Penguins once again are the best \ + hockey team in the NHL.", + ), + }; + + println!("New article available! {}", article.summarize()); + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/lib.rs new file mode 100644 index 0000000..643906f --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/lib.rs @@ -0,0 +1,24 @@ +// ANCHOR: here +pub trait Summary { + fn summarize_author(&self) -> String; + + fn summarize(&self) -> String { + format!("(Read more from {}...)", self.summarize_author()) + } +} +// ANCHOR_END: here + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +// ANCHOR: impl +impl Summary for Tweet { + fn summarize_author(&self) -> String { + format!("@{}", self.username) + } +} +// ANCHOR_END: impl diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/main.rs new file mode 100644 index 0000000..466dc4d --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/main.rs @@ -0,0 +1,16 @@ +use chapter10::{self, Summary, Tweet}; + +fn main() { + // ANCHOR: here + let tweet = Tweet { + username: String::from("horse_ebooks"), + content: String::from( + "of course, as you probably already know, people", + ), + reply: false, + retweet: false, + }; + + println!("1 new tweet: {}", tweet.summarize()); + // ANCHOR_END: here +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/src/lib.rs new file mode 100644 index 0000000..2619943 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/src/lib.rs @@ -0,0 +1,35 @@ +pub trait Summary { + fn summarize(&self) -> String; +} + +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle { + fn summarize(&self) -> String { + format!("{}, by {} ({})", self.headline, self.author, self.location) + } +} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} + +// ANCHOR: here +pub fn notify(item: &impl Summary) { + println!("Breaking news! {}", item.summarize()); +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/src/lib.rs new file mode 100644 index 0000000..a611fce --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/src/lib.rs @@ -0,0 +1,42 @@ +pub trait Summary { + fn summarize(&self) -> String; +} + +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle { + fn summarize(&self) -> String { + format!("{}, by {} ({})", self.headline, self.author, self.location) + } +} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} + +// ANCHOR: here +fn returns_summarizable() -> impl Summary { + Tweet { + username: String::from("horse_ebooks"), + content: String::from( + "of course, as you probably already know, people", + ), + reply: false, + retweet: false, + } +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/src/lib.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/src/lib.rs new file mode 100644 index 0000000..7cd81d4 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/src/lib.rs @@ -0,0 +1,56 @@ +pub trait Summary { + fn summarize(&self) -> String; +} + +pub struct NewsArticle { + pub headline: String, + pub location: String, + pub author: String, + pub content: String, +} + +impl Summary for NewsArticle { + fn summarize(&self) -> String { + format!("{}, by {} ({})", self.headline, self.author, self.location) + } +} + +pub struct Tweet { + pub username: String, + pub content: String, + pub reply: bool, + pub retweet: bool, +} + +impl Summary for Tweet { + fn summarize(&self) -> String { + format!("{}: {}", self.username, self.content) + } +} + +// ANCHOR: here +fn returns_summarizable(switch: bool) -> impl Summary { + if switch { + NewsArticle { + headline: String::from( + "Penguins win the Stanley Cup Championship!", + ), + location: String::from("Pittsburgh, PA, USA"), + author: String::from("Iceburgh"), + content: String::from( + "The Pittsburgh Penguins once again are the best \ + hockey team in the NHL.", + ), + } + } else { + Tweet { + username: String::from("horse_ebooks"), + content: String::from( + "of course, as you probably already know, people", + ), + reply: false, + retweet: false, + } + } +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/output.txt new file mode 100644 index 0000000..0a3e7f5 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/output.txt @@ -0,0 +1,29 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0508]: cannot move out of type `[T]`, a non-copy slice + --> src/main.rs:2:23 + | +2 | let mut largest = list[0]; + | ^^^^^^^ + | | + | cannot move out of here + | move occurs because `list[_]` has type `T`, which does not implement the `Copy` trait + | help: consider borrowing here: `&list[0]` + +error[E0507]: cannot move out of a shared reference + --> src/main.rs:4:18 + | +4 | for &item in list { + | ----- ^^^^ + | || + | |data moved here + | |move occurs because `item` has type `T`, which does not implement the `Copy` trait + | help: consider removing the `&`: `item` + +error: aborting due to 2 previous errors + +Some errors have detailed explanations: E0507, E0508. +For more information about an error, try `rustc --explain E0507`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/src/main.rs new file mode 100644 index 0000000..525ce81 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/src/main.rs @@ -0,0 +1,25 @@ +// ANCHOR: here +fn largest(list: &[T]) -> T { + // ANCHOR_END: here + let mut largest = list[0]; + + for &item in list { + if item > largest { + largest = item; + } + } + + largest +} + +fn main() { + let number_list = vec![34, 50, 25, 100, 65]; + + let result = largest(&number_list); + println!("The largest number is {}", result); + + let char_list = vec!['y', 'm', 'a', 'q']; + + let result = largest(&char_list); + println!("The largest char is {}", result); +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/src/main.rs new file mode 100644 index 0000000..d144305 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + let string1 = String::from("abcd"); + let string2 = "efghijklmnopqrstuvwxyz"; + + let result = longest(string1.as_str(), string2); + println!("The longest string is {}", result); +} + +// ANCHOR: here +fn longest<'a>(x: &'a str, y: &str) -> &'a str { + x +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/output.txt b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/output.txt new file mode 100644 index 0000000..de29d4f --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/output.txt @@ -0,0 +1,17 @@ +$ cargo run + Compiling chapter10 v0.1.0 (file:///projects/chapter10) +error[E0515]: cannot return value referencing local variable `result` + --> src/main.rs:11:5 + | +11 | result.as_str() + | ------^^^^^^^^^ + | | + | returns a value referencing data owned by the current function + | `result` is borrowed here + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0515`. +error: could not compile `chapter10` + +To learn more, run the command again with --verbose. diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/src/main.rs new file mode 100644 index 0000000..aca4be0 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/src/main.rs @@ -0,0 +1,14 @@ +fn main() { + let string1 = String::from("abcd"); + let string2 = "xyz"; + + let result = longest(string1.as_str(), string2); + println!("The longest string is {}", result); +} + +// ANCHOR: here +fn longest<'a>(x: &str, y: &str) -> &'a str { + let result = String::from("really long string"); + result.as_str() +} +// ANCHOR_END: here diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/src/main.rs new file mode 100644 index 0000000..32ad530 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/src/main.rs @@ -0,0 +1,28 @@ +struct ImportantExcerpt<'a> { + part: &'a str, +} + +// ANCHOR: 1st +impl<'a> ImportantExcerpt<'a> { + fn level(&self) -> i32 { + 3 + } +} +// ANCHOR_END: 1st + +// ANCHOR: 3rd +impl<'a> ImportantExcerpt<'a> { + fn announce_and_return_part(&self, announcement: &str) -> &str { + println!("Attention please: {}", announcement); + self.part + } +} +// ANCHOR_END: 3rd + +fn main() { + let novel = String::from("Call me Ishmael. Some years ago..."); + let first_sentence = novel.split('.').next().expect("Could not find a '.'"); + let i = ImportantExcerpt { + part: first_sentence, + }; +} diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/Cargo.lock b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/Cargo.lock new file mode 100644 index 0000000..e8007a1 --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "chapter10" +version = "0.1.0" + diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/Cargo.toml b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/Cargo.toml new file mode 100644 index 0000000..6d5a0ff --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "chapter10" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/src/main.rs b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/src/main.rs new file mode 100644 index 0000000..cfafa9a --- /dev/null +++ b/listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/src/main.rs @@ -0,0 +1,31 @@ +fn main() { + let string1 = String::from("abcd"); + let string2 = "xyz"; + + let result = longest_with_an_announcement( + string1.as_str(), + string2, + "Today is someone's birthday!", + ); + println!("The longest string is {}", result); +} + +// ANCHOR: here +use std::fmt::Display; + +fn longest_with_an_announcement<'a, T>( + x: &'a str, + y: &'a str, + ann: T, +) -> &'a str +where + T: Display, +{ + println!("Announcement! {}", ann); + if x.len() > y.len() { + x + } else { + y + } +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/listing-11-01/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-01/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-01/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-01/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-01/output.txt b/listings/ch11-writing-automated-tests/listing-11-01/output.txt new file mode 100644 index 0000000..c07ffd2 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-01/output.txt @@ -0,0 +1,16 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.57s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test tests::it_works ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/listing-11-01/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-01/src/lib.rs new file mode 100644 index 0000000..31e1bb2 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-01/src/lib.rs @@ -0,0 +1,7 @@ +#[cfg(test)] +mod tests { + #[test] + fn it_works() { + assert_eq!(2 + 2, 4); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-03/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-03/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-03/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-03/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-03/output.txt b/listings/ch11-writing-automated-tests/listing-11-03/output.txt new file mode 100644 index 0000000..9680e7c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-03/output.txt @@ -0,0 +1,22 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.72s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 2 tests +test tests::another ... FAILED +test tests::exploration ... ok + +failures: + +---- tests::another stdout ---- +thread 'main' panicked at 'Make this test fail', src/lib.rs:10:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::another + +test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/listing-11-03/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-03/src/lib.rs new file mode 100644 index 0000000..a9ec008 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-03/src/lib.rs @@ -0,0 +1,14 @@ +// ANCHOR: here +#[cfg(test)] +mod tests { + #[test] + fn exploration() { + assert_eq!(2 + 2, 4); + } + + #[test] + fn another() { + panic!("Make this test fail"); + } +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/listing-11-05/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-05/Cargo.lock new file mode 100644 index 0000000..9dcd543 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangle" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-05/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-05/Cargo.toml new file mode 100644 index 0000000..32efee5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangle" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-05/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-05/src/lib.rs new file mode 100644 index 0000000..0f1bc4e --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-05/src/lib.rs @@ -0,0 +1,13 @@ +// ANCHOR: here +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +impl Rectangle { + fn can_hold(&self, other: &Rectangle) -> bool { + self.width > other.width && self.height > other.height + } +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/listing-11-06/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-06/Cargo.lock new file mode 100644 index 0000000..9dcd543 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangle" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-06/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-06/Cargo.toml new file mode 100644 index 0000000..32efee5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangle" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-06/output.txt b/listings/ch11-writing-automated-tests/listing-11-06/output.txt new file mode 100644 index 0000000..820c75b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-06/output.txt @@ -0,0 +1,16 @@ +$ cargo test + Compiling rectangle v0.1.0 (file:///projects/rectangle) + Finished test [unoptimized + debuginfo] target(s) in 0.66s + Running unittests (target/debug/deps/rectangle-6584c4561e48942e) + +running 1 test +test tests::larger_can_hold_smaller ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests rectangle + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/listing-11-06/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-06/src/lib.rs new file mode 100644 index 0000000..6ad1512 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-06/src/lib.rs @@ -0,0 +1,32 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +impl Rectangle { + fn can_hold(&self, other: &Rectangle) -> bool { + self.width > other.width && self.height > other.height + } +} + +// ANCHOR: here +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn larger_can_hold_smaller() { + let larger = Rectangle { + width: 8, + height: 7, + }; + let smaller = Rectangle { + width: 5, + height: 1, + }; + + assert!(larger.can_hold(&smaller)); + } +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/listing-11-07/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-07/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-07/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-07/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-07/output.txt b/listings/ch11-writing-automated-tests/listing-11-07/output.txt new file mode 100644 index 0000000..aa30cdb --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-07/output.txt @@ -0,0 +1,16 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.58s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test tests::it_adds_two ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/listing-11-07/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-07/src/lib.rs new file mode 100644 index 0000000..3e5d66b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-07/src/lib.rs @@ -0,0 +1,13 @@ +pub fn add_two(a: i32) -> i32 { + a + 2 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn it_adds_two() { + assert_eq!(4, add_two(2)); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-08/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-08/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-08/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-08/Cargo.toml new file mode 100644 index 0000000..922762a --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-08/output.txt b/listings/ch11-writing-automated-tests/listing-11-08/output.txt new file mode 100644 index 0000000..8372eee --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-08/output.txt @@ -0,0 +1,16 @@ +$ cargo test + Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished test [unoptimized + debuginfo] target(s) in 0.58s + Running unittests (target/debug/deps/guessing_game-57d70c3acb738f4d) + +running 1 test +test tests::greater_than_100 ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests guessing_game + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/listing-11-08/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-08/src/lib.rs new file mode 100644 index 0000000..9391be5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-08/src/lib.rs @@ -0,0 +1,24 @@ +pub struct Guess { + value: i32, +} + +impl Guess { + pub fn new(value: i32) -> Guess { + if value < 1 || value > 100 { + panic!("Guess value must be between 1 and 100, got {}.", value); + } + + Guess { value } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + #[should_panic] + fn greater_than_100() { + Guess::new(200); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-09/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-09/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-09/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-09/Cargo.toml new file mode 100644 index 0000000..922762a --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-09/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-09/src/lib.rs new file mode 100644 index 0000000..475d4b9 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-09/src/lib.rs @@ -0,0 +1,35 @@ +pub struct Guess { + value: i32, +} + +// ANCHOR: here +// --snip-- +impl Guess { + pub fn new(value: i32) -> Guess { + if value < 1 { + panic!( + "Guess value must be greater than or equal to 1, got {}.", + value + ); + } else if value > 100 { + panic!( + "Guess value must be less than or equal to 100, got {}.", + value + ); + } + + Guess { value } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + #[should_panic(expected = "Guess value must be less than or equal to 100")] + fn greater_than_100() { + Guess::new(200); + } +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/listing-11-10/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-10/Cargo.lock new file mode 100644 index 0000000..a6d35e3 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "silly-function" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-10/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-10/Cargo.toml new file mode 100644 index 0000000..4e0f185 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "silly-function" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-10/output.txt b/listings/ch11-writing-automated-tests/listing-11-10/output.txt new file mode 100644 index 0000000..ce98316 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-10/output.txt @@ -0,0 +1,25 @@ +$ cargo test + Compiling silly-function v0.1.0 (file:///projects/silly-function) + Finished test [unoptimized + debuginfo] target(s) in 0.58s + Running unittests (target/debug/deps/silly_function-160869f38cff9166) + +running 2 tests +test tests::this_test_will_fail ... FAILED +test tests::this_test_will_pass ... ok + +failures: + +---- tests::this_test_will_fail stdout ---- +I got the value 8 +thread 'main' panicked at 'assertion failed: `(left == right)` + left: `5`, + right: `10`', src/lib.rs:19:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::this_test_will_fail + +test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/listing-11-10/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-10/src/lib.rs new file mode 100644 index 0000000..6fd76ce --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-10/src/lib.rs @@ -0,0 +1,21 @@ +fn prints_and_returns_10(a: i32) -> i32 { + println!("I got the value {}", a); + 10 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn this_test_will_pass() { + let value = prints_and_returns_10(4); + assert_eq!(10, value); + } + + #[test] + fn this_test_will_fail() { + let value = prints_and_returns_10(8); + assert_eq!(5, value); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-11/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-11/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-11/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-11/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-11/output.txt b/listings/ch11-writing-automated-tests/listing-11-11/output.txt new file mode 100644 index 0000000..9be5abe --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-11/output.txt @@ -0,0 +1,18 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.62s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 3 tests +test tests::add_three_and_two ... ok +test tests::add_two_and_two ... ok +test tests::one_hundred ... ok + +test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/listing-11-11/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-11/src/lib.rs new file mode 100644 index 0000000..f567152 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-11/src/lib.rs @@ -0,0 +1,23 @@ +pub fn add_two(a: i32) -> i32 { + a + 2 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn add_two_and_two() { + assert_eq!(4, add_two(2)); + } + + #[test] + fn add_three_and_two() { + assert_eq!(5, add_two(3)); + } + + #[test] + fn one_hundred() { + assert_eq!(102, add_two(100)); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-12/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-12/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-12/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-12/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-12/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-12/src/lib.rs new file mode 100644 index 0000000..c3961b1 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-12/src/lib.rs @@ -0,0 +1,17 @@ +pub fn add_two(a: i32) -> i32 { + internal_adder(a, 2) +} + +fn internal_adder(a: i32, b: i32) -> i32 { + a + b +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn internal() { + assert_eq!(4, internal_adder(2, 2)); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-13/Cargo.lock b/listings/ch11-writing-automated-tests/listing-11-13/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/listing-11-13/Cargo.toml b/listings/ch11-writing-automated-tests/listing-11-13/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/listing-11-13/output.txt b/listings/ch11-writing-automated-tests/listing-11-13/output.txt new file mode 100644 index 0000000..12e231c --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-13/output.txt @@ -0,0 +1,23 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 1.31s + Running unittests (target/debug/deps/adder-1082c4b063a8fbe6) + +running 1 test +test tests::internal ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Running tests/integration_test.rs (target/debug/deps/integration_test-1082c4b063a8fbe6) + +running 1 test +test it_adds_two ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/listing-11-13/src/lib.rs b/listings/ch11-writing-automated-tests/listing-11-13/src/lib.rs new file mode 100644 index 0000000..c3961b1 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-13/src/lib.rs @@ -0,0 +1,17 @@ +pub fn add_two(a: i32) -> i32 { + internal_adder(a, 2) +} + +fn internal_adder(a: i32, b: i32) -> i32 { + a + b +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn internal() { + assert_eq!(4, internal_adder(2, 2)); + } +} diff --git a/listings/ch11-writing-automated-tests/listing-11-13/tests/integration_test.rs b/listings/ch11-writing-automated-tests/listing-11-13/tests/integration_test.rs new file mode 100644 index 0000000..e26fa71 --- /dev/null +++ b/listings/ch11-writing-automated-tests/listing-11-13/tests/integration_test.rs @@ -0,0 +1,6 @@ +use adder; + +#[test] +fn it_adds_two() { + assert_eq!(4, adder::add_two(2)); +} diff --git a/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/output.txt b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/output.txt new file mode 100644 index 0000000..5de1386 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/output.txt @@ -0,0 +1,16 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.59s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test tests::exploration ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/src/lib.rs new file mode 100644 index 0000000..330bddf --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/src/lib.rs @@ -0,0 +1,7 @@ +#[cfg(test)] +mod tests { + #[test] + fn exploration() { + assert_eq!(2 + 2, 4); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/Cargo.lock new file mode 100644 index 0000000..9dcd543 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangle" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/Cargo.toml new file mode 100644 index 0000000..32efee5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangle" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/output.txt b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/output.txt new file mode 100644 index 0000000..29320be --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/output.txt @@ -0,0 +1,17 @@ +$ cargo test + Compiling rectangle v0.1.0 (file:///projects/rectangle) + Finished test [unoptimized + debuginfo] target(s) in 0.66s + Running unittests (target/debug/deps/rectangle-6584c4561e48942e) + +running 2 tests +test tests::larger_can_hold_smaller ... ok +test tests::smaller_cannot_hold_larger ... ok + +test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests rectangle + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/src/lib.rs new file mode 100644 index 0000000..ee4fc45 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/src/lib.rs @@ -0,0 +1,49 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +impl Rectangle { + fn can_hold(&self, other: &Rectangle) -> bool { + self.width > other.width && self.height > other.height + } +} + +// ANCHOR: here +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn larger_can_hold_smaller() { + // --snip-- + // ANCHOR_END: here + let larger = Rectangle { + width: 8, + height: 7, + }; + let smaller = Rectangle { + width: 5, + height: 1, + }; + + assert!(larger.can_hold(&smaller)); + // ANCHOR: here + } + + #[test] + fn smaller_cannot_hold_larger() { + let larger = Rectangle { + width: 8, + height: 7, + }; + let smaller = Rectangle { + width: 5, + height: 1, + }; + + assert!(!smaller.can_hold(&larger)); + } +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/Cargo.lock new file mode 100644 index 0000000..9dcd543 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "rectangle" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/Cargo.toml new file mode 100644 index 0000000..32efee5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "rectangle" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/output.txt b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/output.txt new file mode 100644 index 0000000..6629b53 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/output.txt @@ -0,0 +1,22 @@ +$ cargo test + Compiling rectangle v0.1.0 (file:///projects/rectangle) + Finished test [unoptimized + debuginfo] target(s) in 0.66s + Running unittests (target/debug/deps/rectangle-6584c4561e48942e) + +running 2 tests +test tests::larger_can_hold_smaller ... FAILED +test tests::smaller_cannot_hold_larger ... ok + +failures: + +---- tests::larger_can_hold_smaller stdout ---- +thread 'main' panicked at 'assertion failed: larger.can_hold(&smaller)', src/lib.rs:28:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::larger_can_hold_smaller + +test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/src/lib.rs new file mode 100644 index 0000000..f5968fc --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/src/lib.rs @@ -0,0 +1,47 @@ +#[derive(Debug)] +struct Rectangle { + width: u32, + height: u32, +} + +// ANCHOR: here +// --snip-- +impl Rectangle { + fn can_hold(&self, other: &Rectangle) -> bool { + self.width < other.width && self.height > other.height + } +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn larger_can_hold_smaller() { + let larger = Rectangle { + width: 8, + height: 7, + }; + let smaller = Rectangle { + width: 5, + height: 1, + }; + + assert!(larger.can_hold(&smaller)); + } + + #[test] + fn smaller_cannot_hold_larger() { + let larger = Rectangle { + width: 8, + height: 7, + }; + let smaller = Rectangle { + width: 5, + height: 1, + }; + + assert!(!smaller.can_hold(&larger)); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/output.txt b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/output.txt new file mode 100644 index 0000000..2c0ffe8 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/output.txt @@ -0,0 +1,23 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.61s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test tests::it_adds_two ... FAILED + +failures: + +---- tests::it_adds_two stdout ---- +thread 'main' panicked at 'assertion failed: `(left == right)` + left: `4`, + right: `5`', src/lib.rs:11:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::it_adds_two + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/src/lib.rs new file mode 100644 index 0000000..f186625 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/src/lib.rs @@ -0,0 +1,15 @@ +// ANCHOR: here +pub fn add_two(a: i32) -> i32 { + a + 3 +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn it_adds_two() { + assert_eq!(4, add_two(2)); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-05-greeter/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-05-greeter/Cargo.lock new file mode 100644 index 0000000..9a7ecdd --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-05-greeter/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "greeter" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-05-greeter/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-05-greeter/Cargo.toml new file mode 100644 index 0000000..c289e83 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-05-greeter/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "greeter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-05-greeter/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-05-greeter/src/lib.rs new file mode 100644 index 0000000..3ba3d88 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-05-greeter/src/lib.rs @@ -0,0 +1,14 @@ +pub fn greeting(name: &str) -> String { + format!("Hello {}!", name) +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn greeting_contains_name() { + let result = greeting("Carol"); + assert!(result.contains("Carol")); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/Cargo.lock new file mode 100644 index 0000000..9a7ecdd --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "greeter" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/Cargo.toml new file mode 100644 index 0000000..c289e83 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "greeter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/output.txt b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/output.txt new file mode 100644 index 0000000..d54451f --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/output.txt @@ -0,0 +1,21 @@ +$ cargo test + Compiling greeter v0.1.0 (file:///projects/greeter) + Finished test [unoptimized + debuginfo] target(s) in 0.91s + Running unittests (target/debug/deps/greeter-170b942eb5bf5e3a) + +running 1 test +test tests::greeting_contains_name ... FAILED + +failures: + +---- tests::greeting_contains_name stdout ---- +thread 'main' panicked at 'assertion failed: result.contains(\"Carol\")', src/lib.rs:12:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::greeting_contains_name + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/src/lib.rs new file mode 100644 index 0000000..6f28fc5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/src/lib.rs @@ -0,0 +1,16 @@ +// ANCHOR: here +pub fn greeting(name: &str) -> String { + String::from("Hello!") +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn greeting_contains_name() { + let result = greeting("Carol"); + assert!(result.contains("Carol")); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/Cargo.lock new file mode 100644 index 0000000..9a7ecdd --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "greeter" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/Cargo.toml new file mode 100644 index 0000000..c289e83 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "greeter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/output.txt b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/output.txt new file mode 100644 index 0000000..2ecf804 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/output.txt @@ -0,0 +1,21 @@ +$ cargo test + Compiling greeter v0.1.0 (file:///projects/greeter) + Finished test [unoptimized + debuginfo] target(s) in 0.93s + Running unittests (target/debug/deps/greeter-170b942eb5bf5e3a) + +running 1 test +test tests::greeting_contains_name ... FAILED + +failures: + +---- tests::greeting_contains_name stdout ---- +thread 'main' panicked at 'Greeting did not contain name, value was `Hello!`', src/lib.rs:12:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::greeting_contains_name + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/src/lib.rs new file mode 100644 index 0000000..519c7a4 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/src/lib.rs @@ -0,0 +1,20 @@ +pub fn greeting(name: &str) -> String { + String::from("Hello!") +} + +#[cfg(test)] +mod tests { + use super::*; + + // ANCHOR: here + #[test] + fn greeting_contains_name() { + let result = greeting("Carol"); + assert!( + result.contains("Carol"), + "Greeting did not contain name, value was `{}`", + result + ); + } + // ANCHOR_END: here +} diff --git a/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/Cargo.toml new file mode 100644 index 0000000..922762a --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/output.txt b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/output.txt new file mode 100644 index 0000000..c624c24 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/output.txt @@ -0,0 +1,19 @@ +$ cargo test + Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished test [unoptimized + debuginfo] target(s) in 0.62s + Running unittests (target/debug/deps/guessing_game-57d70c3acb738f4d) + +running 1 test +test tests::greater_than_100 ... FAILED + +failures: + +---- tests::greater_than_100 stdout ---- +note: test did not panic as expected + +failures: + tests::greater_than_100 + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/src/lib.rs new file mode 100644 index 0000000..32540ba --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/src/lib.rs @@ -0,0 +1,27 @@ +pub struct Guess { + value: i32, +} + +// ANCHOR: here +// --snip-- +impl Guess { + pub fn new(value: i32) -> Guess { + if value < 1 { + panic!("Guess value must be between 1 and 100, got {}.", value); + } + + Guess { value } + } +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + #[should_panic] + fn greater_than_100() { + Guess::new(200); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/Cargo.lock new file mode 100644 index 0000000..5802b7d --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "guessing_game" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/Cargo.toml new file mode 100644 index 0000000..922762a --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "guessing_game" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/output.txt b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/output.txt new file mode 100644 index 0000000..d79268c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/output.txt @@ -0,0 +1,23 @@ +$ cargo test + Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished test [unoptimized + debuginfo] target(s) in 0.66s + Running unittests (target/debug/deps/guessing_game-57d70c3acb738f4d) + +running 1 test +test tests::greater_than_100 ... FAILED + +failures: + +---- tests::greater_than_100 stdout ---- +thread 'main' panicked at 'Guess value must be greater than or equal to 1, got 200.', src/lib.rs:13:13 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace +note: panic did not contain expected string + panic message: `"Guess value must be greater than or equal to 1, got 200."`, + expected substring: `"Guess value must be less than or equal to 100"` + +failures: + tests::greater_than_100 + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/src/lib.rs new file mode 100644 index 0000000..2165004 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/src/lib.rs @@ -0,0 +1,34 @@ +pub struct Guess { + value: i32, +} + +impl Guess { + pub fn new(value: i32) -> Guess { + // ANCHOR: here + if value < 1 { + panic!( + "Guess value must be less than or equal to 100, got {}.", + value + ); + } else if value > 100 { + panic!( + "Guess value must be greater than or equal to 1, got {}.", + value + ); + } + // ANCHOR_END: here + + Guess { value } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + #[should_panic(expected = "Guess value must be less than or equal to 100")] + fn greater_than_100() { + Guess::new(200); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/src/lib.rs new file mode 100644 index 0000000..6284f4f --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/src/lib.rs @@ -0,0 +1,11 @@ +#[cfg(test)] +mod tests { + #[test] + fn it_works() -> Result<(), String> { + if 2 + 2 == 4 { + Ok(()) + } else { + Err(String::from("two plus two does not equal four")) + } + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/output.txt b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/output.txt new file mode 100644 index 0000000..fcdff25 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/output.txt @@ -0,0 +1,17 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.60s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 2 tests +test expensive_test ... ignored +test it_works ... ok + +test result: ok. 1 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/src/lib.rs new file mode 100644 index 0000000..d54a609 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/src/lib.rs @@ -0,0 +1,10 @@ +#[test] +fn it_works() { + assert_eq!(2 + 2, 4); +} + +#[test] +#[ignore] +fn expensive_test() { + // code that takes an hour to run +} diff --git a/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/output.txt b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/output.txt new file mode 100644 index 0000000..0afdb52 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/output.txt @@ -0,0 +1,29 @@ +$ cargo test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.89s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test tests::internal ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Running tests/common.rs (target/debug/deps/common-92948b65e88960b4) + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Running tests/integration_test.rs (target/debug/deps/integration_test-92948b65e88960b4) + +running 1 test +test it_adds_two ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/src/lib.rs new file mode 100644 index 0000000..c3961b1 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/src/lib.rs @@ -0,0 +1,17 @@ +pub fn add_two(a: i32) -> i32 { + internal_adder(a, 2) +} + +fn internal_adder(a: i32, b: i32) -> i32 { + a + b +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn internal() { + assert_eq!(4, internal_adder(2, 2)); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/common.rs b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/common.rs new file mode 100644 index 0000000..5fb7a39 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/common.rs @@ -0,0 +1,3 @@ +pub fn setup() { + // setup code specific to your library's tests would go here +} diff --git a/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/integration_test.rs b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/integration_test.rs new file mode 100644 index 0000000..e26fa71 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/integration_test.rs @@ -0,0 +1,6 @@ +use adder; + +#[test] +fn it_adds_two() { + assert_eq!(4, adder::add_two(2)); +} diff --git a/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/Cargo.lock b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/Cargo.toml b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/src/lib.rs b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/src/lib.rs new file mode 100644 index 0000000..c3961b1 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/src/lib.rs @@ -0,0 +1,17 @@ +pub fn add_two(a: i32) -> i32 { + internal_adder(a, 2) +} + +fn internal_adder(a: i32, b: i32) -> i32 { + a + b +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn internal() { + assert_eq!(4, internal_adder(2, 2)); + } +} diff --git a/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/common/mod.rs b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/common/mod.rs new file mode 100644 index 0000000..5fb7a39 --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/common/mod.rs @@ -0,0 +1,3 @@ +pub fn setup() { + // setup code specific to your library's tests would go here +} diff --git a/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/integration_test.rs b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/integration_test.rs new file mode 100644 index 0000000..58b8b7b --- /dev/null +++ b/listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/integration_test.rs @@ -0,0 +1,9 @@ +use adder; + +mod common; + +#[test] +fn it_adds_two() { + common::setup(); + assert_eq!(4, adder::add_two(2)); +} diff --git a/listings/ch11-writing-automated-tests/output-only-01-show-output/Cargo.lock b/listings/ch11-writing-automated-tests/output-only-01-show-output/Cargo.lock new file mode 100644 index 0000000..a6d35e3 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-01-show-output/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "silly-function" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/output-only-01-show-output/Cargo.toml b/listings/ch11-writing-automated-tests/output-only-01-show-output/Cargo.toml new file mode 100644 index 0000000..4e0f185 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-01-show-output/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "silly-function" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/output-only-01-show-output/output.txt b/listings/ch11-writing-automated-tests/output-only-01-show-output/output.txt new file mode 100644 index 0000000..94b0b4b --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-01-show-output/output.txt @@ -0,0 +1,34 @@ +$ cargo test -- --show-output + Compiling silly-function v0.1.0 (file:///projects/silly-function) + Finished test [unoptimized + debuginfo] target(s) in 0.60s + Running unittests (target/debug/deps/silly_function-160869f38cff9166) + +running 2 tests +test tests::this_test_will_fail ... FAILED +test tests::this_test_will_pass ... ok + +successes: + +---- tests::this_test_will_pass stdout ---- +I got the value 4 + + +successes: + tests::this_test_will_pass + +failures: + +---- tests::this_test_will_fail stdout ---- +I got the value 8 +thread 'main' panicked at 'assertion failed: `(left == right)` + left: `5`, + right: `10`', src/lib.rs:19:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::this_test_will_fail + +test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch11-writing-automated-tests/output-only-01-show-output/src/lib.rs b/listings/ch11-writing-automated-tests/output-only-01-show-output/src/lib.rs new file mode 100644 index 0000000..43c4c92 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-01-show-output/src/lib.rs @@ -0,0 +1,21 @@ +pub fn prints_and_returns_10(a: i32) -> i32 { + println!("I got the value {}", a); + 10 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn this_test_will_pass() { + let value = prints_and_returns_10(4); + assert_eq!(10, value); + } + + #[test] + fn this_test_will_fail() { + let value = prints_and_returns_10(8); + assert_eq!(5, value); + } +} diff --git a/listings/ch11-writing-automated-tests/output-only-02-single-test/Cargo.lock b/listings/ch11-writing-automated-tests/output-only-02-single-test/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-02-single-test/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/output-only-02-single-test/Cargo.toml b/listings/ch11-writing-automated-tests/output-only-02-single-test/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-02-single-test/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/output-only-02-single-test/output.txt b/listings/ch11-writing-automated-tests/output-only-02-single-test/output.txt new file mode 100644 index 0000000..e5e9ffd --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-02-single-test/output.txt @@ -0,0 +1,10 @@ +$ cargo test one_hundred + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.69s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test tests::one_hundred ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 2 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/output-only-02-single-test/src/lib.rs b/listings/ch11-writing-automated-tests/output-only-02-single-test/src/lib.rs new file mode 100644 index 0000000..f567152 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-02-single-test/src/lib.rs @@ -0,0 +1,23 @@ +pub fn add_two(a: i32) -> i32 { + a + 2 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn add_two_and_two() { + assert_eq!(4, add_two(2)); + } + + #[test] + fn add_three_and_two() { + assert_eq!(5, add_two(3)); + } + + #[test] + fn one_hundred() { + assert_eq!(102, add_two(100)); + } +} diff --git a/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/Cargo.lock b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/Cargo.toml b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/output.txt b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/output.txt new file mode 100644 index 0000000..822cbb5 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/output.txt @@ -0,0 +1,11 @@ +$ cargo test add + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.61s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 2 tests +test tests::add_three_and_two ... ok +test tests::add_two_and_two ... ok + +test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/src/lib.rs b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/src/lib.rs new file mode 100644 index 0000000..f567152 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-03-multiple-tests/src/lib.rs @@ -0,0 +1,23 @@ +pub fn add_two(a: i32) -> i32 { + a + 2 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn add_two_and_two() { + assert_eq!(4, add_two(2)); + } + + #[test] + fn add_three_and_two() { + assert_eq!(5, add_two(3)); + } + + #[test] + fn one_hundred() { + assert_eq!(102, add_two(100)); + } +} diff --git a/listings/ch11-writing-automated-tests/output-only-04-running-ignored/Cargo.lock b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/output-only-04-running-ignored/Cargo.toml b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/output-only-04-running-ignored/output.txt b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/output.txt new file mode 100644 index 0000000..009ac4a --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/output.txt @@ -0,0 +1,16 @@ +$ cargo test -- --ignored + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.61s + Running unittests (target/debug/deps/adder-92948b65e88960b4) + +running 1 test +test expensive_test ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out; finished in 0.00s + + Doc-tests adder + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/output-only-04-running-ignored/src/lib.rs b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/src/lib.rs new file mode 100644 index 0000000..2290c69 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-04-running-ignored/src/lib.rs @@ -0,0 +1,12 @@ +// ANCHOR: here +#[test] +fn it_works() { + assert_eq!(2 + 2, 4); +} + +#[test] +#[ignore] +fn expensive_test() { + // code that takes an hour to run +} +// ANCHOR_END: here diff --git a/listings/ch11-writing-automated-tests/output-only-05-single-integration/Cargo.lock b/listings/ch11-writing-automated-tests/output-only-05-single-integration/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-05-single-integration/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch11-writing-automated-tests/output-only-05-single-integration/Cargo.toml b/listings/ch11-writing-automated-tests/output-only-05-single-integration/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-05-single-integration/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch11-writing-automated-tests/output-only-05-single-integration/output.txt b/listings/ch11-writing-automated-tests/output-only-05-single-integration/output.txt new file mode 100644 index 0000000..260beaa --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-05-single-integration/output.txt @@ -0,0 +1,10 @@ +$ cargo test --test integration_test + Compiling adder v0.1.0 (file:///projects/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.64s + Running tests/integration_test.rs (target/debug/deps/integration_test-82e7799c1bc62298) + +running 1 test +test it_adds_two ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch11-writing-automated-tests/output-only-05-single-integration/src/lib.rs b/listings/ch11-writing-automated-tests/output-only-05-single-integration/src/lib.rs new file mode 100644 index 0000000..c3961b1 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-05-single-integration/src/lib.rs @@ -0,0 +1,17 @@ +pub fn add_two(a: i32) -> i32 { + internal_adder(a, 2) +} + +fn internal_adder(a: i32, b: i32) -> i32 { + a + b +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn internal() { + assert_eq!(4, internal_adder(2, 2)); + } +} diff --git a/listings/ch11-writing-automated-tests/output-only-05-single-integration/tests/integration_test.rs b/listings/ch11-writing-automated-tests/output-only-05-single-integration/tests/integration_test.rs new file mode 100644 index 0000000..e26fa71 --- /dev/null +++ b/listings/ch11-writing-automated-tests/output-only-05-single-integration/tests/integration_test.rs @@ -0,0 +1,6 @@ +use adder; + +#[test] +fn it_adds_two() { + assert_eq!(4, adder::add_two(2)); +} diff --git a/listings/ch12-an-io-project/listing-12-01/Cargo.lock b/listings/ch12-an-io-project/listing-12-01/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-01/Cargo.toml b/listings/ch12-an-io-project/listing-12-01/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-01/output.txt b/listings/ch12-an-io-project/listing-12-01/output.txt new file mode 100644 index 0000000..d0ef998 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-01/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.61s + Running `target/debug/minigrep` +["target/debug/minigrep"] diff --git a/listings/ch12-an-io-project/listing-12-01/src/main.rs b/listings/ch12-an-io-project/listing-12-01/src/main.rs new file mode 100644 index 0000000..aa3056d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-01/src/main.rs @@ -0,0 +1,6 @@ +use std::env; + +fn main() { + let args: Vec = env::args().collect(); + println!("{:?}", args); +} diff --git a/listings/ch12-an-io-project/listing-12-02/Cargo.lock b/listings/ch12-an-io-project/listing-12-02/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-02/Cargo.toml b/listings/ch12-an-io-project/listing-12-02/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-02/output.txt b/listings/ch12-an-io-project/listing-12-02/output.txt new file mode 100644 index 0000000..f759eea --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-02/output.txt @@ -0,0 +1,6 @@ +$ cargo run test sample.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep test sample.txt` +Searching for test +In file sample.txt diff --git a/listings/ch12-an-io-project/listing-12-02/src/main.rs b/listings/ch12-an-io-project/listing-12-02/src/main.rs new file mode 100644 index 0000000..8daf125 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-02/src/main.rs @@ -0,0 +1,11 @@ +use std::env; + +fn main() { + let args: Vec = env::args().collect(); + + let query = &args[1]; + let filename = &args[2]; + + println!("Searching for {}", query); + println!("In file {}", filename); +} diff --git a/listings/ch12-an-io-project/listing-12-03/Cargo.lock b/listings/ch12-an-io-project/listing-12-03/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-03/Cargo.toml b/listings/ch12-an-io-project/listing-12-03/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-03/poem.txt b/listings/ch12-an-io-project/listing-12-03/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-03/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-03/src/main.rs b/listings/ch12-an-io-project/listing-12-03/src/main.rs new file mode 100644 index 0000000..8daf125 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-03/src/main.rs @@ -0,0 +1,11 @@ +use std::env; + +fn main() { + let args: Vec = env::args().collect(); + + let query = &args[1]; + let filename = &args[2]; + + println!("Searching for {}", query); + println!("In file {}", filename); +} diff --git a/listings/ch12-an-io-project/listing-12-04/Cargo.lock b/listings/ch12-an-io-project/listing-12-04/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-04/Cargo.toml b/listings/ch12-an-io-project/listing-12-04/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-04/output.txt b/listings/ch12-an-io-project/listing-12-04/output.txt new file mode 100644 index 0000000..5f31c8c --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-04/output.txt @@ -0,0 +1,17 @@ +$ cargo run the poem.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep the poem.txt` +Searching for the +In file poem.txt +With text: +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! + diff --git a/listings/ch12-an-io-project/listing-12-04/poem.txt b/listings/ch12-an-io-project/listing-12-04/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-04/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-04/src/main.rs b/listings/ch12-an-io-project/listing-12-04/src/main.rs new file mode 100644 index 0000000..9a0eade --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-04/src/main.rs @@ -0,0 +1,22 @@ +// ANCHOR: here +use std::env; +use std::fs; + +fn main() { + // --snip-- + // ANCHOR_END: here + let args: Vec = env::args().collect(); + + let query = &args[1]; + let filename = &args[2]; + + println!("Searching for {}", query); + // ANCHOR: here + println!("In file {}", filename); + + let contents = fs::read_to_string(filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-05/Cargo.lock b/listings/ch12-an-io-project/listing-12-05/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-05/Cargo.toml b/listings/ch12-an-io-project/listing-12-05/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-05/poem.txt b/listings/ch12-an-io-project/listing-12-05/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-05/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-05/src/main.rs b/listings/ch12-an-io-project/listing-12-05/src/main.rs new file mode 100644 index 0000000..fb88056 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-05/src/main.rs @@ -0,0 +1,29 @@ +use std::env; +use std::fs; + +// ANCHOR: here +fn main() { + let args: Vec = env::args().collect(); + + let (query, filename) = parse_config(&args); + + // --snip-- + // ANCHOR_END: here + + println!("Searching for {}", query); + println!("In file {}", filename); + + let contents = fs::read_to_string(filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); + // ANCHOR: here +} + +fn parse_config(args: &[String]) -> (&str, &str) { + let query = &args[1]; + let filename = &args[2]; + + (query, filename) +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-06/Cargo.lock b/listings/ch12-an-io-project/listing-12-06/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-06/Cargo.toml b/listings/ch12-an-io-project/listing-12-06/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-06/poem.txt b/listings/ch12-an-io-project/listing-12-06/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-06/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-06/src/main.rs b/listings/ch12-an-io-project/listing-12-06/src/main.rs new file mode 100644 index 0000000..b5d89bc --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-06/src/main.rs @@ -0,0 +1,34 @@ +use std::env; +use std::fs; + +// ANCHOR: here +fn main() { + let args: Vec = env::args().collect(); + + let config = parse_config(&args); + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + let contents = fs::read_to_string(config.filename) + .expect("Something went wrong reading the file"); + + // --snip-- + // ANCHOR_END: here + + println!("With text:\n{}", contents); + // ANCHOR: here +} + +struct Config { + query: String, + filename: String, +} + +fn parse_config(args: &[String]) -> Config { + let query = args[1].clone(); + let filename = args[2].clone(); + + Config { query, filename } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-07/Cargo.lock b/listings/ch12-an-io-project/listing-12-07/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-07/Cargo.toml b/listings/ch12-an-io-project/listing-12-07/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-07/output.txt b/listings/ch12-an-io-project/listing-12-07/output.txt new file mode 100644 index 0000000..d3fa777 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-07/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep` +thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1', src/main.rs:27:21 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace diff --git a/listings/ch12-an-io-project/listing-12-07/poem.txt b/listings/ch12-an-io-project/listing-12-07/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-07/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-07/src/main.rs b/listings/ch12-an-io-project/listing-12-07/src/main.rs new file mode 100644 index 0000000..36d35ce --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-07/src/main.rs @@ -0,0 +1,40 @@ +use std::env; +use std::fs; + +// ANCHOR: here +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args); + // ANCHOR_END: here + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + let contents = fs::read_to_string(config.filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); + // ANCHOR: here + + // --snip-- +} + +// --snip-- + +// ANCHOR_END: here +struct Config { + query: String, + filename: String, +} + +// ANCHOR: here +impl Config { + fn new(args: &[String]) -> Config { + let query = args[1].clone(); + let filename = args[2].clone(); + + Config { query, filename } + } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-08/Cargo.lock b/listings/ch12-an-io-project/listing-12-08/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-08/Cargo.toml b/listings/ch12-an-io-project/listing-12-08/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-08/output.txt b/listings/ch12-an-io-project/listing-12-08/output.txt new file mode 100644 index 0000000..de2abd1 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-08/output.txt @@ -0,0 +1,6 @@ +$ cargo run + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep` +thread 'main' panicked at 'not enough arguments', src/main.rs:26:13 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace diff --git a/listings/ch12-an-io-project/listing-12-08/poem.txt b/listings/ch12-an-io-project/listing-12-08/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-08/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-08/src/main.rs b/listings/ch12-an-io-project/listing-12-08/src/main.rs new file mode 100644 index 0000000..dddf10b --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-08/src/main.rs @@ -0,0 +1,38 @@ +use std::env; +use std::fs; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args); + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + let contents = fs::read_to_string(config.filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); +} + +struct Config { + query: String, + filename: String, +} + +impl Config { + // ANCHOR: here + // --snip-- + fn new(args: &[String]) -> Config { + if args.len() < 3 { + panic!("not enough arguments"); + } + // --snip-- + // ANCHOR_END: here + + let query = args[1].clone(); + let filename = args[2].clone(); + + Config { query, filename } + } +} diff --git a/listings/ch12-an-io-project/listing-12-09/Cargo.lock b/listings/ch12-an-io-project/listing-12-09/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-09/Cargo.toml b/listings/ch12-an-io-project/listing-12-09/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-09/poem.txt b/listings/ch12-an-io-project/listing-12-09/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-09/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-09/src/main.rs b/listings/ch12-an-io-project/listing-12-09/src/main.rs new file mode 100644 index 0000000..8bee254 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-09/src/main.rs @@ -0,0 +1,36 @@ +use std::env; +use std::fs; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args); + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + let contents = fs::read_to_string(config.filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); +} + +struct Config { + query: String, + filename: String, +} + +// ANCHOR: here +impl Config { + fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-10/Cargo.lock b/listings/ch12-an-io-project/listing-12-10/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-10/Cargo.toml b/listings/ch12-an-io-project/listing-12-10/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-10/output.txt b/listings/ch12-an-io-project/listing-12-10/output.txt new file mode 100644 index 0000000..7aad57f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-10/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.48s + Running `target/debug/minigrep` +Problem parsing arguments: not enough arguments diff --git a/listings/ch12-an-io-project/listing-12-10/poem.txt b/listings/ch12-an-io-project/listing-12-10/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-10/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-10/src/main.rs b/listings/ch12-an-io-project/listing-12-10/src/main.rs new file mode 100644 index 0000000..2b8cac4 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-10/src/main.rs @@ -0,0 +1,42 @@ +use std::env; +use std::fs; +// ANCHOR: here +use std::process; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + // --snip-- + // ANCHOR_END: here + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + let contents = fs::read_to_string(config.filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); +} + +struct Config { + query: String, + filename: String, +} + +impl Config { + fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} diff --git a/listings/ch12-an-io-project/listing-12-11/Cargo.lock b/listings/ch12-an-io-project/listing-12-11/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-11/Cargo.toml b/listings/ch12-an-io-project/listing-12-11/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-11/poem.txt b/listings/ch12-an-io-project/listing-12-11/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-11/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-11/src/main.rs b/listings/ch12-an-io-project/listing-12-11/src/main.rs new file mode 100644 index 0000000..15aa709 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-11/src/main.rs @@ -0,0 +1,50 @@ +use std::env; +use std::fs; +use std::process; + +// ANCHOR: here +fn main() { + // --snip-- + + // ANCHOR_END: here + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + // ANCHOR: here + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + run(config); +} + +fn run(config: Config) { + let contents = fs::read_to_string(config.filename) + .expect("Something went wrong reading the file"); + + println!("With text:\n{}", contents); +} + +// --snip-- +// ANCHOR_END: here + +struct Config { + query: String, + filename: String, +} + +impl Config { + fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} diff --git a/listings/ch12-an-io-project/listing-12-12/Cargo.lock b/listings/ch12-an-io-project/listing-12-12/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-12/Cargo.toml b/listings/ch12-an-io-project/listing-12-12/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-12/output.txt b/listings/ch12-an-io-project/listing-12-12/output.txt new file mode 100644 index 0000000..91ee1df --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-12/output.txt @@ -0,0 +1,28 @@ +$ cargo run the poem.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) +warning: unused `Result` that must be used + --> src/main.rs:19:5 + | +19 | run(config); + | ^^^^^^^^^^^^ + | + = note: `#[warn(unused_must_use)]` on by default + = note: this `Result` may be an `Err` variant, which should be handled + +warning: 1 warning emitted + + Finished dev [unoptimized + debuginfo] target(s) in 0.71s + Running `target/debug/minigrep the poem.txt` +Searching for the +In file poem.txt +With text: +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! + diff --git a/listings/ch12-an-io-project/listing-12-12/poem.txt b/listings/ch12-an-io-project/listing-12-12/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-12/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-12/src/main.rs b/listings/ch12-an-io-project/listing-12-12/src/main.rs new file mode 100644 index 0000000..337dac1 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-12/src/main.rs @@ -0,0 +1,51 @@ +use std::env; +use std::fs; +use std::process; +// ANCHOR: here +use std::error::Error; + +// --snip-- + +// ANCHOR_END: here + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + run(config); +} + +// ANCHOR: here +fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + println!("With text:\n{}", contents); + + Ok(()) +} +// ANCHOR_END: here + +struct Config { + query: String, + filename: String, +} + +impl Config { + fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} diff --git a/listings/ch12-an-io-project/listing-12-13/Cargo.lock b/listings/ch12-an-io-project/listing-12-13/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-13/Cargo.toml b/listings/ch12-an-io-project/listing-12-13/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-13/poem.txt b/listings/ch12-an-io-project/listing-12-13/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-13/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-13/src/lib.rs b/listings/ch12-an-io-project/listing-12-13/src/lib.rs new file mode 100644 index 0000000..5a877fc --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-13/src/lib.rs @@ -0,0 +1,36 @@ +// ANCHOR: here +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + // --snip-- + // ANCHOR_END: here + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + // ANCHOR: here + } +} + +pub fn run(config: Config) -> Result<(), Box> { + // --snip-- + // ANCHOR_END: here + let contents = fs::read_to_string(config.filename)?; + + println!("With text:\n{}", contents); + + Ok(()) + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-13/src/main.rs b/listings/ch12-an-io-project/listing-12-13/src/main.rs new file mode 100644 index 0000000..b2447dc --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-13/src/main.rs @@ -0,0 +1,20 @@ +use std::env; +use std::process; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + if let Err(e) = run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-14/Cargo.lock b/listings/ch12-an-io-project/listing-12-14/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-14/Cargo.toml b/listings/ch12-an-io-project/listing-12-14/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-14/poem.txt b/listings/ch12-an-io-project/listing-12-14/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-14/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-14/src/lib.rs b/listings/ch12-an-io-project/listing-12-14/src/lib.rs new file mode 100644 index 0000000..40ee7ca --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-14/src/lib.rs @@ -0,0 +1,28 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + println!("With text:\n{}", contents); + + Ok(()) +} diff --git a/listings/ch12-an-io-project/listing-12-14/src/main.rs b/listings/ch12-an-io-project/listing-12-14/src/main.rs new file mode 100644 index 0000000..5eb4024 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-14/src/main.rs @@ -0,0 +1,30 @@ +// ANCHOR: here +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + // --snip-- + // ANCHOR_END: here + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + // ANCHOR: here + if let Err(e) = minigrep::run(config) { + // --snip-- + // ANCHOR_END: here + println!("Application error: {}", e); + + process::exit(1); + // ANCHOR: here + } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-15/Cargo.lock b/listings/ch12-an-io-project/listing-12-15/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-15/Cargo.toml b/listings/ch12-an-io-project/listing-12-15/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-15/poem.txt b/listings/ch12-an-io-project/listing-12-15/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-15/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-15/src/lib.rs b/listings/ch12-an-io-project/listing-12-15/src/lib.rs new file mode 100644 index 0000000..a0f611a --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-15/src/lib.rs @@ -0,0 +1,44 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + Ok(()) +} + +// ANCHOR: here +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-15/src/main.rs b/listings/ch12-an-io-project/listing-12-15/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-15/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-16/Cargo.lock b/listings/ch12-an-io-project/listing-12-16/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-16/Cargo.toml b/listings/ch12-an-io-project/listing-12-16/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-16/output.txt b/listings/ch12-an-io-project/listing-12-16/output.txt new file mode 100644 index 0000000..1c9196e --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-16/output.txt @@ -0,0 +1,23 @@ +$ cargo test + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished test [unoptimized + debuginfo] target(s) in 0.97s + Running target/debug/deps/minigrep-4672b652f7794785 + +running 1 test +test tests::one_result ... FAILED + +failures: + +---- tests::one_result stdout ---- +thread 'main' panicked at 'assertion failed: `(left == right)` + left: `["safe, fast, productive."]`, + right: `[]`', src/lib.rs:44:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::one_result + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch12-an-io-project/listing-12-16/poem.txt b/listings/ch12-an-io-project/listing-12-16/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-16/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-16/src/lib.rs b/listings/ch12-an-io-project/listing-12-16/src/lib.rs new file mode 100644 index 0000000..4df625e --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-16/src/lib.rs @@ -0,0 +1,48 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + Ok(()) +} + +// ANCHOR: here +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + vec![] +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/listing-12-16/src/main.rs b/listings/ch12-an-io-project/listing-12-16/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-16/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-17/Cargo.lock b/listings/ch12-an-io-project/listing-12-17/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-17/Cargo.toml b/listings/ch12-an-io-project/listing-12-17/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-17/poem.txt b/listings/ch12-an-io-project/listing-12-17/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-17/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-17/src/lib.rs b/listings/ch12-an-io-project/listing-12-17/src/lib.rs new file mode 100644 index 0000000..e7ddee9 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-17/src/lib.rs @@ -0,0 +1,50 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + Ok(()) +} + +// ANCHOR: here +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + for line in contents.lines() { + // do something with line + } +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/listing-12-17/src/main.rs b/listings/ch12-an-io-project/listing-12-17/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-17/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-18/Cargo.lock b/listings/ch12-an-io-project/listing-12-18/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-18/Cargo.toml b/listings/ch12-an-io-project/listing-12-18/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-18/poem.txt b/listings/ch12-an-io-project/listing-12-18/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-18/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-18/src/lib.rs b/listings/ch12-an-io-project/listing-12-18/src/lib.rs new file mode 100644 index 0000000..8984d1a --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-18/src/lib.rs @@ -0,0 +1,52 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + Ok(()) +} + +// ANCHOR: here +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + for line in contents.lines() { + if line.contains(query) { + // do something with line + } + } +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/listing-12-18/src/main.rs b/listings/ch12-an-io-project/listing-12-18/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-18/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-19/Cargo.lock b/listings/ch12-an-io-project/listing-12-19/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-19/Cargo.toml b/listings/ch12-an-io-project/listing-12-19/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-19/output.txt b/listings/ch12-an-io-project/listing-12-19/output.txt new file mode 100644 index 0000000..3699130 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-19/output.txt @@ -0,0 +1,22 @@ +$ cargo test + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished test [unoptimized + debuginfo] target(s) in 1.22s + Running target/debug/deps/minigrep-4672b652f7794785 + +running 1 test +test tests::one_result ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Running target/debug/deps/minigrep-4672b652f7794785 + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests minigrep + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch12-an-io-project/listing-12-19/poem.txt b/listings/ch12-an-io-project/listing-12-19/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-19/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-19/src/lib.rs b/listings/ch12-an-io-project/listing-12-19/src/lib.rs new file mode 100644 index 0000000..5a9e345 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-19/src/lib.rs @@ -0,0 +1,58 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + Ok(()) +} + +// ANCHOR: here +// ANCHOR: ch13 +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} +// ANCHOR_END: ch13 +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/listing-12-19/src/main.rs b/listings/ch12-an-io-project/listing-12-19/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-19/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-20/Cargo.lock b/listings/ch12-an-io-project/listing-12-20/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-20/Cargo.toml b/listings/ch12-an-io-project/listing-12-20/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-20/poem.txt b/listings/ch12-an-io-project/listing-12-20/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-20/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-20/src/lib.rs b/listings/ch12-an-io-project/listing-12-20/src/lib.rs new file mode 100644 index 0000000..d36f151 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-20/src/lib.rs @@ -0,0 +1,76 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + for line in search(&config.query, &contents) { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +// ANCHOR: here +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/listing-12-20/src/main.rs b/listings/ch12-an-io-project/listing-12-20/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-20/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-21/Cargo.lock b/listings/ch12-an-io-project/listing-12-21/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-21/Cargo.toml b/listings/ch12-an-io-project/listing-12-21/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-21/output.txt b/listings/ch12-an-io-project/listing-12-21/output.txt new file mode 100644 index 0000000..5b0f7b6 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-21/output.txt @@ -0,0 +1,23 @@ +$ cargo test + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished test [unoptimized + debuginfo] target(s) in 1.33s + Running target/debug/deps/minigrep-4672b652f7794785 + +running 2 tests +test tests::case_insensitive ... ok +test tests::case_sensitive ... ok + +test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Running target/debug/deps/minigrep-4672b652f7794785 + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests minigrep + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + diff --git a/listings/ch12-an-io-project/listing-12-21/poem.txt b/listings/ch12-an-io-project/listing-12-21/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-21/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-21/src/lib.rs b/listings/ch12-an-io-project/listing-12-21/src/lib.rs new file mode 100644 index 0000000..79f166b --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-21/src/lib.rs @@ -0,0 +1,92 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + for line in search(&config.query, &contents) { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +// ANCHOR: here +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch12-an-io-project/listing-12-21/src/main.rs b/listings/ch12-an-io-project/listing-12-21/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-21/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-22/Cargo.lock b/listings/ch12-an-io-project/listing-12-22/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-22/Cargo.toml b/listings/ch12-an-io-project/listing-12-22/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-22/poem.txt b/listings/ch12-an-io-project/listing-12-22/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-22/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-22/src/lib.rs b/listings/ch12-an-io-project/listing-12-22/src/lib.rs new file mode 100644 index 0000000..8feb1b1 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-22/src/lib.rs @@ -0,0 +1,101 @@ +use std::error::Error; +use std::fs; + +// ANCHOR: here +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} +// ANCHOR_END: here + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +// ANCHOR: there +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} +// ANCHOR_END: there + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch12-an-io-project/listing-12-22/src/main.rs b/listings/ch12-an-io-project/listing-12-22/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-22/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-23/Cargo.lock b/listings/ch12-an-io-project/listing-12-23/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-23/Cargo.toml b/listings/ch12-an-io-project/listing-12-23/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-23/output.txt b/listings/ch12-an-io-project/listing-12-23/output.txt new file mode 100644 index 0000000..0f0f07f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-23/output.txt @@ -0,0 +1,6 @@ +$ cargo run to poem.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep to poem.txt` +Are you nobody, too? +How dreary to be somebody! diff --git a/listings/ch12-an-io-project/listing-12-23/poem.txt b/listings/ch12-an-io-project/listing-12-23/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-23/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-23/src/lib.rs b/listings/ch12-an-io-project/listing-12-23/src/lib.rs new file mode 100644 index 0000000..719d3fe --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-23/src/lib.rs @@ -0,0 +1,110 @@ +// ANCHOR: here +use std::env; +// --snip-- + +// ANCHOR_END: here +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +// ANCHOR: here +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} +// ANCHOR_END: here + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch12-an-io-project/listing-12-23/src/main.rs b/listings/ch12-an-io-project/listing-12-23/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-23/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/listing-12-24/Cargo.lock b/listings/ch12-an-io-project/listing-12-24/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/listing-12-24/Cargo.toml b/listings/ch12-an-io-project/listing-12-24/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/listing-12-24/poem.txt b/listings/ch12-an-io-project/listing-12-24/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-24/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/listing-12-24/src/lib.rs b/listings/ch12-an-io-project/listing-12-24/src/lib.rs new file mode 100644 index 0000000..d0d0eb3 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-24/src/lib.rs @@ -0,0 +1,104 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch12-an-io-project/listing-12-24/src/main.rs b/listings/ch12-an-io-project/listing-12-24/src/main.rs new file mode 100644 index 0000000..9e38553 --- /dev/null +++ b/listings/ch12-an-io-project/listing-12-24/src/main.rs @@ -0,0 +1,21 @@ +use std::env; +use std::process; + +use minigrep::Config; + +// ANCHOR: here +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + eprintln!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + eprintln!("Application error: {}", e); + + process::exit(1); + } +} +// ANCHOR_END: here diff --git a/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/Cargo.lock b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/Cargo.toml b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/poem.txt b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/src/main.rs b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/src/main.rs new file mode 100644 index 0000000..e40109c --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/src/main.rs @@ -0,0 +1,54 @@ +use std::env; +use std::error::Error; +use std::fs; +use std::process; + +// ANCHOR: here +fn main() { + // --snip-- + + // ANCHOR_END: here + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + // ANCHOR: here + println!("Searching for {}", config.query); + println!("In file {}", config.filename); + + if let Err(e) = run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} +// ANCHOR_END: here + +fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + println!("With text:\n{}", contents); + + Ok(()) +} + +struct Config { + query: String, + filename: String, +} + +impl Config { + fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} diff --git a/listings/ch12-an-io-project/no-listing-02-using-search-in-run/Cargo.lock b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/no-listing-02-using-search-in-run/Cargo.toml b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/no-listing-02-using-search-in-run/output.txt b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/output.txt new file mode 100644 index 0000000..91532d0 --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/output.txt @@ -0,0 +1,5 @@ +$ cargo run frog poem.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.38s + Running `target/debug/minigrep frog poem.txt` +How public, like a frog diff --git a/listings/ch12-an-io-project/no-listing-02-using-search-in-run/poem.txt b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/lib.rs b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/lib.rs new file mode 100644 index 0000000..c3c5ffe --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/lib.rs @@ -0,0 +1,60 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +// ANCHOR: here +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + for line in search(&config.query, &contents) { + println!("{}", line); + } + + Ok(()) +} +// ANCHOR_END: here + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/main.rs b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/output-only-01-with-args/Cargo.lock b/listings/ch12-an-io-project/output-only-01-with-args/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/output-only-01-with-args/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/output-only-01-with-args/Cargo.toml b/listings/ch12-an-io-project/output-only-01-with-args/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-01-with-args/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/output-only-01-with-args/output.txt b/listings/ch12-an-io-project/output-only-01-with-args/output.txt new file mode 100644 index 0000000..eb88d9a --- /dev/null +++ b/listings/ch12-an-io-project/output-only-01-with-args/output.txt @@ -0,0 +1,5 @@ +$ cargo run needle haystack + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 1.57s + Running `target/debug/minigrep needle haystack` +["target/debug/minigrep", "needle", "haystack"] diff --git a/listings/ch12-an-io-project/output-only-01-with-args/src/main.rs b/listings/ch12-an-io-project/output-only-01-with-args/src/main.rs new file mode 100644 index 0000000..aa3056d --- /dev/null +++ b/listings/ch12-an-io-project/output-only-01-with-args/src/main.rs @@ -0,0 +1,6 @@ +use std::env; + +fn main() { + let args: Vec = env::args().collect(); + println!("{:?}", args); +} diff --git a/listings/ch12-an-io-project/output-only-02-missing-lifetimes/Cargo.lock b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/output-only-02-missing-lifetimes/Cargo.toml b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/output-only-02-missing-lifetimes/output.txt b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/output.txt new file mode 100644 index 0000000..8ba8fac --- /dev/null +++ b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/output.txt @@ -0,0 +1,20 @@ +$ cargo build + Compiling minigrep v0.1.0 (file:///projects/minigrep) +error[E0106]: missing lifetime specifier + --> src/lib.rs:28:51 + | +28 | pub fn search(query: &str, contents: &str) -> Vec<&str> { + | ---- ---- ^ expected named lifetime parameter + | + = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `query` or `contents` +help: consider introducing a named lifetime parameter + | +28 | pub fn search<'a>(query: &'a str, contents: &'a str) -> Vec<&'a str> { + | ^^^^ ^^^^^^^ ^^^^^^^ ^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0106`. +error: could not compile `minigrep` + +To learn more, run the command again with --verbose. diff --git a/listings/ch12-an-io-project/output-only-02-missing-lifetimes/poem.txt b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/output-only-02-missing-lifetimes/src/lib.rs b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/src/lib.rs new file mode 100644 index 0000000..97e41c8 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/src/lib.rs @@ -0,0 +1,48 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + Ok(()) +} + +// ANCHOR: here +pub fn search(query: &str, contents: &str) -> Vec<&str> { + vec![] +} +// ANCHOR_END: here + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/output-only-02-missing-lifetimes/src/main.rs b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/output-only-02-missing-lifetimes/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/output-only-03-multiple-matches/Cargo.lock b/listings/ch12-an-io-project/output-only-03-multiple-matches/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/output-only-03-multiple-matches/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/output-only-03-multiple-matches/Cargo.toml b/listings/ch12-an-io-project/output-only-03-multiple-matches/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-03-multiple-matches/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/output-only-03-multiple-matches/output.txt b/listings/ch12-an-io-project/output-only-03-multiple-matches/output.txt new file mode 100644 index 0000000..2b19bf9 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-03-multiple-matches/output.txt @@ -0,0 +1,7 @@ +$ cargo run body poem.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep body poem.txt` +I'm nobody! Who are you? +Are you nobody, too? +How dreary to be somebody! diff --git a/listings/ch12-an-io-project/output-only-03-multiple-matches/poem.txt b/listings/ch12-an-io-project/output-only-03-multiple-matches/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-03-multiple-matches/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/output-only-03-multiple-matches/src/lib.rs b/listings/ch12-an-io-project/output-only-03-multiple-matches/src/lib.rs new file mode 100644 index 0000000..c3c5ffe --- /dev/null +++ b/listings/ch12-an-io-project/output-only-03-multiple-matches/src/lib.rs @@ -0,0 +1,60 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +// ANCHOR: here +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + for line in search(&config.query, &contents) { + println!("{}", line); + } + + Ok(()) +} +// ANCHOR_END: here + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/output-only-03-multiple-matches/src/main.rs b/listings/ch12-an-io-project/output-only-03-multiple-matches/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/output-only-03-multiple-matches/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch12-an-io-project/output-only-04-no-matches/Cargo.lock b/listings/ch12-an-io-project/output-only-04-no-matches/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch12-an-io-project/output-only-04-no-matches/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch12-an-io-project/output-only-04-no-matches/Cargo.toml b/listings/ch12-an-io-project/output-only-04-no-matches/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-04-no-matches/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch12-an-io-project/output-only-04-no-matches/output.txt b/listings/ch12-an-io-project/output-only-04-no-matches/output.txt new file mode 100644 index 0000000..4cd6c8a --- /dev/null +++ b/listings/ch12-an-io-project/output-only-04-no-matches/output.txt @@ -0,0 +1,4 @@ +$ cargo run monomorphization poem.txt + Compiling minigrep v0.1.0 (file:///projects/minigrep) + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep monomorphization poem.txt` diff --git a/listings/ch12-an-io-project/output-only-04-no-matches/poem.txt b/listings/ch12-an-io-project/output-only-04-no-matches/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch12-an-io-project/output-only-04-no-matches/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch12-an-io-project/output-only-04-no-matches/src/lib.rs b/listings/ch12-an-io-project/output-only-04-no-matches/src/lib.rs new file mode 100644 index 0000000..c3c5ffe --- /dev/null +++ b/listings/ch12-an-io-project/output-only-04-no-matches/src/lib.rs @@ -0,0 +1,60 @@ +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + Ok(Config { query, filename }) + } +} + +// ANCHOR: here +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + for line in search(&config.query, &contents) { + println!("{}", line); + } + + Ok(()) +} +// ANCHOR_END: here + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn one_result() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } +} diff --git a/listings/ch12-an-io-project/output-only-04-no-matches/src/main.rs b/listings/ch12-an-io-project/output-only-04-no-matches/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch12-an-io-project/output-only-04-no-matches/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch13-functional-features/listing-12-23-reproduced/Cargo.lock b/listings/ch13-functional-features/listing-12-23-reproduced/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch13-functional-features/listing-12-23-reproduced/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-12-23-reproduced/Cargo.toml b/listings/ch13-functional-features/listing-12-23-reproduced/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch13-functional-features/listing-12-23-reproduced/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-12-23-reproduced/poem.txt b/listings/ch13-functional-features/listing-12-23-reproduced/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch13-functional-features/listing-12-23-reproduced/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch13-functional-features/listing-12-23-reproduced/src/lib.rs b/listings/ch13-functional-features/listing-12-23-reproduced/src/lib.rs new file mode 100644 index 0000000..7721acd --- /dev/null +++ b/listings/ch13-functional-features/listing-12-23-reproduced/src/lib.rs @@ -0,0 +1,106 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +// ANCHOR: ch13 +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} +// ANCHOR_END: ch13 + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch13-functional-features/listing-12-23-reproduced/src/main.rs b/listings/ch13-functional-features/listing-12-23-reproduced/src/main.rs new file mode 100644 index 0000000..53af83f --- /dev/null +++ b/listings/ch13-functional-features/listing-12-23-reproduced/src/main.rs @@ -0,0 +1,19 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + println!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + println!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch13-functional-features/listing-12-24-reproduced/Cargo.lock b/listings/ch13-functional-features/listing-12-24-reproduced/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch13-functional-features/listing-12-24-reproduced/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-12-24-reproduced/Cargo.toml b/listings/ch13-functional-features/listing-12-24-reproduced/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch13-functional-features/listing-12-24-reproduced/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-12-24-reproduced/poem.txt b/listings/ch13-functional-features/listing-12-24-reproduced/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch13-functional-features/listing-12-24-reproduced/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch13-functional-features/listing-12-24-reproduced/src/lib.rs b/listings/ch13-functional-features/listing-12-24-reproduced/src/lib.rs new file mode 100644 index 0000000..d0d0eb3 --- /dev/null +++ b/listings/ch13-functional-features/listing-12-24-reproduced/src/lib.rs @@ -0,0 +1,104 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch13-functional-features/listing-12-24-reproduced/src/main.rs b/listings/ch13-functional-features/listing-12-24-reproduced/src/main.rs new file mode 100644 index 0000000..ec27e67 --- /dev/null +++ b/listings/ch13-functional-features/listing-12-24-reproduced/src/main.rs @@ -0,0 +1,25 @@ +use std::env; +use std::process; + +use minigrep::Config; + +// ANCHOR: ch13 +fn main() { + let args: Vec = env::args().collect(); + + let config = Config::new(&args).unwrap_or_else(|err| { + eprintln!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + // --snip-- + // ANCHOR_END: ch13 + + if let Err(e) = minigrep::run(config) { + eprintln!("Application error: {}", e); + + process::exit(1); + } + // ANCHOR: ch13 +} +// ANCHOR_END: ch13 diff --git a/listings/ch13-functional-features/listing-13-01/Cargo.lock b/listings/ch13-functional-features/listing-13-01/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-01/Cargo.toml b/listings/ch13-functional-features/listing-13-01/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-01/src/main.rs b/listings/ch13-functional-features/listing-13-01/src/main.rs new file mode 100644 index 0000000..97eace0 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-01/src/main.rs @@ -0,0 +1,12 @@ +// ANCHOR: here +use std::thread; +use std::time::Duration; + +fn simulated_expensive_calculation(intensity: u32) -> u32 { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + intensity +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch13-functional-features/listing-13-02/Cargo.lock b/listings/ch13-functional-features/listing-13-02/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-02/Cargo.toml b/listings/ch13-functional-features/listing-13-02/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-02/src/main.rs b/listings/ch13-functional-features/listing-13-02/src/main.rs new file mode 100644 index 0000000..96d06c7 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-02/src/main.rs @@ -0,0 +1,19 @@ +use std::thread; +use std::time::Duration; + +fn simulated_expensive_calculation(intensity: u32) -> u32 { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + intensity +} + +fn generate_workout(intensity: u32, random_number: u32) {} + +// ANCHOR: here +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} +// ANCHOR_END: here diff --git a/listings/ch13-functional-features/listing-13-03/Cargo.lock b/listings/ch13-functional-features/listing-13-03/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-03/Cargo.toml b/listings/ch13-functional-features/listing-13-03/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-03/src/main.rs b/listings/ch13-functional-features/listing-13-03/src/main.rs new file mode 100644 index 0000000..d43c9b2 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-03/src/main.rs @@ -0,0 +1,39 @@ +use std::thread; +use std::time::Duration; + +fn simulated_expensive_calculation(intensity: u32) -> u32 { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + intensity +} + +// ANCHOR: here +fn generate_workout(intensity: u32, random_number: u32) { + if intensity < 25 { + println!( + "Today, do {} pushups!", + simulated_expensive_calculation(intensity) + ); + println!( + "Next, do {} situps!", + simulated_expensive_calculation(intensity) + ); + } else { + if random_number == 3 { + println!("Take a break today! Remember to stay hydrated!"); + } else { + println!( + "Today, run for {} minutes!", + simulated_expensive_calculation(intensity) + ); + } + } +} +// ANCHOR_END: here + +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} diff --git a/listings/ch13-functional-features/listing-13-04/Cargo.lock b/listings/ch13-functional-features/listing-13-04/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-04/Cargo.toml b/listings/ch13-functional-features/listing-13-04/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-04/src/main.rs b/listings/ch13-functional-features/listing-13-04/src/main.rs new file mode 100644 index 0000000..fabe0fb --- /dev/null +++ b/listings/ch13-functional-features/listing-13-04/src/main.rs @@ -0,0 +1,32 @@ +use std::thread; +use std::time::Duration; + +fn simulated_expensive_calculation(intensity: u32) -> u32 { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + intensity +} + +// ANCHOR: here +fn generate_workout(intensity: u32, random_number: u32) { + let expensive_result = simulated_expensive_calculation(intensity); + + if intensity < 25 { + println!("Today, do {} pushups!", expensive_result); + println!("Next, do {} situps!", expensive_result); + } else { + if random_number == 3 { + println!("Take a break today! Remember to stay hydrated!"); + } else { + println!("Today, run for {} minutes!", expensive_result); + } + } +} +// ANCHOR_END: here + +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} diff --git a/listings/ch13-functional-features/listing-13-05/Cargo.lock b/listings/ch13-functional-features/listing-13-05/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-05/Cargo.toml b/listings/ch13-functional-features/listing-13-05/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-05/src/main.rs b/listings/ch13-functional-features/listing-13-05/src/main.rs new file mode 100644 index 0000000..6984a27 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-05/src/main.rs @@ -0,0 +1,33 @@ +use std::thread; +use std::time::Duration; + +fn generate_workout(intensity: u32, random_number: u32) { + // ANCHOR: here + let expensive_closure = |num| { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + num + }; + // ANCHOR_END: here + + if intensity < 25 { + println!("Today, do {} pushups!", expensive_closure(intensity)); + println!("Next, do {} situps!", expensive_closure(intensity)); + } else { + if random_number == 3 { + println!("Take a break today! Remember to stay hydrated!"); + } else { + println!( + "Today, run for {} minutes!", + expensive_closure(intensity) + ); + } + } +} + +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} diff --git a/listings/ch13-functional-features/listing-13-06/Cargo.lock b/listings/ch13-functional-features/listing-13-06/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-06/Cargo.toml b/listings/ch13-functional-features/listing-13-06/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-06/src/main.rs b/listings/ch13-functional-features/listing-13-06/src/main.rs new file mode 100644 index 0000000..8850e58 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-06/src/main.rs @@ -0,0 +1,33 @@ +use std::thread; +use std::time::Duration; + +// ANCHOR: here +fn generate_workout(intensity: u32, random_number: u32) { + let expensive_closure = |num| { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + num + }; + + if intensity < 25 { + println!("Today, do {} pushups!", expensive_closure(intensity)); + println!("Next, do {} situps!", expensive_closure(intensity)); + } else { + if random_number == 3 { + println!("Take a break today! Remember to stay hydrated!"); + } else { + println!( + "Today, run for {} minutes!", + expensive_closure(intensity) + ); + } + } +} +// ANCHOR_END: here + +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} diff --git a/listings/ch13-functional-features/listing-13-07/Cargo.lock b/listings/ch13-functional-features/listing-13-07/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-07/Cargo.toml b/listings/ch13-functional-features/listing-13-07/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-07/src/main.rs b/listings/ch13-functional-features/listing-13-07/src/main.rs new file mode 100644 index 0000000..b3f4cc2 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-07/src/main.rs @@ -0,0 +1,33 @@ +use std::thread; +use std::time::Duration; + +fn generate_workout(intensity: u32, random_number: u32) { + // ANCHOR: here + let expensive_closure = |num: u32| -> u32 { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + num + }; + // ANCHOR_END: here + + if intensity < 25 { + println!("Today, do {} pushups!", expensive_closure(intensity)); + println!("Next, do {} situps!", expensive_closure(intensity)); + } else { + if random_number == 3 { + println!("Take a break today! Remember to stay hydrated!"); + } else { + println!( + "Today, run for {} minutes!", + expensive_closure(intensity) + ); + } + } +} + +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} diff --git a/listings/ch13-functional-features/listing-13-08/Cargo.lock b/listings/ch13-functional-features/listing-13-08/Cargo.lock new file mode 100644 index 0000000..c190d3a --- /dev/null +++ b/listings/ch13-functional-features/listing-13-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "closure-example" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-08/Cargo.toml b/listings/ch13-functional-features/listing-13-08/Cargo.toml new file mode 100644 index 0000000..54b904e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "closure-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-08/output.txt b/listings/ch13-functional-features/listing-13-08/output.txt new file mode 100644 index 0000000..a90814c --- /dev/null +++ b/listings/ch13-functional-features/listing-13-08/output.txt @@ -0,0 +1,17 @@ +$ cargo run + Compiling closure-example v0.1.0 (file:///projects/closure-example) +error[E0308]: mismatched types + --> src/main.rs:5:29 + | +5 | let n = example_closure(5); + | ^ + | | + | expected struct `String`, found integer + | help: try using a conversion method: `5.to_string()` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `closure-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch13-functional-features/listing-13-08/src/main.rs b/listings/ch13-functional-features/listing-13-08/src/main.rs new file mode 100644 index 0000000..ebb2489 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-08/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let example_closure = |x| x; + + let s = example_closure(String::from("hello")); + let n = example_closure(5); + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-09/Cargo.lock b/listings/ch13-functional-features/listing-13-09/Cargo.lock new file mode 100644 index 0000000..e090432 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cacher" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-09/Cargo.toml b/listings/ch13-functional-features/listing-13-09/Cargo.toml new file mode 100644 index 0000000..54ab6f2 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cacher" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-09/src/main.rs b/listings/ch13-functional-features/listing-13-09/src/main.rs new file mode 100644 index 0000000..3fd4ed0 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-09/src/main.rs @@ -0,0 +1,11 @@ +// ANCHOR: here +struct Cacher +where + T: Fn(u32) -> u32, +{ + calculation: T, + value: Option, +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch13-functional-features/listing-13-10/Cargo.lock b/listings/ch13-functional-features/listing-13-10/Cargo.lock new file mode 100644 index 0000000..e090432 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cacher" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-10/Cargo.toml b/listings/ch13-functional-features/listing-13-10/Cargo.toml new file mode 100644 index 0000000..54ab6f2 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cacher" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-10/src/main.rs b/listings/ch13-functional-features/listing-13-10/src/main.rs new file mode 100644 index 0000000..4d1034d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-10/src/main.rs @@ -0,0 +1,34 @@ +struct Cacher +where + T: Fn(u32) -> u32, +{ + calculation: T, + value: Option, +} + +// ANCHOR: here +impl Cacher +where + T: Fn(u32) -> u32, +{ + fn new(calculation: T) -> Cacher { + Cacher { + calculation, + value: None, + } + } + + fn value(&mut self, arg: u32) -> u32 { + match self.value { + Some(v) => v, + None => { + let v = (self.calculation)(arg); + self.value = Some(v); + v + } + } + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch13-functional-features/listing-13-11/Cargo.lock b/listings/ch13-functional-features/listing-13-11/Cargo.lock new file mode 100644 index 0000000..75ff09e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "workout-app" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-11/Cargo.toml b/listings/ch13-functional-features/listing-13-11/Cargo.toml new file mode 100644 index 0000000..8e64540 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "workout-app" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-11/src/main.rs b/listings/ch13-functional-features/listing-13-11/src/main.rs new file mode 100644 index 0000000..9f378b7 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-11/src/main.rs @@ -0,0 +1,64 @@ +use std::thread; +use std::time::Duration; + +struct Cacher +where + T: Fn(u32) -> u32, +{ + calculation: T, + value: Option, +} + +impl Cacher +where + T: Fn(u32) -> u32, +{ + fn new(calculation: T) -> Cacher { + Cacher { + calculation, + value: None, + } + } + + fn value(&mut self, arg: u32) -> u32 { + match self.value { + Some(v) => v, + None => { + let v = (self.calculation)(arg); + self.value = Some(v); + v + } + } + } +} + +// ANCHOR: here +fn generate_workout(intensity: u32, random_number: u32) { + let mut expensive_result = Cacher::new(|num| { + println!("calculating slowly..."); + thread::sleep(Duration::from_secs(2)); + num + }); + + if intensity < 25 { + println!("Today, do {} pushups!", expensive_result.value(intensity)); + println!("Next, do {} situps!", expensive_result.value(intensity)); + } else { + if random_number == 3 { + println!("Take a break today! Remember to stay hydrated!"); + } else { + println!( + "Today, run for {} minutes!", + expensive_result.value(intensity) + ); + } + } +} +// ANCHOR_END: here + +fn main() { + let simulated_user_specified_value = 10; + let simulated_random_number = 7; + + generate_workout(simulated_user_specified_value, simulated_random_number); +} diff --git a/listings/ch13-functional-features/listing-13-12/Cargo.lock b/listings/ch13-functional-features/listing-13-12/Cargo.lock new file mode 100644 index 0000000..a96532a --- /dev/null +++ b/listings/ch13-functional-features/listing-13-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "equal-to-x" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-12/Cargo.toml b/listings/ch13-functional-features/listing-13-12/Cargo.toml new file mode 100644 index 0000000..4fd5d85 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "equal-to-x" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-12/src/main.rs b/listings/ch13-functional-features/listing-13-12/src/main.rs new file mode 100644 index 0000000..7352b80 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-12/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let x = 4; + + let equal_to_x = |z| z == x; + + let y = 4; + + assert!(equal_to_x(y)); +} diff --git a/listings/ch13-functional-features/listing-13-13/Cargo.lock b/listings/ch13-functional-features/listing-13-13/Cargo.lock new file mode 100644 index 0000000..e91eaa8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "iterators" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-13/Cargo.toml b/listings/ch13-functional-features/listing-13-13/Cargo.toml new file mode 100644 index 0000000..015f951 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "iterators" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-13/src/main.rs b/listings/ch13-functional-features/listing-13-13/src/main.rs new file mode 100644 index 0000000..55a0dd3 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-13/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + let v1 = vec![1, 2, 3]; + + let v1_iter = v1.iter(); + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-14/Cargo.lock b/listings/ch13-functional-features/listing-13-14/Cargo.lock new file mode 100644 index 0000000..e91eaa8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "iterators" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-14/Cargo.toml b/listings/ch13-functional-features/listing-13-14/Cargo.toml new file mode 100644 index 0000000..015f951 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "iterators" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-14/src/main.rs b/listings/ch13-functional-features/listing-13-14/src/main.rs new file mode 100644 index 0000000..712aff4 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-14/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let v1 = vec![1, 2, 3]; + + let v1_iter = v1.iter(); + + for val in v1_iter { + println!("Got: {}", val); + } + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-15/Cargo.lock b/listings/ch13-functional-features/listing-13-15/Cargo.lock new file mode 100644 index 0000000..e91eaa8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "iterators" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-15/Cargo.toml b/listings/ch13-functional-features/listing-13-15/Cargo.toml new file mode 100644 index 0000000..015f951 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "iterators" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-15/src/lib.rs b/listings/ch13-functional-features/listing-13-15/src/lib.rs new file mode 100644 index 0000000..7582840 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-15/src/lib.rs @@ -0,0 +1,16 @@ +#[cfg(test)] +mod tests { + // ANCHOR: here + #[test] + fn iterator_demonstration() { + let v1 = vec![1, 2, 3]; + + let mut v1_iter = v1.iter(); + + assert_eq!(v1_iter.next(), Some(&1)); + assert_eq!(v1_iter.next(), Some(&2)); + assert_eq!(v1_iter.next(), Some(&3)); + assert_eq!(v1_iter.next(), None); + } + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-16/Cargo.lock b/listings/ch13-functional-features/listing-13-16/Cargo.lock new file mode 100644 index 0000000..e91eaa8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "iterators" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-16/Cargo.toml b/listings/ch13-functional-features/listing-13-16/Cargo.toml new file mode 100644 index 0000000..015f951 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "iterators" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-16/src/lib.rs b/listings/ch13-functional-features/listing-13-16/src/lib.rs new file mode 100644 index 0000000..d1cb54d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-16/src/lib.rs @@ -0,0 +1,15 @@ +#[cfg(test)] +mod tests { + // ANCHOR: here + #[test] + fn iterator_sum() { + let v1 = vec![1, 2, 3]; + + let v1_iter = v1.iter(); + + let total: i32 = v1_iter.sum(); + + assert_eq!(total, 6); + } + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-17/Cargo.lock b/listings/ch13-functional-features/listing-13-17/Cargo.lock new file mode 100644 index 0000000..e91eaa8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "iterators" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-17/Cargo.toml b/listings/ch13-functional-features/listing-13-17/Cargo.toml new file mode 100644 index 0000000..015f951 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "iterators" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-17/output.txt b/listings/ch13-functional-features/listing-13-17/output.txt new file mode 100644 index 0000000..67f0557 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-17/output.txt @@ -0,0 +1,15 @@ +$ cargo run + Compiling iterators v0.1.0 (file:///projects/iterators) +warning: unused `Map` that must be used + --> src/main.rs:4:5 + | +4 | v1.iter().map(|x| x + 1); + | ^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: `#[warn(unused_must_use)]` on by default + = note: iterators are lazy and do nothing unless consumed + +warning: 1 warning emitted + + Finished dev [unoptimized + debuginfo] target(s) in 0.47s + Running `target/debug/iterators` diff --git a/listings/ch13-functional-features/listing-13-17/src/main.rs b/listings/ch13-functional-features/listing-13-17/src/main.rs new file mode 100644 index 0000000..62a68be --- /dev/null +++ b/listings/ch13-functional-features/listing-13-17/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + let v1: Vec = vec![1, 2, 3]; + + v1.iter().map(|x| x + 1); + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-18/Cargo.lock b/listings/ch13-functional-features/listing-13-18/Cargo.lock new file mode 100644 index 0000000..e91eaa8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "iterators" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-18/Cargo.toml b/listings/ch13-functional-features/listing-13-18/Cargo.toml new file mode 100644 index 0000000..015f951 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "iterators" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-18/src/main.rs b/listings/ch13-functional-features/listing-13-18/src/main.rs new file mode 100644 index 0000000..db9025d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-18/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + let v1: Vec = vec![1, 2, 3]; + + let v2: Vec<_> = v1.iter().map(|x| x + 1).collect(); + + assert_eq!(v2, vec![2, 3, 4]); + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-19/Cargo.lock b/listings/ch13-functional-features/listing-13-19/Cargo.lock new file mode 100644 index 0000000..0b15e21 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "shoe_size" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-19/Cargo.toml b/listings/ch13-functional-features/listing-13-19/Cargo.toml new file mode 100644 index 0000000..d0ecdac --- /dev/null +++ b/listings/ch13-functional-features/listing-13-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "shoe_size" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-19/src/lib.rs b/listings/ch13-functional-features/listing-13-19/src/lib.rs new file mode 100644 index 0000000..281c3c9 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-19/src/lib.rs @@ -0,0 +1,48 @@ +#[derive(PartialEq, Debug)] +struct Shoe { + size: u32, + style: String, +} + +fn shoes_in_size(shoes: Vec, shoe_size: u32) -> Vec { + shoes.into_iter().filter(|s| s.size == shoe_size).collect() +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn filters_by_size() { + let shoes = vec![ + Shoe { + size: 10, + style: String::from("sneaker"), + }, + Shoe { + size: 13, + style: String::from("sandal"), + }, + Shoe { + size: 10, + style: String::from("boot"), + }, + ]; + + let in_my_size = shoes_in_size(shoes, 10); + + assert_eq!( + in_my_size, + vec![ + Shoe { + size: 10, + style: String::from("sneaker") + }, + Shoe { + size: 10, + style: String::from("boot") + }, + ] + ); + } +} diff --git a/listings/ch13-functional-features/listing-13-20/Cargo.lock b/listings/ch13-functional-features/listing-13-20/Cargo.lock new file mode 100644 index 0000000..58b70c5 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "counter" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-20/Cargo.toml b/listings/ch13-functional-features/listing-13-20/Cargo.toml new file mode 100644 index 0000000..4eb29e8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "counter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-20/src/lib.rs b/listings/ch13-functional-features/listing-13-20/src/lib.rs new file mode 100644 index 0000000..fb8a0cb --- /dev/null +++ b/listings/ch13-functional-features/listing-13-20/src/lib.rs @@ -0,0 +1,9 @@ +struct Counter { + count: u32, +} + +impl Counter { + fn new() -> Counter { + Counter { count: 0 } + } +} diff --git a/listings/ch13-functional-features/listing-13-21/Cargo.lock b/listings/ch13-functional-features/listing-13-21/Cargo.lock new file mode 100644 index 0000000..58b70c5 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "counter" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-21/Cargo.toml b/listings/ch13-functional-features/listing-13-21/Cargo.toml new file mode 100644 index 0000000..4eb29e8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "counter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-21/src/lib.rs b/listings/ch13-functional-features/listing-13-21/src/lib.rs new file mode 100644 index 0000000..35ea8e5 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-21/src/lib.rs @@ -0,0 +1,24 @@ +struct Counter { + count: u32, +} + +impl Counter { + fn new() -> Counter { + Counter { count: 0 } + } +} + +// ANCHOR: here +impl Iterator for Counter { + type Item = u32; + + fn next(&mut self) -> Option { + if self.count < 5 { + self.count += 1; + Some(self.count) + } else { + None + } + } +} +// ANCHOR_END: here diff --git a/listings/ch13-functional-features/listing-13-22/Cargo.lock b/listings/ch13-functional-features/listing-13-22/Cargo.lock new file mode 100644 index 0000000..58b70c5 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "counter" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-22/Cargo.toml b/listings/ch13-functional-features/listing-13-22/Cargo.toml new file mode 100644 index 0000000..4eb29e8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "counter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-22/src/lib.rs b/listings/ch13-functional-features/listing-13-22/src/lib.rs new file mode 100644 index 0000000..05afa41 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-22/src/lib.rs @@ -0,0 +1,41 @@ +struct Counter { + count: u32, +} + +impl Counter { + fn new() -> Counter { + Counter { count: 0 } + } +} + +impl Iterator for Counter { + type Item = u32; + + fn next(&mut self) -> Option { + if self.count < 5 { + self.count += 1; + Some(self.count) + } else { + None + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + // ANCHOR: here + #[test] + fn calling_next_directly() { + let mut counter = Counter::new(); + + assert_eq!(counter.next(), Some(1)); + assert_eq!(counter.next(), Some(2)); + assert_eq!(counter.next(), Some(3)); + assert_eq!(counter.next(), Some(4)); + assert_eq!(counter.next(), Some(5)); + assert_eq!(counter.next(), None); + } + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-23/Cargo.lock b/listings/ch13-functional-features/listing-13-23/Cargo.lock new file mode 100644 index 0000000..58b70c5 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "counter" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-23/Cargo.toml b/listings/ch13-functional-features/listing-13-23/Cargo.toml new file mode 100644 index 0000000..4eb29e8 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "counter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-23/src/lib.rs b/listings/ch13-functional-features/listing-13-23/src/lib.rs new file mode 100644 index 0000000..f04d730 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-23/src/lib.rs @@ -0,0 +1,51 @@ +struct Counter { + count: u32, +} + +impl Counter { + fn new() -> Counter { + Counter { count: 0 } + } +} + +impl Iterator for Counter { + type Item = u32; + + fn next(&mut self) -> Option { + if self.count < 5 { + self.count += 1; + Some(self.count) + } else { + None + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn calling_next_directly() { + let mut counter = Counter::new(); + + assert_eq!(counter.next(), Some(1)); + assert_eq!(counter.next(), Some(2)); + assert_eq!(counter.next(), Some(3)); + assert_eq!(counter.next(), Some(4)); + assert_eq!(counter.next(), Some(5)); + assert_eq!(counter.next(), None); + } + + // ANCHOR: here + #[test] + fn using_other_iterator_trait_methods() { + let sum: u32 = Counter::new() + .zip(Counter::new().skip(1)) + .map(|(a, b)| a * b) + .filter(|x| x % 3 == 0) + .sum(); + assert_eq!(18, sum); + } + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/listing-13-25/Cargo.lock b/listings/ch13-functional-features/listing-13-25/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-25/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-25/Cargo.toml b/listings/ch13-functional-features/listing-13-25/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-25/poem.txt b/listings/ch13-functional-features/listing-13-25/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-25/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch13-functional-features/listing-13-25/src/lib.rs b/listings/ch13-functional-features/listing-13-25/src/lib.rs new file mode 100644 index 0000000..d0d0eb3 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-25/src/lib.rs @@ -0,0 +1,104 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +impl Config { + pub fn new(args: &[String]) -> Result { + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch13-functional-features/listing-13-25/src/main.rs b/listings/ch13-functional-features/listing-13-25/src/main.rs new file mode 100644 index 0000000..d09966e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-25/src/main.rs @@ -0,0 +1,23 @@ +use std::env; +use std::process; + +use minigrep::Config; + +// ANCHOR: here +fn main() { + let config = Config::new(env::args()).unwrap_or_else(|err| { + eprintln!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + // --snip-- + // ANCHOR_END: here + + if let Err(e) = minigrep::run(config) { + eprintln!("Application error: {}", e); + + process::exit(1); + } + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch13-functional-features/listing-13-26/Cargo.lock b/listings/ch13-functional-features/listing-13-26/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-26/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-26/Cargo.toml b/listings/ch13-functional-features/listing-13-26/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-26/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-26/poem.txt b/listings/ch13-functional-features/listing-13-26/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-26/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch13-functional-features/listing-13-26/src/lib.rs b/listings/ch13-functional-features/listing-13-26/src/lib.rs new file mode 100644 index 0000000..2cb0bea --- /dev/null +++ b/listings/ch13-functional-features/listing-13-26/src/lib.rs @@ -0,0 +1,107 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +// ANCHOR: here +impl Config { + pub fn new(mut args: env::Args) -> Result { + // --snip-- + // ANCHOR_END: here + if args.len() < 3 { + return Err("not enough arguments"); + } + + let query = args[1].clone(); + let filename = args[2].clone(); + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch13-functional-features/listing-13-26/src/main.rs b/listings/ch13-functional-features/listing-13-26/src/main.rs new file mode 100644 index 0000000..06aac30 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-26/src/main.rs @@ -0,0 +1,17 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let config = Config::new(env::args()).unwrap_or_else(|err| { + eprintln!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + eprintln!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch13-functional-features/listing-13-27/Cargo.lock b/listings/ch13-functional-features/listing-13-27/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-27/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-27/Cargo.toml b/listings/ch13-functional-features/listing-13-27/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-27/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-27/poem.txt b/listings/ch13-functional-features/listing-13-27/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-27/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch13-functional-features/listing-13-27/src/lib.rs b/listings/ch13-functional-features/listing-13-27/src/lib.rs new file mode 100644 index 0000000..7a33565 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-27/src/lib.rs @@ -0,0 +1,111 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +// ANCHOR: here +impl Config { + pub fn new(mut args: env::Args) -> Result { + args.next(); + + let query = match args.next() { + Some(arg) => arg, + None => return Err("Didn't get a query string"), + }; + + let filename = match args.next() { + Some(arg) => arg, + None => return Err("Didn't get a file name"), + }; + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} +// ANCHOR_END: here + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + let mut results = Vec::new(); + + for line in contents.lines() { + if line.contains(query) { + results.push(line); + } + } + + results +} + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch13-functional-features/listing-13-27/src/main.rs b/listings/ch13-functional-features/listing-13-27/src/main.rs new file mode 100644 index 0000000..06aac30 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-27/src/main.rs @@ -0,0 +1,17 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let config = Config::new(env::args()).unwrap_or_else(|err| { + eprintln!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + eprintln!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch13-functional-features/listing-13-29/Cargo.lock b/listings/ch13-functional-features/listing-13-29/Cargo.lock new file mode 100644 index 0000000..88bf82d --- /dev/null +++ b/listings/ch13-functional-features/listing-13-29/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "minigrep" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/listing-13-29/Cargo.toml b/listings/ch13-functional-features/listing-13-29/Cargo.toml new file mode 100644 index 0000000..8260642 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-29/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "minigrep" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/listing-13-29/poem.txt b/listings/ch13-functional-features/listing-13-29/poem.txt new file mode 100644 index 0000000..8707527 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-29/poem.txt @@ -0,0 +1,9 @@ +I'm nobody! Who are you? +Are you nobody, too? +Then there's a pair of us - don't tell! +They'd banish us, you know. + +How dreary to be somebody! +How public, like a frog +To tell your name the livelong day +To an admiring bog! diff --git a/listings/ch13-functional-features/listing-13-29/src/lib.rs b/listings/ch13-functional-features/listing-13-29/src/lib.rs new file mode 100644 index 0000000..bc8a77e --- /dev/null +++ b/listings/ch13-functional-features/listing-13-29/src/lib.rs @@ -0,0 +1,106 @@ +use std::env; +use std::error::Error; +use std::fs; + +pub struct Config { + pub query: String, + pub filename: String, + pub case_sensitive: bool, +} + +impl Config { + pub fn new(mut args: std::env::Args) -> Result { + args.next(); + + let query = match args.next() { + Some(arg) => arg, + None => return Err("Didn't get a query string"), + }; + + let filename = match args.next() { + Some(arg) => arg, + None => return Err("Didn't get a file name"), + }; + + let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); + + Ok(Config { + query, + filename, + case_sensitive, + }) + } +} + +pub fn run(config: Config) -> Result<(), Box> { + let contents = fs::read_to_string(config.filename)?; + + let results = if config.case_sensitive { + search(&config.query, &contents) + } else { + search_case_insensitive(&config.query, &contents) + }; + + for line in results { + println!("{}", line); + } + + Ok(()) +} + +// ANCHOR: here +pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> { + contents + .lines() + .filter(|line| line.contains(query)) + .collect() +} +// ANCHOR_END: here + +pub fn search_case_insensitive<'a>( + query: &str, + contents: &'a str, +) -> Vec<&'a str> { + let query = query.to_lowercase(); + let mut results = Vec::new(); + + for line in contents.lines() { + if line.to_lowercase().contains(&query) { + results.push(line); + } + } + + results +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn case_sensitive() { + let query = "duct"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Duct tape."; + + assert_eq!(vec!["safe, fast, productive."], search(query, contents)); + } + + #[test] + fn case_insensitive() { + let query = "rUsT"; + let contents = "\ +Rust: +safe, fast, productive. +Pick three. +Trust me."; + + assert_eq!( + vec!["Rust:", "Trust me."], + search_case_insensitive(query, contents) + ); + } +} diff --git a/listings/ch13-functional-features/listing-13-29/src/main.rs b/listings/ch13-functional-features/listing-13-29/src/main.rs new file mode 100644 index 0000000..06aac30 --- /dev/null +++ b/listings/ch13-functional-features/listing-13-29/src/main.rs @@ -0,0 +1,17 @@ +use std::env; +use std::process; + +use minigrep::Config; + +fn main() { + let config = Config::new(env::args()).unwrap_or_else(|err| { + eprintln!("Problem parsing arguments: {}", err); + process::exit(1); + }); + + if let Err(e) = minigrep::run(config) { + eprintln!("Application error: {}", e); + + process::exit(1); + } +} diff --git a/listings/ch13-functional-features/no-listing-01-failing-cacher-test/Cargo.lock b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/Cargo.lock new file mode 100644 index 0000000..e090432 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cacher" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/no-listing-01-failing-cacher-test/Cargo.toml b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/Cargo.toml new file mode 100644 index 0000000..54ab6f2 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cacher" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/no-listing-01-failing-cacher-test/output.txt b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/output.txt new file mode 100644 index 0000000..33437ab --- /dev/null +++ b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/output.txt @@ -0,0 +1,23 @@ +$ cargo test + Compiling cacher v0.1.0 (file:///projects/cacher) + Finished test [unoptimized + debuginfo] target(s) in 0.72s + Running target/debug/deps/cacher-4116485fb32b3fff + +running 1 test +test tests::call_with_different_values ... FAILED + +failures: + +---- tests::call_with_different_values stdout ---- +thread 'main' panicked at 'assertion failed: `(left == right)` + left: `1`, + right: `2`', src/lib.rs:43:9 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::call_with_different_values + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch13-functional-features/no-listing-01-failing-cacher-test/src/lib.rs b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/src/lib.rs new file mode 100644 index 0000000..e7d677d --- /dev/null +++ b/listings/ch13-functional-features/no-listing-01-failing-cacher-test/src/lib.rs @@ -0,0 +1,47 @@ +struct Cacher +where + T: Fn(u32) -> u32, +{ + calculation: T, + value: Option, +} + +impl Cacher +where + T: Fn(u32) -> u32, +{ + fn new(calculation: T) -> Cacher { + Cacher { + calculation, + value: None, + } + } + + fn value(&mut self, arg: u32) -> u32 { + match self.value { + Some(v) => v, + None => { + let v = (self.calculation)(arg); + self.value = Some(v); + v + } + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + // ANCHOR: here + #[test] + fn call_with_different_values() { + let mut c = Cacher::new(|a| a); + + let v1 = c.value(1); + let v2 = c.value(2); + + assert_eq!(v2, 2); + } + // ANCHOR_END: here +} diff --git a/listings/ch13-functional-features/no-listing-02-functions-cant-capture/Cargo.lock b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/Cargo.lock new file mode 100644 index 0000000..a96532a --- /dev/null +++ b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "equal-to-x" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/no-listing-02-functions-cant-capture/Cargo.toml b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/Cargo.toml new file mode 100644 index 0000000..4fd5d85 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "equal-to-x" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/no-listing-02-functions-cant-capture/output.txt b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/output.txt new file mode 100644 index 0000000..8fa9df0 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling equal-to-x v0.1.0 (file:///projects/equal-to-x) +error[E0434]: can't capture dynamic environment in a fn item + --> src/main.rs:5:14 + | +5 | z == x + | ^ + | + = help: use the `|| { ... }` closure form instead + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0434`. +error: could not compile `equal-to-x` + +To learn more, run the command again with --verbose. diff --git a/listings/ch13-functional-features/no-listing-02-functions-cant-capture/src/main.rs b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/src/main.rs new file mode 100644 index 0000000..1b5d2b9 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-02-functions-cant-capture/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + let x = 4; + + fn equal_to_x(z: i32) -> bool { + z == x + } + + let y = 4; + + assert!(equal_to_x(y)); +} diff --git a/listings/ch13-functional-features/no-listing-03-move-closures/Cargo.lock b/listings/ch13-functional-features/no-listing-03-move-closures/Cargo.lock new file mode 100644 index 0000000..a96532a --- /dev/null +++ b/listings/ch13-functional-features/no-listing-03-move-closures/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "equal-to-x" +version = "0.1.0" + diff --git a/listings/ch13-functional-features/no-listing-03-move-closures/Cargo.toml b/listings/ch13-functional-features/no-listing-03-move-closures/Cargo.toml new file mode 100644 index 0000000..4fd5d85 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-03-move-closures/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "equal-to-x" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch13-functional-features/no-listing-03-move-closures/output.txt b/listings/ch13-functional-features/no-listing-03-move-closures/output.txt new file mode 100644 index 0000000..3ca1901 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-03-move-closures/output.txt @@ -0,0 +1,22 @@ +$ cargo run + Compiling equal-to-x v0.1.0 (file:///projects/equal-to-x) +error[E0382]: borrow of moved value: `x` + --> src/main.rs:6:40 + | +2 | let x = vec![1, 2, 3]; + | - move occurs because `x` has type `Vec`, which does not implement the `Copy` trait +3 | +4 | let equal_to_x = move |z| z == x; + | -------- - variable moved due to use in closure + | | + | value moved into closure here +5 | +6 | println!("can't use x here: {:?}", x); + | ^ value borrowed here after move + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `equal-to-x` + +To learn more, run the command again with --verbose. diff --git a/listings/ch13-functional-features/no-listing-03-move-closures/src/main.rs b/listings/ch13-functional-features/no-listing-03-move-closures/src/main.rs new file mode 100644 index 0000000..19d4776 --- /dev/null +++ b/listings/ch13-functional-features/no-listing-03-move-closures/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + let x = vec![1, 2, 3]; + + let equal_to_x = move |z| z == x; + + println!("can't use x here: {:?}", x); + + let y = vec![1, 2, 3]; + + assert!(equal_to_x(y)); +} diff --git a/listings/ch14-more-about-cargo/listing-14-01/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-01/Cargo.lock new file mode 100644 index 0000000..b304dd7 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "my_crate" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/listing-14-01/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-01/Cargo.toml new file mode 100644 index 0000000..716953a --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "my_crate" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-01/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-01/src/lib.rs new file mode 100644 index 0000000..ed7abb7 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-01/src/lib.rs @@ -0,0 +1,13 @@ +/// Adds one to the number given. +/// +/// # Examples +/// +/// ``` +/// let arg = 5; +/// let answer = my_crate::add_one(arg); +/// +/// assert_eq!(6, answer); +/// ``` +pub fn add_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch14-more-about-cargo/listing-14-02/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-02/Cargo.lock new file mode 100644 index 0000000..b304dd7 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "my_crate" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/listing-14-02/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-02/Cargo.toml new file mode 100644 index 0000000..716953a --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "my_crate" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-02/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-02/src/lib.rs new file mode 100644 index 0000000..64c9c43 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-02/src/lib.rs @@ -0,0 +1,21 @@ +// ANCHOR: here +//! # My Crate +//! +//! `my_crate` is a collection of utilities to make performing certain +//! calculations more convenient. + +/// Adds one to the number given. +// --snip-- +// ANCHOR_END: here +/// +/// # Examples +/// +/// ``` +/// let arg = 5; +/// let answer = my_crate::add_one(arg); +/// +/// assert_eq!(6, answer); +/// ``` +pub fn add_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch14-more-about-cargo/listing-14-03/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-03/Cargo.lock new file mode 100644 index 0000000..df19c24 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "art" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/listing-14-03/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-03/Cargo.toml new file mode 100644 index 0000000..a2e9e36 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "art" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-03/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-03/src/lib.rs new file mode 100644 index 0000000..09c043b --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-03/src/lib.rs @@ -0,0 +1,32 @@ +//! # Art +//! +//! A library for modeling artistic concepts. + +pub mod kinds { + /// The primary colors according to the RYB color model. + pub enum PrimaryColor { + Red, + Yellow, + Blue, + } + + /// The secondary colors according to the RYB color model. + pub enum SecondaryColor { + Orange, + Green, + Purple, + } +} + +pub mod utils { + use crate::kinds::*; + + /// Combines two primary colors in equal amounts to create + /// a secondary color. + pub fn mix(c1: PrimaryColor, c2: PrimaryColor) -> SecondaryColor { + // --snip-- + // ANCHOR_END: here + SecondaryColor::Orange + // ANCHOR: here + } +} diff --git a/listings/ch14-more-about-cargo/listing-14-04/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-04/Cargo.lock new file mode 100644 index 0000000..df19c24 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "art" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/listing-14-04/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-04/Cargo.toml new file mode 100644 index 0000000..a2e9e36 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "art" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-04/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-04/src/lib.rs new file mode 100644 index 0000000..b077a9a --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-04/src/lib.rs @@ -0,0 +1,29 @@ +//! # Art +//! +//! A library for modeling artistic concepts. + +pub mod kinds { + /// The primary colors according to the RYB color model. + pub enum PrimaryColor { + Red, + Yellow, + Blue, + } + + /// The secondary colors according to the RYB color model. + pub enum SecondaryColor { + Orange, + Green, + Purple, + } +} + +pub mod utils { + use crate::kinds::*; + + /// Combines two primary colors in equal amounts to create + /// a secondary color. + pub fn mix(c1: PrimaryColor, c2: PrimaryColor) -> SecondaryColor { + SecondaryColor::Orange + } +} diff --git a/listings/ch14-more-about-cargo/listing-14-04/src/main.rs b/listings/ch14-more-about-cargo/listing-14-04/src/main.rs new file mode 100644 index 0000000..b1a4bf7 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-04/src/main.rs @@ -0,0 +1,8 @@ +use art::kinds::PrimaryColor; +use art::utils::mix; + +fn main() { + let red = PrimaryColor::Red; + let yellow = PrimaryColor::Yellow; + mix(red, yellow); +} diff --git a/listings/ch14-more-about-cargo/listing-14-05/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-05/Cargo.lock new file mode 100644 index 0000000..df19c24 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "art" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/listing-14-05/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-05/Cargo.toml new file mode 100644 index 0000000..a2e9e36 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "art" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-05/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-05/src/lib.rs new file mode 100644 index 0000000..c5aa9e7 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-05/src/lib.rs @@ -0,0 +1,41 @@ +// ANCHOR: here +//! # Art +//! +//! A library for modeling artistic concepts. + +pub use self::kinds::PrimaryColor; +pub use self::kinds::SecondaryColor; +pub use self::utils::mix; + +pub mod kinds { + // --snip-- + // ANCHOR_END: here + /// The primary colors according to the RYB color model. + pub enum PrimaryColor { + Red, + Yellow, + Blue, + } + + /// The secondary colors according to the RYB color model. + pub enum SecondaryColor { + Orange, + Green, + Purple, + } + // ANCHOR: here +} + +pub mod utils { + // --snip-- + // ANCHOR_END: here + use crate::kinds::*; + + /// Combines two primary colors in equal amounts to create + /// a secondary color. + pub fn mix(c1: PrimaryColor, c2: PrimaryColor) -> SecondaryColor { + SecondaryColor::Orange + } + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch14-more-about-cargo/listing-14-06/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-06/Cargo.lock new file mode 100644 index 0000000..df19c24 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "art" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/listing-14-06/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-06/Cargo.toml new file mode 100644 index 0000000..a2e9e36 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "art" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-06/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-06/src/lib.rs new file mode 100644 index 0000000..daabd00 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-06/src/lib.rs @@ -0,0 +1,33 @@ +//! # Art +//! +//! A library for modeling artistic concepts. + +pub use self::kinds::PrimaryColor; +pub use self::kinds::SecondaryColor; +pub use self::utils::mix; + +pub mod kinds { + /// The primary colors according to the RYB color model. + pub enum PrimaryColor { + Red, + Yellow, + Blue, + } + + /// The secondary colors according to the RYB color model. + pub enum SecondaryColor { + Orange, + Green, + Purple, + } +} + +pub mod utils { + use crate::kinds::*; + + /// Combines two primary colors in equal amounts to create + /// a secondary color. + pub fn mix(c1: PrimaryColor, c2: PrimaryColor) -> SecondaryColor { + SecondaryColor::Orange + } +} diff --git a/listings/ch14-more-about-cargo/listing-14-06/src/main.rs b/listings/ch14-more-about-cargo/listing-14-06/src/main.rs new file mode 100644 index 0000000..51f3b76 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-06/src/main.rs @@ -0,0 +1,13 @@ +// ANCHOR: here +use art::mix; +use art::PrimaryColor; + +fn main() { + // --snip-- + // ANCHOR_END: here + let red = PrimaryColor::Red; + let yellow = PrimaryColor::Yellow; + mix(red, yellow); + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch14-more-about-cargo/listing-14-07/add/Cargo.lock b/listings/ch14-more-about-cargo/listing-14-07/add/Cargo.lock new file mode 100644 index 0000000..77292f6 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-07/add/Cargo.lock @@ -0,0 +1,13 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "add-one" +version = "0.1.0" + +[[package]] +name = "adder" +version = "0.1.0" +dependencies = [ + "add-one 0.1.0", +] + diff --git a/listings/ch14-more-about-cargo/listing-14-07/add/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-07/add/Cargo.toml new file mode 100644 index 0000000..d26e7cf --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-07/add/Cargo.toml @@ -0,0 +1,6 @@ +[workspace] + +members = [ + "adder", + "add-one", +] diff --git a/listings/ch14-more-about-cargo/listing-14-07/add/add-one/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-07/add/add-one/Cargo.toml new file mode 100644 index 0000000..8260fb5 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-07/add/add-one/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "add-one" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/listing-14-07/add/add-one/src/lib.rs b/listings/ch14-more-about-cargo/listing-14-07/add/add-one/src/lib.rs new file mode 100644 index 0000000..b0bb869 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-07/add/add-one/src/lib.rs @@ -0,0 +1,3 @@ +pub fn add_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch14-more-about-cargo/listing-14-07/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/listing-14-07/add/adder/Cargo.toml new file mode 100644 index 0000000..e73f1be --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-07/add/adder/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] + +add-one = { path = "../add-one" } diff --git a/listings/ch14-more-about-cargo/listing-14-07/add/adder/src/main.rs b/listings/ch14-more-about-cargo/listing-14-07/add/adder/src/main.rs new file mode 100644 index 0000000..7deb796 --- /dev/null +++ b/listings/ch14-more-about-cargo/listing-14-07/add/adder/src/main.rs @@ -0,0 +1,10 @@ +use add_one; + +fn main() { + let num = 10; + println!( + "Hello, world! {} plus one is {}!", + num, + add_one::add_one(num) + ); +} diff --git a/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.lock b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.lock new file mode 100644 index 0000000..d37189b --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" + diff --git a/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.toml new file mode 100644 index 0000000..c5ea8e5 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.toml @@ -0,0 +1,5 @@ +[workspace] + +members = [ + "adder", +] diff --git a/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/adder/Cargo.toml new file mode 100644 index 0000000..0e3940c --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/adder/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/adder/src/main.rs b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/adder/src/main.rs new file mode 100644 index 0000000..e7a11a9 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/adder/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + println!("Hello, world!"); +} diff --git a/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.lock b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.lock new file mode 100644 index 0000000..77292f6 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.lock @@ -0,0 +1,13 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "add-one" +version = "0.1.0" + +[[package]] +name = "adder" +version = "0.1.0" +dependencies = [ + "add-one 0.1.0", +] + diff --git a/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.toml new file mode 100644 index 0000000..d26e7cf --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.toml @@ -0,0 +1,6 @@ +[workspace] + +members = [ + "adder", + "add-one", +] diff --git a/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/Cargo.toml new file mode 100644 index 0000000..8260fb5 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "add-one" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/src/lib.rs b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/src/lib.rs new file mode 100644 index 0000000..b0bb869 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/src/lib.rs @@ -0,0 +1,3 @@ +pub fn add_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/Cargo.toml new file mode 100644 index 0000000..e73f1be --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] + +add-one = { path = "../add-one" } diff --git a/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/src/main.rs b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/src/main.rs new file mode 100644 index 0000000..e7a11a9 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + println!("Hello, world!"); +} diff --git a/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/Cargo.lock b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/Cargo.lock new file mode 100644 index 0000000..28663ec --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/Cargo.lock @@ -0,0 +1,90 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "add-one" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "adder" +version = "0.1.0" +dependencies = [ + "add-one", +] + +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/Cargo.toml new file mode 100644 index 0000000..d26e7cf --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/Cargo.toml @@ -0,0 +1,6 @@ +[workspace] + +members = [ + "adder", + "add-one", +] diff --git a/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/Cargo.toml new file mode 100644 index 0000000..3b0bb1a --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "add-one" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/src/lib.rs b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/src/lib.rs new file mode 100644 index 0000000..7b61b40 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/src/lib.rs @@ -0,0 +1,5 @@ +use rand; + +pub fn add_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/adder/Cargo.toml new file mode 100644 index 0000000..e73f1be --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/adder/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] + +add-one = { path = "../add-one" } diff --git a/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/adder/src/main.rs b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/adder/src/main.rs new file mode 100644 index 0000000..7deb796 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/adder/src/main.rs @@ -0,0 +1,10 @@ +use add_one; + +fn main() { + let num = 10; + println!( + "Hello, world! {} plus one is {}!", + num, + add_one::add_one(num) + ); +} diff --git a/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/Cargo.lock b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/Cargo.lock new file mode 100644 index 0000000..77292f6 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/Cargo.lock @@ -0,0 +1,13 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "add-one" +version = "0.1.0" + +[[package]] +name = "adder" +version = "0.1.0" +dependencies = [ + "add-one 0.1.0", +] + diff --git a/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/Cargo.toml new file mode 100644 index 0000000..d26e7cf --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/Cargo.toml @@ -0,0 +1,6 @@ +[workspace] + +members = [ + "adder", + "add-one", +] diff --git a/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/Cargo.toml new file mode 100644 index 0000000..8260fb5 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "add-one" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/src/lib.rs b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/src/lib.rs new file mode 100644 index 0000000..40ceb12 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/src/lib.rs @@ -0,0 +1,13 @@ +pub fn add_one(x: i32) -> i32 { + x + 1 +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn it_works() { + assert_eq!(3, add_one(2)); + } +} diff --git a/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/adder/Cargo.toml new file mode 100644 index 0000000..e73f1be --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/adder/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] + +add-one = { path = "../add-one" } diff --git a/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/adder/src/main.rs b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/adder/src/main.rs new file mode 100644 index 0000000..7deb796 --- /dev/null +++ b/listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/adder/src/main.rs @@ -0,0 +1,10 @@ +use add_one; + +fn main() { + let num = 10; + println!( + "Hello, world! {} plus one is {}!", + num, + add_one::add_one(num) + ); +} diff --git a/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/.gitignore b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/.gitignore new file mode 100644 index 0000000..b46d5c4 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/.gitignore @@ -0,0 +1 @@ +adder diff --git a/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/Cargo.lock b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/Cargo.lock new file mode 100644 index 0000000..d98623d --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/Cargo.lock @@ -0,0 +1,5 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "adder" +version = "0.1.0" diff --git a/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/Cargo.toml b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/Cargo.toml new file mode 100644 index 0000000..c5ea8e5 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/Cargo.toml @@ -0,0 +1,5 @@ +[workspace] + +members = [ + "adder", +] diff --git a/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/rustfmt-ignore b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/rustfmt-ignore new file mode 100644 index 0000000..958e568 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-01-adder-crate/add/rustfmt-ignore @@ -0,0 +1,2 @@ +This listing is used for demonstrating how to set up a workspace, but the workspace isn't +completely set up yet, so rustfmt complains the crate mentioned in Cargo.toml doesn't exist yet. diff --git a/listings/ch14-more-about-cargo/output-only-02-add-one/add/.gitignore b/listings/ch14-more-about-cargo/output-only-02-add-one/add/.gitignore new file mode 100644 index 0000000..64904e0 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-02-add-one/add/.gitignore @@ -0,0 +1 @@ +add-one diff --git a/listings/ch14-more-about-cargo/output-only-02-add-one/add/Cargo.lock b/listings/ch14-more-about-cargo/output-only-02-add-one/add/Cargo.lock new file mode 100644 index 0000000..77292f6 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-02-add-one/add/Cargo.lock @@ -0,0 +1,13 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "add-one" +version = "0.1.0" + +[[package]] +name = "adder" +version = "0.1.0" +dependencies = [ + "add-one 0.1.0", +] + diff --git a/listings/ch14-more-about-cargo/output-only-02-add-one/add/Cargo.toml b/listings/ch14-more-about-cargo/output-only-02-add-one/add/Cargo.toml new file mode 100644 index 0000000..d26e7cf --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-02-add-one/add/Cargo.toml @@ -0,0 +1,6 @@ +[workspace] + +members = [ + "adder", + "add-one", +] diff --git a/listings/ch14-more-about-cargo/output-only-02-add-one/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/output-only-02-add-one/add/adder/Cargo.toml new file mode 100644 index 0000000..e73f1be --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-02-add-one/add/adder/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] + +add-one = { path = "../add-one" } diff --git a/listings/ch14-more-about-cargo/output-only-02-add-one/add/adder/src/main.rs b/listings/ch14-more-about-cargo/output-only-02-add-one/add/adder/src/main.rs new file mode 100644 index 0000000..e7a11a9 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-02-add-one/add/adder/src/main.rs @@ -0,0 +1,3 @@ +fn main() { + println!("Hello, world!"); +} diff --git a/listings/ch14-more-about-cargo/output-only-03-use-rand/add/Cargo.lock b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/Cargo.lock new file mode 100644 index 0000000..28663ec --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/Cargo.lock @@ -0,0 +1,90 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "add-one" +version = "0.1.0" +dependencies = [ + "rand", +] + +[[package]] +name = "adder" +version = "0.1.0" +dependencies = [ + "add-one", +] + +[[package]] +name = "cfg-if" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd" + +[[package]] +name = "getrandom" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8" +dependencies = [ + "cfg-if", + "libc", + "wasi", +] + +[[package]] +name = "libc" +version = "0.2.86" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c" + +[[package]] +name = "ppv-lite86" +version = "0.2.10" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857" + +[[package]] +name = "rand" +version = "0.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e" +dependencies = [ + "libc", + "rand_chacha", + "rand_core", + "rand_hc", +] + +[[package]] +name = "rand_chacha" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d" +dependencies = [ + "ppv-lite86", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.6.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7" +dependencies = [ + "getrandom", +] + +[[package]] +name = "rand_hc" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73" +dependencies = [ + "rand_core", +] + +[[package]] +name = "wasi" +version = "0.10.2+wasi-snapshot-preview1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6" diff --git a/listings/ch14-more-about-cargo/output-only-03-use-rand/add/Cargo.toml b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/Cargo.toml new file mode 100644 index 0000000..d26e7cf --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/Cargo.toml @@ -0,0 +1,6 @@ +[workspace] + +members = [ + "adder", + "add-one", +] diff --git a/listings/ch14-more-about-cargo/output-only-03-use-rand/add/add-one/Cargo.toml b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/add-one/Cargo.toml new file mode 100644 index 0000000..3b0bb1a --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/add-one/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "add-one" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +rand = "0.8.3" diff --git a/listings/ch14-more-about-cargo/output-only-03-use-rand/add/add-one/src/lib.rs b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/add-one/src/lib.rs new file mode 100644 index 0000000..7b61b40 --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/add-one/src/lib.rs @@ -0,0 +1,5 @@ +use rand; + +pub fn add_one(x: i32) -> i32 { + x + 1 +} diff --git a/listings/ch14-more-about-cargo/output-only-03-use-rand/add/adder/Cargo.toml b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/adder/Cargo.toml new file mode 100644 index 0000000..e73f1be --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/adder/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "adder" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] + +add-one = { path = "../add-one" } diff --git a/listings/ch14-more-about-cargo/output-only-03-use-rand/add/adder/src/main.rs b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/adder/src/main.rs new file mode 100644 index 0000000..eb4050d --- /dev/null +++ b/listings/ch14-more-about-cargo/output-only-03-use-rand/add/adder/src/main.rs @@ -0,0 +1,11 @@ +use add_one; +use rand; + +fn main() { + let num = 10; + println!( + "Hello, world! {} plus one is {}!", + num, + add_one::add_one(num) + ); +} diff --git a/listings/ch15-smart-pointers/listing-15-01/Cargo.lock b/listings/ch15-smart-pointers/listing-15-01/Cargo.lock new file mode 100644 index 0000000..8c125fc --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "box-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-01/Cargo.toml b/listings/ch15-smart-pointers/listing-15-01/Cargo.toml new file mode 100644 index 0000000..4a0bb9d --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "box-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-01/src/main.rs b/listings/ch15-smart-pointers/listing-15-01/src/main.rs new file mode 100644 index 0000000..8da1d90 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-01/src/main.rs @@ -0,0 +1,4 @@ +fn main() { + let b = Box::new(5); + println!("b = {}", b); +} diff --git a/listings/ch15-smart-pointers/listing-15-02/Cargo.lock b/listings/ch15-smart-pointers/listing-15-02/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-02/Cargo.toml b/listings/ch15-smart-pointers/listing-15-02/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-02/src/main.rs b/listings/ch15-smart-pointers/listing-15-02/src/main.rs new file mode 100644 index 0000000..84640b9 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-02/src/main.rs @@ -0,0 +1,8 @@ +// ANCHOR: here +enum List { + Cons(i32, List), + Nil, +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch15-smart-pointers/listing-15-03/Cargo.lock b/listings/ch15-smart-pointers/listing-15-03/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-03/Cargo.toml b/listings/ch15-smart-pointers/listing-15-03/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-03/output.txt b/listings/ch15-smart-pointers/listing-15-03/output.txt new file mode 100644 index 0000000..741e404 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-03/output.txt @@ -0,0 +1,31 @@ +$ cargo run + Compiling cons-list v0.1.0 (file:///projects/cons-list) +error[E0072]: recursive type `List` has infinite size + --> src/main.rs:1:1 + | +1 | enum List { + | ^^^^^^^^^ recursive type has infinite size +2 | Cons(i32, List), + | ---- recursive without indirection + | +help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `List` representable + | +2 | Cons(i32, Box), + | ^^^^ ^ + +error[E0391]: cycle detected when computing drop-check constraints for `List` + --> src/main.rs:1:1 + | +1 | enum List { + | ^^^^^^^^^ + | + = note: ...which again requires computing drop-check constraints for `List`, completing the cycle + = note: cycle used when computing dropck types for `Canonical { max_universe: U0, variables: [], value: ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing }, value: List } }` + +error: aborting due to 2 previous errors + +Some errors have detailed explanations: E0072, E0391. +For more information about an error, try `rustc --explain E0072`. +error: could not compile `cons-list` + +To learn more, run the command again with --verbose. diff --git a/listings/ch15-smart-pointers/listing-15-03/src/main.rs b/listings/ch15-smart-pointers/listing-15-03/src/main.rs new file mode 100644 index 0000000..a96f3d7 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-03/src/main.rs @@ -0,0 +1,12 @@ +enum List { + Cons(i32, List), + Nil, +} + +// ANCHOR: here +use crate::List::{Cons, Nil}; + +fn main() { + let list = Cons(1, Cons(2, Cons(3, Nil))); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-05/Cargo.lock b/listings/ch15-smart-pointers/listing-15-05/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-05/Cargo.toml b/listings/ch15-smart-pointers/listing-15-05/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-05/src/main.rs b/listings/ch15-smart-pointers/listing-15-05/src/main.rs new file mode 100644 index 0000000..22f7d83 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-05/src/main.rs @@ -0,0 +1,10 @@ +enum List { + Cons(i32, Box), + Nil, +} + +use crate::List::{Cons, Nil}; + +fn main() { + let list = Cons(1, Box::new(Cons(2, Box::new(Cons(3, Box::new(Nil)))))); +} diff --git a/listings/ch15-smart-pointers/listing-15-06/Cargo.lock b/listings/ch15-smart-pointers/listing-15-06/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-06/Cargo.toml b/listings/ch15-smart-pointers/listing-15-06/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-06/src/main.rs b/listings/ch15-smart-pointers/listing-15-06/src/main.rs new file mode 100644 index 0000000..174b620 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-06/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let x = 5; + let y = &x; + + assert_eq!(5, x); + assert_eq!(5, *y); +} diff --git a/listings/ch15-smart-pointers/listing-15-07/Cargo.lock b/listings/ch15-smart-pointers/listing-15-07/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-07/Cargo.toml b/listings/ch15-smart-pointers/listing-15-07/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-07/src/main.rs b/listings/ch15-smart-pointers/listing-15-07/src/main.rs new file mode 100644 index 0000000..4933a41 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-07/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let x = 5; + let y = Box::new(x); + + assert_eq!(5, x); + assert_eq!(5, *y); +} diff --git a/listings/ch15-smart-pointers/listing-15-08/Cargo.lock b/listings/ch15-smart-pointers/listing-15-08/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-08/Cargo.toml b/listings/ch15-smart-pointers/listing-15-08/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-08/src/main.rs b/listings/ch15-smart-pointers/listing-15-08/src/main.rs new file mode 100644 index 0000000..f485946 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-08/src/main.rs @@ -0,0 +1,11 @@ +// ANCHOR: here +struct MyBox(T); + +impl MyBox { + fn new(x: T) -> MyBox { + MyBox(x) + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch15-smart-pointers/listing-15-09/Cargo.lock b/listings/ch15-smart-pointers/listing-15-09/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-09/Cargo.toml b/listings/ch15-smart-pointers/listing-15-09/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-09/output.txt b/listings/ch15-smart-pointers/listing-15-09/output.txt new file mode 100644 index 0000000..a2b7995 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-09/output.txt @@ -0,0 +1,14 @@ +$ cargo run + Compiling deref-example v0.1.0 (file:///projects/deref-example) +error[E0614]: type `MyBox<{integer}>` cannot be dereferenced + --> src/main.rs:14:19 + | +14 | assert_eq!(5, *y); + | ^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0614`. +error: could not compile `deref-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch15-smart-pointers/listing-15-09/src/main.rs b/listings/ch15-smart-pointers/listing-15-09/src/main.rs new file mode 100644 index 0000000..d07f2d7 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-09/src/main.rs @@ -0,0 +1,17 @@ +struct MyBox(T); + +impl MyBox { + fn new(x: T) -> MyBox { + MyBox(x) + } +} + +// ANCHOR: here +fn main() { + let x = 5; + let y = MyBox::new(x); + + assert_eq!(5, x); + assert_eq!(5, *y); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-10/Cargo.lock b/listings/ch15-smart-pointers/listing-15-10/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-10/Cargo.toml b/listings/ch15-smart-pointers/listing-15-10/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-10/src/main.rs b/listings/ch15-smart-pointers/listing-15-10/src/main.rs new file mode 100644 index 0000000..cce754d --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-10/src/main.rs @@ -0,0 +1,27 @@ +// ANCHOR: here +use std::ops::Deref; + +impl Deref for MyBox { + type Target = T; + + fn deref(&self) -> &Self::Target { + &self.0 + } +} +// ANCHOR_END: here + +struct MyBox(T); + +impl MyBox { + fn new(x: T) -> MyBox { + MyBox(x) + } +} + +fn main() { + let x = 5; + let y = MyBox::new(x); + + assert_eq!(5, x); + assert_eq!(5, *y); +} diff --git a/listings/ch15-smart-pointers/listing-15-11/Cargo.lock b/listings/ch15-smart-pointers/listing-15-11/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-11/Cargo.toml b/listings/ch15-smart-pointers/listing-15-11/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-11/src/main.rs b/listings/ch15-smart-pointers/listing-15-11/src/main.rs new file mode 100644 index 0000000..b73ad89 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-11/src/main.rs @@ -0,0 +1,7 @@ +// ANCHOR: here +fn hello(name: &str) { + println!("Hello, {}!", name); +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch15-smart-pointers/listing-15-12/Cargo.lock b/listings/ch15-smart-pointers/listing-15-12/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-12/Cargo.toml b/listings/ch15-smart-pointers/listing-15-12/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-12/src/main.rs b/listings/ch15-smart-pointers/listing-15-12/src/main.rs new file mode 100644 index 0000000..6a3e143 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-12/src/main.rs @@ -0,0 +1,28 @@ +use std::ops::Deref; + +impl Deref for MyBox { + type Target = T; + + fn deref(&self) -> &T { + &self.0 + } +} + +struct MyBox(T); + +impl MyBox { + fn new(x: T) -> MyBox { + MyBox(x) + } +} + +fn hello(name: &str) { + println!("Hello, {}!", name); +} + +// ANCHOR: here +fn main() { + let m = MyBox::new(String::from("Rust")); + hello(&m); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-13/Cargo.lock b/listings/ch15-smart-pointers/listing-15-13/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-13/Cargo.toml b/listings/ch15-smart-pointers/listing-15-13/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-13/src/main.rs b/listings/ch15-smart-pointers/listing-15-13/src/main.rs new file mode 100644 index 0000000..ef5361c --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-13/src/main.rs @@ -0,0 +1,28 @@ +use std::ops::Deref; + +impl Deref for MyBox { + type Target = T; + + fn deref(&self) -> &T { + &self.0 + } +} + +struct MyBox(T); + +impl MyBox { + fn new(x: T) -> MyBox { + MyBox(x) + } +} + +fn hello(name: &str) { + println!("Hello, {}!", name); +} + +// ANCHOR: here +fn main() { + let m = MyBox::new(String::from("Rust")); + hello(&(*m)[..]); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-14/Cargo.lock b/listings/ch15-smart-pointers/listing-15-14/Cargo.lock new file mode 100644 index 0000000..eb8a281 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "drop-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-14/Cargo.toml b/listings/ch15-smart-pointers/listing-15-14/Cargo.toml new file mode 100644 index 0000000..e9ad457 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "drop-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-14/output.txt b/listings/ch15-smart-pointers/listing-15-14/output.txt new file mode 100644 index 0000000..4e79594 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-14/output.txt @@ -0,0 +1,7 @@ +$ cargo run + Compiling drop-example v0.1.0 (file:///projects/drop-example) + Finished dev [unoptimized + debuginfo] target(s) in 0.60s + Running `target/debug/drop-example` +CustomSmartPointers created. +Dropping CustomSmartPointer with data `other stuff`! +Dropping CustomSmartPointer with data `my stuff`! diff --git a/listings/ch15-smart-pointers/listing-15-14/src/main.rs b/listings/ch15-smart-pointers/listing-15-14/src/main.rs new file mode 100644 index 0000000..231612a --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-14/src/main.rs @@ -0,0 +1,19 @@ +struct CustomSmartPointer { + data: String, +} + +impl Drop for CustomSmartPointer { + fn drop(&mut self) { + println!("Dropping CustomSmartPointer with data `{}`!", self.data); + } +} + +fn main() { + let c = CustomSmartPointer { + data: String::from("my stuff"), + }; + let d = CustomSmartPointer { + data: String::from("other stuff"), + }; + println!("CustomSmartPointers created."); +} diff --git a/listings/ch15-smart-pointers/listing-15-15/Cargo.lock b/listings/ch15-smart-pointers/listing-15-15/Cargo.lock new file mode 100644 index 0000000..eb8a281 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "drop-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-15/Cargo.toml b/listings/ch15-smart-pointers/listing-15-15/Cargo.toml new file mode 100644 index 0000000..e9ad457 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "drop-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-15/output.txt b/listings/ch15-smart-pointers/listing-15-15/output.txt new file mode 100644 index 0000000..86fe810 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-15/output.txt @@ -0,0 +1,17 @@ +$ cargo run + Compiling drop-example v0.1.0 (file:///projects/drop-example) +error[E0040]: explicit use of destructor method + --> src/main.rs:16:7 + | +16 | c.drop(); + | --^^^^-- + | | | + | | explicit destructor calls not allowed + | help: consider using `drop` function: `drop(c)` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0040`. +error: could not compile `drop-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch15-smart-pointers/listing-15-15/src/main.rs b/listings/ch15-smart-pointers/listing-15-15/src/main.rs new file mode 100644 index 0000000..ff3b391 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-15/src/main.rs @@ -0,0 +1,20 @@ +struct CustomSmartPointer { + data: String, +} + +impl Drop for CustomSmartPointer { + fn drop(&mut self) { + println!("Dropping CustomSmartPointer with data `{}`!", self.data); + } +} + +// ANCHOR: here +fn main() { + let c = CustomSmartPointer { + data: String::from("some data"), + }; + println!("CustomSmartPointer created."); + c.drop(); + println!("CustomSmartPointer dropped before the end of main."); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-16/Cargo.lock b/listings/ch15-smart-pointers/listing-15-16/Cargo.lock new file mode 100644 index 0000000..eb8a281 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "drop-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-16/Cargo.toml b/listings/ch15-smart-pointers/listing-15-16/Cargo.toml new file mode 100644 index 0000000..e9ad457 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "drop-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-16/output.txt b/listings/ch15-smart-pointers/listing-15-16/output.txt new file mode 100644 index 0000000..e960cd8 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-16/output.txt @@ -0,0 +1,7 @@ +$ cargo run + Compiling drop-example v0.1.0 (file:///projects/drop-example) + Finished dev [unoptimized + debuginfo] target(s) in 0.73s + Running `target/debug/drop-example` +CustomSmartPointer created. +Dropping CustomSmartPointer with data `some data`! +CustomSmartPointer dropped before the end of main. diff --git a/listings/ch15-smart-pointers/listing-15-16/src/main.rs b/listings/ch15-smart-pointers/listing-15-16/src/main.rs new file mode 100644 index 0000000..f11715c --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-16/src/main.rs @@ -0,0 +1,20 @@ +struct CustomSmartPointer { + data: String, +} + +impl Drop for CustomSmartPointer { + fn drop(&mut self) { + println!("Dropping CustomSmartPointer with data `{}`!", self.data); + } +} + +// ANCHOR: here +fn main() { + let c = CustomSmartPointer { + data: String::from("some data"), + }; + println!("CustomSmartPointer created."); + drop(c); + println!("CustomSmartPointer dropped before the end of main."); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-17/Cargo.lock b/listings/ch15-smart-pointers/listing-15-17/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-17/Cargo.toml b/listings/ch15-smart-pointers/listing-15-17/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-17/output.txt b/listings/ch15-smart-pointers/listing-15-17/output.txt new file mode 100644 index 0000000..a4aaeba --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-17/output.txt @@ -0,0 +1,18 @@ +$ cargo run + Compiling cons-list v0.1.0 (file:///projects/cons-list) +error[E0382]: use of moved value: `a` + --> src/main.rs:11:30 + | +9 | let a = Cons(5, Box::new(Cons(10, Box::new(Nil)))); + | - move occurs because `a` has type `List`, which does not implement the `Copy` trait +10 | let b = Cons(3, Box::new(a)); + | - value moved here +11 | let c = Cons(4, Box::new(a)); + | ^ value used here after move + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `cons-list` + +To learn more, run the command again with --verbose. diff --git a/listings/ch15-smart-pointers/listing-15-17/src/main.rs b/listings/ch15-smart-pointers/listing-15-17/src/main.rs new file mode 100644 index 0000000..47c33e4 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-17/src/main.rs @@ -0,0 +1,12 @@ +enum List { + Cons(i32, Box), + Nil, +} + +use crate::List::{Cons, Nil}; + +fn main() { + let a = Cons(5, Box::new(Cons(10, Box::new(Nil)))); + let b = Cons(3, Box::new(a)); + let c = Cons(4, Box::new(a)); +} diff --git a/listings/ch15-smart-pointers/listing-15-18/Cargo.lock b/listings/ch15-smart-pointers/listing-15-18/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-18/Cargo.toml b/listings/ch15-smart-pointers/listing-15-18/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-18/src/main.rs b/listings/ch15-smart-pointers/listing-15-18/src/main.rs new file mode 100644 index 0000000..602f7de --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-18/src/main.rs @@ -0,0 +1,13 @@ +enum List { + Cons(i32, Rc), + Nil, +} + +use crate::List::{Cons, Nil}; +use std::rc::Rc; + +fn main() { + let a = Rc::new(Cons(5, Rc::new(Cons(10, Rc::new(Nil))))); + let b = Cons(3, Rc::clone(&a)); + let c = Cons(4, Rc::clone(&a)); +} diff --git a/listings/ch15-smart-pointers/listing-15-19/Cargo.lock b/listings/ch15-smart-pointers/listing-15-19/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-19/Cargo.toml b/listings/ch15-smart-pointers/listing-15-19/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-19/output.txt b/listings/ch15-smart-pointers/listing-15-19/output.txt new file mode 100644 index 0000000..6a8cc8e --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-19/output.txt @@ -0,0 +1,8 @@ +$ cargo run + Compiling cons-list v0.1.0 (file:///projects/cons-list) + Finished dev [unoptimized + debuginfo] target(s) in 0.45s + Running `target/debug/cons-list` +count after creating a = 1 +count after creating b = 2 +count after creating c = 3 +count after c goes out of scope = 2 diff --git a/listings/ch15-smart-pointers/listing-15-19/src/main.rs b/listings/ch15-smart-pointers/listing-15-19/src/main.rs new file mode 100644 index 0000000..1bd7bc5 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-19/src/main.rs @@ -0,0 +1,21 @@ +enum List { + Cons(i32, Rc), + Nil, +} + +use crate::List::{Cons, Nil}; +use std::rc::Rc; + +// ANCHOR: here +fn main() { + let a = Rc::new(Cons(5, Rc::new(Cons(10, Rc::new(Nil))))); + println!("count after creating a = {}", Rc::strong_count(&a)); + let b = Cons(3, Rc::clone(&a)); + println!("count after creating b = {}", Rc::strong_count(&a)); + { + let c = Cons(4, Rc::clone(&a)); + println!("count after creating c = {}", Rc::strong_count(&a)); + } + println!("count after c goes out of scope = {}", Rc::strong_count(&a)); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-20/Cargo.lock b/listings/ch15-smart-pointers/listing-15-20/Cargo.lock new file mode 100644 index 0000000..4dc2226 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "limit-tracker" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-20/Cargo.toml b/listings/ch15-smart-pointers/listing-15-20/Cargo.toml new file mode 100644 index 0000000..b230a23 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "limit-tracker" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-20/src/lib.rs b/listings/ch15-smart-pointers/listing-15-20/src/lib.rs new file mode 100644 index 0000000..d3a9003 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-20/src/lib.rs @@ -0,0 +1,38 @@ +pub trait Messenger { + fn send(&self, msg: &str); +} + +pub struct LimitTracker<'a, T: Messenger> { + messenger: &'a T, + value: usize, + max: usize, +} + +impl<'a, T> LimitTracker<'a, T> +where + T: Messenger, +{ + pub fn new(messenger: &T, max: usize) -> LimitTracker { + LimitTracker { + messenger, + value: 0, + max, + } + } + + pub fn set_value(&mut self, value: usize) { + self.value = value; + + let percentage_of_max = self.value as f64 / self.max as f64; + + if percentage_of_max >= 1.0 { + self.messenger.send("Error: You are over your quota!"); + } else if percentage_of_max >= 0.9 { + self.messenger + .send("Urgent warning: You've used up over 90% of your quota!"); + } else if percentage_of_max >= 0.75 { + self.messenger + .send("Warning: You've used up over 75% of your quota!"); + } + } +} diff --git a/listings/ch15-smart-pointers/listing-15-21/Cargo.lock b/listings/ch15-smart-pointers/listing-15-21/Cargo.lock new file mode 100644 index 0000000..4dc2226 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "limit-tracker" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-21/Cargo.toml b/listings/ch15-smart-pointers/listing-15-21/Cargo.toml new file mode 100644 index 0000000..b230a23 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "limit-tracker" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-21/output.txt b/listings/ch15-smart-pointers/listing-15-21/output.txt new file mode 100644 index 0000000..7cfa86b --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-21/output.txt @@ -0,0 +1,18 @@ +$ cargo test + Compiling limit-tracker v0.1.0 (file:///projects/limit-tracker) +error[E0596]: cannot borrow `self.sent_messages` as mutable, as it is behind a `&` reference + --> src/lib.rs:58:13 + | +57 | fn send(&self, message: &str) { + | ----- help: consider changing this to be a mutable reference: `&mut self` +58 | self.sent_messages.push(String::from(message)); + | ^^^^^^^^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0596`. +error: could not compile `limit-tracker` + +To learn more, run the command again with --verbose. +warning: build failed, waiting for other jobs to finish... +error: build failed diff --git a/listings/ch15-smart-pointers/listing-15-21/src/lib.rs b/listings/ch15-smart-pointers/listing-15-21/src/lib.rs new file mode 100644 index 0000000..9e403e3 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-21/src/lib.rs @@ -0,0 +1,73 @@ +pub trait Messenger { + fn send(&self, msg: &str); +} + +pub struct LimitTracker<'a, T: Messenger> { + messenger: &'a T, + value: usize, + max: usize, +} + +impl<'a, T> LimitTracker<'a, T> +where + T: Messenger, +{ + pub fn new(messenger: &T, max: usize) -> LimitTracker { + LimitTracker { + messenger, + value: 0, + max, + } + } + + pub fn set_value(&mut self, value: usize) { + self.value = value; + + let percentage_of_max = self.value as f64 / self.max as f64; + + if percentage_of_max >= 1.0 { + self.messenger.send("Error: You are over your quota!"); + } else if percentage_of_max >= 0.9 { + self.messenger + .send("Urgent warning: You've used up over 90% of your quota!"); + } else if percentage_of_max >= 0.75 { + self.messenger + .send("Warning: You've used up over 75% of your quota!"); + } + } +} + +// ANCHOR: here +#[cfg(test)] +mod tests { + use super::*; + + struct MockMessenger { + sent_messages: Vec, + } + + impl MockMessenger { + fn new() -> MockMessenger { + MockMessenger { + sent_messages: vec![], + } + } + } + + impl Messenger for MockMessenger { + fn send(&self, message: &str) { + self.sent_messages.push(String::from(message)); + } + } + + #[test] + fn it_sends_an_over_75_percent_warning_message() { + let mock_messenger = MockMessenger::new(); + let mut limit_tracker = LimitTracker::new(&mock_messenger, 100); + + limit_tracker.set_value(80); + + assert_eq!(mock_messenger.sent_messages.len(), 1); + } +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-22/Cargo.lock b/listings/ch15-smart-pointers/listing-15-22/Cargo.lock new file mode 100644 index 0000000..4dc2226 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "limit-tracker" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-22/Cargo.toml b/listings/ch15-smart-pointers/listing-15-22/Cargo.toml new file mode 100644 index 0000000..b230a23 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "limit-tracker" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-22/src/lib.rs b/listings/ch15-smart-pointers/listing-15-22/src/lib.rs new file mode 100644 index 0000000..539578e --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-22/src/lib.rs @@ -0,0 +1,78 @@ +pub trait Messenger { + fn send(&self, msg: &str); +} + +pub struct LimitTracker<'a, T: Messenger> { + messenger: &'a T, + value: usize, + max: usize, +} + +impl<'a, T> LimitTracker<'a, T> +where + T: Messenger, +{ + pub fn new(messenger: &T, max: usize) -> LimitTracker { + LimitTracker { + messenger, + value: 0, + max, + } + } + + pub fn set_value(&mut self, value: usize) { + self.value = value; + + let percentage_of_max = self.value as f64 / self.max as f64; + + if percentage_of_max >= 1.0 { + self.messenger.send("Error: You are over your quota!"); + } else if percentage_of_max >= 0.9 { + self.messenger + .send("Urgent warning: You've used up over 90% of your quota!"); + } else if percentage_of_max >= 0.75 { + self.messenger + .send("Warning: You've used up over 75% of your quota!"); + } + } +} + +// ANCHOR: here +#[cfg(test)] +mod tests { + use super::*; + use std::cell::RefCell; + + struct MockMessenger { + sent_messages: RefCell>, + } + + impl MockMessenger { + fn new() -> MockMessenger { + MockMessenger { + sent_messages: RefCell::new(vec![]), + } + } + } + + impl Messenger for MockMessenger { + fn send(&self, message: &str) { + self.sent_messages.borrow_mut().push(String::from(message)); + } + } + + #[test] + fn it_sends_an_over_75_percent_warning_message() { + // --snip-- + // ANCHOR_END: here + let mock_messenger = MockMessenger::new(); + let mut limit_tracker = LimitTracker::new(&mock_messenger, 100); + + limit_tracker.set_value(80); + // ANCHOR: here + + // ANCHOR: here + assert_eq!(mock_messenger.sent_messages.borrow().len(), 1); + } +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-23/Cargo.lock b/listings/ch15-smart-pointers/listing-15-23/Cargo.lock new file mode 100644 index 0000000..4dc2226 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "limit-tracker" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-23/Cargo.toml b/listings/ch15-smart-pointers/listing-15-23/Cargo.toml new file mode 100644 index 0000000..b230a23 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "limit-tracker" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-23/output.txt b/listings/ch15-smart-pointers/listing-15-23/output.txt new file mode 100644 index 0000000..802dc26 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-23/output.txt @@ -0,0 +1,21 @@ +$ cargo test + Compiling limit-tracker v0.1.0 (file:///projects/limit-tracker) + Finished test [unoptimized + debuginfo] target(s) in 0.91s + Running target/debug/deps/limit_tracker-d1b2637139dca6ca + +running 1 test +test tests::it_sends_an_over_75_percent_warning_message ... FAILED + +failures: + +---- tests::it_sends_an_over_75_percent_warning_message stdout ---- +thread 'main' panicked at 'already borrowed: BorrowMutError', src/lib.rs:60:53 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace + + +failures: + tests::it_sends_an_over_75_percent_warning_message + +test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + +error: test failed, to rerun pass '--lib' diff --git a/listings/ch15-smart-pointers/listing-15-23/src/lib.rs b/listings/ch15-smart-pointers/listing-15-23/src/lib.rs new file mode 100644 index 0000000..4e599dd --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-23/src/lib.rs @@ -0,0 +1,78 @@ +pub trait Messenger { + fn send(&self, msg: &str); +} + +pub struct LimitTracker<'a, T: Messenger> { + messenger: &'a T, + value: usize, + max: usize, +} + +impl<'a, T> LimitTracker<'a, T> +where + T: Messenger, +{ + pub fn new(messenger: &T, max: usize) -> LimitTracker { + LimitTracker { + messenger, + value: 0, + max, + } + } + + pub fn set_value(&mut self, value: usize) { + self.value = value; + + let percentage_of_max = self.value as f64 / self.max as f64; + + if percentage_of_max >= 1.0 { + self.messenger.send("Error: You are over your quota!"); + } else if percentage_of_max >= 0.9 { + self.messenger + .send("Urgent warning: You've used up over 90% of your quota!"); + } else if percentage_of_max >= 0.75 { + self.messenger + .send("Warning: You've used up over 75% of your quota!"); + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + use std::cell::RefCell; + + struct MockMessenger { + sent_messages: RefCell>, + } + + impl MockMessenger { + fn new() -> MockMessenger { + MockMessenger { + sent_messages: RefCell::new(vec![]), + } + } + } + + // ANCHOR: here + impl Messenger for MockMessenger { + fn send(&self, message: &str) { + let mut one_borrow = self.sent_messages.borrow_mut(); + let mut two_borrow = self.sent_messages.borrow_mut(); + + one_borrow.push(String::from(message)); + two_borrow.push(String::from(message)); + } + } + // ANCHOR_END: here + + #[test] + fn it_sends_an_over_75_percent_warning_message() { + let mock_messenger = MockMessenger::new(); + let mut limit_tracker = LimitTracker::new(&mock_messenger, 100); + + limit_tracker.set_value(80); + + assert_eq!(mock_messenger.sent_messages.borrow().len(), 1); + } +} diff --git a/listings/ch15-smart-pointers/listing-15-24/Cargo.lock b/listings/ch15-smart-pointers/listing-15-24/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-24/Cargo.toml b/listings/ch15-smart-pointers/listing-15-24/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-24/output.txt b/listings/ch15-smart-pointers/listing-15-24/output.txt new file mode 100644 index 0000000..21b3530 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-24/output.txt @@ -0,0 +1,7 @@ +$ cargo run + Compiling cons-list v0.1.0 (file:///projects/cons-list) + Finished dev [unoptimized + debuginfo] target(s) in 0.63s + Running `target/debug/cons-list` +a after = Cons(RefCell { value: 15 }, Nil) +b after = Cons(RefCell { value: 3 }, Cons(RefCell { value: 15 }, Nil)) +c after = Cons(RefCell { value: 4 }, Cons(RefCell { value: 15 }, Nil)) diff --git a/listings/ch15-smart-pointers/listing-15-24/src/main.rs b/listings/ch15-smart-pointers/listing-15-24/src/main.rs new file mode 100644 index 0000000..e225bd8 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-24/src/main.rs @@ -0,0 +1,24 @@ +#[derive(Debug)] +enum List { + Cons(Rc>, Rc), + Nil, +} + +use crate::List::{Cons, Nil}; +use std::cell::RefCell; +use std::rc::Rc; + +fn main() { + let value = Rc::new(RefCell::new(5)); + + let a = Rc::new(Cons(Rc::clone(&value), Rc::new(Nil))); + + let b = Cons(Rc::new(RefCell::new(3)), Rc::clone(&a)); + let c = Cons(Rc::new(RefCell::new(4)), Rc::clone(&a)); + + *value.borrow_mut() += 10; + + println!("a after = {:?}", a); + println!("b after = {:?}", b); + println!("c after = {:?}", c); +} diff --git a/listings/ch15-smart-pointers/listing-15-25/Cargo.lock b/listings/ch15-smart-pointers/listing-15-25/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-25/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-25/Cargo.toml b/listings/ch15-smart-pointers/listing-15-25/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-25/src/main.rs b/listings/ch15-smart-pointers/listing-15-25/src/main.rs new file mode 100644 index 0000000..f36c7fd --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-25/src/main.rs @@ -0,0 +1,20 @@ +use crate::List::{Cons, Nil}; +use std::cell::RefCell; +use std::rc::Rc; + +#[derive(Debug)] +enum List { + Cons(i32, RefCell>), + Nil, +} + +impl List { + fn tail(&self) -> Option<&RefCell>> { + match self { + Cons(_, item) => Some(item), + Nil => None, + } + } +} + +fn main() {} diff --git a/listings/ch15-smart-pointers/listing-15-26/Cargo.lock b/listings/ch15-smart-pointers/listing-15-26/Cargo.lock new file mode 100644 index 0000000..a792c49 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-26/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "cons-list" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-26/Cargo.toml b/listings/ch15-smart-pointers/listing-15-26/Cargo.toml new file mode 100644 index 0000000..86c8e95 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-26/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "cons-list" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-26/output.txt b/listings/ch15-smart-pointers/listing-15-26/output.txt new file mode 100644 index 0000000..8b8eb40 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-26/output.txt @@ -0,0 +1,11 @@ +$ cargo run + Compiling cons-list v0.1.0 (file:///projects/cons-list) + Finished dev [unoptimized + debuginfo] target(s) in 0.53s + Running `target/debug/cons-list` +a initial rc count = 1 +a next item = Some(RefCell { value: Nil }) +a rc count after b creation = 2 +b initial rc count = 1 +b next item = Some(RefCell { value: Cons(5, RefCell { value: Nil }) }) +b rc count after changing a = 2 +a rc count after changing a = 2 diff --git a/listings/ch15-smart-pointers/listing-15-26/src/main.rs b/listings/ch15-smart-pointers/listing-15-26/src/main.rs new file mode 100644 index 0000000..08963aa --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-26/src/main.rs @@ -0,0 +1,44 @@ +use crate::List::{Cons, Nil}; +use std::cell::RefCell; +use std::rc::Rc; + +#[derive(Debug)] +enum List { + Cons(i32, RefCell>), + Nil, +} + +impl List { + fn tail(&self) -> Option<&RefCell>> { + match self { + Cons(_, item) => Some(item), + Nil => None, + } + } +} + +// ANCHOR: here +fn main() { + let a = Rc::new(Cons(5, RefCell::new(Rc::new(Nil)))); + + println!("a initial rc count = {}", Rc::strong_count(&a)); + println!("a next item = {:?}", a.tail()); + + let b = Rc::new(Cons(10, RefCell::new(Rc::clone(&a)))); + + println!("a rc count after b creation = {}", Rc::strong_count(&a)); + println!("b initial rc count = {}", Rc::strong_count(&b)); + println!("b next item = {:?}", b.tail()); + + if let Some(link) = a.tail() { + *link.borrow_mut() = Rc::clone(&b); + } + + println!("b rc count after changing a = {}", Rc::strong_count(&b)); + println!("a rc count after changing a = {}", Rc::strong_count(&a)); + + // Uncomment the next line to see that we have a cycle; + // it will overflow the stack + // println!("a next item = {:?}", a.tail()); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/listing-15-27/Cargo.lock b/listings/ch15-smart-pointers/listing-15-27/Cargo.lock new file mode 100644 index 0000000..dd1f00a --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-27/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "tree" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-27/Cargo.toml b/listings/ch15-smart-pointers/listing-15-27/Cargo.toml new file mode 100644 index 0000000..d6774b8 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-27/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "tree" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-27/src/main.rs b/listings/ch15-smart-pointers/listing-15-27/src/main.rs new file mode 100644 index 0000000..335d154 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-27/src/main.rs @@ -0,0 +1,24 @@ +// ANCHOR: here +use std::cell::RefCell; +use std::rc::Rc; + +#[derive(Debug)] +struct Node { + value: i32, + children: RefCell>>, +} +// ANCHOR_END: here + +// ANCHOR: there +fn main() { + let leaf = Rc::new(Node { + value: 3, + children: RefCell::new(vec![]), + }); + + let branch = Rc::new(Node { + value: 5, + children: RefCell::new(vec![Rc::clone(&leaf)]), + }); +} +// ANCHOR_END: there diff --git a/listings/ch15-smart-pointers/listing-15-28/Cargo.lock b/listings/ch15-smart-pointers/listing-15-28/Cargo.lock new file mode 100644 index 0000000..dd1f00a --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-28/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "tree" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-28/Cargo.toml b/listings/ch15-smart-pointers/listing-15-28/Cargo.toml new file mode 100644 index 0000000..d6774b8 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-28/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "tree" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-28/src/main.rs b/listings/ch15-smart-pointers/listing-15-28/src/main.rs new file mode 100644 index 0000000..fabd1cb --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-28/src/main.rs @@ -0,0 +1,33 @@ +// ANCHOR: here +use std::cell::RefCell; +use std::rc::{Rc, Weak}; + +#[derive(Debug)] +struct Node { + value: i32, + parent: RefCell>, + children: RefCell>>, +} +// ANCHOR_END: here + +// ANCHOR: there +fn main() { + let leaf = Rc::new(Node { + value: 3, + parent: RefCell::new(Weak::new()), + children: RefCell::new(vec![]), + }); + + println!("leaf parent = {:?}", leaf.parent.borrow().upgrade()); + + let branch = Rc::new(Node { + value: 5, + parent: RefCell::new(Weak::new()), + children: RefCell::new(vec![Rc::clone(&leaf)]), + }); + + *leaf.parent.borrow_mut() = Rc::downgrade(&branch); + + println!("leaf parent = {:?}", leaf.parent.borrow().upgrade()); +} +// ANCHOR_END: there diff --git a/listings/ch15-smart-pointers/listing-15-29/Cargo.lock b/listings/ch15-smart-pointers/listing-15-29/Cargo.lock new file mode 100644 index 0000000..dd1f00a --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-29/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "tree" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/listing-15-29/Cargo.toml b/listings/ch15-smart-pointers/listing-15-29/Cargo.toml new file mode 100644 index 0000000..d6774b8 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-29/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "tree" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/listing-15-29/src/main.rs b/listings/ch15-smart-pointers/listing-15-29/src/main.rs new file mode 100644 index 0000000..ea13df0 --- /dev/null +++ b/listings/ch15-smart-pointers/listing-15-29/src/main.rs @@ -0,0 +1,54 @@ +use std::cell::RefCell; +use std::rc::{Rc, Weak}; + +#[derive(Debug)] +struct Node { + value: i32, + parent: RefCell>, + children: RefCell>>, +} + +// ANCHOR: here +fn main() { + let leaf = Rc::new(Node { + value: 3, + parent: RefCell::new(Weak::new()), + children: RefCell::new(vec![]), + }); + + println!( + "leaf strong = {}, weak = {}", + Rc::strong_count(&leaf), + Rc::weak_count(&leaf), + ); + + { + let branch = Rc::new(Node { + value: 5, + parent: RefCell::new(Weak::new()), + children: RefCell::new(vec![Rc::clone(&leaf)]), + }); + + *leaf.parent.borrow_mut() = Rc::downgrade(&branch); + + println!( + "branch strong = {}, weak = {}", + Rc::strong_count(&branch), + Rc::weak_count(&branch), + ); + + println!( + "leaf strong = {}, weak = {}", + Rc::strong_count(&leaf), + Rc::weak_count(&leaf), + ); + } + + println!("leaf parent = {:?}", leaf.parent.borrow().upgrade()); + println!( + "leaf strong = {}, weak = {}", + Rc::strong_count(&leaf), + Rc::weak_count(&leaf), + ); +} +// ANCHOR_END: here diff --git a/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/Cargo.lock b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/Cargo.lock new file mode 100644 index 0000000..340f660 --- /dev/null +++ b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "borrowing" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/Cargo.toml b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/Cargo.toml new file mode 100644 index 0000000..1558eb6 --- /dev/null +++ b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "borrowing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/output.txt b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/output.txt new file mode 100644 index 0000000..2892426 --- /dev/null +++ b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling borrowing v0.1.0 (file:///projects/borrowing) +error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable + --> src/main.rs:3:13 + | +2 | let x = 5; + | - help: consider changing this to be mutable: `mut x` +3 | let y = &mut x; + | ^^^^^^ cannot borrow as mutable + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0596`. +error: could not compile `borrowing` + +To learn more, run the command again with --verbose. diff --git a/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/src/main.rs b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/src/main.rs new file mode 100644 index 0000000..8f48d41 --- /dev/null +++ b/listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/src/main.rs @@ -0,0 +1,4 @@ +fn main() { + let x = 5; + let y = &mut x; +} diff --git a/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/Cargo.lock b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/Cargo.lock new file mode 100644 index 0000000..4297c67 --- /dev/null +++ b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "deref-example" +version = "0.1.0" + diff --git a/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/Cargo.toml b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/Cargo.toml new file mode 100644 index 0000000..2a9630f --- /dev/null +++ b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "deref-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/output.txt b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/output.txt new file mode 100644 index 0000000..5eaa969 --- /dev/null +++ b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/output.txt @@ -0,0 +1,17 @@ +$ cargo run + Compiling deref-example v0.1.0 (file:///projects/deref-example) +error[E0277]: can't compare `{integer}` with `&{integer}` + --> src/main.rs:6:5 + | +6 | assert_eq!(5, y); + | ^^^^^^^^^^^^^^^^^ no implementation for `{integer} == &{integer}` + | + = help: the trait `PartialEq<&{integer}>` is not implemented for `{integer}` + = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info) + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `deref-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/src/main.rs b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/src/main.rs new file mode 100644 index 0000000..4e20cae --- /dev/null +++ b/listings/ch15-smart-pointers/output-only-01-comparing-to-reference/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + let x = 5; + let y = &x; + + assert_eq!(5, x); + assert_eq!(5, y); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-01/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-01/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-01/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-01/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-01/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-01/src/main.rs new file mode 100644 index 0000000..6305a98 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-01/src/main.rs @@ -0,0 +1,16 @@ +use std::thread; +use std::time::Duration; + +fn main() { + thread::spawn(|| { + for i in 1..10 { + println!("hi number {} from the spawned thread!", i); + thread::sleep(Duration::from_millis(1)); + } + }); + + for i in 1..5 { + println!("hi number {} from the main thread!", i); + thread::sleep(Duration::from_millis(1)); + } +} diff --git a/listings/ch16-fearless-concurrency/listing-16-02/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-02/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-02/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-02/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-02/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-02/src/main.rs new file mode 100644 index 0000000..e37607f --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-02/src/main.rs @@ -0,0 +1,18 @@ +use std::thread; +use std::time::Duration; + +fn main() { + let handle = thread::spawn(|| { + for i in 1..10 { + println!("hi number {} from the spawned thread!", i); + thread::sleep(Duration::from_millis(1)); + } + }); + + for i in 1..5 { + println!("hi number {} from the main thread!", i); + thread::sleep(Duration::from_millis(1)); + } + + handle.join().unwrap(); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-03/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-03/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-03/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-03/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-03/output.txt b/listings/ch16-fearless-concurrency/listing-16-03/output.txt new file mode 100644 index 0000000..1223d38 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-03/output.txt @@ -0,0 +1,29 @@ +$ cargo run + Compiling threads v0.1.0 (file:///projects/threads) +error[E0373]: closure may outlive the current function, but it borrows `v`, which is owned by the current function + --> src/main.rs:6:32 + | +6 | let handle = thread::spawn(|| { + | ^^ may outlive borrowed value `v` +7 | println!("Here's a vector: {:?}", v); + | - `v` is borrowed here + | +note: function requires argument type to outlive `'static` + --> src/main.rs:6:18 + | +6 | let handle = thread::spawn(|| { + | __________________^ +7 | | println!("Here's a vector: {:?}", v); +8 | | }); + | |______^ +help: to force the closure to take ownership of `v` (and any other referenced variables), use the `move` keyword + | +6 | let handle = thread::spawn(move || { + | ^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0373`. +error: could not compile `threads` + +To learn more, run the command again with --verbose. diff --git a/listings/ch16-fearless-concurrency/listing-16-03/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-03/src/main.rs new file mode 100644 index 0000000..defc876 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-03/src/main.rs @@ -0,0 +1,11 @@ +use std::thread; + +fn main() { + let v = vec![1, 2, 3]; + + let handle = thread::spawn(|| { + println!("Here's a vector: {:?}", v); + }); + + handle.join().unwrap(); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-04/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-04/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-04/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-04/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-04/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-04/src/main.rs new file mode 100644 index 0000000..0bccc5f --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-04/src/main.rs @@ -0,0 +1,13 @@ +use std::thread; + +fn main() { + let v = vec![1, 2, 3]; + + let handle = thread::spawn(|| { + println!("Here's a vector: {:?}", v); + }); + + drop(v); // oh no! + + handle.join().unwrap(); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-05/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-05/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-05/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-05/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-05/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-05/src/main.rs new file mode 100644 index 0000000..a6547dc --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-05/src/main.rs @@ -0,0 +1,11 @@ +use std::thread; + +fn main() { + let v = vec![1, 2, 3]; + + let handle = thread::spawn(move || { + println!("Here's a vector: {:?}", v); + }); + + handle.join().unwrap(); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-06/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-06/Cargo.lock new file mode 100644 index 0000000..55d2252 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "message-passing" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-06/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-06/Cargo.toml new file mode 100644 index 0000000..8fd8808 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "message-passing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-06/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-06/src/main.rs new file mode 100644 index 0000000..d80dac4 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-06/src/main.rs @@ -0,0 +1,5 @@ +use std::sync::mpsc; + +fn main() { + let (tx, rx) = mpsc::channel(); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-07/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-07/Cargo.lock new file mode 100644 index 0000000..55d2252 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "message-passing" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-07/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-07/Cargo.toml new file mode 100644 index 0000000..8fd8808 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "message-passing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-07/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-07/src/main.rs new file mode 100644 index 0000000..7859b64 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-07/src/main.rs @@ -0,0 +1,11 @@ +use std::sync::mpsc; +use std::thread; + +fn main() { + let (tx, rx) = mpsc::channel(); + + thread::spawn(move || { + let val = String::from("hi"); + tx.send(val).unwrap(); + }); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-08/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-08/Cargo.lock new file mode 100644 index 0000000..55d2252 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "message-passing" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-08/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-08/Cargo.toml new file mode 100644 index 0000000..8fd8808 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "message-passing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-08/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-08/src/main.rs new file mode 100644 index 0000000..fbba916 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-08/src/main.rs @@ -0,0 +1,14 @@ +use std::sync::mpsc; +use std::thread; + +fn main() { + let (tx, rx) = mpsc::channel(); + + thread::spawn(move || { + let val = String::from("hi"); + tx.send(val).unwrap(); + }); + + let received = rx.recv().unwrap(); + println!("Got: {}", received); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-09/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-09/Cargo.lock new file mode 100644 index 0000000..55d2252 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "message-passing" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-09/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-09/Cargo.toml new file mode 100644 index 0000000..8fd8808 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "message-passing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-09/output.txt b/listings/ch16-fearless-concurrency/listing-16-09/output.txt new file mode 100644 index 0000000..deb47c9 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-09/output.txt @@ -0,0 +1,18 @@ +$ cargo run + Compiling message-passing v0.1.0 (file:///projects/message-passing) +error[E0382]: borrow of moved value: `val` + --> src/main.rs:10:31 + | +8 | let val = String::from("hi"); + | --- move occurs because `val` has type `String`, which does not implement the `Copy` trait +9 | tx.send(val).unwrap(); + | --- value moved here +10 | println!("val is {}", val); + | ^^^ value borrowed here after move + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `message-passing` + +To learn more, run the command again with --verbose. diff --git a/listings/ch16-fearless-concurrency/listing-16-09/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-09/src/main.rs new file mode 100644 index 0000000..98a8129 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-09/src/main.rs @@ -0,0 +1,15 @@ +use std::sync::mpsc; +use std::thread; + +fn main() { + let (tx, rx) = mpsc::channel(); + + thread::spawn(move || { + let val = String::from("hi"); + tx.send(val).unwrap(); + println!("val is {}", val); + }); + + let received = rx.recv().unwrap(); + println!("Got: {}", received); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-10/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-10/Cargo.lock new file mode 100644 index 0000000..55d2252 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "message-passing" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-10/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-10/Cargo.toml new file mode 100644 index 0000000..8fd8808 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "message-passing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-10/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-10/src/main.rs new file mode 100644 index 0000000..82b220d --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-10/src/main.rs @@ -0,0 +1,25 @@ +use std::sync::mpsc; +use std::thread; +use std::time::Duration; + +fn main() { + let (tx, rx) = mpsc::channel(); + + thread::spawn(move || { + let vals = vec![ + String::from("hi"), + String::from("from"), + String::from("the"), + String::from("thread"), + ]; + + for val in vals { + tx.send(val).unwrap(); + thread::sleep(Duration::from_secs(1)); + } + }); + + for received in rx { + println!("Got: {}", received); + } +} diff --git a/listings/ch16-fearless-concurrency/listing-16-11/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-11/Cargo.lock new file mode 100644 index 0000000..55d2252 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "message-passing" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-11/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-11/Cargo.toml new file mode 100644 index 0000000..8fd8808 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "message-passing" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-11/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-11/src/main.rs new file mode 100644 index 0000000..d92deab --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-11/src/main.rs @@ -0,0 +1,46 @@ +use std::sync::mpsc; +use std::thread; +use std::time::Duration; + +fn main() { + // ANCHOR: here + // --snip-- + + let (tx, rx) = mpsc::channel(); + + let tx1 = tx.clone(); + thread::spawn(move || { + let vals = vec![ + String::from("hi"), + String::from("from"), + String::from("the"), + String::from("thread"), + ]; + + for val in vals { + tx1.send(val).unwrap(); + thread::sleep(Duration::from_secs(1)); + } + }); + + thread::spawn(move || { + let vals = vec![ + String::from("more"), + String::from("messages"), + String::from("for"), + String::from("you"), + ]; + + for val in vals { + tx.send(val).unwrap(); + thread::sleep(Duration::from_secs(1)); + } + }); + + for received in rx { + println!("Got: {}", received); + } + + // --snip-- + // ANCHOR_END: here +} diff --git a/listings/ch16-fearless-concurrency/listing-16-12/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-12/Cargo.lock new file mode 100644 index 0000000..8e7ba9c --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "shared-state" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-12/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-12/Cargo.toml new file mode 100644 index 0000000..e7c75ac --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "shared-state" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-12/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-12/src/main.rs new file mode 100644 index 0000000..0c0d676 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-12/src/main.rs @@ -0,0 +1,12 @@ +use std::sync::Mutex; + +fn main() { + let m = Mutex::new(5); + + { + let mut num = m.lock().unwrap(); + *num = 6; + } + + println!("m = {:?}", m); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-13/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-13/Cargo.lock new file mode 100644 index 0000000..8e7ba9c --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "shared-state" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-13/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-13/Cargo.toml new file mode 100644 index 0000000..e7c75ac --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "shared-state" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-13/output.txt b/listings/ch16-fearless-concurrency/listing-16-13/output.txt new file mode 100644 index 0000000..69e0b09 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-13/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling shared-state v0.1.0 (file:///projects/shared-state) +error[E0382]: use of moved value: `counter` + --> src/main.rs:9:36 + | +5 | let counter = Mutex::new(0); + | ------- move occurs because `counter` has type `Mutex`, which does not implement the `Copy` trait +... +9 | let handle = thread::spawn(move || { + | ^^^^^^^ value moved into closure here, in previous iteration of loop +10 | let mut num = counter.lock().unwrap(); + | ------- use occurs due to use in closure + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `shared-state` + +To learn more, run the command again with --verbose. diff --git a/listings/ch16-fearless-concurrency/listing-16-13/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-13/src/main.rs new file mode 100644 index 0000000..4e380a5 --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-13/src/main.rs @@ -0,0 +1,22 @@ +use std::sync::Mutex; +use std::thread; + +fn main() { + let counter = Mutex::new(0); + let mut handles = vec![]; + + for _ in 0..10 { + let handle = thread::spawn(move || { + let mut num = counter.lock().unwrap(); + + *num += 1; + }); + handles.push(handle); + } + + for handle in handles { + handle.join().unwrap(); + } + + println!("Result: {}", *counter.lock().unwrap()); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-14/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-14/Cargo.lock new file mode 100644 index 0000000..8e7ba9c --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "shared-state" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-14/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-14/Cargo.toml new file mode 100644 index 0000000..e7c75ac --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "shared-state" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-14/output.txt b/listings/ch16-fearless-concurrency/listing-16-14/output.txt new file mode 100644 index 0000000..cd2d05b --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-14/output.txt @@ -0,0 +1,24 @@ +$ cargo run + Compiling shared-state v0.1.0 (file:///projects/shared-state) +error[E0277]: `Rc>` cannot be sent between threads safely + --> src/main.rs:11:22 + | +11 | let handle = thread::spawn(move || { + | ______________________^^^^^^^^^^^^^_- + | | | + | | `Rc>` cannot be sent between threads safely +12 | | let mut num = counter.lock().unwrap(); +13 | | +14 | | *num += 1; +15 | | }); + | |_________- within this `[closure@src/main.rs:11:36: 15:10]` + | + = help: within `[closure@src/main.rs:11:36: 15:10]`, the trait `Send` is not implemented for `Rc>` + = note: required because it appears within the type `[closure@src/main.rs:11:36: 15:10]` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `shared-state` + +To learn more, run the command again with --verbose. diff --git a/listings/ch16-fearless-concurrency/listing-16-14/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-14/src/main.rs new file mode 100644 index 0000000..d940b1a --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-14/src/main.rs @@ -0,0 +1,24 @@ +use std::rc::Rc; +use std::sync::Mutex; +use std::thread; + +fn main() { + let counter = Rc::new(Mutex::new(0)); + let mut handles = vec![]; + + for _ in 0..10 { + let counter = Rc::clone(&counter); + let handle = thread::spawn(move || { + let mut num = counter.lock().unwrap(); + + *num += 1; + }); + handles.push(handle); + } + + for handle in handles { + handle.join().unwrap(); + } + + println!("Result: {}", *counter.lock().unwrap()); +} diff --git a/listings/ch16-fearless-concurrency/listing-16-15/Cargo.lock b/listings/ch16-fearless-concurrency/listing-16-15/Cargo.lock new file mode 100644 index 0000000..8e7ba9c --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "shared-state" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/listing-16-15/Cargo.toml b/listings/ch16-fearless-concurrency/listing-16-15/Cargo.toml new file mode 100644 index 0000000..e7c75ac --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "shared-state" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/listing-16-15/src/main.rs b/listings/ch16-fearless-concurrency/listing-16-15/src/main.rs new file mode 100644 index 0000000..30247dd --- /dev/null +++ b/listings/ch16-fearless-concurrency/listing-16-15/src/main.rs @@ -0,0 +1,23 @@ +use std::sync::{Arc, Mutex}; +use std::thread; + +fn main() { + let counter = Arc::new(Mutex::new(0)); + let mut handles = vec![]; + + for _ in 0..10 { + let counter = Arc::clone(&counter); + let handle = thread::spawn(move || { + let mut num = counter.lock().unwrap(); + + *num += 1; + }); + handles.push(handle); + } + + for handle in handles { + handle.join().unwrap(); + } + + println!("Result: {}", *counter.lock().unwrap()); +} diff --git a/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/Cargo.lock b/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/Cargo.toml b/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/src/main.rs b/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/src/main.rs new file mode 100644 index 0000000..6205e57 --- /dev/null +++ b/listings/ch16-fearless-concurrency/no-listing-01-join-too-early/src/main.rs @@ -0,0 +1,18 @@ +use std::thread; +use std::time::Duration; + +fn main() { + let handle = thread::spawn(|| { + for i in 1..10 { + println!("hi number {} from the spawned thread!", i); + thread::sleep(Duration::from_millis(1)); + } + }); + + handle.join().unwrap(); + + for i in 1..5 { + println!("hi number {} from the main thread!", i); + thread::sleep(Duration::from_millis(1)); + } +} diff --git a/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/Cargo.lock b/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/Cargo.lock new file mode 100644 index 0000000..8e7ba9c --- /dev/null +++ b/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "shared-state" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/Cargo.toml b/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/Cargo.toml new file mode 100644 index 0000000..e7c75ac --- /dev/null +++ b/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "shared-state" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/src/main.rs b/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/src/main.rs new file mode 100644 index 0000000..dbb1397 --- /dev/null +++ b/listings/ch16-fearless-concurrency/no-listing-02-no-loop-to-understand-error/src/main.rs @@ -0,0 +1,27 @@ +use std::sync::Mutex; +use std::thread; + +fn main() { + let counter = Mutex::new(0); + let mut handles = vec![]; + + let handle = thread::spawn(move || { + let mut num = counter.lock().unwrap(); + + *num += 1; + }); + handles.push(handle); + + let handle2 = thread::spawn(move || { + let mut num2 = counter.lock().unwrap(); + + *num2 += 1; + }); + handles.push(handle2); + + for handle in handles { + handle.join().unwrap(); + } + + println!("Result: {}", *counter.lock().unwrap()); +} diff --git a/listings/ch16-fearless-concurrency/output-only-01-move-drop/Cargo.lock b/listings/ch16-fearless-concurrency/output-only-01-move-drop/Cargo.lock new file mode 100644 index 0000000..8ecc3ae --- /dev/null +++ b/listings/ch16-fearless-concurrency/output-only-01-move-drop/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "threads" +version = "0.1.0" + diff --git a/listings/ch16-fearless-concurrency/output-only-01-move-drop/Cargo.toml b/listings/ch16-fearless-concurrency/output-only-01-move-drop/Cargo.toml new file mode 100644 index 0000000..68a31e1 --- /dev/null +++ b/listings/ch16-fearless-concurrency/output-only-01-move-drop/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "threads" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch16-fearless-concurrency/output-only-01-move-drop/output.txt b/listings/ch16-fearless-concurrency/output-only-01-move-drop/output.txt new file mode 100644 index 0000000..0a73128 --- /dev/null +++ b/listings/ch16-fearless-concurrency/output-only-01-move-drop/output.txt @@ -0,0 +1,22 @@ +$ cargo run + Compiling threads v0.1.0 (file:///projects/threads) +error[E0382]: use of moved value: `v` + --> src/main.rs:10:10 + | +4 | let v = vec![1, 2, 3]; + | - move occurs because `v` has type `Vec`, which does not implement the `Copy` trait +5 | +6 | let handle = thread::spawn(move || { + | ------- value moved into closure here +7 | println!("Here's a vector: {:?}", v); + | - variable moved due to use in closure +... +10 | drop(v); // oh no! + | ^ value used here after move + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `threads` + +To learn more, run the command again with --verbose. diff --git a/listings/ch16-fearless-concurrency/output-only-01-move-drop/src/main.rs b/listings/ch16-fearless-concurrency/output-only-01-move-drop/src/main.rs new file mode 100644 index 0000000..70f659c --- /dev/null +++ b/listings/ch16-fearless-concurrency/output-only-01-move-drop/src/main.rs @@ -0,0 +1,13 @@ +use std::thread; + +fn main() { + let v = vec![1, 2, 3]; + + let handle = thread::spawn(move || { + println!("Here's a vector: {:?}", v); + }); + + drop(v); // oh no! + + handle.join().unwrap(); +} diff --git a/listings/ch17-oop/listing-17-01/Cargo.lock b/listings/ch17-oop/listing-17-01/Cargo.lock new file mode 100644 index 0000000..471d8df --- /dev/null +++ b/listings/ch17-oop/listing-17-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "averaged-collection" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-01/Cargo.toml b/listings/ch17-oop/listing-17-01/Cargo.toml new file mode 100644 index 0000000..ab96488 --- /dev/null +++ b/listings/ch17-oop/listing-17-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "averaged-collection" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-01/src/lib.rs b/listings/ch17-oop/listing-17-01/src/lib.rs new file mode 100644 index 0000000..b5ce2ab --- /dev/null +++ b/listings/ch17-oop/listing-17-01/src/lib.rs @@ -0,0 +1,4 @@ +pub struct AveragedCollection { + list: Vec, + average: f64, +} diff --git a/listings/ch17-oop/listing-17-02/Cargo.lock b/listings/ch17-oop/listing-17-02/Cargo.lock new file mode 100644 index 0000000..471d8df --- /dev/null +++ b/listings/ch17-oop/listing-17-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "averaged-collection" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-02/Cargo.toml b/listings/ch17-oop/listing-17-02/Cargo.toml new file mode 100644 index 0000000..ab96488 --- /dev/null +++ b/listings/ch17-oop/listing-17-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "averaged-collection" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-02/src/lib.rs b/listings/ch17-oop/listing-17-02/src/lib.rs new file mode 100644 index 0000000..bb407ec --- /dev/null +++ b/listings/ch17-oop/listing-17-02/src/lib.rs @@ -0,0 +1,33 @@ +pub struct AveragedCollection { + list: Vec, + average: f64, +} + +// ANCHOR: here +impl AveragedCollection { + pub fn add(&mut self, value: i32) { + self.list.push(value); + self.update_average(); + } + + pub fn remove(&mut self) -> Option { + let result = self.list.pop(); + match result { + Some(value) => { + self.update_average(); + Some(value) + } + None => None, + } + } + + pub fn average(&self) -> f64 { + self.average + } + + fn update_average(&mut self) { + let total: i32 = self.list.iter().sum(); + self.average = total as f64 / self.list.len() as f64; + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-03/Cargo.lock b/listings/ch17-oop/listing-17-03/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-03/Cargo.toml b/listings/ch17-oop/listing-17-03/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-03/src/lib.rs b/listings/ch17-oop/listing-17-03/src/lib.rs new file mode 100644 index 0000000..3a5cb77 --- /dev/null +++ b/listings/ch17-oop/listing-17-03/src/lib.rs @@ -0,0 +1,3 @@ +pub trait Draw { + fn draw(&self); +} diff --git a/listings/ch17-oop/listing-17-04/Cargo.lock b/listings/ch17-oop/listing-17-04/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-04/Cargo.toml b/listings/ch17-oop/listing-17-04/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-04/src/lib.rs b/listings/ch17-oop/listing-17-04/src/lib.rs new file mode 100644 index 0000000..0c45e2a --- /dev/null +++ b/listings/ch17-oop/listing-17-04/src/lib.rs @@ -0,0 +1,9 @@ +pub trait Draw { + fn draw(&self); +} + +// ANCHOR: here +pub struct Screen { + pub components: Vec>, +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-05/Cargo.lock b/listings/ch17-oop/listing-17-05/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-05/Cargo.toml b/listings/ch17-oop/listing-17-05/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-05/src/lib.rs b/listings/ch17-oop/listing-17-05/src/lib.rs new file mode 100644 index 0000000..57ebb57 --- /dev/null +++ b/listings/ch17-oop/listing-17-05/src/lib.rs @@ -0,0 +1,17 @@ +pub trait Draw { + fn draw(&self); +} + +pub struct Screen { + pub components: Vec>, +} + +// ANCHOR: here +impl Screen { + pub fn run(&self) { + for component in self.components.iter() { + component.draw(); + } + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-06/Cargo.lock b/listings/ch17-oop/listing-17-06/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-06/Cargo.toml b/listings/ch17-oop/listing-17-06/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-06/src/lib.rs b/listings/ch17-oop/listing-17-06/src/lib.rs new file mode 100644 index 0000000..63a8907 --- /dev/null +++ b/listings/ch17-oop/listing-17-06/src/lib.rs @@ -0,0 +1,20 @@ +pub trait Draw { + fn draw(&self); +} + +// ANCHOR: here +pub struct Screen { + pub components: Vec, +} + +impl Screen +where + T: Draw, +{ + pub fn run(&self) { + for component in self.components.iter() { + component.draw(); + } + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-07/Cargo.lock b/listings/ch17-oop/listing-17-07/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-07/Cargo.toml b/listings/ch17-oop/listing-17-07/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-07/src/lib.rs b/listings/ch17-oop/listing-17-07/src/lib.rs new file mode 100644 index 0000000..b16cd01 --- /dev/null +++ b/listings/ch17-oop/listing-17-07/src/lib.rs @@ -0,0 +1,29 @@ +pub trait Draw { + fn draw(&self); +} + +pub struct Screen { + pub components: Vec>, +} + +impl Screen { + pub fn run(&self) { + for component in self.components.iter() { + component.draw(); + } + } +} + +// ANCHOR: here +pub struct Button { + pub width: u32, + pub height: u32, + pub label: String, +} + +impl Draw for Button { + fn draw(&self) { + // code to actually draw a button + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-08/Cargo.lock b/listings/ch17-oop/listing-17-08/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-08/Cargo.toml b/listings/ch17-oop/listing-17-08/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-08/src/lib.rs b/listings/ch17-oop/listing-17-08/src/lib.rs new file mode 100644 index 0000000..960fee2 --- /dev/null +++ b/listings/ch17-oop/listing-17-08/src/lib.rs @@ -0,0 +1,27 @@ +pub trait Draw { + fn draw(&self); +} + +pub struct Screen { + pub components: Vec>, +} + +impl Screen { + pub fn run(&self) { + for component in self.components.iter() { + component.draw(); + } + } +} + +pub struct Button { + pub width: u32, + pub height: u32, + pub label: String, +} + +impl Draw for Button { + fn draw(&self) { + // code to actually draw a button + } +} diff --git a/listings/ch17-oop/listing-17-08/src/main.rs b/listings/ch17-oop/listing-17-08/src/main.rs new file mode 100644 index 0000000..9575d40 --- /dev/null +++ b/listings/ch17-oop/listing-17-08/src/main.rs @@ -0,0 +1,17 @@ +// ANCHOR: here +use gui::Draw; + +struct SelectBox { + width: u32, + height: u32, + options: Vec, +} + +impl Draw for SelectBox { + fn draw(&self) { + // code to actually draw a select box + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch17-oop/listing-17-09/Cargo.lock b/listings/ch17-oop/listing-17-09/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-09/Cargo.toml b/listings/ch17-oop/listing-17-09/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-09/src/lib.rs b/listings/ch17-oop/listing-17-09/src/lib.rs new file mode 100644 index 0000000..960fee2 --- /dev/null +++ b/listings/ch17-oop/listing-17-09/src/lib.rs @@ -0,0 +1,27 @@ +pub trait Draw { + fn draw(&self); +} + +pub struct Screen { + pub components: Vec>, +} + +impl Screen { + pub fn run(&self) { + for component in self.components.iter() { + component.draw(); + } + } +} + +pub struct Button { + pub width: u32, + pub height: u32, + pub label: String, +} + +impl Draw for Button { + fn draw(&self) { + // code to actually draw a button + } +} diff --git a/listings/ch17-oop/listing-17-09/src/main.rs b/listings/ch17-oop/listing-17-09/src/main.rs new file mode 100644 index 0000000..4eb13f6 --- /dev/null +++ b/listings/ch17-oop/listing-17-09/src/main.rs @@ -0,0 +1,40 @@ +use gui::Draw; + +struct SelectBox { + width: u32, + height: u32, + options: Vec, +} + +impl Draw for SelectBox { + fn draw(&self) { + // code to actually draw a select box + } +} + +// ANCHOR: here +use gui::{Button, Screen}; + +fn main() { + let screen = Screen { + components: vec![ + Box::new(SelectBox { + width: 75, + height: 10, + options: vec![ + String::from("Yes"), + String::from("Maybe"), + String::from("No"), + ], + }), + Box::new(Button { + width: 50, + height: 10, + label: String::from("OK"), + }), + ], + }; + + screen.run(); +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-10/Cargo.lock b/listings/ch17-oop/listing-17-10/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/listing-17-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-10/Cargo.toml b/listings/ch17-oop/listing-17-10/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/listing-17-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-10/output.txt b/listings/ch17-oop/listing-17-10/output.txt new file mode 100644 index 0000000..893abd6 --- /dev/null +++ b/listings/ch17-oop/listing-17-10/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling gui v0.1.0 (file:///projects/gui) +error[E0277]: the trait bound `String: Draw` is not satisfied + --> src/main.rs:5:26 + | +5 | components: vec![Box::new(String::from("Hi"))], + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Draw` is not implemented for `String` + | + = note: required for the cast to the object type `dyn Draw` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `gui` + +To learn more, run the command again with --verbose. diff --git a/listings/ch17-oop/listing-17-10/src/lib.rs b/listings/ch17-oop/listing-17-10/src/lib.rs new file mode 100644 index 0000000..960fee2 --- /dev/null +++ b/listings/ch17-oop/listing-17-10/src/lib.rs @@ -0,0 +1,27 @@ +pub trait Draw { + fn draw(&self); +} + +pub struct Screen { + pub components: Vec>, +} + +impl Screen { + pub fn run(&self) { + for component in self.components.iter() { + component.draw(); + } + } +} + +pub struct Button { + pub width: u32, + pub height: u32, + pub label: String, +} + +impl Draw for Button { + fn draw(&self) { + // code to actually draw a button + } +} diff --git a/listings/ch17-oop/listing-17-10/src/main.rs b/listings/ch17-oop/listing-17-10/src/main.rs new file mode 100644 index 0000000..2ede87a --- /dev/null +++ b/listings/ch17-oop/listing-17-10/src/main.rs @@ -0,0 +1,9 @@ +use gui::Screen; + +fn main() { + let screen = Screen { + components: vec![Box::new(String::from("Hi"))], + }; + + screen.run(); +} diff --git a/listings/ch17-oop/listing-17-11/Cargo.lock b/listings/ch17-oop/listing-17-11/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-11/Cargo.toml b/listings/ch17-oop/listing-17-11/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-11/src/main.rs b/listings/ch17-oop/listing-17-11/src/main.rs new file mode 100644 index 0000000..d99170a --- /dev/null +++ b/listings/ch17-oop/listing-17-11/src/main.rs @@ -0,0 +1,20 @@ +// ANCHOR: all +use blog::Post; + +// ANCHOR: here +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + // ANCHOR_END: here + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); + // ANCHOR: here +} +// ANCHOR_END: here +// ANCHOR_END: all diff --git a/listings/ch17-oop/listing-17-12/Cargo.lock b/listings/ch17-oop/listing-17-12/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-12/Cargo.toml b/listings/ch17-oop/listing-17-12/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-12/src/lib.rs b/listings/ch17-oop/listing-17-12/src/lib.rs new file mode 100644 index 0000000..b8156c3 --- /dev/null +++ b/listings/ch17-oop/listing-17-12/src/lib.rs @@ -0,0 +1,19 @@ +pub struct Post { + state: Option>, + content: String, +} + +impl Post { + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } +} + +trait State {} + +struct Draft {} + +impl State for Draft {} diff --git a/listings/ch17-oop/listing-17-12/src/main.rs b/listings/ch17-oop/listing-17-12/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-12/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-13/Cargo.lock b/listings/ch17-oop/listing-17-13/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-13/Cargo.toml b/listings/ch17-oop/listing-17-13/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-13/src/lib.rs b/listings/ch17-oop/listing-17-13/src/lib.rs new file mode 100644 index 0000000..bd68557 --- /dev/null +++ b/listings/ch17-oop/listing-17-13/src/lib.rs @@ -0,0 +1,28 @@ +pub struct Post { + state: Option>, + content: String, +} + +// ANCHOR: here +impl Post { + // --snip-- + // ANCHOR_END: here + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } + + // ANCHOR: here + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } +} +// ANCHOR_END: here + +trait State {} + +struct Draft {} + +impl State for Draft {} diff --git a/listings/ch17-oop/listing-17-13/src/main.rs b/listings/ch17-oop/listing-17-13/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-13/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-14/Cargo.lock b/listings/ch17-oop/listing-17-14/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-14/Cargo.toml b/listings/ch17-oop/listing-17-14/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-14/src/lib.rs b/listings/ch17-oop/listing-17-14/src/lib.rs new file mode 100644 index 0000000..09cf0c4 --- /dev/null +++ b/listings/ch17-oop/listing-17-14/src/lib.rs @@ -0,0 +1,32 @@ +pub struct Post { + state: Option>, + content: String, +} + +// ANCHOR: here +impl Post { + // --snip-- + // ANCHOR_END: here + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } + + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + // ANCHOR: here + pub fn content(&self) -> &str { + "" + } +} +// ANCHOR_END: here + +trait State {} + +struct Draft {} + +impl State for Draft {} diff --git a/listings/ch17-oop/listing-17-14/src/main.rs b/listings/ch17-oop/listing-17-14/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-14/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-15/Cargo.lock b/listings/ch17-oop/listing-17-15/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-15/Cargo.toml b/listings/ch17-oop/listing-17-15/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-15/src/lib.rs b/listings/ch17-oop/listing-17-15/src/lib.rs new file mode 100644 index 0000000..909dd52 --- /dev/null +++ b/listings/ch17-oop/listing-17-15/src/lib.rs @@ -0,0 +1,52 @@ +pub struct Post { + state: Option>, + content: String, +} + +// ANCHOR: here +impl Post { + // --snip-- + // ANCHOR_END: here + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } + + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + pub fn content(&self) -> &str { + "" + } + + // ANCHOR: here + pub fn request_review(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.request_review()) + } + } +} + +trait State { + fn request_review(self: Box) -> Box; +} + +struct Draft {} + +impl State for Draft { + fn request_review(self: Box) -> Box { + Box::new(PendingReview {}) + } +} + +struct PendingReview {} + +impl State for PendingReview { + fn request_review(self: Box) -> Box { + self + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-15/src/main.rs b/listings/ch17-oop/listing-17-15/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-15/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-16/Cargo.lock b/listings/ch17-oop/listing-17-16/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-16/Cargo.toml b/listings/ch17-oop/listing-17-16/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-16/src/lib.rs b/listings/ch17-oop/listing-17-16/src/lib.rs new file mode 100644 index 0000000..92cb298 --- /dev/null +++ b/listings/ch17-oop/listing-17-16/src/lib.rs @@ -0,0 +1,85 @@ +pub struct Post { + state: Option>, + content: String, +} + +// ANCHOR: here +impl Post { + // --snip-- + // ANCHOR_END: here + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } + + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + pub fn content(&self) -> &str { + "" + } + + pub fn request_review(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.request_review()) + } + } + + // ANCHOR: here + pub fn approve(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.approve()) + } + } +} + +trait State { + fn request_review(self: Box) -> Box; + fn approve(self: Box) -> Box; +} + +struct Draft {} + +impl State for Draft { + // --snip-- + // ANCHOR_END: here + fn request_review(self: Box) -> Box { + Box::new(PendingReview {}) + } + + // ANCHOR: here + fn approve(self: Box) -> Box { + self + } +} + +struct PendingReview {} + +impl State for PendingReview { + // --snip-- + // ANCHOR_END: here + fn request_review(self: Box) -> Box { + self + } + + // ANCHOR: here + fn approve(self: Box) -> Box { + Box::new(Published {}) + } +} + +struct Published {} + +impl State for Published { + fn request_review(self: Box) -> Box { + self + } + + fn approve(self: Box) -> Box { + self + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-16/src/main.rs b/listings/ch17-oop/listing-17-16/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-16/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-17/Cargo.lock b/listings/ch17-oop/listing-17-17/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-17/Cargo.toml b/listings/ch17-oop/listing-17-17/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-17/src/lib.rs b/listings/ch17-oop/listing-17-17/src/lib.rs new file mode 100644 index 0000000..0beee7b --- /dev/null +++ b/listings/ch17-oop/listing-17-17/src/lib.rs @@ -0,0 +1,82 @@ +pub struct Post { + state: Option>, + content: String, +} + +// ANCHOR: here +impl Post { + // --snip-- + // ANCHOR_END: here + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } + + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + // ANCHOR: here + pub fn content(&self) -> &str { + self.state.as_ref().unwrap().content(self) + } + // --snip-- + // ANCHOR_END: here + + pub fn request_review(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.request_review()) + } + } + + pub fn approve(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.approve()) + } + } + // ANCHOR: here +} +// ANCHOR_END: here + +trait State { + fn request_review(self: Box) -> Box; + fn approve(self: Box) -> Box; +} + +struct Draft {} + +impl State for Draft { + fn request_review(self: Box) -> Box { + Box::new(PendingReview {}) + } + + fn approve(self: Box) -> Box { + self + } +} + +struct PendingReview {} + +impl State for PendingReview { + fn request_review(self: Box) -> Box { + self + } + + fn approve(self: Box) -> Box { + Box::new(Published {}) + } +} + +struct Published {} + +impl State for Published { + fn request_review(self: Box) -> Box { + self + } + + fn approve(self: Box) -> Box { + self + } +} diff --git a/listings/ch17-oop/listing-17-17/src/main.rs b/listings/ch17-oop/listing-17-17/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-17/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-18/Cargo.lock b/listings/ch17-oop/listing-17-18/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-18/Cargo.toml b/listings/ch17-oop/listing-17-18/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-18/src/lib.rs b/listings/ch17-oop/listing-17-18/src/lib.rs new file mode 100644 index 0000000..1bac8a8 --- /dev/null +++ b/listings/ch17-oop/listing-17-18/src/lib.rs @@ -0,0 +1,94 @@ +pub struct Post { + state: Option>, + content: String, +} + +impl Post { + pub fn new() -> Post { + Post { + state: Some(Box::new(Draft {})), + content: String::new(), + } + } + + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + pub fn content(&self) -> &str { + self.state.as_ref().unwrap().content(self) + } + + pub fn request_review(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.request_review()) + } + } + + pub fn approve(&mut self) { + if let Some(s) = self.state.take() { + self.state = Some(s.approve()) + } + } +} + +// ANCHOR: here +trait State { + // --snip-- + // ANCHOR_END: here + fn request_review(self: Box) -> Box; + fn approve(self: Box) -> Box; + + // ANCHOR: here + fn content<'a>(&self, post: &'a Post) -> &'a str { + "" + } +} + +// --snip-- +// ANCHOR_END: here + +struct Draft {} + +impl State for Draft { + fn request_review(self: Box) -> Box { + Box::new(PendingReview {}) + } + + fn approve(self: Box) -> Box { + self + } +} + +struct PendingReview {} + +impl State for PendingReview { + fn request_review(self: Box) -> Box { + self + } + + fn approve(self: Box) -> Box { + Box::new(Published {}) + } +} + +// ANCHOR: here +struct Published {} + +impl State for Published { + // --snip-- + // ANCHOR_END: here + fn request_review(self: Box) -> Box { + self + } + + fn approve(self: Box) -> Box { + self + } + + // ANCHOR: here + fn content<'a>(&self, post: &'a Post) -> &'a str { + &post.content + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-18/src/main.rs b/listings/ch17-oop/listing-17-18/src/main.rs new file mode 100644 index 0000000..14b4c08 --- /dev/null +++ b/listings/ch17-oop/listing-17-18/src/main.rs @@ -0,0 +1,14 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + assert_eq!("", post.content()); + + post.request_review(); + assert_eq!("", post.content()); + + post.approve(); + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/listing-17-19/Cargo.lock b/listings/ch17-oop/listing-17-19/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-19/Cargo.toml b/listings/ch17-oop/listing-17-19/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-19/src/lib.rs b/listings/ch17-oop/listing-17-19/src/lib.rs new file mode 100644 index 0000000..bfe034e --- /dev/null +++ b/listings/ch17-oop/listing-17-19/src/lib.rs @@ -0,0 +1,25 @@ +pub struct Post { + content: String, +} + +pub struct DraftPost { + content: String, +} + +impl Post { + pub fn new() -> DraftPost { + DraftPost { + content: String::new(), + } + } + + pub fn content(&self) -> &str { + &self.content + } +} + +impl DraftPost { + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } +} diff --git a/listings/ch17-oop/listing-17-20/Cargo.lock b/listings/ch17-oop/listing-17-20/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-20/Cargo.toml b/listings/ch17-oop/listing-17-20/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-20/src/lib.rs b/listings/ch17-oop/listing-17-20/src/lib.rs new file mode 100644 index 0000000..3b82ec0 --- /dev/null +++ b/listings/ch17-oop/listing-17-20/src/lib.rs @@ -0,0 +1,48 @@ +pub struct Post { + content: String, +} + +pub struct DraftPost { + content: String, +} + +impl Post { + pub fn new() -> DraftPost { + DraftPost { + content: String::new(), + } + } + + pub fn content(&self) -> &str { + &self.content + } +} + +// ANCHOR: here +impl DraftPost { + // --snip-- + // ANCHOR_END: here + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + // ANCHOR: here + pub fn request_review(self) -> PendingReviewPost { + PendingReviewPost { + content: self.content, + } + } +} + +pub struct PendingReviewPost { + content: String, +} + +impl PendingReviewPost { + pub fn approve(self) -> Post { + Post { + content: self.content, + } + } +} +// ANCHOR_END: here diff --git a/listings/ch17-oop/listing-17-21/Cargo.lock b/listings/ch17-oop/listing-17-21/Cargo.lock new file mode 100644 index 0000000..b6f4232 --- /dev/null +++ b/listings/ch17-oop/listing-17-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "blog" +version = "0.1.0" + diff --git a/listings/ch17-oop/listing-17-21/Cargo.toml b/listings/ch17-oop/listing-17-21/Cargo.toml new file mode 100644 index 0000000..9a395e2 --- /dev/null +++ b/listings/ch17-oop/listing-17-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "blog" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/listing-17-21/src/lib.rs b/listings/ch17-oop/listing-17-21/src/lib.rs new file mode 100644 index 0000000..38500a6 --- /dev/null +++ b/listings/ch17-oop/listing-17-21/src/lib.rs @@ -0,0 +1,43 @@ +pub struct Post { + content: String, +} + +pub struct DraftPost { + content: String, +} + +impl Post { + pub fn new() -> DraftPost { + DraftPost { + content: String::new(), + } + } + + pub fn content(&self) -> &str { + &self.content + } +} + +impl DraftPost { + pub fn add_text(&mut self, text: &str) { + self.content.push_str(text); + } + + pub fn request_review(self) -> PendingReviewPost { + PendingReviewPost { + content: self.content, + } + } +} + +pub struct PendingReviewPost { + content: String, +} + +impl PendingReviewPost { + pub fn approve(self) -> Post { + Post { + content: self.content, + } + } +} diff --git a/listings/ch17-oop/listing-17-21/src/main.rs b/listings/ch17-oop/listing-17-21/src/main.rs new file mode 100644 index 0000000..720c55e --- /dev/null +++ b/listings/ch17-oop/listing-17-21/src/main.rs @@ -0,0 +1,13 @@ +use blog::Post; + +fn main() { + let mut post = Post::new(); + + post.add_text("I ate a salad for lunch today"); + + let post = post.request_review(); + + let post = post.approve(); + + assert_eq!("I ate a salad for lunch today", post.content()); +} diff --git a/listings/ch17-oop/no-listing-01-trait-object-of-clone/Cargo.lock b/listings/ch17-oop/no-listing-01-trait-object-of-clone/Cargo.lock new file mode 100644 index 0000000..00d7b21 --- /dev/null +++ b/listings/ch17-oop/no-listing-01-trait-object-of-clone/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "gui" +version = "0.1.0" + diff --git a/listings/ch17-oop/no-listing-01-trait-object-of-clone/Cargo.toml b/listings/ch17-oop/no-listing-01-trait-object-of-clone/Cargo.toml new file mode 100644 index 0000000..1f61cd2 --- /dev/null +++ b/listings/ch17-oop/no-listing-01-trait-object-of-clone/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "gui" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch17-oop/no-listing-01-trait-object-of-clone/output.txt b/listings/ch17-oop/no-listing-01-trait-object-of-clone/output.txt new file mode 100644 index 0000000..40d6c7f --- /dev/null +++ b/listings/ch17-oop/no-listing-01-trait-object-of-clone/output.txt @@ -0,0 +1,17 @@ +$ cargo build + Compiling gui v0.1.0 (file:///projects/gui) +error[E0038]: the trait `Clone` cannot be made into an object + --> src/lib.rs:2:21 + | +2 | pub components: Vec>, + | ^^^^^^^^^^^^^^^^^^^ `Clone` cannot be made into an object + | + = note: the trait cannot be made into an object because it requires `Self: Sized` + = note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0038`. +error: could not compile `gui` + +To learn more, run the command again with --verbose. diff --git a/listings/ch17-oop/no-listing-01-trait-object-of-clone/src/lib.rs b/listings/ch17-oop/no-listing-01-trait-object-of-clone/src/lib.rs new file mode 100644 index 0000000..e6b1a37 --- /dev/null +++ b/listings/ch17-oop/no-listing-01-trait-object-of-clone/src/lib.rs @@ -0,0 +1,3 @@ +pub struct Screen { + pub components: Vec>, +} diff --git a/listings/ch18-patterns-and-matching/listing-18-01/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-01/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-01/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-01/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-01/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-01/src/main.rs new file mode 100644 index 0000000..d28c369 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-01/src/main.rs @@ -0,0 +1,19 @@ +fn main() { + let favorite_color: Option<&str> = None; + let is_tuesday = false; + let age: Result = "34".parse(); + + if let Some(color) = favorite_color { + println!("Using your favorite color, {}, as the background", color); + } else if is_tuesday { + println!("Tuesday is green day!"); + } else if let Ok(age) = age { + if age > 30 { + println!("Using purple as the background color"); + } else { + println!("Using orange as the background color"); + } + } else { + println!("Using blue as the background color"); + } +} diff --git a/listings/ch18-patterns-and-matching/listing-18-02/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-02/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-02/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-02/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-02/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-02/src/main.rs new file mode 100644 index 0000000..5f75a4f --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-02/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + let mut stack = Vec::new(); + + stack.push(1); + stack.push(2); + stack.push(3); + + while let Some(top) = stack.pop() { + println!("{}", top); + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-03/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-03/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-03/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-03/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-03/output.txt b/listings/ch18-patterns-and-matching/listing-18-03/output.txt new file mode 100644 index 0000000..02fdecb --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-03/output.txt @@ -0,0 +1,7 @@ +$ cargo run + Compiling patterns v0.1.0 (file:///projects/patterns) + Finished dev [unoptimized + debuginfo] target(s) in 0.52s + Running `target/debug/patterns` +a is at index 0 +b is at index 1 +c is at index 2 diff --git a/listings/ch18-patterns-and-matching/listing-18-03/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-03/src/main.rs new file mode 100644 index 0000000..eb922d6 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-03/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + let v = vec!['a', 'b', 'c']; + + for (index, value) in v.iter().enumerate() { + println!("{} is at index {}", value, index); + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-04/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-04/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-04/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-04/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-04/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-04/src/main.rs new file mode 100644 index 0000000..27b0c3f --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-04/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + // ANCHOR: here + let (x, y, z) = (1, 2, 3); + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-05/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-05/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-05/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-05/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-05/output.txt b/listings/ch18-patterns-and-matching/listing-18-05/output.txt new file mode 100644 index 0000000..12eeda7 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-05/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling patterns v0.1.0 (file:///projects/patterns) +error[E0308]: mismatched types + --> src/main.rs:2:9 + | +2 | let (x, y) = (1, 2, 3); + | ^^^^^^ --------- this expression has type `({integer}, {integer}, {integer})` + | | + | expected a tuple with 3 elements, found one with 2 elements + | + = note: expected tuple `({integer}, {integer}, {integer})` + found tuple `(_, _)` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. +error: could not compile `patterns` + +To learn more, run the command again with --verbose. diff --git a/listings/ch18-patterns-and-matching/listing-18-05/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-05/src/main.rs new file mode 100644 index 0000000..39f768e --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-05/src/main.rs @@ -0,0 +1,5 @@ +fn main() { + // ANCHOR: here + let (x, y) = (1, 2, 3); + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-06/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-06/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-06/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-06/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-06/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-06/src/main.rs new file mode 100644 index 0000000..c5d71e6 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-06/src/main.rs @@ -0,0 +1,7 @@ +// ANCHOR: here +fn foo(x: i32) { + // code goes here +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch18-patterns-and-matching/listing-18-07/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-07/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-07/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-07/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-07/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-07/src/main.rs new file mode 100644 index 0000000..4eccb80 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-07/src/main.rs @@ -0,0 +1,8 @@ +fn print_coordinates(&(x, y): &(i32, i32)) { + println!("Current location: ({}, {})", x, y); +} + +fn main() { + let point = (3, 5); + print_coordinates(&point); +} diff --git a/listings/ch18-patterns-and-matching/listing-18-08/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-08/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-08/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-08/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-08/output.txt b/listings/ch18-patterns-and-matching/listing-18-08/output.txt new file mode 100644 index 0000000..1843ece --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-08/output.txt @@ -0,0 +1,22 @@ +$ cargo run + Compiling patterns v0.1.0 (file:///projects/patterns) +error[E0005]: refutable pattern in local binding: `None` not covered + --> src/main.rs:3:9 + | +3 | let Some(x) = some_option_value; + | ^^^^^^^ pattern `None` not covered + | + = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant + = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html + = note: the matched value is of type `Option` +help: you might want to use `if let` to ignore the variant that isn't matched + | +3 | if let Some(x) = some_option_value { /* */ } + | + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0005`. +error: could not compile `patterns` + +To learn more, run the command again with --verbose. diff --git a/listings/ch18-patterns-and-matching/listing-18-08/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-08/src/main.rs new file mode 100644 index 0000000..7baa02a --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-08/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + let some_option_value: Option = None; + // ANCHOR: here + let Some(x) = some_option_value; + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-09/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-09/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-09/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-09/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-09/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-09/src/main.rs new file mode 100644 index 0000000..d6274fc --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-09/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + let some_option_value: Option = None; + // ANCHOR: here + if let Some(x) = some_option_value { + println!("{}", x); + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-10/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-10/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-10/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-10/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-10/output.txt b/listings/ch18-patterns-and-matching/listing-18-10/output.txt new file mode 100644 index 0000000..f30dd5f --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-10/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling patterns v0.1.0 (file:///projects/patterns) +warning: irrefutable `if let` pattern + --> src/main.rs:2:5 + | +2 | / if let x = 5 { +3 | | println!("{}", x); +4 | | }; + | |_____^ + | + = note: `#[warn(irrefutable_let_patterns)]` on by default + = note: this pattern will always match, so the `if let` is useless + = help: consider replacing the `if let` with a `let` + +warning: 1 warning emitted + + Finished dev [unoptimized + debuginfo] target(s) in 0.39s + Running `target/debug/patterns` +5 diff --git a/listings/ch18-patterns-and-matching/listing-18-10/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-10/src/main.rs new file mode 100644 index 0000000..cb81772 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-10/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + if let x = 5 { + println!("{}", x); + }; + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-11/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-11/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-11/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-11/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-11/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-11/src/main.rs new file mode 100644 index 0000000..25eaa79 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-11/src/main.rs @@ -0,0 +1,14 @@ +fn main() { + // ANCHOR: here + let x = Some(5); + let y = 10; + + match x { + Some(50) => println!("Got 50"), + Some(y) => println!("Matched, y = {:?}", y), + _ => println!("Default case, x = {:?}", x), + } + + println!("at the end: x = {:?}, y = {:?}", x, y); + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-12/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-12/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-12/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-12/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-12/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-12/src/main.rs new file mode 100644 index 0000000..62f4ccb --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-12/src/main.rs @@ -0,0 +1,12 @@ +struct Point { + x: i32, + y: i32, +} + +fn main() { + let p = Point { x: 0, y: 7 }; + + let Point { x: a, y: b } = p; + assert_eq!(0, a); + assert_eq!(7, b); +} diff --git a/listings/ch18-patterns-and-matching/listing-18-13/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-13/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-13/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-13/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-13/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-13/src/main.rs new file mode 100644 index 0000000..5badc15 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-13/src/main.rs @@ -0,0 +1,12 @@ +struct Point { + x: i32, + y: i32, +} + +fn main() { + let p = Point { x: 0, y: 7 }; + + let Point { x, y } = p; + assert_eq!(0, x); + assert_eq!(7, y); +} diff --git a/listings/ch18-patterns-and-matching/listing-18-14/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-14/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-14/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-14/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-14/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-14/src/main.rs new file mode 100644 index 0000000..8d445d9 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-14/src/main.rs @@ -0,0 +1,16 @@ +struct Point { + x: i32, + y: i32, +} + +// ANCHOR: here +fn main() { + let p = Point { x: 0, y: 7 }; + + match p { + Point { x, y: 0 } => println!("On the x axis at {}", x), + Point { x: 0, y } => println!("On the y axis at {}", y), + Point { x, y } => println!("On neither axis: ({}, {})", x, y), + } +} +// ANCHOR_END: here diff --git a/listings/ch18-patterns-and-matching/listing-18-15/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-15/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-15/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-15/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-15/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-15/src/main.rs new file mode 100644 index 0000000..9b8dac1 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-15/src/main.rs @@ -0,0 +1,27 @@ +enum Message { + Quit, + Move { x: i32, y: i32 }, + Write(String), + ChangeColor(i32, i32, i32), +} + +fn main() { + let msg = Message::ChangeColor(0, 160, 255); + + match msg { + Message::Quit => { + println!("The Quit variant has no data to destructure.") + } + Message::Move { x, y } => { + println!( + "Move in the x direction {} and in the y direction {}", + x, y + ); + } + Message::Write(text) => println!("Text message: {}", text), + Message::ChangeColor(r, g, b) => println!( + "Change the color to red {}, green {}, and blue {}", + r, g, b + ), + } +} diff --git a/listings/ch18-patterns-and-matching/listing-18-16/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-16/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-16/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-16/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-16/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-16/src/main.rs new file mode 100644 index 0000000..ed6a20b --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-16/src/main.rs @@ -0,0 +1,27 @@ +enum Color { + Rgb(i32, i32, i32), + Hsv(i32, i32, i32), +} + +enum Message { + Quit, + Move { x: i32, y: i32 }, + Write(String), + ChangeColor(Color), +} + +fn main() { + let msg = Message::ChangeColor(Color::Hsv(0, 160, 255)); + + match msg { + Message::ChangeColor(Color::Rgb(r, g, b)) => println!( + "Change the color to red {}, green {}, and blue {}", + r, g, b + ), + Message::ChangeColor(Color::Hsv(h, s, v)) => println!( + "Change the color to hue {}, saturation {}, and value {}", + h, s, v + ), + _ => (), + } +} diff --git a/listings/ch18-patterns-and-matching/listing-18-17/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-17/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-17/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-17/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-17/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-17/src/main.rs new file mode 100644 index 0000000..cf1fbe0 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-17/src/main.rs @@ -0,0 +1,7 @@ +fn foo(_: i32, y: i32) { + println!("This code only uses the y parameter: {}", y); +} + +fn main() { + foo(3, 4); +} diff --git a/listings/ch18-patterns-and-matching/listing-18-18/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-18/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-18/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-18/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-18/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-18/src/main.rs new file mode 100644 index 0000000..b776c64 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-18/src/main.rs @@ -0,0 +1,17 @@ +fn main() { + // ANCHOR: here + let mut setting_value = Some(5); + let new_setting_value = Some(10); + + match (setting_value, new_setting_value) { + (Some(_), Some(_)) => { + println!("Can't overwrite an existing customized value"); + } + _ => { + setting_value = new_setting_value; + } + } + + println!("setting is {:?}", setting_value); + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-19/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-19/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-19/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-19/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-19/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-19/src/main.rs new file mode 100644 index 0000000..59b48c9 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-19/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let numbers = (2, 4, 8, 16, 32); + + match numbers { + (first, _, third, _, fifth) => { + println!("Some numbers: {}, {}, {}", first, third, fifth) + } + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-20/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-20/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-20/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-20/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-20/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-20/src/main.rs new file mode 100644 index 0000000..1ffc46b --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-20/src/main.rs @@ -0,0 +1,4 @@ +fn main() { + let _x = 5; + let y = 10; +} diff --git a/listings/ch18-patterns-and-matching/listing-18-21/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-21/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-21/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-21/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-21/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-21/src/main.rs new file mode 100644 index 0000000..9806105 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-21/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let s = Some(String::from("Hello!")); + + if let Some(_s) = s { + println!("found a string"); + } + + println!("{:?}", s); + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-22/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-22/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-22/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-22/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-22/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-22/src/main.rs new file mode 100644 index 0000000..e2faa34 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-22/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let s = Some(String::from("Hello!")); + + if let Some(_) = s { + println!("found a string"); + } + + println!("{:?}", s); + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-23/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-23/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-23/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-23/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-23/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-23/src/main.rs new file mode 100644 index 0000000..7a9d9bb --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-23/src/main.rs @@ -0,0 +1,15 @@ +fn main() { + // ANCHOR: here + struct Point { + x: i32, + y: i32, + z: i32, + } + + let origin = Point { x: 0, y: 0, z: 0 }; + + match origin { + Point { x, .. } => println!("x is {}", x), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-24/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-24/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-24/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-24/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-24/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-24/src/main.rs new file mode 100644 index 0000000..f22dbe8 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-24/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let numbers = (2, 4, 8, 16, 32); + + match numbers { + (first, .., last) => { + println!("Some numbers: {}, {}", first, last); + } + } +} diff --git a/listings/ch18-patterns-and-matching/listing-18-25/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-25/Cargo.lock new file mode 100644 index 0000000..a233623 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-25/Cargo.lock @@ -0,0 +1,4 @@ +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-25/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-25/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-25/output.txt b/listings/ch18-patterns-and-matching/listing-18-25/output.txt new file mode 100644 index 0000000..9ba40fa --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-25/output.txt @@ -0,0 +1,15 @@ +$ cargo run + Compiling patterns v0.1.0 (file:///projects/patterns) +error: `..` can only be used once per tuple pattern + --> src/main.rs:5:22 + | +5 | (.., second, ..) => { + | -- ^^ can only be used once per tuple pattern + | | + | previously used here + +error: aborting due to previous error + +error: could not compile `patterns` + +To learn more, run the command again with --verbose. diff --git a/listings/ch18-patterns-and-matching/listing-18-25/rustfmt-ignore b/listings/ch18-patterns-and-matching/listing-18-25/rustfmt-ignore new file mode 100644 index 0000000..06a976d --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-25/rustfmt-ignore @@ -0,0 +1 @@ +This listing deliberately doesn't parse so rustfmt fails. diff --git a/listings/ch18-patterns-and-matching/listing-18-25/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-25/src/main.rs new file mode 100644 index 0000000..b90884e --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-25/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let numbers = (2, 4, 8, 16, 32); + + match numbers { + (.., second, ..) => { + println!("Some numbers: {}", second) + }, + } +} diff --git a/listings/ch18-patterns-and-matching/listing-18-26/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-26/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-26/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-26/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-26/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-26/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-26/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-26/src/main.rs new file mode 100644 index 0000000..4ec86cb --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-26/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let num = Some(4); + + match num { + Some(x) if x < 5 => println!("less than five: {}", x), + Some(x) => println!("{}", x), + None => (), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-27/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-27/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-27/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-27/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-27/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-27/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-27/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-27/src/main.rs new file mode 100644 index 0000000..348e367 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-27/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + let x = Some(5); + let y = 10; + + match x { + Some(50) => println!("Got 50"), + Some(n) if n == y => println!("Matched, n = {}", n), + _ => println!("Default case, x = {:?}", x), + } + + println!("at the end: x = {:?}, y = {}", x, y); +} diff --git a/listings/ch18-patterns-and-matching/listing-18-28/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-28/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-28/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-28/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-28/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-28/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-28/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-28/src/main.rs new file mode 100644 index 0000000..1580455 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-28/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let x = 4; + let y = false; + + match x { + 4 | 5 | 6 if y => println!("yes"), + _ => println!("no"), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/listing-18-29/Cargo.lock b/listings/ch18-patterns-and-matching/listing-18-29/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-29/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/listing-18-29/Cargo.toml b/listings/ch18-patterns-and-matching/listing-18-29/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-29/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/listing-18-29/src/main.rs b/listings/ch18-patterns-and-matching/listing-18-29/src/main.rs new file mode 100644 index 0000000..3514deb --- /dev/null +++ b/listings/ch18-patterns-and-matching/listing-18-29/src/main.rs @@ -0,0 +1,19 @@ +fn main() { + // ANCHOR: here + enum Message { + Hello { id: i32 }, + } + + let msg = Message::Hello { id: 5 }; + + match msg { + Message::Hello { + id: id_variable @ 3..=7, + } => println!("Found an id in range: {}", id_variable), + Message::Hello { id: 10..=12 } => { + println!("Found an id in another range") + } + Message::Hello { id } => println!("Found some other id: {}", id), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/no-listing-01-literals/Cargo.lock b/listings/ch18-patterns-and-matching/no-listing-01-literals/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-01-literals/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/no-listing-01-literals/Cargo.toml b/listings/ch18-patterns-and-matching/no-listing-01-literals/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-01-literals/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/no-listing-01-literals/src/main.rs b/listings/ch18-patterns-and-matching/no-listing-01-literals/src/main.rs new file mode 100644 index 0000000..7978e1a --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-01-literals/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + let x = 1; + + match x { + 1 => println!("one"), + 2 => println!("two"), + 3 => println!("three"), + _ => println!("anything"), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/Cargo.lock b/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/Cargo.toml b/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/src/main.rs b/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/src/main.rs new file mode 100644 index 0000000..e52d815 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-02-multiple-patterns/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let x = 1; + + match x { + 1 | 2 => println!("one or two"), + 3 => println!("three"), + _ => println!("anything"), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/no-listing-03-ranges/Cargo.lock b/listings/ch18-patterns-and-matching/no-listing-03-ranges/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-03-ranges/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/no-listing-03-ranges/Cargo.toml b/listings/ch18-patterns-and-matching/no-listing-03-ranges/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-03-ranges/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/no-listing-03-ranges/src/main.rs b/listings/ch18-patterns-and-matching/no-listing-03-ranges/src/main.rs new file mode 100644 index 0000000..a3ebe7a --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-03-ranges/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + let x = 5; + + match x { + 1..=5 => println!("one through five"), + _ => println!("something else"), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/Cargo.lock b/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/Cargo.toml b/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/src/main.rs b/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/src/main.rs new file mode 100644 index 0000000..8cebfef --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-04-ranges-of-char/src/main.rs @@ -0,0 +1,11 @@ +fn main() { + // ANCHOR: here + let x = 'c'; + + match x { + 'a'..='j' => println!("early ASCII letter"), + 'k'..='z' => println!("late ASCII letter"), + _ => println!("something else"), + } + // ANCHOR_END: here +} diff --git a/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/Cargo.lock b/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/Cargo.lock new file mode 100644 index 0000000..2b4fa29 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "patterns" +version = "0.1.0" + diff --git a/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/Cargo.toml b/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/Cargo.toml new file mode 100644 index 0000000..f77be07 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "patterns" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/src/main.rs b/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/src/main.rs new file mode 100644 index 0000000..962d093 --- /dev/null +++ b/listings/ch18-patterns-and-matching/no-listing-05-destructuring-structs-and-tuples/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + struct Point { + x: i32, + y: i32, + } + + // ANCHOR: here + let ((feet, inches), Point { x, y }) = ((3, 10), Point { x: 3, y: -10 }); + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-13-21-reproduced/Cargo.lock b/listings/ch19-advanced-features/listing-13-21-reproduced/Cargo.lock new file mode 100644 index 0000000..58b70c5 --- /dev/null +++ b/listings/ch19-advanced-features/listing-13-21-reproduced/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "counter" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-13-21-reproduced/Cargo.toml b/listings/ch19-advanced-features/listing-13-21-reproduced/Cargo.toml new file mode 100644 index 0000000..4eb29e8 --- /dev/null +++ b/listings/ch19-advanced-features/listing-13-21-reproduced/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "counter" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-13-21-reproduced/src/lib.rs b/listings/ch19-advanced-features/listing-13-21-reproduced/src/lib.rs new file mode 100644 index 0000000..04c7f38 --- /dev/null +++ b/listings/ch19-advanced-features/listing-13-21-reproduced/src/lib.rs @@ -0,0 +1,25 @@ +struct Counter { + count: u32, +} + +impl Counter { + fn new() -> Counter { + Counter { count: 0 } + } +} + +// ANCHOR: ch19 +impl Iterator for Counter { + type Item = u32; + + fn next(&mut self) -> Option { + // --snip-- + // ANCHOR_END: ch19 + if self.count < 5 { + self.count += 1; + Some(self.count) + } else { + None + } + } +} diff --git a/listings/ch19-advanced-features/listing-19-01/Cargo.lock b/listings/ch19-advanced-features/listing-19-01/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-01/Cargo.toml b/listings/ch19-advanced-features/listing-19-01/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-01/src/main.rs b/listings/ch19-advanced-features/listing-19-01/src/main.rs new file mode 100644 index 0000000..893f578 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-01/src/main.rs @@ -0,0 +1,8 @@ +fn main() { + // ANCHOR: here + let mut num = 5; + + let r1 = &num as *const i32; + let r2 = &mut num as *mut i32; + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-02/Cargo.lock b/listings/ch19-advanced-features/listing-19-02/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-02/Cargo.toml b/listings/ch19-advanced-features/listing-19-02/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-02/src/main.rs b/listings/ch19-advanced-features/listing-19-02/src/main.rs new file mode 100644 index 0000000..849629a --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-02/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let address = 0x012345usize; + let r = address as *const i32; + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-03/Cargo.lock b/listings/ch19-advanced-features/listing-19-03/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-03/Cargo.toml b/listings/ch19-advanced-features/listing-19-03/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-03/src/main.rs b/listings/ch19-advanced-features/listing-19-03/src/main.rs new file mode 100644 index 0000000..02a0be6 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-03/src/main.rs @@ -0,0 +1,13 @@ +fn main() { + // ANCHOR: here + let mut num = 5; + + let r1 = &num as *const i32; + let r2 = &mut num as *mut i32; + + unsafe { + println!("r1 is: {}", *r1); + println!("r2 is: {}", *r2); + } + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-04/Cargo.lock b/listings/ch19-advanced-features/listing-19-04/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-04/Cargo.toml b/listings/ch19-advanced-features/listing-19-04/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-04/src/main.rs b/listings/ch19-advanced-features/listing-19-04/src/main.rs new file mode 100644 index 0000000..6ac5844 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-04/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: here + let mut v = vec![1, 2, 3, 4, 5, 6]; + + let r = &mut v[..]; + + let (a, b) = r.split_at_mut(3); + + assert_eq!(a, &mut [1, 2, 3]); + assert_eq!(b, &mut [4, 5, 6]); + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-05/Cargo.lock b/listings/ch19-advanced-features/listing-19-05/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-05/Cargo.toml b/listings/ch19-advanced-features/listing-19-05/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-05/output.txt b/listings/ch19-advanced-features/listing-19-05/output.txt new file mode 100644 index 0000000..559729f --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-05/output.txt @@ -0,0 +1,21 @@ +$ cargo run + Compiling unsafe-example v0.1.0 (file:///projects/unsafe-example) +error[E0499]: cannot borrow `*slice` as mutable more than once at a time + --> src/main.rs:6:30 + | +1 | fn split_at_mut(slice: &mut [i32], mid: usize) -> (&mut [i32], &mut [i32]) { + | - let's call the lifetime of this reference `'1` +... +6 | (&mut slice[..mid], &mut slice[mid..]) + | -------------------------^^^^^-------- + | | | | + | | | second mutable borrow occurs here + | | first mutable borrow occurs here + | returning this value requires that `*slice` is borrowed for `'1` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0499`. +error: could not compile `unsafe-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch19-advanced-features/listing-19-05/src/main.rs b/listings/ch19-advanced-features/listing-19-05/src/main.rs new file mode 100644 index 0000000..c4b83ef --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-05/src/main.rs @@ -0,0 +1,14 @@ +// ANCHOR: here +fn split_at_mut(slice: &mut [i32], mid: usize) -> (&mut [i32], &mut [i32]) { + let len = slice.len(); + + assert!(mid <= len); + + (&mut slice[..mid], &mut slice[mid..]) +} +// ANCHOR_END: here + +fn main() { + let mut vector = vec![1, 2, 3, 4, 5, 6]; + let (left, right) = split_at_mut(&mut vector, 3); +} diff --git a/listings/ch19-advanced-features/listing-19-06/Cargo.lock b/listings/ch19-advanced-features/listing-19-06/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-06/Cargo.toml b/listings/ch19-advanced-features/listing-19-06/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-06/src/main.rs b/listings/ch19-advanced-features/listing-19-06/src/main.rs new file mode 100644 index 0000000..f25cbf4 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-06/src/main.rs @@ -0,0 +1,22 @@ +// ANCHOR: here +use std::slice; + +fn split_at_mut(slice: &mut [i32], mid: usize) -> (&mut [i32], &mut [i32]) { + let len = slice.len(); + let ptr = slice.as_mut_ptr(); + + assert!(mid <= len); + + unsafe { + ( + slice::from_raw_parts_mut(ptr, mid), + slice::from_raw_parts_mut(ptr.add(mid), len - mid), + ) + } +} +// ANCHOR_END: here + +fn main() { + let mut vector = vec![1, 2, 3, 4, 5, 6]; + let (left, right) = split_at_mut(&mut vector, 3); +} diff --git a/listings/ch19-advanced-features/listing-19-07/Cargo.lock b/listings/ch19-advanced-features/listing-19-07/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-07/Cargo.toml b/listings/ch19-advanced-features/listing-19-07/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-07/src/main.rs b/listings/ch19-advanced-features/listing-19-07/src/main.rs new file mode 100644 index 0000000..0ab39ae --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-07/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + use std::slice; + + let address = 0x01234usize; + let r = address as *mut i32; + + let slice: &[i32] = unsafe { slice::from_raw_parts_mut(r, 10000) }; + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-08/Cargo.lock b/listings/ch19-advanced-features/listing-19-08/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-08/Cargo.toml b/listings/ch19-advanced-features/listing-19-08/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-08/src/main.rs b/listings/ch19-advanced-features/listing-19-08/src/main.rs new file mode 100644 index 0000000..8b56630 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-08/src/main.rs @@ -0,0 +1,9 @@ +extern "C" { + fn abs(input: i32) -> i32; +} + +fn main() { + unsafe { + println!("Absolute value of -3 according to C: {}", abs(-3)); + } +} diff --git a/listings/ch19-advanced-features/listing-19-09/Cargo.lock b/listings/ch19-advanced-features/listing-19-09/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-09/Cargo.toml b/listings/ch19-advanced-features/listing-19-09/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-09/src/main.rs b/listings/ch19-advanced-features/listing-19-09/src/main.rs new file mode 100644 index 0000000..82a4b42 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-09/src/main.rs @@ -0,0 +1,5 @@ +static HELLO_WORLD: &str = "Hello, world!"; + +fn main() { + println!("name is: {}", HELLO_WORLD); +} diff --git a/listings/ch19-advanced-features/listing-19-10/Cargo.lock b/listings/ch19-advanced-features/listing-19-10/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-10/Cargo.toml b/listings/ch19-advanced-features/listing-19-10/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-10/src/main.rs b/listings/ch19-advanced-features/listing-19-10/src/main.rs new file mode 100644 index 0000000..e8dab68 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-10/src/main.rs @@ -0,0 +1,15 @@ +static mut COUNTER: u32 = 0; + +fn add_to_count(inc: u32) { + unsafe { + COUNTER += inc; + } +} + +fn main() { + add_to_count(3); + + unsafe { + println!("COUNTER: {}", COUNTER); + } +} diff --git a/listings/ch19-advanced-features/listing-19-11/Cargo.lock b/listings/ch19-advanced-features/listing-19-11/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-11/Cargo.toml b/listings/ch19-advanced-features/listing-19-11/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-11/src/main.rs b/listings/ch19-advanced-features/listing-19-11/src/main.rs new file mode 100644 index 0000000..885c1aa --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-11/src/main.rs @@ -0,0 +1,9 @@ +unsafe trait Foo { + // methods go here +} + +unsafe impl Foo for i32 { + // method implementations go here +} + +fn main() {} diff --git a/listings/ch19-advanced-features/listing-19-12/Cargo.lock b/listings/ch19-advanced-features/listing-19-12/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-12/Cargo.toml b/listings/ch19-advanced-features/listing-19-12/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-12/src/lib.rs b/listings/ch19-advanced-features/listing-19-12/src/lib.rs new file mode 100644 index 0000000..dbe0462 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-12/src/lib.rs @@ -0,0 +1,5 @@ +pub trait Iterator { + type Item; + + fn next(&mut self) -> Option; +} diff --git a/listings/ch19-advanced-features/listing-19-13/Cargo.lock b/listings/ch19-advanced-features/listing-19-13/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-13/Cargo.toml b/listings/ch19-advanced-features/listing-19-13/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-13/src/lib.rs b/listings/ch19-advanced-features/listing-19-13/src/lib.rs new file mode 100644 index 0000000..7c9479c --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-13/src/lib.rs @@ -0,0 +1,3 @@ +pub trait Iterator { + fn next(&mut self) -> Option; +} diff --git a/listings/ch19-advanced-features/listing-19-14/Cargo.lock b/listings/ch19-advanced-features/listing-19-14/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-14/Cargo.toml b/listings/ch19-advanced-features/listing-19-14/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-14/src/main.rs b/listings/ch19-advanced-features/listing-19-14/src/main.rs new file mode 100644 index 0000000..7dea568 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-14/src/main.rs @@ -0,0 +1,25 @@ +use std::ops::Add; + +#[derive(Debug, PartialEq)] +struct Point { + x: i32, + y: i32, +} + +impl Add for Point { + type Output = Point; + + fn add(self, other: Point) -> Point { + Point { + x: self.x + other.x, + y: self.y + other.y, + } + } +} + +fn main() { + assert_eq!( + Point { x: 1, y: 0 } + Point { x: 2, y: 3 }, + Point { x: 3, y: 3 } + ); +} diff --git a/listings/ch19-advanced-features/listing-19-15/Cargo.lock b/listings/ch19-advanced-features/listing-19-15/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-15/Cargo.toml b/listings/ch19-advanced-features/listing-19-15/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-15/src/lib.rs b/listings/ch19-advanced-features/listing-19-15/src/lib.rs new file mode 100644 index 0000000..f38bf47 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-15/src/lib.rs @@ -0,0 +1,12 @@ +use std::ops::Add; + +struct Millimeters(u32); +struct Meters(u32); + +impl Add for Millimeters { + type Output = Millimeters; + + fn add(self, other: Meters) -> Millimeters { + Millimeters(self.0 + (other.0 * 1000)) + } +} diff --git a/listings/ch19-advanced-features/listing-19-16/Cargo.lock b/listings/ch19-advanced-features/listing-19-16/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-16/Cargo.toml b/listings/ch19-advanced-features/listing-19-16/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-16/src/main.rs b/listings/ch19-advanced-features/listing-19-16/src/main.rs new file mode 100644 index 0000000..d854e28 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-16/src/main.rs @@ -0,0 +1,31 @@ +// ANCHOR: here +trait Pilot { + fn fly(&self); +} + +trait Wizard { + fn fly(&self); +} + +struct Human; + +impl Pilot for Human { + fn fly(&self) { + println!("This is your captain speaking."); + } +} + +impl Wizard for Human { + fn fly(&self) { + println!("Up!"); + } +} + +impl Human { + fn fly(&self) { + println!("*waving arms furiously*"); + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch19-advanced-features/listing-19-17/Cargo.lock b/listings/ch19-advanced-features/listing-19-17/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-17/Cargo.toml b/listings/ch19-advanced-features/listing-19-17/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-17/src/main.rs b/listings/ch19-advanced-features/listing-19-17/src/main.rs new file mode 100644 index 0000000..3df65a7 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-17/src/main.rs @@ -0,0 +1,34 @@ +trait Pilot { + fn fly(&self); +} + +trait Wizard { + fn fly(&self); +} + +struct Human; + +impl Pilot for Human { + fn fly(&self) { + println!("This is your captain speaking."); + } +} + +impl Wizard for Human { + fn fly(&self) { + println!("Up!"); + } +} + +impl Human { + fn fly(&self) { + println!("*waving arms furiously*"); + } +} + +// ANCHOR: here +fn main() { + let person = Human; + person.fly(); +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/listing-19-18/Cargo.lock b/listings/ch19-advanced-features/listing-19-18/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-18/Cargo.toml b/listings/ch19-advanced-features/listing-19-18/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-18/output.txt b/listings/ch19-advanced-features/listing-19-18/output.txt new file mode 100644 index 0000000..2e9da17 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-18/output.txt @@ -0,0 +1,7 @@ +$ cargo run + Compiling traits-example v0.1.0 (file:///projects/traits-example) + Finished dev [unoptimized + debuginfo] target(s) in 0.46s + Running `target/debug/traits-example` +This is your captain speaking. +Up! +*waving arms furiously* diff --git a/listings/ch19-advanced-features/listing-19-18/src/main.rs b/listings/ch19-advanced-features/listing-19-18/src/main.rs new file mode 100644 index 0000000..fa01c09 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-18/src/main.rs @@ -0,0 +1,36 @@ +trait Pilot { + fn fly(&self); +} + +trait Wizard { + fn fly(&self); +} + +struct Human; + +impl Pilot for Human { + fn fly(&self) { + println!("This is your captain speaking."); + } +} + +impl Wizard for Human { + fn fly(&self) { + println!("Up!"); + } +} + +impl Human { + fn fly(&self) { + println!("*waving arms furiously*"); + } +} + +// ANCHOR: here +fn main() { + let person = Human; + Pilot::fly(&person); + Wizard::fly(&person); + person.fly(); +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/listing-19-19/Cargo.lock b/listings/ch19-advanced-features/listing-19-19/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-19/Cargo.toml b/listings/ch19-advanced-features/listing-19-19/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-19/output.txt b/listings/ch19-advanced-features/listing-19-19/output.txt new file mode 100644 index 0000000..087e802 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-19/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling traits-example v0.1.0 (file:///projects/traits-example) + Finished dev [unoptimized + debuginfo] target(s) in 0.54s + Running `target/debug/traits-example` +A baby dog is called a Spot diff --git a/listings/ch19-advanced-features/listing-19-19/src/main.rs b/listings/ch19-advanced-features/listing-19-19/src/main.rs new file mode 100644 index 0000000..44affe0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-19/src/main.rs @@ -0,0 +1,21 @@ +trait Animal { + fn baby_name() -> String; +} + +struct Dog; + +impl Dog { + fn baby_name() -> String { + String::from("Spot") + } +} + +impl Animal for Dog { + fn baby_name() -> String { + String::from("puppy") + } +} + +fn main() { + println!("A baby dog is called a {}", Dog::baby_name()); +} diff --git a/listings/ch19-advanced-features/listing-19-20/Cargo.lock b/listings/ch19-advanced-features/listing-19-20/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-20/Cargo.toml b/listings/ch19-advanced-features/listing-19-20/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-20/output.txt b/listings/ch19-advanced-features/listing-19-20/output.txt new file mode 100644 index 0000000..b95dde7 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-20/output.txt @@ -0,0 +1,19 @@ +$ cargo run + Compiling traits-example v0.1.0 (file:///projects/traits-example) +error[E0283]: type annotations needed + --> src/main.rs:20:43 + | +2 | fn baby_name() -> String; + | ------------------------- required by `Animal::baby_name` +... +20 | println!("A baby dog is called a {}", Animal::baby_name()); + | ^^^^^^^^^^^^^^^^^ cannot infer type + | + = note: cannot satisfy `_: Animal` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0283`. +error: could not compile `traits-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch19-advanced-features/listing-19-20/src/main.rs b/listings/ch19-advanced-features/listing-19-20/src/main.rs new file mode 100644 index 0000000..8e295c9 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-20/src/main.rs @@ -0,0 +1,23 @@ +trait Animal { + fn baby_name() -> String; +} + +struct Dog; + +impl Dog { + fn baby_name() -> String { + String::from("Spot") + } +} + +impl Animal for Dog { + fn baby_name() -> String { + String::from("puppy") + } +} + +// ANCHOR: here +fn main() { + println!("A baby dog is called a {}", Animal::baby_name()); +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/listing-19-21/Cargo.lock b/listings/ch19-advanced-features/listing-19-21/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-21/Cargo.toml b/listings/ch19-advanced-features/listing-19-21/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-21/output.txt b/listings/ch19-advanced-features/listing-19-21/output.txt new file mode 100644 index 0000000..4d1ee5a --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-21/output.txt @@ -0,0 +1,5 @@ +$ cargo run + Compiling traits-example v0.1.0 (file:///projects/traits-example) + Finished dev [unoptimized + debuginfo] target(s) in 0.48s + Running `target/debug/traits-example` +A baby dog is called a puppy diff --git a/listings/ch19-advanced-features/listing-19-21/src/main.rs b/listings/ch19-advanced-features/listing-19-21/src/main.rs new file mode 100644 index 0000000..b1df728 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-21/src/main.rs @@ -0,0 +1,23 @@ +trait Animal { + fn baby_name() -> String; +} + +struct Dog; + +impl Dog { + fn baby_name() -> String { + String::from("Spot") + } +} + +impl Animal for Dog { + fn baby_name() -> String { + String::from("puppy") + } +} + +// ANCHOR: here +fn main() { + println!("A baby dog is called a {}", ::baby_name()); +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/listing-19-22/Cargo.lock b/listings/ch19-advanced-features/listing-19-22/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-22/Cargo.toml b/listings/ch19-advanced-features/listing-19-22/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-22/src/main.rs b/listings/ch19-advanced-features/listing-19-22/src/main.rs new file mode 100644 index 0000000..febe58b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-22/src/main.rs @@ -0,0 +1,17 @@ +// ANCHOR: here +use std::fmt; + +trait OutlinePrint: fmt::Display { + fn outline_print(&self) { + let output = self.to_string(); + let len = output.len(); + println!("{}", "*".repeat(len + 4)); + println!("*{}*", " ".repeat(len + 2)); + println!("* {} *", output); + println!("*{}*", " ".repeat(len + 2)); + println!("{}", "*".repeat(len + 4)); + } +} +// ANCHOR_END: here + +fn main() {} diff --git a/listings/ch19-advanced-features/listing-19-23/Cargo.lock b/listings/ch19-advanced-features/listing-19-23/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-23/Cargo.toml b/listings/ch19-advanced-features/listing-19-23/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-23/src/main.rs b/listings/ch19-advanced-features/listing-19-23/src/main.rs new file mode 100644 index 0000000..eae46c9 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-23/src/main.rs @@ -0,0 +1,14 @@ +use std::fmt; + +struct Wrapper(Vec); + +impl fmt::Display for Wrapper { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!(f, "[{}]", self.0.join(", ")) + } +} + +fn main() { + let w = Wrapper(vec![String::from("hello"), String::from("world")]); + println!("w = {}", w); +} diff --git a/listings/ch19-advanced-features/listing-19-24/Cargo.lock b/listings/ch19-advanced-features/listing-19-24/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-24/Cargo.toml b/listings/ch19-advanced-features/listing-19-24/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-24/src/main.rs b/listings/ch19-advanced-features/listing-19-24/src/main.rs new file mode 100644 index 0000000..d604ae8 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-24/src/main.rs @@ -0,0 +1,16 @@ +fn main() { + // ANCHOR: here + let f: Box = Box::new(|| println!("hi")); + + fn takes_long_type(f: Box) { + // --snip-- + } + + fn returns_long_type() -> Box { + // --snip-- + // ANCHOR_END: here + Box::new(|| ()) + // ANCHOR: here + } + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-25/Cargo.lock b/listings/ch19-advanced-features/listing-19-25/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-25/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-25/Cargo.toml b/listings/ch19-advanced-features/listing-19-25/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-25/src/main.rs b/listings/ch19-advanced-features/listing-19-25/src/main.rs new file mode 100644 index 0000000..af35bed --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-25/src/main.rs @@ -0,0 +1,18 @@ +fn main() { + // ANCHOR: here + type Thunk = Box; + + let f: Thunk = Box::new(|| println!("hi")); + + fn takes_long_type(f: Thunk) { + // --snip-- + } + + fn returns_long_type() -> Thunk { + // --snip-- + // ANCHOR_END: here + Box::new(|| ()) + // ANCHOR: here + } + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/listing-19-27/Cargo.lock b/listings/ch19-advanced-features/listing-19-27/Cargo.lock new file mode 100644 index 0000000..b2327c7 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-27/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-27/Cargo.toml b/listings/ch19-advanced-features/listing-19-27/Cargo.toml new file mode 100644 index 0000000..2bed56c --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-27/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-27/src/main.rs b/listings/ch19-advanced-features/listing-19-27/src/main.rs new file mode 100644 index 0000000..91b2cf0 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-27/src/main.rs @@ -0,0 +1,13 @@ +fn add_one(x: i32) -> i32 { + x + 1 +} + +fn do_twice(f: fn(i32) -> i32, arg: i32) -> i32 { + f(arg) + f(arg) +} + +fn main() { + let answer = do_twice(add_one, 5); + + println!("The answer is: {}", answer); +} diff --git a/listings/ch19-advanced-features/listing-19-28/Cargo.lock b/listings/ch19-advanced-features/listing-19-28/Cargo.lock new file mode 100644 index 0000000..b2d9257 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-28/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "macros-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-28/Cargo.toml b/listings/ch19-advanced-features/listing-19-28/Cargo.toml new file mode 100644 index 0000000..1829b0f --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-28/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "macros-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-28/src/lib.rs b/listings/ch19-advanced-features/listing-19-28/src/lib.rs new file mode 100644 index 0000000..7c7c475 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-28/src/lib.rs @@ -0,0 +1,12 @@ +#[macro_export] +macro_rules! vec { + ( $( $x:expr ),* ) => { + { + let mut temp_vec = Vec::new(); + $( + temp_vec.push($x); + )* + temp_vec + } + }; +} diff --git a/listings/ch19-advanced-features/listing-19-30/Cargo.lock b/listings/ch19-advanced-features/listing-19-30/Cargo.lock new file mode 100644 index 0000000..39afcf2 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-30/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-30/Cargo.toml b/listings/ch19-advanced-features/listing-19-30/Cargo.toml new file mode 100644 index 0000000..5a93a68 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-30/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello_macro" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-30/src/main.rs b/listings/ch19-advanced-features/listing-19-30/src/main.rs new file mode 100644 index 0000000..468c30a --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-30/src/main.rs @@ -0,0 +1,9 @@ +use hello_macro::HelloMacro; +use hello_macro_derive::HelloMacro; + +#[derive(HelloMacro)] +struct Pancakes; + +fn main() { + Pancakes::hello_macro(); +} diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/Cargo.lock b/listings/ch19-advanced-features/listing-19-31/hello_macro/Cargo.lock new file mode 100644 index 0000000..39afcf2 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/Cargo.toml b/listings/ch19-advanced-features/listing-19-31/hello_macro/Cargo.toml new file mode 100644 index 0000000..5a93a68 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello_macro" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/Cargo.lock b/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/Cargo.lock new file mode 100644 index 0000000..9a38c8a --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/Cargo.lock @@ -0,0 +1,46 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro_derive" +version = "0.1.0" +dependencies = [ + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "proc-macro2" +version = "1.0.8" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "quote" +version = "1.0.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "syn" +version = "1.0.14" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "unicode-xid" +version = "0.2.0" +source = "registry+https://github.com/rust-lang/crates.io-index" + +[metadata] +"checksum proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548" +"checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe" +"checksum syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)" = "af6f3550d8dff9ef7dc34d384ac6f107e5d31c8f57d9f28e0081503f547ac8f5" +"checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c" diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/Cargo.toml b/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/Cargo.toml new file mode 100644 index 0000000..168cbae --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "hello_macro_derive" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[lib] +proc-macro = true + +[dependencies] +syn = "1.0" +quote = "1.0" diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/src/lib.rs b/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/src/lib.rs new file mode 100644 index 0000000..4bcec44 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/hello_macro_derive/src/lib.rs @@ -0,0 +1,15 @@ +extern crate proc_macro; + +use proc_macro::TokenStream; +use quote::quote; +use syn; + +#[proc_macro_derive(HelloMacro)] +pub fn hello_macro_derive(input: TokenStream) -> TokenStream { + // Construct a representation of Rust code as a syntax tree + // that we can manipulate + let ast = syn::parse(input).unwrap(); + + // Build the trait implementation + impl_hello_macro(&ast) +} diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/src/lib.rs b/listings/ch19-advanced-features/listing-19-31/hello_macro/src/lib.rs new file mode 100644 index 0000000..e747931 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/src/lib.rs @@ -0,0 +1,3 @@ +pub trait HelloMacro { + fn hello_macro(); +} diff --git a/listings/ch19-advanced-features/listing-19-31/hello_macro/src/main.rs b/listings/ch19-advanced-features/listing-19-31/hello_macro/src/main.rs new file mode 100644 index 0000000..10b028b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-31/hello_macro/src/main.rs @@ -0,0 +1,13 @@ +use hello_macro::HelloMacro; + +struct Pancakes; + +impl HelloMacro for Pancakes { + fn hello_macro() { + println!("Hello, Macro! My name is Pancakes!"); + } +} + +fn main() { + Pancakes::hello_macro(); +} diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/Cargo.lock b/listings/ch19-advanced-features/listing-19-33/hello_macro/Cargo.lock new file mode 100644 index 0000000..39afcf2 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/Cargo.toml b/listings/ch19-advanced-features/listing-19-33/hello_macro/Cargo.toml new file mode 100644 index 0000000..5a93a68 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello_macro" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/Cargo.lock b/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/Cargo.lock new file mode 100644 index 0000000..9a38c8a --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/Cargo.lock @@ -0,0 +1,46 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro_derive" +version = "0.1.0" +dependencies = [ + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "proc-macro2" +version = "1.0.8" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "quote" +version = "1.0.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "syn" +version = "1.0.14" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "unicode-xid" +version = "0.2.0" +source = "registry+https://github.com/rust-lang/crates.io-index" + +[metadata] +"checksum proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548" +"checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe" +"checksum syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)" = "af6f3550d8dff9ef7dc34d384ac6f107e5d31c8f57d9f28e0081503f547ac8f5" +"checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c" diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/Cargo.toml b/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/Cargo.toml new file mode 100644 index 0000000..168cbae --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "hello_macro_derive" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[lib] +proc-macro = true + +[dependencies] +syn = "1.0" +quote = "1.0" diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/src/lib.rs b/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/src/lib.rs new file mode 100644 index 0000000..591f0c3 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/hello_macro_derive/src/lib.rs @@ -0,0 +1,29 @@ +extern crate proc_macro; + +use proc_macro::TokenStream; +use quote::quote; +use syn; + +#[proc_macro_derive(HelloMacro)] +pub fn hello_macro_derive(input: TokenStream) -> TokenStream { + // Construct a representation of Rust code as a syntax tree + // that we can manipulate + let ast = syn::parse(input).unwrap(); + + // Build the trait implementation + impl_hello_macro(&ast) +} + +// ANCHOR: here +fn impl_hello_macro(ast: &syn::DeriveInput) -> TokenStream { + let name = &ast.ident; + let gen = quote! { + impl HelloMacro for #name { + fn hello_macro() { + println!("Hello, Macro! My name is {}!", stringify!(#name)); + } + } + }; + gen.into() +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/src/lib.rs b/listings/ch19-advanced-features/listing-19-33/hello_macro/src/lib.rs new file mode 100644 index 0000000..e747931 --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/src/lib.rs @@ -0,0 +1,3 @@ +pub trait HelloMacro { + fn hello_macro(); +} diff --git a/listings/ch19-advanced-features/listing-19-33/hello_macro/src/main.rs b/listings/ch19-advanced-features/listing-19-33/hello_macro/src/main.rs new file mode 100644 index 0000000..10b028b --- /dev/null +++ b/listings/ch19-advanced-features/listing-19-33/hello_macro/src/main.rs @@ -0,0 +1,13 @@ +use hello_macro::HelloMacro; + +struct Pancakes; + +impl HelloMacro for Pancakes { + fn hello_macro() { + println!("Hello, Macro! My name is Pancakes!"); + } +} + +fn main() { + Pancakes::hello_macro(); +} diff --git a/listings/ch19-advanced-features/no-listing-01-unsafe-fn/Cargo.lock b/listings/ch19-advanced-features/no-listing-01-unsafe-fn/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-01-unsafe-fn/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-01-unsafe-fn/Cargo.toml b/listings/ch19-advanced-features/no-listing-01-unsafe-fn/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-01-unsafe-fn/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-01-unsafe-fn/src/main.rs b/listings/ch19-advanced-features/no-listing-01-unsafe-fn/src/main.rs new file mode 100644 index 0000000..21ecdbe --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-01-unsafe-fn/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + unsafe fn dangerous() {} + + unsafe { + dangerous(); + } + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/Cargo.lock b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/Cargo.toml b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/output.txt b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/output.txt new file mode 100644 index 0000000..b9bb3f0 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/output.txt @@ -0,0 +1,20 @@ +$ cargo run + Compiling traits-example v0.1.0 (file:///projects/traits-example) +error[E0277]: `Point` doesn't implement `std::fmt::Display` + --> src/main.rs:20:6 + | +3 | trait OutlinePrint: fmt::Display { + | ------------ required by this bound in `OutlinePrint` +... +20 | impl OutlinePrint for Point {} + | ^^^^^^^^^^^^ `Point` cannot be formatted with the default formatter + | + = help: the trait `std::fmt::Display` is not implemented for `Point` + = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. +error: could not compile `traits-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/src/main.rs b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/src/main.rs new file mode 100644 index 0000000..a1e2fe4 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-02-impl-outlineprint-for-point/src/main.rs @@ -0,0 +1,27 @@ +use std::fmt; + +trait OutlinePrint: fmt::Display { + fn outline_print(&self) { + let output = self.to_string(); + let len = output.len(); + println!("{}", "*".repeat(len + 4)); + println!("*{}*", " ".repeat(len + 2)); + println!("* {} *", output); + println!("*{}*", " ".repeat(len + 2)); + println!("{}", "*".repeat(len + 4)); + } +} + +// ANCHOR: here +struct Point { + x: i32, + y: i32, +} + +impl OutlinePrint for Point {} +// ANCHOR_END: here + +fn main() { + let p = Point { x: 1, y: 3 }; + p.outline_print(); +} diff --git a/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/Cargo.lock b/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/Cargo.toml b/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/src/main.rs b/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/src/main.rs new file mode 100644 index 0000000..c7bbb6a --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-03-impl-display-for-point/src/main.rs @@ -0,0 +1,33 @@ +trait OutlinePrint: fmt::Display { + fn outline_print(&self) { + let output = self.to_string(); + let len = output.len(); + println!("{}", "*".repeat(len + 4)); + println!("*{}*", " ".repeat(len + 2)); + println!("* {} *", output); + println!("*{}*", " ".repeat(len + 2)); + println!("{}", "*".repeat(len + 4)); + } +} + +struct Point { + x: i32, + y: i32, +} + +impl OutlinePrint for Point {} + +// ANCHOR: here +use std::fmt; + +impl fmt::Display for Point { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!(f, "({}, {})", self.x, self.y) + } +} +// ANCHOR_END: here + +fn main() { + let p = Point { x: 1, y: 3 }; + p.outline_print(); +} diff --git a/listings/ch19-advanced-features/no-listing-04-kilometers-alias/Cargo.lock b/listings/ch19-advanced-features/no-listing-04-kilometers-alias/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-04-kilometers-alias/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-04-kilometers-alias/Cargo.toml b/listings/ch19-advanced-features/no-listing-04-kilometers-alias/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-04-kilometers-alias/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-04-kilometers-alias/src/main.rs b/listings/ch19-advanced-features/no-listing-04-kilometers-alias/src/main.rs new file mode 100644 index 0000000..d3fe32e --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-04-kilometers-alias/src/main.rs @@ -0,0 +1,12 @@ +fn main() { + // ANCHOR: there + // ANCHOR: here + type Kilometers = i32; + // ANCHOR_END: here + + let x: i32 = 5; + let y: Kilometers = 5; + + println!("x + y = {}", x + y); + // ANCHOR_END: there +} diff --git a/listings/ch19-advanced-features/no-listing-05-write-trait/Cargo.lock b/listings/ch19-advanced-features/no-listing-05-write-trait/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-05-write-trait/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-05-write-trait/Cargo.toml b/listings/ch19-advanced-features/no-listing-05-write-trait/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-05-write-trait/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-05-write-trait/src/lib.rs b/listings/ch19-advanced-features/no-listing-05-write-trait/src/lib.rs new file mode 100644 index 0000000..8300dcc --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-05-write-trait/src/lib.rs @@ -0,0 +1,10 @@ +use std::fmt; +use std::io::Error; + +pub trait Write { + fn write(&mut self, buf: &[u8]) -> Result; + fn flush(&mut self) -> Result<(), Error>; + + fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>; + fn write_fmt(&mut self, fmt: fmt::Arguments) -> Result<(), Error>; +} diff --git a/listings/ch19-advanced-features/no-listing-06-result-alias/Cargo.lock b/listings/ch19-advanced-features/no-listing-06-result-alias/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-06-result-alias/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-06-result-alias/Cargo.toml b/listings/ch19-advanced-features/no-listing-06-result-alias/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-06-result-alias/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-06-result-alias/src/lib.rs b/listings/ch19-advanced-features/no-listing-06-result-alias/src/lib.rs new file mode 100644 index 0000000..5735599 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-06-result-alias/src/lib.rs @@ -0,0 +1,15 @@ +use std::fmt; + +// ANCHOR: here +type Result = std::result::Result; +// ANCHOR_END: here + +// ANCHOR: there +pub trait Write { + fn write(&mut self, buf: &[u8]) -> Result; + fn flush(&mut self) -> Result<()>; + + fn write_all(&mut self, buf: &[u8]) -> Result<()>; + fn write_fmt(&mut self, fmt: fmt::Arguments) -> Result<()>; +} +// ANCHOR_END: there diff --git a/listings/ch19-advanced-features/no-listing-07-never-type/Cargo.lock b/listings/ch19-advanced-features/no-listing-07-never-type/Cargo.lock new file mode 100644 index 0000000..b1977d0 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-07-never-type/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "traits-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-07-never-type/Cargo.toml b/listings/ch19-advanced-features/no-listing-07-never-type/Cargo.toml new file mode 100644 index 0000000..1e3df02 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-07-never-type/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "traits-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-07-never-type/src/lib.rs b/listings/ch19-advanced-features/no-listing-07-never-type/src/lib.rs new file mode 100644 index 0000000..f0f7aca --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-07-never-type/src/lib.rs @@ -0,0 +1,8 @@ +// ANCHOR: here +fn bar() -> ! { + // --snip-- + // ANCHOR_END: here + panic!(); + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/Cargo.lock b/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/Cargo.toml b/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/src/main.rs b/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/src/main.rs new file mode 100644 index 0000000..6d56008 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-08-match-arms-different-types/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + let guess = "3"; + // ANCHOR: here + let guess = match guess.trim().parse() { + Ok(_) => 5, + Err(_) => "hello", + }; + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-09-unwrap-definition/Cargo.lock b/listings/ch19-advanced-features/no-listing-09-unwrap-definition/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-09-unwrap-definition/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-09-unwrap-definition/Cargo.toml b/listings/ch19-advanced-features/no-listing-09-unwrap-definition/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-09-unwrap-definition/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-09-unwrap-definition/src/lib.rs b/listings/ch19-advanced-features/no-listing-09-unwrap-definition/src/lib.rs new file mode 100644 index 0000000..aa4f937 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-09-unwrap-definition/src/lib.rs @@ -0,0 +1,17 @@ +enum Option { + Some(T), + None, +} + +use crate::Option::*; + +// ANCHOR: here +impl Option { + pub fn unwrap(self) -> T { + match self { + Some(val) => val, + None => panic!("called `Option::unwrap()` on a `None` value"), + } + } +} +// ANCHOR_END: here diff --git a/listings/ch19-advanced-features/no-listing-10-loop-returns-never/Cargo.lock b/listings/ch19-advanced-features/no-listing-10-loop-returns-never/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-10-loop-returns-never/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-10-loop-returns-never/Cargo.toml b/listings/ch19-advanced-features/no-listing-10-loop-returns-never/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-10-loop-returns-never/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-10-loop-returns-never/src/main.rs b/listings/ch19-advanced-features/no-listing-10-loop-returns-never/src/main.rs new file mode 100644 index 0000000..e776891 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-10-loop-returns-never/src/main.rs @@ -0,0 +1,9 @@ +fn main() { + // ANCHOR: here + print!("forever "); + + loop { + print!("and ever "); + } + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-11-cant-create-str/Cargo.lock b/listings/ch19-advanced-features/no-listing-11-cant-create-str/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-11-cant-create-str/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-11-cant-create-str/Cargo.toml b/listings/ch19-advanced-features/no-listing-11-cant-create-str/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-11-cant-create-str/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-11-cant-create-str/src/main.rs b/listings/ch19-advanced-features/no-listing-11-cant-create-str/src/main.rs new file mode 100644 index 0000000..075d511 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-11-cant-create-str/src/main.rs @@ -0,0 +1,6 @@ +fn main() { + // ANCHOR: here + let s1: str = "Hello there!"; + let s2: str = "How's it going?"; + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/Cargo.lock b/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/Cargo.toml b/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/src/lib.rs b/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/src/lib.rs new file mode 100644 index 0000000..69186dd --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-12-generic-fn-definition/src/lib.rs @@ -0,0 +1,3 @@ +fn generic(t: T) { + // --snip-- +} diff --git a/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/Cargo.lock b/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/Cargo.toml b/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/src/lib.rs b/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/src/lib.rs new file mode 100644 index 0000000..c2d00e2 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-13-generic-implicit-sized-bound/src/lib.rs @@ -0,0 +1,3 @@ +fn generic(t: T) { + // --snip-- +} diff --git a/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/Cargo.lock b/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/Cargo.lock new file mode 100644 index 0000000..c0c98a7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "types-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/Cargo.toml b/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/Cargo.toml new file mode 100644 index 0000000..9b4ee68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "types-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/src/lib.rs b/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/src/lib.rs new file mode 100644 index 0000000..e472226 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-14-generic-maybe-sized/src/lib.rs @@ -0,0 +1,3 @@ +fn generic(t: &T) { + // --snip-- +} diff --git a/listings/ch19-advanced-features/no-listing-15-map-closure/Cargo.lock b/listings/ch19-advanced-features/no-listing-15-map-closure/Cargo.lock new file mode 100644 index 0000000..b2327c7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-15-map-closure/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-15-map-closure/Cargo.toml b/listings/ch19-advanced-features/no-listing-15-map-closure/Cargo.toml new file mode 100644 index 0000000..2bed56c --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-15-map-closure/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-15-map-closure/src/main.rs b/listings/ch19-advanced-features/no-listing-15-map-closure/src/main.rs new file mode 100644 index 0000000..b4fcf7e --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-15-map-closure/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + let list_of_numbers = vec![1, 2, 3]; + let list_of_strings: Vec = + list_of_numbers.iter().map(|i| i.to_string()).collect(); + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-16-map-function/Cargo.lock b/listings/ch19-advanced-features/no-listing-16-map-function/Cargo.lock new file mode 100644 index 0000000..b2327c7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-16-map-function/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-16-map-function/Cargo.toml b/listings/ch19-advanced-features/no-listing-16-map-function/Cargo.toml new file mode 100644 index 0000000..2bed56c --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-16-map-function/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-16-map-function/src/main.rs b/listings/ch19-advanced-features/no-listing-16-map-function/src/main.rs new file mode 100644 index 0000000..dff20fe --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-16-map-function/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + let list_of_numbers = vec![1, 2, 3]; + let list_of_strings: Vec = + list_of_numbers.iter().map(ToString::to_string).collect(); + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-17-map-initializer/Cargo.lock b/listings/ch19-advanced-features/no-listing-17-map-initializer/Cargo.lock new file mode 100644 index 0000000..b2327c7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-17-map-initializer/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-17-map-initializer/Cargo.toml b/listings/ch19-advanced-features/no-listing-17-map-initializer/Cargo.toml new file mode 100644 index 0000000..2bed56c --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-17-map-initializer/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-17-map-initializer/src/main.rs b/listings/ch19-advanced-features/no-listing-17-map-initializer/src/main.rs new file mode 100644 index 0000000..60fb730 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-17-map-initializer/src/main.rs @@ -0,0 +1,10 @@ +fn main() { + // ANCHOR: here + enum Status { + Value(u32), + Stop, + } + + let list_of_statuses: Vec = (0u32..20).map(Status::Value).collect(); + // ANCHOR_END: here +} diff --git a/listings/ch19-advanced-features/no-listing-18-returns-closure/Cargo.lock b/listings/ch19-advanced-features/no-listing-18-returns-closure/Cargo.lock new file mode 100644 index 0000000..b2327c7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-18-returns-closure/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-18-returns-closure/Cargo.toml b/listings/ch19-advanced-features/no-listing-18-returns-closure/Cargo.toml new file mode 100644 index 0000000..2bed56c --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-18-returns-closure/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-18-returns-closure/output.txt b/listings/ch19-advanced-features/no-listing-18-returns-closure/output.txt new file mode 100644 index 0000000..be5584a --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-18-returns-closure/output.txt @@ -0,0 +1,20 @@ +$ cargo build + Compiling functions-example v0.1.0 (file:///projects/functions-example) +error[E0746]: return type cannot have an unboxed trait object + --> src/lib.rs:1:25 + | +1 | fn returns_closure() -> dyn Fn(i32) -> i32 { + | ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time + | + = note: for information on `impl Trait`, see +help: use `impl Fn(i32) -> i32` as the return type, as all return paths are of type `[closure@src/lib.rs:2:5: 2:14]`, which implements `Fn(i32) -> i32` + | +1 | fn returns_closure() -> impl Fn(i32) -> i32 { + | ^^^^^^^^^^^^^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0746`. +error: could not compile `functions-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch19-advanced-features/no-listing-18-returns-closure/src/lib.rs b/listings/ch19-advanced-features/no-listing-18-returns-closure/src/lib.rs new file mode 100644 index 0000000..d699ac3 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-18-returns-closure/src/lib.rs @@ -0,0 +1,3 @@ +fn returns_closure() -> dyn Fn(i32) -> i32 { + |x| x + 1 +} diff --git a/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/Cargo.lock b/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/Cargo.lock new file mode 100644 index 0000000..b2327c7 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "functions-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/Cargo.toml b/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/Cargo.toml new file mode 100644 index 0000000..2bed56c --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "functions-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/src/lib.rs b/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/src/lib.rs new file mode 100644 index 0000000..b114077 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-19-returns-closure-trait-object/src/lib.rs @@ -0,0 +1,3 @@ +fn returns_closure() -> Box i32> { + Box::new(|x| x + 1) +} diff --git a/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/Cargo.lock b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/Cargo.lock new file mode 100644 index 0000000..39afcf2 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/Cargo.toml b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/Cargo.toml new file mode 100644 index 0000000..5a93a68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello_macro" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/src/lib.rs b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/src/lib.rs new file mode 100644 index 0000000..e747931 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/hello_macro/src/lib.rs @@ -0,0 +1,3 @@ +pub trait HelloMacro { + fn hello_macro(); +} diff --git a/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/Cargo.lock b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/Cargo.lock new file mode 100644 index 0000000..881cd3f --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/Cargo.lock @@ -0,0 +1,13 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + +[[package]] +name = "pancakes" +version = "0.1.0" +dependencies = [ + "hello_macro 0.1.0", +] + diff --git a/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/Cargo.toml b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/Cargo.toml new file mode 100644 index 0000000..4b6c267 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "pancakes" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +hello_macro = { path = "../hello_macro" } \ No newline at end of file diff --git a/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/src/main.rs b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/src/main.rs new file mode 100644 index 0000000..10b028b --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-20-impl-hellomacro-for-pancakes/pancakes/src/main.rs @@ -0,0 +1,13 @@ +use hello_macro::HelloMacro; + +struct Pancakes; + +impl HelloMacro for Pancakes { + fn hello_macro() { + println!("Hello, Macro! My name is Pancakes!"); + } +} + +fn main() { + Pancakes::hello_macro(); +} diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/Cargo.lock b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/Cargo.lock new file mode 100644 index 0000000..39afcf2 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/Cargo.toml b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/Cargo.toml new file mode 100644 index 0000000..5a93a68 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello_macro" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/Cargo.lock b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/Cargo.lock new file mode 100644 index 0000000..9a38c8a --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/Cargo.lock @@ -0,0 +1,46 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro_derive" +version = "0.1.0" +dependencies = [ + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "proc-macro2" +version = "1.0.8" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "quote" +version = "1.0.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "syn" +version = "1.0.14" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "unicode-xid" +version = "0.2.0" +source = "registry+https://github.com/rust-lang/crates.io-index" + +[metadata] +"checksum proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548" +"checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe" +"checksum syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)" = "af6f3550d8dff9ef7dc34d384ac6f107e5d31c8f57d9f28e0081503f547ac8f5" +"checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c" diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/Cargo.toml b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/Cargo.toml new file mode 100644 index 0000000..168cbae --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "hello_macro_derive" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[lib] +proc-macro = true + +[dependencies] +syn = "1.0" +quote = "1.0" diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/src/lib.rs b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/src/lib.rs new file mode 100644 index 0000000..7a3279d --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/hello_macro_derive/src/lib.rs @@ -0,0 +1,27 @@ +extern crate proc_macro; + +use proc_macro::TokenStream; +use quote::quote; +use syn; + +#[proc_macro_derive(HelloMacro)] +pub fn hello_macro_derive(input: TokenStream) -> TokenStream { + // Construct a representation of Rust code as a syntax tree + // that we can manipulate + let ast = syn::parse(input).unwrap(); + + // Build the trait implementation + impl_hello_macro(&ast) +} + +fn impl_hello_macro(ast: &syn::DeriveInput) -> TokenStream { + let name = &ast.ident; + let gen = quote! { + impl HelloMacro for #name { + fn hello_macro() { + println!("Hello, Macro! My name is {}!", stringify!(#name)); + } + } + }; + gen.into() +} diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/src/lib.rs b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/src/lib.rs new file mode 100644 index 0000000..e747931 --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/src/lib.rs @@ -0,0 +1,3 @@ +pub trait HelloMacro { + fn hello_macro(); +} diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/src/main.rs b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/src/main.rs new file mode 100644 index 0000000..10b028b --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/hello_macro/src/main.rs @@ -0,0 +1,13 @@ +use hello_macro::HelloMacro; + +struct Pancakes; + +impl HelloMacro for Pancakes { + fn hello_macro() { + println!("Hello, Macro! My name is Pancakes!"); + } +} + +fn main() { + Pancakes::hello_macro(); +} diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/Cargo.lock b/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/Cargo.lock new file mode 100644 index 0000000..dee23ec --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/Cargo.lock @@ -0,0 +1,58 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello_macro" +version = "0.1.0" + +[[package]] +name = "hello_macro_derive" +version = "0.1.0" +dependencies = [ + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "pancakes" +version = "0.1.0" +dependencies = [ + "hello_macro 0.1.0", + "hello_macro_derive 0.1.0", +] + +[[package]] +name = "proc-macro2" +version = "1.0.8" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "quote" +version = "1.0.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "syn" +version = "1.0.14" +source = "registry+https://github.com/rust-lang/crates.io-index" +dependencies = [ + "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)", + "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)", + "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)", +] + +[[package]] +name = "unicode-xid" +version = "0.2.0" +source = "registry+https://github.com/rust-lang/crates.io-index" + +[metadata] +"checksum proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548" +"checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe" +"checksum syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)" = "af6f3550d8dff9ef7dc34d384ac6f107e5d31c8f57d9f28e0081503f547ac8f5" +"checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c" diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/Cargo.toml b/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/Cargo.toml new file mode 100644 index 0000000..cc0adda --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "pancakes" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +hello_macro = { path = "../hello_macro" } +hello_macro_derive = { path = "../hello_macro/hello_macro_derive" } diff --git a/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/src/main.rs b/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/src/main.rs new file mode 100644 index 0000000..468c30a --- /dev/null +++ b/listings/ch19-advanced-features/no-listing-21-pancakes/pancakes/src/main.rs @@ -0,0 +1,9 @@ +use hello_macro::HelloMacro; +use hello_macro_derive::HelloMacro; + +#[derive(HelloMacro)] +struct Pancakes; + +fn main() { + Pancakes::hello_macro(); +} diff --git a/listings/ch19-advanced-features/output-only-01-missing-unsafe/Cargo.lock b/listings/ch19-advanced-features/output-only-01-missing-unsafe/Cargo.lock new file mode 100644 index 0000000..497817b --- /dev/null +++ b/listings/ch19-advanced-features/output-only-01-missing-unsafe/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "unsafe-example" +version = "0.1.0" + diff --git a/listings/ch19-advanced-features/output-only-01-missing-unsafe/Cargo.toml b/listings/ch19-advanced-features/output-only-01-missing-unsafe/Cargo.toml new file mode 100644 index 0000000..aabe3bd --- /dev/null +++ b/listings/ch19-advanced-features/output-only-01-missing-unsafe/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "unsafe-example" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch19-advanced-features/output-only-01-missing-unsafe/output.txt b/listings/ch19-advanced-features/output-only-01-missing-unsafe/output.txt new file mode 100644 index 0000000..65e1200 --- /dev/null +++ b/listings/ch19-advanced-features/output-only-01-missing-unsafe/output.txt @@ -0,0 +1,16 @@ +$ cargo run + Compiling unsafe-example v0.1.0 (file:///projects/unsafe-example) +error[E0133]: call to unsafe function is unsafe and requires unsafe function or block + --> src/main.rs:4:5 + | +4 | dangerous(); + | ^^^^^^^^^^^ call to unsafe function + | + = note: consult the function's documentation for information on how to avoid undefined behavior + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0133`. +error: could not compile `unsafe-example` + +To learn more, run the command again with --verbose. diff --git a/listings/ch19-advanced-features/output-only-01-missing-unsafe/src/main.rs b/listings/ch19-advanced-features/output-only-01-missing-unsafe/src/main.rs new file mode 100644 index 0000000..01305be --- /dev/null +++ b/listings/ch19-advanced-features/output-only-01-missing-unsafe/src/main.rs @@ -0,0 +1,7 @@ +fn main() { + // ANCHOR: here + unsafe fn dangerous() {} + + dangerous(); + // ANCHOR_END: here +} diff --git a/listings/ch20-web-server/listing-20-01/Cargo.lock b/listings/ch20-web-server/listing-20-01/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-01/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-01/Cargo.toml b/listings/ch20-web-server/listing-20-01/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-01/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-01/src/main.rs b/listings/ch20-web-server/listing-20-01/src/main.rs new file mode 100644 index 0000000..d868c3e --- /dev/null +++ b/listings/ch20-web-server/listing-20-01/src/main.rs @@ -0,0 +1,11 @@ +use std::net::TcpListener; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + println!("Connection established!"); + } +} diff --git a/listings/ch20-web-server/listing-20-02/Cargo.lock b/listings/ch20-web-server/listing-20-02/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-02/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-02/Cargo.toml b/listings/ch20-web-server/listing-20-02/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-02/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-02/src/main.rs b/listings/ch20-web-server/listing-20-02/src/main.rs new file mode 100644 index 0000000..2e68f2f --- /dev/null +++ b/listings/ch20-web-server/listing-20-02/src/main.rs @@ -0,0 +1,21 @@ +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + + stream.read(&mut buffer).unwrap(); + + println!("Request: {}", String::from_utf8_lossy(&buffer[..])); +} diff --git a/listings/ch20-web-server/listing-20-03/Cargo.lock b/listings/ch20-web-server/listing-20-03/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-03/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-03/Cargo.toml b/listings/ch20-web-server/listing-20-03/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-03/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-03/src/main.rs b/listings/ch20-web-server/listing-20-03/src/main.rs new file mode 100644 index 0000000..afa579a --- /dev/null +++ b/listings/ch20-web-server/listing-20-03/src/main.rs @@ -0,0 +1,26 @@ +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +// ANCHOR: here +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + + stream.read(&mut buffer).unwrap(); + + let response = "HTTP/1.1 200 OK\r\n\r\n"; + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-04/Cargo.lock b/listings/ch20-web-server/listing-20-04/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-04/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-04/Cargo.toml b/listings/ch20-web-server/listing-20-04/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-04/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-04/hello.html b/listings/ch20-web-server/listing-20-04/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-04/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-04/src/main.rs b/listings/ch20-web-server/listing-20-04/src/main.rs new file mode 100644 index 0000000..818eac9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-04/src/main.rs @@ -0,0 +1,24 @@ +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + + stream.read(&mut buffer).unwrap(); + + let response = "HTTP/1.1 200 OK\r\n\r\n"; + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-05/Cargo.lock b/listings/ch20-web-server/listing-20-05/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-05/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-05/Cargo.toml b/listings/ch20-web-server/listing-20-05/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-05/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-05/hello.html b/listings/ch20-web-server/listing-20-05/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-05/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-05/src/main.rs b/listings/ch20-web-server/listing-20-05/src/main.rs new file mode 100644 index 0000000..d20417c --- /dev/null +++ b/listings/ch20-web-server/listing-20-05/src/main.rs @@ -0,0 +1,36 @@ +// ANCHOR: here +use std::fs; +// --snip-- + +// ANCHOR_END: here +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +// ANCHOR: here +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let contents = fs::read_to_string("hello.html").unwrap(); + + let response = format!( + "HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}", + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-06/Cargo.lock b/listings/ch20-web-server/listing-20-06/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-06/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-06/Cargo.toml b/listings/ch20-web-server/listing-20-06/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-06/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-06/hello.html b/listings/ch20-web-server/listing-20-06/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-06/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-06/src/main.rs b/listings/ch20-web-server/listing-20-06/src/main.rs new file mode 100644 index 0000000..8353244 --- /dev/null +++ b/listings/ch20-web-server/listing-20-06/src/main.rs @@ -0,0 +1,40 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +// ANCHOR: here +// --snip-- + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + + if buffer.starts_with(get) { + let contents = fs::read_to_string("hello.html").unwrap(); + + let response = format!( + "HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}", + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); + } else { + // some other request + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-07/Cargo.lock b/listings/ch20-web-server/listing-20-07/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-07/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-07/Cargo.toml b/listings/ch20-web-server/listing-20-07/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-07/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-07/hello.html b/listings/ch20-web-server/listing-20-07/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-07/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-07/src/main.rs b/listings/ch20-web-server/listing-20-07/src/main.rs new file mode 100644 index 0000000..4d19e04 --- /dev/null +++ b/listings/ch20-web-server/listing-20-07/src/main.rs @@ -0,0 +1,50 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + + if buffer.starts_with(get) { + let contents = fs::read_to_string("hello.html").unwrap(); + + let response = format!( + "HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}", + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); + // ANCHOR: here + // --snip-- + } else { + let status_line = "HTTP/1.1 404 NOT FOUND"; + let contents = fs::read_to_string("404.html").unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); + } + // ANCHOR_END: here +} diff --git a/listings/ch20-web-server/listing-20-08/404.html b/listings/ch20-web-server/listing-20-08/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-08/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-08/Cargo.lock b/listings/ch20-web-server/listing-20-08/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-08/Cargo.toml b/listings/ch20-web-server/listing-20-08/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-08/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-08/hello.html b/listings/ch20-web-server/listing-20-08/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-08/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-08/src/main.rs b/listings/ch20-web-server/listing-20-08/src/main.rs new file mode 100644 index 0000000..6dfaa97 --- /dev/null +++ b/listings/ch20-web-server/listing-20-08/src/main.rs @@ -0,0 +1,47 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + + if buffer.starts_with(get) { + let contents = fs::read_to_string("hello.html").unwrap(); + + let response = format!( + "HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}", + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); + } else { + let status_line = "HTTP/1.1 404 NOT FOUND"; + let contents = fs::read_to_string("404.html").unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); + } +} diff --git a/listings/ch20-web-server/listing-20-09/404.html b/listings/ch20-web-server/listing-20-09/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-09/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-09/Cargo.lock b/listings/ch20-web-server/listing-20-09/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-09/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-09/Cargo.toml b/listings/ch20-web-server/listing-20-09/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-09/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-09/hello.html b/listings/ch20-web-server/listing-20-09/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-09/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-09/src/main.rs b/listings/ch20-web-server/listing-20-09/src/main.rs new file mode 100644 index 0000000..e2f2f9f --- /dev/null +++ b/listings/ch20-web-server/listing-20-09/src/main.rs @@ -0,0 +1,47 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} + +// ANCHOR: here +// --snip-- + +fn handle_connection(mut stream: TcpStream) { + // --snip-- + + // ANCHOR_END: here + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + + // ANCHOR: here + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-10/404.html b/listings/ch20-web-server/listing-20-10/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-10/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-10/Cargo.lock b/listings/ch20-web-server/listing-20-10/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-10/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-10/Cargo.toml b/listings/ch20-web-server/listing-20-10/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-10/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-10/hello.html b/listings/ch20-web-server/listing-20-10/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-10/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-10/src/main.rs b/listings/ch20-web-server/listing-20-10/src/main.rs new file mode 100644 index 0000000..c4361e5 --- /dev/null +++ b/listings/ch20-web-server/listing-20-10/src/main.rs @@ -0,0 +1,58 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +// ANCHOR: here +use std::thread; +use std::time::Duration; +// --snip-- +// ANCHOR_END: here + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + handle_connection(stream); + } +} +// ANCHOR: here + +fn handle_connection(mut stream: TcpStream) { + // --snip-- + + // ANCHOR_END: here + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + // ANCHOR: here + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + // --snip-- + // ANCHOR_END: here + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-11/404.html b/listings/ch20-web-server/listing-20-11/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-11/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-11/Cargo.lock b/listings/ch20-web-server/listing-20-11/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-11/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-11/Cargo.toml b/listings/ch20-web-server/listing-20-11/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-11/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-11/hello.html b/listings/ch20-web-server/listing-20-11/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-11/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-11/src/main.rs b/listings/ch20-web-server/listing-20-11/src/main.rs new file mode 100644 index 0000000..bf88f94 --- /dev/null +++ b/listings/ch20-web-server/listing-20-11/src/main.rs @@ -0,0 +1,49 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +// ANCHOR: here +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + thread::spawn(|| { + handle_connection(stream); + }); + } +} +// ANCHOR_END: here + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-12/404.html b/listings/ch20-web-server/listing-20-12/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-12/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-12/Cargo.lock b/listings/ch20-web-server/listing-20-12/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-12/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-12/Cargo.toml b/listings/ch20-web-server/listing-20-12/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-12/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-12/hello.html b/listings/ch20-web-server/listing-20-12/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-12/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-12/output.txt b/listings/ch20-web-server/listing-20-12/output.txt new file mode 100644 index 0000000..0bf6178 --- /dev/null +++ b/listings/ch20-web-server/listing-20-12/output.txt @@ -0,0 +1,14 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) +error[E0433]: failed to resolve: use of undeclared type `ThreadPool` + --> src/main.rs:10:16 + | +10 | let pool = ThreadPool::new(4); + | ^^^^^^^^^^ use of undeclared type `ThreadPool` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0433`. +error: could not compile `hello` + +To learn more, run the command again with --verbose. diff --git a/listings/ch20-web-server/listing-20-12/src/main.rs b/listings/ch20-web-server/listing-20-12/src/main.rs new file mode 100644 index 0000000..ff0fd45 --- /dev/null +++ b/listings/ch20-web-server/listing-20-12/src/main.rs @@ -0,0 +1,50 @@ +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +// ANCHOR: here +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} +// ANCHOR_END: here + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-13/404.html b/listings/ch20-web-server/listing-20-13/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-13/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-13/Cargo.lock b/listings/ch20-web-server/listing-20-13/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-13/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-13/Cargo.toml b/listings/ch20-web-server/listing-20-13/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-13/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-13/hello.html b/listings/ch20-web-server/listing-20-13/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-13/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-13/src/bin/main.rs b/listings/ch20-web-server/listing-20-13/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-13/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-13/src/lib.rs b/listings/ch20-web-server/listing-20-13/src/lib.rs new file mode 100644 index 0000000..e60c902 --- /dev/null +++ b/listings/ch20-web-server/listing-20-13/src/lib.rs @@ -0,0 +1,28 @@ +pub struct ThreadPool; + +// ANCHOR: here +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + ThreadPool + } + + // --snip-- + // ANCHOR_END: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-14/404.html b/listings/ch20-web-server/listing-20-14/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-14/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-14/Cargo.lock b/listings/ch20-web-server/listing-20-14/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-14/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-14/Cargo.toml b/listings/ch20-web-server/listing-20-14/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-14/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-14/hello.html b/listings/ch20-web-server/listing-20-14/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-14/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-14/src/bin/main.rs b/listings/ch20-web-server/listing-20-14/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-14/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-14/src/lib.rs b/listings/ch20-web-server/listing-20-14/src/lib.rs new file mode 100644 index 0000000..509a62e --- /dev/null +++ b/listings/ch20-web-server/listing-20-14/src/lib.rs @@ -0,0 +1,41 @@ +// ANCHOR: here +use std::thread; + +pub struct ThreadPool { + threads: Vec>, +} + +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + // ANCHOR: here + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let mut threads = Vec::with_capacity(size); + + for _ in 0..size { + // create some threads and store them in the vector + } + + ThreadPool { threads } + } + + // --snip-- + // ANCHOR_END: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } + // ANCHOR: here +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-15/404.html b/listings/ch20-web-server/listing-20-15/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-15/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-15/Cargo.lock b/listings/ch20-web-server/listing-20-15/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-15/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-15/Cargo.toml b/listings/ch20-web-server/listing-20-15/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-15/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-15/hello.html b/listings/ch20-web-server/listing-20-15/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-15/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-15/src/bin/main.rs b/listings/ch20-web-server/listing-20-15/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-15/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-15/src/lib.rs b/listings/ch20-web-server/listing-20-15/src/lib.rs new file mode 100644 index 0000000..80a6eee --- /dev/null +++ b/listings/ch20-web-server/listing-20-15/src/lib.rs @@ -0,0 +1,53 @@ +// ANCHOR: here +use std::thread; + +pub struct ThreadPool { + workers: Vec, +} + +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + // ANCHOR: here + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id)); + } + + ThreadPool { workers } + } + // --snip-- + // ANCHOR_END: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } + // ANCHOR: here +} + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +impl Worker { + fn new(id: usize) -> Worker { + let thread = thread::spawn(|| {}); + + Worker { id, thread } + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-16/404.html b/listings/ch20-web-server/listing-20-16/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-16/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-16/Cargo.lock b/listings/ch20-web-server/listing-20-16/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-16/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-16/Cargo.toml b/listings/ch20-web-server/listing-20-16/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-16/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-16/hello.html b/listings/ch20-web-server/listing-20-16/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-16/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-16/src/bin/main.rs b/listings/ch20-web-server/listing-20-16/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-16/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-16/src/lib.rs b/listings/ch20-web-server/listing-20-16/src/lib.rs new file mode 100644 index 0000000..02d20cb --- /dev/null +++ b/listings/ch20-web-server/listing-20-16/src/lib.rs @@ -0,0 +1,60 @@ +use std::thread; +// ANCHOR: here +// --snip-- +use std::sync::mpsc; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +struct Job; + +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + // ANCHOR: here + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id)); + } + + ThreadPool { workers, sender } + } + // --snip-- + // ANCHOR_END: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } + // ANCHOR: here +} +// ANCHOR_END: here + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +impl Worker { + fn new(id: usize) -> Worker { + let thread = thread::spawn(|| {}); + + Worker { id, thread } + } +} diff --git a/listings/ch20-web-server/listing-20-17/404.html b/listings/ch20-web-server/listing-20-17/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-17/Cargo.lock b/listings/ch20-web-server/listing-20-17/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-17/Cargo.toml b/listings/ch20-web-server/listing-20-17/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-17/hello.html b/listings/ch20-web-server/listing-20-17/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-17/output.txt b/listings/ch20-web-server/listing-20-17/output.txt new file mode 100644 index 0000000..4715e23 --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/output.txt @@ -0,0 +1,17 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) +error[E0382]: use of moved value: `receiver` + --> src/lib.rs:27:42 + | +22 | let (sender, receiver) = mpsc::channel(); + | -------- move occurs because `receiver` has type `std::sync::mpsc::Receiver`, which does not implement the `Copy` trait +... +27 | workers.push(Worker::new(id, receiver)); + | ^^^^^^^^ value moved here, in previous iteration of loop + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0382`. +error: could not compile `hello` + +To learn more, run the command again with --verbose. diff --git a/listings/ch20-web-server/listing-20-17/src/bin/main.rs b/listings/ch20-web-server/listing-20-17/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-17/src/lib.rs b/listings/ch20-web-server/listing-20-17/src/lib.rs new file mode 100644 index 0000000..f3ce7d0 --- /dev/null +++ b/listings/ch20-web-server/listing-20-17/src/lib.rs @@ -0,0 +1,66 @@ +use std::sync::mpsc; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +struct Job; + +// ANCHOR: here +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + // ANCHOR: here + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, receiver)); + } + + ThreadPool { workers, sender } + } + // --snip-- + // ANCHOR_END: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } + // ANCHOR: here +} + +// --snip-- + +// ANCHOR_END: here + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +// ANCHOR: here +impl Worker { + fn new(id: usize, receiver: mpsc::Receiver) -> Worker { + let thread = thread::spawn(|| { + receiver; + }); + + Worker { id, thread } + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-18/404.html b/listings/ch20-web-server/listing-20-18/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-18/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-18/Cargo.lock b/listings/ch20-web-server/listing-20-18/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-18/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-18/Cargo.toml b/listings/ch20-web-server/listing-20-18/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-18/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-18/hello.html b/listings/ch20-web-server/listing-20-18/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-18/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-18/src/bin/main.rs b/listings/ch20-web-server/listing-20-18/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-18/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-18/src/lib.rs b/listings/ch20-web-server/listing-20-18/src/lib.rs new file mode 100644 index 0000000..8197353 --- /dev/null +++ b/listings/ch20-web-server/listing-20-18/src/lib.rs @@ -0,0 +1,76 @@ +use std::sync::mpsc; +use std::thread; +// ANCHOR: here +use std::sync::Arc; +use std::sync::Mutex; +// --snip-- + +// ANCHOR_END: here +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +struct Job; + +// ANCHOR: here +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + // ANCHOR: here + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + // --snip-- + // ANCHOR_END: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } + // ANCHOR: here +} + +// --snip-- + +// ANCHOR_END: here +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +// ANCHOR: here +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + // --snip-- + // ANCHOR_END: here + let thread = thread::spawn(|| { + receiver; + }); + + Worker { id, thread } + // ANCHOR: here + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-19/404.html b/listings/ch20-web-server/listing-20-19/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-19/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-19/Cargo.lock b/listings/ch20-web-server/listing-20-19/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-19/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-19/Cargo.toml b/listings/ch20-web-server/listing-20-19/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-19/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-19/hello.html b/listings/ch20-web-server/listing-20-19/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-19/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-19/src/bin/main.rs b/listings/ch20-web-server/listing-20-19/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-19/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-19/src/lib.rs b/listings/ch20-web-server/listing-20-19/src/lib.rs new file mode 100644 index 0000000..734d4c2 --- /dev/null +++ b/listings/ch20-web-server/listing-20-19/src/lib.rs @@ -0,0 +1,69 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +// ANCHOR: here +// --snip-- + +type Job = Box; + +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + // ANCHOR: here + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +// --snip-- +// ANCHOR_END: here + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(|| { + receiver; + }); + + Worker { id, thread } + } +} diff --git a/listings/ch20-web-server/listing-20-20/404.html b/listings/ch20-web-server/listing-20-20/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-20/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-20/Cargo.lock b/listings/ch20-web-server/listing-20-20/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-20/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-20/Cargo.toml b/listings/ch20-web-server/listing-20-20/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-20/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-20/hello.html b/listings/ch20-web-server/listing-20-20/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-20/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-20/src/bin/main.rs b/listings/ch20-web-server/listing-20-20/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-20/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-20/src/lib.rs b/listings/ch20-web-server/listing-20-20/src/lib.rs new file mode 100644 index 0000000..5fdc32e --- /dev/null +++ b/listings/ch20-web-server/listing-20-20/src/lib.rs @@ -0,0 +1,68 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +// ANCHOR: here +// --snip-- + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let job = receiver.lock().unwrap().recv().unwrap(); + + println!("Worker {} got a job; executing.", id); + + job(); + }); + + Worker { id, thread } + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-21/404.html b/listings/ch20-web-server/listing-20-21/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-21/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-21/Cargo.lock b/listings/ch20-web-server/listing-20-21/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-21/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-21/Cargo.toml b/listings/ch20-web-server/listing-20-21/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-21/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-21/hello.html b/listings/ch20-web-server/listing-20-21/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-21/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-21/src/bin/main.rs b/listings/ch20-web-server/listing-20-21/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-21/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-21/src/lib.rs b/listings/ch20-web-server/listing-20-21/src/lib.rs new file mode 100644 index 0000000..6bde524 --- /dev/null +++ b/listings/ch20-web-server/listing-20-21/src/lib.rs @@ -0,0 +1,67 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} +// ANCHOR: here +// --snip-- + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || { + while let Ok(job) = receiver.lock().unwrap().recv() { + println!("Worker {} got a job; executing.", id); + + job(); + } + }); + + Worker { id, thread } + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-22/404.html b/listings/ch20-web-server/listing-20-22/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-22/Cargo.lock b/listings/ch20-web-server/listing-20-22/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-22/Cargo.toml b/listings/ch20-web-server/listing-20-22/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-22/hello.html b/listings/ch20-web-server/listing-20-22/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-22/output.txt b/listings/ch20-web-server/listing-20-22/output.txt new file mode 100644 index 0000000..e810388 --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/output.txt @@ -0,0 +1,14 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) +error[E0507]: cannot move out of `worker.thread` which is behind a mutable reference + --> src/lib.rs:52:13 + | +52 | worker.thread.join().unwrap(); + | ^^^^^^^^^^^^^ move occurs because `worker.thread` has type `JoinHandle<()>`, which does not implement the `Copy` trait + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0507`. +error: could not compile `hello` + +To learn more, run the command again with --verbose. diff --git a/listings/ch20-web-server/listing-20-22/src/bin/main.rs b/listings/ch20-web-server/listing-20-22/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-22/src/lib.rs b/listings/ch20-web-server/listing-20-22/src/lib.rs new file mode 100644 index 0000000..8242578 --- /dev/null +++ b/listings/ch20-web-server/listing-20-22/src/lib.rs @@ -0,0 +1,76 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +// ANCHOR: here +impl Drop for ThreadPool { + fn drop(&mut self) { + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + worker.thread.join().unwrap(); + } + } +} +// ANCHOR_END: here + +struct Worker { + id: usize, + thread: thread::JoinHandle<()>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let job = receiver.lock().unwrap().recv().unwrap(); + + println!("Worker {} got a job; executing.", id); + + job(); + }); + + Worker { id, thread } + } +} diff --git a/listings/ch20-web-server/listing-20-23/404.html b/listings/ch20-web-server/listing-20-23/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-23/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-23/Cargo.lock b/listings/ch20-web-server/listing-20-23/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-23/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-23/Cargo.toml b/listings/ch20-web-server/listing-20-23/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-23/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-23/hello.html b/listings/ch20-web-server/listing-20-23/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-23/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-23/src/bin/main.rs b/listings/ch20-web-server/listing-20-23/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-23/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-23/src/lib.rs b/listings/ch20-web-server/listing-20-23/src/lib.rs new file mode 100644 index 0000000..6ccaee7 --- /dev/null +++ b/listings/ch20-web-server/listing-20-23/src/lib.rs @@ -0,0 +1,107 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +// ANCHOR: here +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +// --snip-- + +// ANCHOR_END: here +type Job = Box; + +enum Message { + NewJob(Job), + Terminate, +} + +// ANCHOR: here +impl ThreadPool { + // --snip-- + + // ANCHOR_END: here + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + // ANCHOR: here + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(Message::NewJob(job)).unwrap(); + } +} + +// --snip-- + +// ANCHOR_END: here +impl Drop for ThreadPool { + fn drop(&mut self) { + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + if let Some(thread) = worker.thread.take() { + thread.join().unwrap(); + } + } + } +} + +struct Worker { + id: usize, + thread: Option>, +} + +// ANCHOR: here +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let message = receiver.lock().unwrap().recv().unwrap(); + + match message { + Message::NewJob(job) => { + println!("Worker {} got a job; executing.", id); + + job(); + } + Message::Terminate => { + println!("Worker {} was told to terminate.", id); + + break; + } + } + }); + + Worker { + id, + thread: Some(thread), + } + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/listing-20-24/404.html b/listings/ch20-web-server/listing-20-24/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-24/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-24/Cargo.lock b/listings/ch20-web-server/listing-20-24/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-24/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-24/Cargo.toml b/listings/ch20-web-server/listing-20-24/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-24/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-24/hello.html b/listings/ch20-web-server/listing-20-24/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-24/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-24/src/bin/main.rs b/listings/ch20-web-server/listing-20-24/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/listing-20-24/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-24/src/lib.rs b/listings/ch20-web-server/listing-20-24/src/lib.rs new file mode 100644 index 0000000..747bff2 --- /dev/null +++ b/listings/ch20-web-server/listing-20-24/src/lib.rs @@ -0,0 +1,103 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +enum Message { + NewJob(Job), + Terminate, +} + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(Message::NewJob(job)).unwrap(); + } +} + +// ANCHOR: here +impl Drop for ThreadPool { + fn drop(&mut self) { + println!("Sending terminate message to all workers."); + + for _ in &self.workers { + self.sender.send(Message::Terminate).unwrap(); + } + + println!("Shutting down all workers."); + + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + if let Some(thread) = worker.thread.take() { + thread.join().unwrap(); + } + } + } +} +// ANCHOR_END: here + +struct Worker { + id: usize, + thread: Option>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let message = receiver.lock().unwrap().recv().unwrap(); + + match message { + Message::NewJob(job) => { + println!("Worker {} got a job; executing.", id); + + job(); + } + Message::Terminate => { + println!("Worker {} was told to terminate.", id); + + break; + } + } + }); + + Worker { + id, + thread: Some(thread), + } + } +} diff --git a/listings/ch20-web-server/listing-20-25/404.html b/listings/ch20-web-server/listing-20-25/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/listing-20-25/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/listing-20-25/Cargo.lock b/listings/ch20-web-server/listing-20-25/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/listing-20-25/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/listing-20-25/Cargo.toml b/listings/ch20-web-server/listing-20-25/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/listing-20-25/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/listing-20-25/hello.html b/listings/ch20-web-server/listing-20-25/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/listing-20-25/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/listing-20-25/src/bin/main.rs b/listings/ch20-web-server/listing-20-25/src/bin/main.rs new file mode 100644 index 0000000..3b314bc --- /dev/null +++ b/listings/ch20-web-server/listing-20-25/src/bin/main.rs @@ -0,0 +1,53 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +// ANCHOR: here +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming().take(2) { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } + + println!("Shutting down."); +} +// ANCHOR_END: here + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/listing-20-25/src/lib.rs b/listings/ch20-web-server/listing-20-25/src/lib.rs new file mode 100644 index 0000000..68f4263 --- /dev/null +++ b/listings/ch20-web-server/listing-20-25/src/lib.rs @@ -0,0 +1,101 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +enum Message { + NewJob(Job), + Terminate, +} + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(Message::NewJob(job)).unwrap(); + } +} + +impl Drop for ThreadPool { + fn drop(&mut self) { + println!("Sending terminate message to all workers."); + + for _ in &self.workers { + self.sender.send(Message::Terminate).unwrap(); + } + + println!("Shutting down all workers."); + + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + if let Some(thread) = worker.thread.take() { + thread.join().unwrap(); + } + } + } +} + +struct Worker { + id: usize, + thread: Option>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let message = receiver.lock().unwrap().recv().unwrap(); + + match message { + Message::NewJob(job) => { + println!("Worker {} got a job; executing.", id); + + job(); + } + Message::Terminate => { + println!("Worker {} was told to terminate.", id); + + break; + } + } + }); + + Worker { + id, + thread: Some(thread), + } + } +} diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/404.html b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/Cargo.lock b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/Cargo.toml b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/hello.html b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/output.txt b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/output.txt new file mode 100644 index 0000000..187274f --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/output.txt @@ -0,0 +1,14 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) +error[E0599]: no function or associated item named `new` found for struct `ThreadPool` in the current scope + --> src/bin/main.rs:11:28 + | +11 | let pool = ThreadPool::new(4); + | ^^^ function or associated item not found in `ThreadPool` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0599`. +error: could not compile `hello` + +To learn more, run the command again with --verbose. diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/bin/main.rs b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/bin/main.rs new file mode 100644 index 0000000..d2b8c88 --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/bin/main.rs @@ -0,0 +1,51 @@ +// ANCHOR: here +use hello::ThreadPool; +// ANCHOR_END: here +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/lib.rs b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/lib.rs new file mode 100644 index 0000000..7312e29 --- /dev/null +++ b/listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/lib.rs @@ -0,0 +1 @@ +pub struct ThreadPool; diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/404.html b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/Cargo.lock b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/Cargo.toml b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/hello.html b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/output.txt b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/output.txt new file mode 100644 index 0000000..33c8a68 --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/output.txt @@ -0,0 +1,14 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) +error[E0599]: no method named `execute` found for struct `ThreadPool` in the current scope + --> src/bin/main.rs:16:14 + | +16 | pool.execute(|| { + | ^^^^^^^ method not found in `ThreadPool` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0599`. +error: could not compile `hello` + +To learn more, run the command again with --verbose. diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/src/bin/main.rs b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-02-impl-threadpool-new/src/lib.rs b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/src/lib.rs new file mode 100644 index 0000000..f0e1890 --- /dev/null +++ b/listings/ch20-web-server/no-listing-02-impl-threadpool-new/src/lib.rs @@ -0,0 +1,7 @@ +pub struct ThreadPool; + +impl ThreadPool { + pub fn new(size: usize) -> ThreadPool { + ThreadPool + } +} diff --git a/listings/ch20-web-server/no-listing-03-define-execute/404.html b/listings/ch20-web-server/no-listing-03-define-execute/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-03-define-execute/Cargo.lock b/listings/ch20-web-server/no-listing-03-define-execute/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-03-define-execute/Cargo.toml b/listings/ch20-web-server/no-listing-03-define-execute/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-03-define-execute/hello.html b/listings/ch20-web-server/no-listing-03-define-execute/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-03-define-execute/output.txt b/listings/ch20-web-server/no-listing-03-define-execute/output.txt new file mode 100644 index 0000000..dc76c43 --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/output.txt @@ -0,0 +1,3 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) + Finished dev [unoptimized + debuginfo] target(s) in 0.24s diff --git a/listings/ch20-web-server/no-listing-03-define-execute/src/bin/main.rs b/listings/ch20-web-server/no-listing-03-define-execute/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-03-define-execute/src/lib.rs b/listings/ch20-web-server/no-listing-03-define-execute/src/lib.rs new file mode 100644 index 0000000..1321ab8 --- /dev/null +++ b/listings/ch20-web-server/no-listing-03-define-execute/src/lib.rs @@ -0,0 +1,18 @@ +pub struct ThreadPool; + +// ANCHOR: here +impl ThreadPool { + // --snip-- + // ANCHOR_END: here + pub fn new(size: usize) -> ThreadPool { + ThreadPool + } + + // ANCHOR: here + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/404.html b/listings/ch20-web-server/no-listing-04-update-worker-definition/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/Cargo.lock b/listings/ch20-web-server/no-listing-04-update-worker-definition/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/Cargo.toml b/listings/ch20-web-server/no-listing-04-update-worker-definition/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/hello.html b/listings/ch20-web-server/no-listing-04-update-worker-definition/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/output.txt b/listings/ch20-web-server/no-listing-04-update-worker-definition/output.txt new file mode 100644 index 0000000..155e463 --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/output.txt @@ -0,0 +1,27 @@ +$ cargo check + Checking hello v0.1.0 (file:///projects/hello) +error[E0599]: no method named `join` found for enum `Option>` in the current scope + --> src/lib.rs:52:27 + | +52 | worker.thread.join().unwrap(); + | ^^^^ method not found in `Option>` + +error[E0308]: mismatched types + --> src/lib.rs:72:22 + | +72 | Worker { id, thread } + | ^^^^^^ + | | + | expected enum `Option`, found struct `JoinHandle` + | help: try using a variant of the expected enum: `Some(thread)` + | + = note: expected enum `Option>` + found struct `JoinHandle<_>` + +error: aborting due to 2 previous errors + +Some errors have detailed explanations: E0308, E0599. +For more information about an error, try `rustc --explain E0308`. +error: could not compile `hello` + +To learn more, run the command again with --verbose. diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/src/bin/main.rs b/listings/ch20-web-server/no-listing-04-update-worker-definition/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-04-update-worker-definition/src/lib.rs b/listings/ch20-web-server/no-listing-04-update-worker-definition/src/lib.rs new file mode 100644 index 0000000..1098330 --- /dev/null +++ b/listings/ch20-web-server/no-listing-04-update-worker-definition/src/lib.rs @@ -0,0 +1,76 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +impl Drop for ThreadPool { + fn drop(&mut self) { + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + worker.thread.join().unwrap(); + } + } +} + +// ANCHOR: here +struct Worker { + id: usize, + thread: Option>, +} +// ANCHOR_END: here + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let job = receiver.lock().unwrap().recv().unwrap(); + + println!("Worker {} got a job; executing.", id); + + job(); + }); + + Worker { id, thread } + } +} diff --git a/listings/ch20-web-server/no-listing-05-fix-worker-new/404.html b/listings/ch20-web-server/no-listing-05-fix-worker-new/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-05-fix-worker-new/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-05-fix-worker-new/Cargo.lock b/listings/ch20-web-server/no-listing-05-fix-worker-new/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-05-fix-worker-new/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-05-fix-worker-new/Cargo.toml b/listings/ch20-web-server/no-listing-05-fix-worker-new/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-05-fix-worker-new/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-05-fix-worker-new/hello.html b/listings/ch20-web-server/no-listing-05-fix-worker-new/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-05-fix-worker-new/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-05-fix-worker-new/src/bin/main.rs b/listings/ch20-web-server/no-listing-05-fix-worker-new/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/no-listing-05-fix-worker-new/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-05-fix-worker-new/src/lib.rs b/listings/ch20-web-server/no-listing-05-fix-worker-new/src/lib.rs new file mode 100644 index 0000000..6bef23a --- /dev/null +++ b/listings/ch20-web-server/no-listing-05-fix-worker-new/src/lib.rs @@ -0,0 +1,83 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +impl Drop for ThreadPool { + fn drop(&mut self) { + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + worker.thread.join().unwrap(); + } + } +} + +struct Worker { + id: usize, + thread: Option>, +} + +// ANCHOR: here +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + // --snip-- + + // ANCHOR_END: here + let thread = thread::spawn(move || loop { + let job = receiver.lock().unwrap().recv().unwrap(); + + println!("Worker {} got a job; executing.", id); + + job(); + }); + + // ANCHOR: here + Worker { + id, + thread: Some(thread), + } + } +} +// ANCHOR_END: here diff --git a/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/404.html b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/Cargo.lock b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/Cargo.toml b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/hello.html b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/src/bin/main.rs b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/src/lib.rs b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/src/lib.rs new file mode 100644 index 0000000..d5b38a6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-06-fix-threadpool-drop/src/lib.rs @@ -0,0 +1,81 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +// ANCHOR: here +impl Drop for ThreadPool { + fn drop(&mut self) { + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + if let Some(thread) = worker.thread.take() { + thread.join().unwrap(); + } + } + } +} +// ANCHOR_END: here + +struct Worker { + id: usize, + thread: Option>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let job = receiver.lock().unwrap().recv().unwrap(); + + println!("Worker {} got a job; executing.", id); + + job(); + }); + + Worker { + id, + thread: Some(thread), + } + } +} diff --git a/listings/ch20-web-server/no-listing-07-define-message-enum/404.html b/listings/ch20-web-server/no-listing-07-define-message-enum/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-07-define-message-enum/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-07-define-message-enum/Cargo.lock b/listings/ch20-web-server/no-listing-07-define-message-enum/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-07-define-message-enum/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-07-define-message-enum/Cargo.toml b/listings/ch20-web-server/no-listing-07-define-message-enum/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-07-define-message-enum/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-07-define-message-enum/hello.html b/listings/ch20-web-server/no-listing-07-define-message-enum/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-07-define-message-enum/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-07-define-message-enum/src/bin/main.rs b/listings/ch20-web-server/no-listing-07-define-message-enum/src/bin/main.rs new file mode 100644 index 0000000..2078ca9 --- /dev/null +++ b/listings/ch20-web-server/no-listing-07-define-message-enum/src/bin/main.rs @@ -0,0 +1,49 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-07-define-message-enum/src/lib.rs b/listings/ch20-web-server/no-listing-07-define-message-enum/src/lib.rs new file mode 100644 index 0000000..46fb5f1 --- /dev/null +++ b/listings/ch20-web-server/no-listing-07-define-message-enum/src/lib.rs @@ -0,0 +1,86 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +// ANCHOR: here +enum Message { + NewJob(Job), + Terminate, +} +// ANCHOR_END: here + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(job).unwrap(); + } +} + +impl Drop for ThreadPool { + fn drop(&mut self) { + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + if let Some(thread) = worker.thread.take() { + thread.join().unwrap(); + } + } + } +} + +struct Worker { + id: usize, + thread: Option>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let job = receiver.lock().unwrap().recv().unwrap(); + + println!("Worker {} got a job; executing.", id); + + job(); + }); + + Worker { + id, + thread: Some(thread), + } + } +} diff --git a/listings/ch20-web-server/no-listing-08-final-code/404.html b/listings/ch20-web-server/no-listing-08-final-code/404.html new file mode 100644 index 0000000..88d8e91 --- /dev/null +++ b/listings/ch20-web-server/no-listing-08-final-code/404.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Oops!

+

Sorry, I don't know what you're asking for.

+ + diff --git a/listings/ch20-web-server/no-listing-08-final-code/Cargo.lock b/listings/ch20-web-server/no-listing-08-final-code/Cargo.lock new file mode 100644 index 0000000..f2d069f --- /dev/null +++ b/listings/ch20-web-server/no-listing-08-final-code/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "hello" +version = "0.1.0" + diff --git a/listings/ch20-web-server/no-listing-08-final-code/Cargo.toml b/listings/ch20-web-server/no-listing-08-final-code/Cargo.toml new file mode 100644 index 0000000..78dfe6e --- /dev/null +++ b/listings/ch20-web-server/no-listing-08-final-code/Cargo.toml @@ -0,0 +1,7 @@ +[package] +name = "hello" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] diff --git a/listings/ch20-web-server/no-listing-08-final-code/hello.html b/listings/ch20-web-server/no-listing-08-final-code/hello.html new file mode 100644 index 0000000..fe442d6 --- /dev/null +++ b/listings/ch20-web-server/no-listing-08-final-code/hello.html @@ -0,0 +1,11 @@ + + + + + Hello! + + +

Hello!

+

Hi from Rust

+ + diff --git a/listings/ch20-web-server/no-listing-08-final-code/src/bin/main.rs b/listings/ch20-web-server/no-listing-08-final-code/src/bin/main.rs new file mode 100644 index 0000000..d3f8754 --- /dev/null +++ b/listings/ch20-web-server/no-listing-08-final-code/src/bin/main.rs @@ -0,0 +1,51 @@ +use hello::ThreadPool; +use std::fs; +use std::io::prelude::*; +use std::net::TcpListener; +use std::net::TcpStream; +use std::thread; +use std::time::Duration; + +fn main() { + let listener = TcpListener::bind("127.0.0.1:7878").unwrap(); + let pool = ThreadPool::new(4); + + for stream in listener.incoming() { + let stream = stream.unwrap(); + + pool.execute(|| { + handle_connection(stream); + }); + } + + println!("Shutting down."); +} + +fn handle_connection(mut stream: TcpStream) { + let mut buffer = [0; 1024]; + stream.read(&mut buffer).unwrap(); + + let get = b"GET / HTTP/1.1\r\n"; + let sleep = b"GET /sleep HTTP/1.1\r\n"; + + let (status_line, filename) = if buffer.starts_with(get) { + ("HTTP/1.1 200 OK", "hello.html") + } else if buffer.starts_with(sleep) { + thread::sleep(Duration::from_secs(5)); + ("HTTP/1.1 200 OK", "hello.html") + } else { + ("HTTP/1.1 404 NOT FOUND", "404.html") + }; + + let contents = fs::read_to_string(filename).unwrap(); + + let response = format!( + "{}\r\nContent-Length: {}\r\n\r\n{}", + status_line, + contents.len(), + contents + ); + + stream.write(response.as_bytes()).unwrap(); + stream.flush().unwrap(); +} diff --git a/listings/ch20-web-server/no-listing-08-final-code/src/lib.rs b/listings/ch20-web-server/no-listing-08-final-code/src/lib.rs new file mode 100644 index 0000000..68f4263 --- /dev/null +++ b/listings/ch20-web-server/no-listing-08-final-code/src/lib.rs @@ -0,0 +1,101 @@ +use std::sync::mpsc; +use std::sync::Arc; +use std::sync::Mutex; +use std::thread; + +pub struct ThreadPool { + workers: Vec, + sender: mpsc::Sender, +} + +type Job = Box; + +enum Message { + NewJob(Job), + Terminate, +} + +impl ThreadPool { + /// Create a new ThreadPool. + /// + /// The size is the number of threads in the pool. + /// + /// # Panics + /// + /// The `new` function will panic if the size is zero. + pub fn new(size: usize) -> ThreadPool { + assert!(size > 0); + + let (sender, receiver) = mpsc::channel(); + + let receiver = Arc::new(Mutex::new(receiver)); + + let mut workers = Vec::with_capacity(size); + + for id in 0..size { + workers.push(Worker::new(id, Arc::clone(&receiver))); + } + + ThreadPool { workers, sender } + } + + pub fn execute(&self, f: F) + where + F: FnOnce() + Send + 'static, + { + let job = Box::new(f); + + self.sender.send(Message::NewJob(job)).unwrap(); + } +} + +impl Drop for ThreadPool { + fn drop(&mut self) { + println!("Sending terminate message to all workers."); + + for _ in &self.workers { + self.sender.send(Message::Terminate).unwrap(); + } + + println!("Shutting down all workers."); + + for worker in &mut self.workers { + println!("Shutting down worker {}", worker.id); + + if let Some(thread) = worker.thread.take() { + thread.join().unwrap(); + } + } + } +} + +struct Worker { + id: usize, + thread: Option>, +} + +impl Worker { + fn new(id: usize, receiver: Arc>>) -> Worker { + let thread = thread::spawn(move || loop { + let message = receiver.lock().unwrap().recv().unwrap(); + + match message { + Message::NewJob(job) => { + println!("Worker {} got a job; executing.", id); + + job(); + } + Message::Terminate => { + println!("Worker {} was told to terminate.", id); + + break; + } + } + }); + + Worker { + id, + thread: Some(thread), + } + } +} diff --git a/nostarch.sh b/nostarch.sh deleted file mode 100755 index 2eb8175..0000000 --- a/nostarch.sh +++ /dev/null @@ -1,22 +0,0 @@ -#!/bin/bash - -set -eu - -cargo build --release - -mkdir -p tmp -rm -rf tmp/*.md - -# Get all the markdown files in the src dir, -ls src/*.md | \ -# except for SUMMARY.md. -grep -v SUMMARY.md | \ -# Extract just the filename so we can reuse it easily. -xargs -n 1 basename | \ -# Remove all links followed by , then -# Change all remaining links from markdown to italicized inline text. -while IFS= read -r filename; do - < "src/$filename" cargo run --bin remove_links | cargo run --bin link2print > "tmp/$filename" -done -# Concat the files into the nostarch dir. -cargo run --bin concat_chapters tmp nostarch diff --git a/nostarch/appendix.md b/nostarch/appendix.md deleted file mode 100644 index 6f061d7..0000000 --- a/nostarch/appendix.md +++ /dev/null @@ -1,63 +0,0 @@ -# Appendix - -The following sections contain reference material you may find useful in your -Rust journey. - -## Keywords - -The following keywords are reserved by the Rust language and may not be used as -names of functions, variables, macros, modules, crates, constants, static -values, attributes, struct fields, or arguments. - -* `abstract` -* `alignof` -* `as` -* `become` -* `box` -* `break` -* `const` -* `continue` -* `crate` -* `do` -* `else` -* `enum` -* `extern` -* `false` -* `final` -* `fn` -* `for` -* `if` -* `impl` -* `in` -* `let` -* `loop` -* `macro` -* `match` -* `mod` -* `move` -* `mut` -* `offsetof` -* `override` -* `priv` -* `proc` -* `pub` -* `pure` -* `ref` -* `return` -* `Self` -* `self` -* `sizeof` -* `static` -* `struct` -* `super` -* `trait` -* `true` -* `type` -* `typeof` -* `unsafe` -* `unsized` -* `use` -* `virtual` -* `where` -* `while` -* `yield` diff --git a/nostarch/chapter01.md b/nostarch/chapter01.md deleted file mode 100644 index f4dc415..0000000 --- a/nostarch/chapter01.md +++ /dev/null @@ -1,516 +0,0 @@ -# Introduction - -Welcome to “The Rust Programming Language”, an introductory book about Rust. -Rust is a programming language that’s focused on safety, speed, and -concurrency. Its design lets you create programs that have the performance and -control of a low-level language, but with helpful abstractions that feel like a -high-level language. The Rust community welcomes all programmers who have their -experience in languages like C and are looking for a safer alternative, as well -as programmers from languages like Python who are looking for ways to write more -performant code without losing expressiveness. - -Rust provides the majority of its safety checks at compile time and without a -garbage collector so that your program's runtime isn't impacted. This makes it -useful in a number of use cases that other languages aren’t good at: embedding -in other languages, programs with specific space and time requirements, and -writing low-level code, like device drivers and operating systems. It's also -great for web applications: it powers the Rust package registry site, crates.io! -We're excited to see what _you_ create with Rust. - -This book is written for a reader who already knows how to program in at least -one programming language. After reading this book, you should be comfortable -writing Rust programs. We’ll be learning Rust through small, focused examples -that build on each other to demonstrate how to use various features of Rust as -well as how they work behind the scenes. - -## Contributing to the book - -This book is open source. If you find an error, please don’t hesitate to file an -issue or send a pull request on GitHub at *https://github.com/rust-lang/book*. - -## Installation - -The first step to using Rust is to install it. You’ll need an internet -connection to run the commands in this chapter, as we’ll be downloading Rust -from the internet. - -We’ll be showing off a number of commands using a terminal, and those lines all -start with `$`. You don't need to type in the `$`s; they are there to indicate -the start of each command. You’ll see many tutorials and examples around the web -that follow this convention: `$` for commands run as a regular user, and `#` -for commands you should be running as an administrator. Lines that don't start -with `$` are typically showing the output of the previous command. - -### Installing on Linux or Mac - -If you're on Linux or a Mac, all you need to do is open a terminal and type -this: - -```bash -$ curl https://sh.rustup.rs -sSf | sh -``` - -This will download a script and start the installation. You may be prompted for -your password. If it all goes well, you’ll see this appear: - -```bash -Rust is installed now. Great! -``` - -### Installing on Windows - -If you're on Windows, please go to *https://rustup.rs/* and follow -the instructions to download rustup-init.exe. Run that and follow the rest of -the instructions. - -The rest of the Windows-specific commands in the book will assume that you are -using `cmd` as your shell. If you use a different shell, you may be able to run -the same commands that Linux and Mac users do. If neither work, consult the -documentation for the shell you are using. - -### Uninstalling - -Uninstalling Rust is as easy as installing it. From your shell, run -the uninstall script: - -```bash -$ rustup self uninstall -``` - -### Troubleshooting - -If you've got Rust installed, you can open up a shell, and type this: - -```bash -$ rustc --version -``` - -You should see the version number, commit hash, and commit date in a format -similar to this for the latest stable version at the time you install: - -```bash -rustc x.y.z (abcabcabc yyyy-mm-dd) -``` - -If you see this, Rust has been installed successfully! -Congrats! - -If you don't and you're on Windows, check that Rust is in your `%PATH%` system -variable. - -If it still isn't working, there are a number of places where you can get help. -The easiest is the #rust IRC channel on irc.mozilla.org, which you can access -through Mibbit at -*http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust*. Go to that -address, and you'll be chatting with other Rustaceans (a silly nickname we call -ourselves) who can help you out. Other great resources include the user’s forum -at *https://users.rust-lang.org/* and Stack Overflow at -*http://stackoverflow.com/questions/tagged/rust*. - -### Local documentation - -The installer also includes a copy of the documentation locally, so you can -read it offline. Run `rustup doc` to open the local documentation in your -browser. - -## Hello, World! - -Now that you have Rust installed, let’s write your first Rust program. It's -traditional when learning a new language to write a little program to print the -text “Hello, world!” to the screen, and in this section, we'll follow that -tradition. - -> Note: This book assumes basic familiarity with the command line. Rust itself -> makes no specific demands about your editing, tooling, or where your code -> lives, so if you prefer an IDE to the command line, feel free to use your -> favorite IDE. - -### Creating a Project File - -First, make a file to put your Rust code in. Rust doesn't care where your code -lives, but for this book, we'd suggest making a *projects* directory in your -home directory and keeping all your projects there. Open a terminal and enter -the following commands to make a directory for this particular project: - -Linux and Mac: - -```bash -$ mkdir ~/projects -$ cd ~/projects -$ mkdir hello_world -$ cd hello_world -``` - -Windows: - -```bash -$ mkdir %USERPROFILE%\projects -$ cd %USERPROFILE%\projects -$ mkdir hello_world -$ cd hello_world -``` - -### Writing and Running a Rust Program - -Next, make a new source file and call it `main.rs`. Rust files always end with -the `.rs` extension. If you’re using more than one word in your filename, use -an underscore to separate them. For example, you'd use `hello_world.rs` rather -than `helloworld.rs`. - -Now open the `main.rs` file you just created, and type the following code: - -Filename: main.rs - -```rust -fn main() { - println!("Hello, world!"); -} -``` - -Save the file, and go back to your terminal window. On Linux or OSX, enter the -following commands: - -```bash -$ rustc main.rs -$ ./main -Hello, world! -``` - -On Windows, just replace `./main` with `.\main.exe`. Regardless of your -operating system, you should see the string `Hello, world!` print to the -terminal. If you did, then congratulations! You've officially written a Rust -program. That makes you a Rust programmer! Welcome. - -### Anatomy of a Rust Program - -Now, let’s go over what just happened in your "Hello, world!" program in -detail. Here's the first piece of the puzzle: - -```rust -fn main() { - -} -``` - -These lines define a *function* in Rust. The `main` function is special: it's -the first thing that is run for every executable Rust program. The first line -says, “I’m declaring a function named `main` that takes no arguments and -returns nothing.” If there were arguments, they would go inside the parentheses, -`(` and `)`. - -Also note that the function body is wrapped in curly braces, `{` and `}`. Rust -requires these around all function bodies. It's considered good style to put -the opening curly brace on the same line as the function declaration, with one -space in between. - -Inside the `main()` function: - -```rust - println!("Hello, world!"); -``` - -This line does all of the work in this little program: it prints text to the -screen. There are a number of details that are important here. The first is -that it’s indented with four spaces, not a tab. - -The second important part is `println!()`. This is calling a Rust *macro*, -which is how metaprogramming is done in Rust. If it were calling a function -instead, it would look like this: `println()` (without the `!`). We'll discuss -Rust macros in more detail in Chapter XX, but for now you just need to know -that when you see a `!` that means that you’re calling a macro instead of a -normal function. - -Next is `"Hello, world!"` which is a *string*. We pass this string as an -argument to `println!()`, which prints the string to the screen. Easy enough! - -The line ends with a semicolon (`;`). The `;` indicates that this expression is -over, and the next one is ready to begin. Most lines of Rust code end with a -`;`. - -### Compiling and Running Are Separate Steps - -In "Writing and Running a Rust Program", we showed you how to run a newly -created program. We'll break that process down and examine each step now. - -Before running a Rust program, you have to compile it. You can use the Rust -compiler by entering the `rustc` command and passing it the name of your source -file, like this: - -```bash -$ rustc main.rs -``` - -If you come from a C or C++ background, you'll notice that this is similar to -`gcc` or `clang`. After compiling successfully, Rust should output a binary -executable, which you can see on Linux or OSX by entering the `ls` command in -your shell as follows: - -```bash -$ ls -main main.rs -``` - -On Windows, you'd enter: - -```bash -$ dir /B # the /B option says to only show the file names -main.exe -main.rs -``` - -This shows we have two files: the source code, with the `.rs` extension, and the -executable (`main.exe` on Windows, `main` everywhere else). All that's left to -do from here is run the `main` or `main.exe` file, like this: - -```bash -$ ./main # or .\main.exe on Windows -``` - -If `main.rs` were your "Hello, world!" program, this would print `Hello, -world!` to your terminal. - -If you come from a dynamic language like Ruby, Python, or JavaScript, you may -not be used to compiling and running a program being separate steps. Rust is an -*ahead-of-time compiled* language, which means that you can compile a program, -give it to someone else, and they can run it even without having Rust -installed. If you give someone a `.rb`, `.py`, or `.js` file, on the other -hand, they need to have a Ruby, Python, or JavaScript implementation installed -(respectively), but you only need one command to both compile and run your -program. Everything is a tradeoff in language design. - -Just compiling with `rustc` is fine for simple programs, but as your project -grows, you'll want to be able to manage all of the options your project has -and make it easy to share your code with other people and projects. Next, we'll -introduce you to a tool called Cargo, which will help you write real-world Rust -programs. - -## Hello, Cargo! - -Cargo is Rust’s build system and package manager, and Rustaceans use Cargo to -manage their Rust projects because it makes a lot of tasks easier. For example, -Cargo takes care of building your code, downloading the libraries your code -depends on, and building those libraries. We call libraries your code needs -*dependencies*. - -The simplest Rust programs, like the one we've written so far, don’t have any -dependencies, so right now, you'd only be using the part of Cargo that can take -care of building your code. As you write more complex Rust programs, you’ll -want to add dependencies, and if you start off using Cargo, that will be a lot -easier to do. - -As the vast, vast majority of Rust projects use Cargo, we will assume that -you’re using it for the rest of the book. Cargo comes installed with Rust -itself, if you used the official installers as covered in the Installation -chapter. If you installed Rust through some other means, you can check if you -have Cargo installed by typing the following into your terminal: - -```bash -$ cargo --version -``` - -If you see a version number, great! If you see an error like `command not -found`, then you should look at the documentation for your method of -installation to determine how to install Cargo separately. - -### Creating a Project with Cargo - -Let's create a new project using Cargo and look at how it differs from our -project in `hello_world`. Go back to your projects directory (or wherever you -decided to put your code): - -Linux and Mac: - -```bash -$ cd ~/projects -``` - -Windows: - -```bash -$ cd %USERPROFILE%\projects -``` - -And then on any operating system run: - -```bash -$ cargo new hello_cargo --bin -$ cd hello_cargo -``` - -We passed the `--bin` argument to `cargo new` because our goal is to make an -executable application, as opposed to a library. Executables are often called -*binaries* (as in `/usr/bin`, if you’re on a Unix system). We've given -`hello_cargo` as the name for our project, and Cargo creates its files in a -directory of the same name that we can then go into. - -If we list the files in the `hello_cargo` directory, we can see that Cargo has -generated two files and one directory for us: a `Cargo.toml` and a `src` -directory with a `main.rs` file inside. It has also initialized a new `git` -repository in the `hello_cargo` directory for us, along with a `.gitignore` -file; you can change this to use a different version control system, or no -version control system, by using the `--vcs` flag. - -Open up `Cargo.toml` in your text editor of choice. It should look something -like this: - -Filename: Cargo.toml - -```toml -[package] -name = "hello_cargo" -version = "0.1.0" -authors = ["Your Name "] - -[dependencies] -``` - -This file is in the *TOML* (Tom's Obvious, Minimal Language) format. TOML is -similar to INI but has some extra goodies and is used as Cargo’s -configuration format. - -The first line, `[package]`, is a section heading that indicates that the -following statements are configuring a package. As we add more information to -this file, we’ll add other sections. - -The next three lines set the three bits of configuration that Cargo needs to -see in order to know that it should compile your program: its name, what -version it is, and who wrote it. Cargo gets your name and email information -from your environment. If it’s not correct, go ahead and fix that and save the -file. - -The last line, `[dependencies]`, is the start of a section for you to list any -*crates* (which is what we call packages of Rust code) that your project will -depend on so that Cargo knows to download and compile those too. We won't need -any other crates for this project, but we will in the guessing game tutorial in -the next chapter. - -Now let's look at `src/main.rs`: - -Filename: src/main.rs - -```rust -fn main() { - println!("Hello, world!"); -} -``` - -Cargo has generated a "Hello World!" for you, just like the one we wrote -earlier! So that part is the same. The differences between our previous project -and the project generated by Cargo that we've seen so far are: - -1. Our code goes in the `src` directory -2. The top level contains a `Cargo.toml` configuration file - -Cargo expects your source files to live inside the `src` directory so that the -top-level project directory is just for READMEs, license information, -configuration files, and anything else not related to your code. In this way, -using Cargo helps you keep your projects nice and tidy. There's a place for -everything, and everything is in its place. - -If you started a project that doesn't use Cargo, as we did with our project in -the `hello_world` directory, you can convert it to a project that does use -Cargo by moving your code into the `src` directory and creating an appropriate -`Cargo.toml`. - -### Building and Running a Cargo Project - -Now let's look at what's different about building and running your Hello World -program through Cargo! To do so, enter the following commands: - -```bash -$ cargo build - Compiling hello_cargo v0.1.0 (file:///projects/hello_cargo) -``` - -This should have created an executable file in `target/debug/hello_cargo` (or -`target\debug\hello_cargo.exe` on Windows), which you can run with this command: - -```bash -$ ./target/debug/hello_cargo # or .\target\debug\hello_cargo.exe on Windows -Hello, world! -``` - -Bam! If all goes well, `Hello, world!` should print to the terminal once more. - -Running `cargo build` for the first time also causes Cargo to create a new file -at the top level called `Cargo.lock`, which looks like this: - -Filename: Cargo.lock - -```toml -[root] -name = "hello_cargo" -version = "0.1.0" -``` - -Cargo uses the `Cargo.lock` file to keep track of dependencies in your -application. This project doesn't have dependencies, so the file is a bit -sparse. Realistically, you won't ever need to touch this file yourself; just -let Cargo handle it. - -We just built a project with `cargo build` and ran it with -`./target/debug/hello_cargo`, but we can actually do both in one step with -`cargo run` as follows: - -```bash -$ cargo run - Running `target/debug/hello_cargo` -Hello, world! -``` - -Notice that this time, we didn't see the output telling us that Cargo was -compiling `hello_cargo`. Cargo figured out that the files haven’t changed, so -it just ran the binary. If you had modified your source code, Cargo would have -rebuilt the project before running it, and you would have seen something like -this: - -```bash -$ cargo run - Compiling hello_cargo v0.1.0 (file:///projects/hello_cargo) - Running `target/debug/hello_cargo` -Hello, world! -``` - -So a few more differences we've now seen: - -3. Instead of using `rustc`, build a project using `cargo build` (or build and - run it in one step with `cargo run`) -4. Instead of the result of the build being put in the same directory as our - code, Cargo will put it in the `target/debug` directory. - -The other advantage of using Cargo is that the commands are the same no matter -what operating system you're on, so at this point we will no longer be -providing specific instructions for Linux and Mac versus Windows. - -### Building for Release - -When your project is finally ready for release, you can use `cargo build ---release` to compile your project with optimizations. This will create an -executable in `target/release` instead of `target/debug`. These optimizations -make your Rust code run faster, but turning them on makes your program take -longer to compile. This is why there are two different profiles: one for -development when you want to be able to rebuild quickly and often, and one for -building the final program you’ll give to a user that won't be rebuilt and -that we want to run as fast as possible. If you're benchmarking the running -time of your code, be sure to run `cargo build --release` and benchmark with -the executable in `target/release`. - -### Cargo as Convention - -With simple projects, Cargo doesn't provide a whole lot of value over just -using `rustc`, but it will prove its worth as you continue. With complex -projects composed of multiple crates, it’s much easier to let Cargo coordinate -the build. With Cargo, you can just run `cargo build`, and it should work the -right way. Even though this project is simple, it now uses much of the real -tooling you’ll use for the rest of your Rust career. In fact, you can get -started with virtually all Rust projects you want to work -on with the following commands: - -```bash -$ git clone someurl.com/someproject -$ cd someproject -$ cargo build -``` - -> Note: If you want to look at Cargo in more detail, check out the official -Cargo guide at *http://doc.crates.io/guide.html*, which covers all of its features. diff --git a/nostarch/chapter02.md b/nostarch/chapter02.md deleted file mode 100644 index fb500b2..0000000 --- a/nostarch/chapter02.md +++ /dev/null @@ -1,1048 +0,0 @@ - -[TOC] - -# Guessing Game - -Let’s jump into Rust by working through a hands-on project together! This -chapter introduces you to a few common Rust concepts by showing you how to use -them in a real program. You’ll learn about `let`, `match`, methods, associated -functions, using external crates, and more! The following chapters will explore -these ideas in more detail. In this chapter, you’ll practice the fundamentals. - -We’ll implement a classic beginner programming problem: a guessing game. Here’s -how it works: the program will generate a random integer between 1 and 100. It -will then prompt the player to enter a guess. After entering a guess, it will -indicate whether the guess is too low or too high. If the guess is correct, the -game will print congratulations and exit. - -## Setting Up a New Project - -To set up a new project, go to the *projects* directory that you created in -Chapter 1, and make a new project using Cargo, like so: - -```bash -$ cargo new guessing_game --bin -$ cd guessing_game -``` - -The first command, `cargo new`, takes the name of the project (`guessing_game`) -as the first argument. The `--bin` flag tells Cargo to make a binary project, -similar to the one in Chapter 1. The second command changes to the new -project’s directory. - -Look at the generated *Cargo.toml* file: - -Filename: Cargo.toml - -```toml -[package] -name = "guessing_game" -version = "0.1.0" -authors = ["Your Name "] - -[dependencies] -``` - -If the author information that Cargo obtained from your environment is not -correct, fix that in the file and save it again. - -As you saw in Chapter 1, `cargo new` generates a “Hello, world!” program for -you. Check out the *src/main.rs* file: - -Filename: src/main.rs - -```rust -fn main() { - println!("Hello, world!"); -} -``` - -Now let’s compile this “Hello, world!” program and run it in the same step -using the `cargo run` command: - -```bash -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/debug/guessing_game` -Hello, world! -``` - -The `run` command comes in handy when you need to rapidly iterate on a project, -and this game is such a project: we want to quickly test each iteration -before moving on to the next one. - -Reopen the *src/main.rs* file. You’ll be writing all the code in this file. - -## Processing a Guess - -The first part of the program will ask for user input, process that input, and -check that the input is in the expected form. To start, we’ll allow the player -to input a guess. Enter the code in Listing 2-1 into *src/main.rs*. - -Filename: src/main.rs - -```rust,ignore -use std::io; - -fn main() { - println!("Guess the number!"); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - println!("You guessed: {}", guess); -} -``` - - -Listing 2-1: Code to get a guess from the user and print it out - - -This code contains a lot of information, so let’s go over it bit by bit. To -obtain user input and then print the result as output, we need to import the -`io` (input/output) library from the standard library (which is known as `std`): - -```rust,ignore -use std::io; -``` - -By default, Rust imports only a few types into every program in the -*prelude*. If a type you want to use isn’t in the -prelude, you have to import that type into your program explicitly with a `use` -statement. Using the `std::io` library provides you with a number of useful -`io`-related features, including the functionality to accept user input. - -As you saw in Chapter 1, the `main` function is the entry point into the -program: - -```rust,ignore -fn main() { -``` - -The `fn` syntax declares a new function, the `()` indicate there are no -arguments, and `{` starts the body of the function. - -As you also learned in Chapter 1, `println!` is a macro that prints a string to -the screen: - -```rust,ignore -println!("Guess the number!"); - -println!("Please input your guess."); -``` - -This code is just printing a prompt stating what the game is and requesting -input from the user. - -### Storing Values with Variables - -Next, we’ll create a place to store the user input, like this: - -```rust,ignore -let mut guess = String::new(); -``` - -Now the program is getting interesting! There’s a lot going on in this little -line. Notice that this is a `let` statement, which is used to create -*variables*. Here’s another example: - -```rust,ignore -let foo = bar; -``` - -This line will create a new variable named `foo` and bind it to the value -`bar`. In Rust, variables are immutable by default. The following example shows -how to use `mut` before the variable name to make a variable mutable: - -```rust -let foo = 5; // immutable -let mut bar = 5; // mutable -``` - -> Note: The `//` syntax starts a comment that continues until the end of the -> line. Rust ignores everything in comments. - -Now you know that `let mut guess` will introduce a mutable variable named -`guess`. On the other side of the equal sign (`=`) is the value that `guess` is -bound to, which is the result of calling `String::new`, a function that returns -a new instance of a `String`. `String` is a string -type provided by the standard library that is a growable, UTF-8 encoded bit of -text. - -The `::` syntax in the `::new` line indicates that `new` is an *associated -function* of the `String` type. An associated function is implemented on a type, -in this case `String`, rather than on a particular instance of a `String`. Some -languages call this a *static method*. - -This `new` function creates a new, empty `String`. You’ll find a `new` function -on many types, because it’s a common name for a function that makes a new value -of some kind. - -To summarize, the `let mut guess = String::new();` line has created a mutable -variable that is currently bound to a new, empty instance of a `String`. Whew! - -Recall that we included the input/output functionality from the standard -library with `use std::io;` on the first line of the program. Now we’ll call an -associated function, `stdin`, on `io`: - -```rust,ignore -io::stdin().read_line(&mut guess) - .expect("Failed to read line"); -``` - -If we didn’t have the `use std::io` line at the beginning of the program, we -could have written this function call as `std::io::stdin`. The `stdin` function -returns an instance of `std::io::Stdin`, which is a -type that represents a handle to the standard input for your terminal. - -The next part of the code, `.read_line(&mut guess)`, calls the -`read_line` method on the standard input handle to -get input from the user. We’re also passing one argument to `read_line`: `&mut -guess`. - -The job of `read_line` is to take whatever the user types into standard input -and place that into a string, so it takes that string as an argument. The -string argument needs to be mutable so the method can change the string’s -content by adding the user input. - -The `&` indicates that this argument is a *reference*, which gives you a way to -let multiple parts of your code access one piece of data without needing to -copy that data into memory multiple times. References are a complex feature, -and one of Rust’s major advantages is how safe and easy it is to use -references. You don’t need to know a lot of those details to finish this -program: Chapter 4 will explain references more thoroughly. For now, all you -need to know is that like variables, references are immutable by default. -Hence, we need to write `&mut guess` rather than `&guess` to make it mutable. - -We’re not quite done with this line of code. Although it’s a single line of -text, it’s only the first part of the single logical line of code. The second -part is this method: - -```rust,ignore -.expect("Failed to read line"); -``` - -When you call a method with the `.foo()` syntax, it’s often wise to introduce a -newline and other whitespace to help break up long lines. We could have -written this code as: - -```rust,ignore -io::stdin().read_line(&mut guess).expect("Failed to read line"); -``` - -However, one long line is difficult to read, so it’s best to divide it, two -lines for two method calls. Now let’s discuss what this line does. - -### Handling Potential Failure with the `Result` Type - -As mentioned earlier, `read_line` puts what the user types into the string we’re -passing it, but it also returns a value—in this case, an -`io::Result`. Rust has a number of types named -`Result` in its standard library: a generic `Result` as -well as specific versions for submodules, such as `io::Result`. - -The `Result` types are *enumerations*, often referred -to as *enums*. An enumeration is a type that can have a fixed set of values, -and those values are called the enum’s *variants*. Chapter 6 will cover enums -in more detail. - -For `Result`, the variants are `Ok` or `Err`. `Ok` indicates the operation was -successful, and inside the `Ok` variant is the successfully generated value. -`Err` means the operation failed, and `Err` contains information about how or -why the operation failed. - -The purpose of these `Result` types is to encode error handling information. -Values of the `Result` type, like any type, have methods defined on them. An -instance of `io::Result` has an `expect` method that -you can call. If this instance of `io::Result` is an `Err` value, `expect` will -cause the program to crash and display the message that you passed as an -argument to `expect`. If the `read_line` method returns an `Err`, it would -likely be the result of an error coming from the underlying operating system. -If this instance of `io::Result` is an `Ok` value, `expect` will take the -return value that `Ok` is holding and return just that value to you so you -could use it. In this case, that value is the number of characters the user -entered into standard input. - -If we don’t call `expect`, the program will compile, but we’ll get a warning: - -```bash -$ cargo build - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) -src/main.rs:10:5: 10:39 warning: unused result which must be used, -#[warn(unused_must_use)] on by default -src/main.rs:10 io::stdin().read_line(&mut guess); - ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -``` - -Rust warns that we haven’t used the `Result` value returned from `read_line`, -indicating that the program hasn’t handled a possible error. The right way to -suppress the warning is to actually write error handling, but since we just -want to crash this program when a problem occurs, we can use `expect`. You’ll -learn about recovering from errors in Chapter 9. - -### Printing Values with `println!` Placeholders - -Aside from the closing curly brace, there’s only one more line to discuss in -the code added so far, which is the following: - -```rust,ignore -println!("You guessed: {}", guess); -``` - -This line prints out the string we saved the user’s input in. The set of `{}` -is a placeholder that holds a value in place. You can print more than one value -using `{}`: the first set of `{}` holds the first value listed after the format -string, the second set holds the second value, and so on. Printing out multiple -values in one call to `println!` would look like this: - -```rust -let x = 5; -let y = 10; - -println!("x = {} and y = {}", x, y); -``` - -This code would print out `x = 5 and y = 10`. - -### Testing the First Part - -Let’s test the first part of the guessing game. You can run it using `cargo run`: - -```bash -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/debug/guessing_game` -Guess the number! -Please input your guess. -6 -You guessed: 6 -``` - -At this point, the first part of the game is done: we’re getting input from the -keyboard and then printing it. - -## Generating a Secret Number - -Next, we need to generate a secret number that the user will try to guess. The -secret number should be different every time so the game is fun to play more -than once. Let’s use a random number between 1 and 100 so the game isn’t too -difficult. Rust doesn’t yet include random number functionality in its standard -library. However, the Rust team does provide a `rand` crate at *https://crates.io/crates/rand*. - - -### Using a Crate to Get More Functionality - -Remember that a *crate* is a package of Rust code. The project we’ve been -building is a *binary crate*, which is an executable. The `rand` crate is a -*library crate*, which contains code intended to be used in other programs. - -Cargo’s use of external crates is where it really shines. Before we can write -code that uses `rand`, we need to modify the *Cargo.toml* file to include the -`rand` crate as a dependency. Open that file now and add the following line to -the bottom beneath the `[dependencies]` section header that Cargo created for -you: - -Filename: Cargo.toml - -```toml -[dependencies] - -rand = "0.3.14" -``` - -In the *Cargo.toml* file, everything that follows a header is part of a section -that continues until another section starts. The `[dependencies]` section is -where you tell Cargo which external crates your project depends on and which -versions of those crates you require. In this case, we’ll specify the `rand` -crate with the semantic version specifier `0.3.14`. Cargo understands Semantic -Versioning (sometimes called *SemVer*), which is a -standard for writing version numbers. The number `0.3.14` is actually shorthand -for `^0.3.14`, which means “any version that has a public API compatible with -version 0.3.14.” - -Now, without changing any of the code, let’s build the project, as shown in -Listing 2-2: - -```bash -$ cargo build - Updating registry `https://github.com/rust-lang/crates.io-index` - Downloading rand v0.3.14 - Downloading libc v0.2.14 - Compiling libc v0.2.14 - Compiling rand v0.3.14 - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) -``` - - -Listing 2-2: The output from running `cargo build` after adding the rand crate -as a dependency - - -You may see different version numbers (but they will all be compatible with -the code, thanks to SemVer!), and the lines may be in a different order. - -Now that we have an external dependency, Cargo fetches the latest versions of -everything from the *registry*, which is a copy of data from -Crates.io at *https://crates.io*. Crates.io is where people in the Rust ecosystem post -their open source Rust projects for others to use. - - -After updating the registry, Cargo checks the `[dependencies]` section and -downloads any you don’t have yet. In this case, although we only listed `rand` -as a dependency, Cargo also grabbed a copy of `libc`, because `rand` depends on -`libc` to work. After downloading them, Rust compiles them and then compiles -the project with the dependencies available. - -If you immediately run `cargo build` again without making any changes, you won’t -get any output. Cargo knows it has already downloaded and compiled the -dependencies, and you haven't changed anything about them in your *Cargo.toml* -file. Cargo also knows that you haven't changed anything about your code, so it -doesn't recompile that either. With nothing to do, it simply exits. If you open -up the *src/main.rs* file, make a trivial change, then save it and build again, -you’ll only see one line of output: - -```bash -$ cargo build - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) -``` - -This line shows Cargo only updates the build with your tiny change to the -*src/main.rs* file. Your dependencies haven't changed, so Cargo knows it can -reuse what it has already downloaded and compiled for those. It just rebuilds -your part of the code. - -#### The *Cargo.lock* File Ensures Reproducible Builds - -Cargo has a mechanism that ensures you can rebuild the same artifact every time -you or anyone else builds your code: Cargo will use only the versions of the -dependencies you specified until you indicate otherwise. For example, what -happens if next week version `v0.3.15` of the `rand` crate comes out and -contains an important bug fix but also contains a regression that will break -your code? - -The answer to this problem is the *Cargo.lock* file, which was created the -first time you ran `cargo build` and is now in your *guessing_game* directory. -When you build a project for the first time, Cargo figures out all the -versions of the dependencies that fit the criteria and then writes them to -the *Cargo.lock* file. When you build your project in the future, Cargo will -see that the *Cargo.lock* file exists and use the versions specified there -rather than doing all the work of figuring out versions again. This lets you -have a reproducible build automatically. In other words, your project will -remain at `0.3.14` until you explicitly upgrade, thanks to the *Cargo.lock* -file. - -#### Updating a Crate to Get a New Version - -When you *do* want to update a crate, Cargo provides another command, `update`, -which will: - -1. Ignore the *Cargo.lock* file and figure out all the latest versions that fit -your specifications in *Cargo.toml*. -1. If that works, Cargo will write those versions to the *Cargo.lock* file. - -But by default, Cargo will only look for versions larger than `0.3.0` and -smaller than `0.4.0`. If the `rand` crate has released two new versions, -`0.3.15` and `0.4.0`, you would see the following if you ran `cargo update`: - -```bash -$ cargo update - Updating registry `https://github.com/rust-lang/crates.io-index` - Updating rand v0.3.14 -> v0.3.15 -``` - -At this point, you would also notice a change in your *Cargo.lock* file noting -that the version of the `rand` crate you are now using is `0.3.15`. - -If you wanted to use `rand` version `0.4.0` or any version in the `0.4.x` -series, you’d have to update the *Cargo.toml* file to look like this instead: - -```toml -[dependencies] - -rand = "0.4.0" -``` - -The next time you run `cargo build`, Cargo will update the registry of crates -available and reevaluate your `rand` requirements according to the new version -you specified. - -There’s a lot more to say about Cargo and its -ecosystem that Chapter XX will discuss, but for -now, that’s all you need to know. Cargo makes it very easy to reuse libraries, -so Rustaceans are able to write smaller projects that are assembled from a -number of packages. - -### Generating a Random Number - -Let’s start *using* `rand`. The next step is to update *src/main.rs*, as shown -in Listing 2-3: - -Filename: src/main.rs - -```rust,ignore -extern crate rand; - -use std::io; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - println!("You guessed: {}", guess); -} -``` - - -Listing 2-3: Code changes needed in order to generate a random number - - -We’re adding a `extern crate rand;` line to the top that lets Rust know we’ll be -using that external dependency. This also does the equivalent of calling `use -rand`, so now we can call anything in the `rand` crate by prefixing it with -`rand::`. - -Next, we’re adding another `use` line: `use rand::Rng`. `Rng` is a trait that -defines methods that random number generators implement, and this trait must be -in scope for us to use those methods. Chapter 10 will cover traits in detail. - -Also, we’re adding two more lines in the middle. The `rand::thread_rng` function -will give us the particular random number generator that we’re going to use: -one that is local to the current thread of execution and seeded by the -operating system. Next, we call the `gen_range` method on the random number -generator. This method is defined by the `Rng` trait that we brought into -scope with the `use rand::Rng` statement. The `gen_range` method takes two -numbers as arguments and generates a random number between them. It’s inclusive -on the lower bound but exclusive on the upper bound, so we need to specify `1` -and `101` to request a number between 1 and 100. - -Knowing which traits to import and which functions and methods to use from a -crate isn’t something that you’ll just *know*. Instructions for using a crate -are in each crate’s documentation. Another neat feature of Cargo is that you -can run the `cargo doc --open` command that will build documentation provided -by all of your dependencies locally and open it in your browser. If you’re -interested in other functionality in the `rand` crate, for example, run `cargo -doc --open` and click `rand` in the sidebar on the left. - -The second line that we added to the code prints the secret number. This is -useful while we’re developing the program to be able to test it, but we’ll -delete it from the final version. It’s not much of a game if the program prints -the answer as soon as it starts! - -Try running the program a few times: - -```bash -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/debug/guessing_game` -Guess the number! -The secret number is: 7 -Please input your guess. -4 -You guessed: 4 -$ cargo run - Running `target/debug/guessing_game` -Guess the number! -The secret number is: 83 -Please input your guess. -5 -You guessed: 5 -``` - -You should get different random numbers, and they should all be numbers between -1 and 100. Great job! - -## Comparing the Guess to the Secret Number - -Now that we have user input and a random number, we can compare them. That -step is shown in Listing 2-4: - -Filename: src/main.rs - -```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), - } -} -``` - - -Listing 2-4: Handling the possible return values of comparing two numbers - - -The first new bit here is another `use`, bringing a type called -`std::cmp::Ordering` into scope from the standard library. `Ordering` is -another enum, like `Result`, but the variants for `Ordering` are `Less`, -`Greater`, and `Equal`. These are the three outcomes that are possible when you -compare two values. - -Then we add five new lines at the bottom that use the `Ordering` type: - -```rust,ignore -match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), -} -``` - -The `cmp` method compares two values and can be called on anything that can be -compared. It takes a reference to whatever you want to compare with: here it’s -comparing the `guess` to the `secret_number`. `cmp` returns a variant of the -`Ordering` enum we imported with the `use` statement. We use a -`match` expression to decide what to do next based on -which variant of `Ordering` was returned from the call to `cmp` with the values -in `guess` and `secret_number`. - -A `match` expression is made up of *arms*. An arm consists of a *pattern* and -the code that should be run if the value given to the beginning of the `match` -expression fits that arm’s pattern. Rust takes the value given to `match` and -looks through each arm’s pattern in turn. The `match` construct and patterns -are powerful features in Rust that let you express a variety of situations your -code might encounter and helps ensure that you handle them all. These features -will be covered in detail in Chapter 6 and Chapter XX, respectively. - -Let’s walk through an example of what would happen with the `match` expression -used here. Say that the user has guessed 50, and the randomly generated secret -number this time is 38. When the code compares 50 to 38, the `cmp` method will -return `Ordering::Greater`, because 50 is greater than 38. `Ordering::Greater` -is the value that the `match` expression gets. It looks at the first arm’s -pattern, `Ordering::Less`, but the value `Ordering::Greater` does not match -`Ordering::Less`. So it ignores the code in that arm and moves to the next arm. -The next arm’s pattern, `Ordering::Greater`, *does* match -`Ordering::Greater`! The associated code in that arm will execute and print -`Too big!` to the screen. The `match` expression ends because it has no need to -look at the last arm in this particular scenario. - -However, the code in Listing 2-4 won’t compile yet. Let’s try it: - -```bash -$ cargo build - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) -error[E0308]: mismatched types - --> src/main.rs:23:21 - | -23 | match guess.cmp(&secret_number) { - | ^^^^^^^^^^^^^^ expected struct `std::string::String`, found integral variable - | - = note: expected type `&std::string::String` - = note: found type `&{integer}` - -error: aborting due to previous error -Could not compile `guessing_game`. -``` - -The core of the error states that there are *mismatched types*. Rust has a -strong, static type system. However, it also has type inference. When we wrote -`let guess = String::new()`, Rust was able to infer that `guess` should be a -`String` and didn’t make us write the type. The `secret_number`, on the other -hand, is a number type. A few number types can have a value between 1 and 100: -`i32`, a 32-bit number; `u32`, an unsigned 32-bit number; `i64`, a 64-bit -number; as well as others. Rust defaults to an `i32`, which is the type of -`secret_number` unless we add type information elsewhere that would cause Rust -to infer a different numerical type. The reason for the error is that Rust will -not compare a string and a number type. - -Ultimately, we want to convert the `String` the program reads as input into a -real number type so we can compare it to the guess numerically. We can do -that by adding the following two lines to the `main` function body: - -Filename: src/main.rs - -```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), - } -} -``` - -The two new lines are: - -```rust,ignore -let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); -``` - -We create a variable named `guess`. But wait, doesn’t the program -already have a variable named `guess`? It does, but Rust allows us to -*shadow* the previous value of `guess` with a new one. This feature is often -used in similar situations in which you want to convert a value from one type -to another type. Shadowing lets us reuse the `guess` variable name rather than -forcing us to create two unique variables, like `guess_str` and `guess` for -example. (Chapter 3 covers shadowing in more detail.) - -We bind `guess` to the expression `guess.trim().parse()`. The `guess` in the -expression refers to the original `guess` that was a `String` with the input in -it. The `trim` method on a `String` instance will eliminate any whitespace at -the beginning and end. `u32` can only contain numerical characters, but the -user must press the Return key to satisfy `read_line`. When the user presses -Return, a newline character is added to the string. For example, if the user -types 5 and presses return, `guess` looks like this: `5\n`. The `\n` represents -“newline,” the return key. The `trim` method eliminates `\n`, resulting in just -`5`. - -The `parse` method on strings parses a string into some -kind of number. Because this method can parse a variety of number types, we -need to tell Rust the exact number type we want by using `let guess: u32`. The -colon (`:`) after `guess` tells Rust we’ll annotate the variable’s type. Rust -has a few built-in number types; the `u32` seen here is an unsigned, 32-bit -integer. It’s a good default choice for a small positive number. You’ll learn -about other number types in Chapter 3. Additionally, the `u32` annotation in -this example program and the comparison with `secret_number` means that Rust -will infer that `secret_number` should be a `u32` as well. So now the -comparison will be between two values of the same type! - -The call to `parse` could easily cause an error. If, for example, the string -contained `A👍%`, there would be no way to convert that to a number. Because it -might fail, the `parse` method returns a `Result` type, much like the -`read_line` method does as discussed earlier in “Handling Potential Failure -with the Result Type” on page XX. We’ll treat this `Result` the same way by -using the `expect` method again. If `parse` returns an `Err` `Result` variant -because it couldn’t create a number from the string, the `expect` call will -crash the game and print the message we give it. If `parse` can successfully -convert the string to a number, it will return the `Ok` variant of `Result`, -and `expect` will return the number that we want from the `Ok` value. - -Let’s run the program now! - -```bash -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/guessing_game` -Guess the number! -The secret number is: 58 -Please input your guess. - 76 -You guessed: 76 -Too big! -``` - -Nice! Even though spaces were added before the guess, the program still figured -out that the user guessed 76. Run the program a few times to verify the -different behavior with different kinds of input: guess the number correctly, -guess a number that is too high, and guess a number that is too low. - -We have most of the game working now, but the user can make only one guess. -Let’s change that by adding a loop! - -## Allowing Multiple Guesses with Looping - -The `loop` keyword gives us an infinite loop. Add that now to give users more -chances at guessing the number: - -Filename: src/main.rs - -```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - loop { - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), - } - } -} -``` - -As you can see, we’ve moved everything into a loop from the guess input prompt -onward. Be sure to indent those lines another four spaces each, and run the -program again. Notice that there is a new problem because the program is doing -exactly what we told it to do: ask for another guess forever! It doesn’t seem -like the user can quit! - -The user could always halt the program by using the keyboard shortcut `Ctrl-C`. -But there’s another way to escape this insatiable monster that we mentioned in -the `parse` discussion in “Comparing the Guesses” on page XX: if the user -enters a non-number answer, the program will crash. The user can take advantage -of that in order to quit, as shown here: - -```bash -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/guessing_game` -Guess the number! -The secret number is: 59 -Please input your guess. -45 -You guessed: 45 -Too small! -Please input your guess. -60 -You guessed: 60 -Too big! -Please input your guess. -59 -You guessed: 59 -You win! -Please input your guess. -quit -thread 'main' panicked at 'Please type a number!: ParseIntError { kind: InvalidDigit }', src/libcore/result.rs:785 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/guess` (exit code: 101) -``` - -Typing `quit` actually quits the game, but so will any other non-number input. -However, this is suboptimal to say the least. We want the game to automatically -stop when the correct number is guessed. - -### Quitting After a Correct Guess - -Let’s program the game to quit when the user wins by adding a `break`: - -Filename: src/main.rs - -```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - loop { - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => { - println!("You win!"); - break; - } - } - } -} -``` - -By adding the `break` line after `You win!`, the program will exit the loop -when the user guesses the secret number correctly. Exiting the loop also means -exiting the program, because the loop is the last part of `main`. - -### Handling Invalid Input - -To further refine the game’s behavior, rather than crashing the program when -the user inputs a non-number, let’s make the game ignore a non-number so the -user can continue guessing. We can do that by altering the line where `guess` is -converted from a `String` to a `u32`: - -```rust,ignore -let guess: u32 = match guess.trim().parse() { - Ok(num) => num, - Err(_) => continue, -}; -``` - -Switching from an `expect` call to a `match` expression is how you generally -move from crash on error to actually handling the error. Remember that `parse` -returns a `Result` type, and `Result` is an enum that has the variants `Ok` or -`Err`. We’re using a `match` expression here, like we did with the `Ordering` -result of the `cmp` method. - -If `parse` is able to successfully turn the string into a number, it will return -an `Ok` value that contains the resulting number. That `Ok` value will match the -first arm’s pattern, and the `match` expression will just return the `num` value -that `parse` produced and put inside the `Ok` value. That number will end up -right where we want it in the new `guess` variable we’re creating. - -If `parse` is *not* able to turn the string into a number, it will return an -`Err` value that contains more information about the error. The `Err` value -does not match the `Ok(num)` pattern in the first `match` arm, but it does match -the `Err(_)` pattern in the second arm. The `_` is a catchall value; in this -example, we’re saying we want to match all `Err` values, no matter what -information they have inside them. So the program will execute the second arm’s -code, `continue`, which means to go to the next iteration of the `loop` and ask -for another guess. So effectively, the program ignores all errors that `parse` -might encounter! - -Now everything in the program should work as expected. Let’s try it by running -`cargo run`: - -```bash -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/guessing_game` -Guess the number! -The secret number is: 61 -Please input your guess. -10 -You guessed: 10 -Too small! -Please input your guess. -99 -You guessed: 99 -Too big! -Please input your guess. -foo -Please input your guess. -61 -You guessed: 61 -You win! -``` - -Awesome! With one tiny final tweak, we will finish the guessing game: recall -that the program is still printing out the secret number. That worked well for -testing, but it ruins the game. Let’s delete the `println!` that outputs the -secret number. Listing 2-5 shows the final code: - -Filename: src/main.rs - -```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - loop { - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = match guess.trim().parse() { - Ok(num) => num, - Err(_) => continue, - }; - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => { - println!("You win!"); - break; - } - } - } -} -``` - - -Listing 2-5: Complete code of the guessing game - - -## Summary - -At this point, you’ve successfully built the guessing game! Congratulations! - -This project was a hands-on way to introduce you to many new Rust concepts: -`let`, `match`, methods, associated functions, using external crates, and more. -In the next few chapters, you’ll learn about these concepts in more detail. -Chapter 3 covers concepts that most programming languages have, such as -variables, data types, and functions, and shows how to use them in Rust. -Chapter 4 explores ownership, which is a Rust feature that is most different -from other languages. Chapter 5 discusses structs and method syntax, and -Chapter 6 endeavors to explain enums. diff --git a/nostarch/chapter03.md b/nostarch/chapter03.md deleted file mode 100644 index a84ce00..0000000 --- a/nostarch/chapter03.md +++ /dev/null @@ -1,1449 +0,0 @@ - -[TOC] - -# Common Programming Concepts - -This chapter covers concepts that appear in almost every programming language -and how they work in Rust. Many programming languages have much in common at -their core. None of the concepts presented in this chapter are unique to Rust, -but we’ll discuss them in the context of Rust and explain their conventions. - -Specifically, you’ll learn about variables, basic types, functions, comments, -and control flow. These foundations will be in every Rust program, and learning -them early will give you a strong core to start from. - -PROD: START BOX - -### Keywords - -The Rust language has a set of *keywords* that have been reserved for use by -the language only, much like other languages do. Keep in mind that you cannot -use these words as names of variables or functions. Most of the keywords have -special meanings, and you’ll be using them to do various tasks in your Rust -programs; a few have no current functionality associated with them but have -been reserved for functionality that might be added to Rust in the future. You -can find a list of the keywords in Appendix A. - -PROD: END BOX - -## Variables and Mutability - -As mentioned in Chapter 2, by default variables are *immutable*. This is one of -many nudges in Rust that encourages you to write your code in a way that takes -advantage of the safety and easy concurrency that Rust offers. However, you -still have the option to make your variables mutable. Let’s explore how and why -Rust encourages you to favor immutability, and why you might want to opt out. - -When a variable is immutable, that means mean once a value is bound to a name, -you can’t change that value. To illustrate, let’s generate a new project called -*variables* in your *projects* directory by using `cargo new --bin variables`. - -Then, in your new *variables* directory, open *src/main.rs* and replace its -code with the following: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let x = 5; - println!("The value of x is: {}", x); - x = 6; - println!("The value of x is: {}", x); -} -``` - -Save and run the program using `cargo run`. You should receive an error -message, as shown in this output: - -```bash -$ cargo run - Compiling variables v0.0.1 (file:///projects/variables) -error[E0384]: re-assignment of immutable variable `x` - --> src/main.rs:4:5 - | -2 | let x = 5; - | - first assignment to `x` -3 | println!("The value of x is: {}", x); -4 | x = 6; - | ^^^^^ re-assignment of immutable variable -``` - -This example shows how the compiler helps you find errors in your programs. -Even though compiler errors can be frustrating, they only mean your program -isn’t safely doing what you want it to do yet; they do *not* mean that you’re -not a good programmer! Experienced Rustaceans still get compiler errors. The -error indicates that the cause of the error is `re-assignment of immutable -variable`, because we tried to assign a second value to the immutable `x` -variable. - -It’s important that we get compile-time errors when we attempt to change a -value that we previously designated as immutable because this very situation -can lead to bugs. If one part of our code operates on the assumption that a -value will never change and another part of our code changes that value, it’s -possible that the first part of the code won’t do what it was designed to do. -This cause of bugs can be difficult to track down after the fact, especially -when the second piece of code changes the value only *sometimes*. - -In Rust the compiler guarantees that when we state that a value won’t change, -it really won’t change. That means that when you’re reading and writing code, -you don’t have to keep track of how and where a value might change, which can -make code easier to reason about. - -But mutability can be very useful. Variables are immutable only by default; we -can make them mutable by adding `mut` in front of the variable name. In -addition to allowing this value to change, it conveys intent to future readers -of the code by indicating that other parts of the code will be changing this -variable value. - -For example, change *src/main.rs* to the following: - -Filename: src/main.rs - -```rust -fn main() { - let mut x = 5; - println!("The value of x is: {}", x); - x = 6; - println!("The value of x is: {}", x); -} -``` - -When we run this program, we get the following: - -```bash -$ cargo run - Compiling variables v0.1.0 (file:///projects/variables) - Running `target/debug/variables` -The value of x is: 5 -The value of x is: 6 -``` - -Using `mut`, we’re allowed to change the value that `x` binds to from `5` to -`6`. In some cases, you’ll want to make a variable mutable because it makes the -code more convenient to write than an implementation that only uses immutable -variables. - -There are multiple trade-offs to consider, in addition to the prevention of -bugs. For example, in cases where you’re using large data structures, mutating -an instance in place may be faster than copying and returning newly allocated -instances. With smaller data structures, always creating new instances and -writing in a more functional programming style may be easier to reason about, -so the lower performance penalty might be worth it to gain that clarity. - -### Differences Between Variables and Constants - -Not being able to change the value of a variable might have reminded you of -another programming concept that most languages have: *constants*. Constants -are also values bound to a name that are not allowed to change, but there are a -few differences between constants and variables. First, using `mut` with -constants is not allowed: constants aren't only immutable by default, they're -always immutable. Constants are declared using the `const` keyword instead of -the `let` keyword, and the type of the value *must* be annotated. We're about -to cover types and type annotations in the next section, “Data Types,” so don't -worry about the details right now. Constants can be declared in any scope, -including the global scope, which makes them useful for a value that many parts -of your code need to know about. The last difference is that constants may only -be set to a constant expression, not the result of a function call or any other -value that could only be used at runtime. - -Here's an example of a constant declaration where the constant's name is -`MAX_POINTS` and its value is set to 100,000. Rust constant naming convention -is to use all upper case with underscores between words: - -``` -const MAX_POINTS: u32 = 100_000; -``` - -Constants are valid for the entire lifetime of a program, within the scope they -were declared in. That makes constants useful for values in your application -domain that multiple part of the program might need to know about, such as the -maximum number of points any player of a game is allowed to earn or the number -of seconds in a year. - -Documenting hardcoded values used throughout your program by naming them as -constants is useful to convey the meaning of that value to future maintainers -of the code. It also helps to have only one place in your code that you would -need to change if the hardcoded value needed to be updated in the future. - -### Shadowing - -As we saw in the guessing game tutorial in Chapter 2, we can declare new -variables with the same name as a previous variables, and the new variable -*shadows* the previous variable. Rustaceans say that the first variable is -*shadowed* by the second, which means that the second variable’s value is what -we’ll see when we use the variable. We can shadow a variable by using the same -variable’s name and repeating the use of the `let` keyword as follows: - -Filename: src/main.rs - -```rust -fn main() { - let x = 5; - - let x = x + 1; - - let x = x * 2; - - println!("The value of x is: {}", x); -} -``` - -This program first binds `x` to a value of `5`. Then it shadows `x` by -repeating `let x =`, taking the original value and adding `1` so the value of -`x` is then `6`. The third `let` statement also shadows `x`, taking the -previous value and multiplying it by `2` to give `x` a final value of `12`. -When you run this program, it will output the following: - -```bash -$ cargo run - Compiling variables v0.1.0 (file:///projects/variables) - Running `target/debug/variables` -The value of x is: 12 -``` - -This is different than marking a variable as `mut`, because unless we use the -`let` keyword again, we’ll get a compile-time error if we accidentally try to -reassign to this variable. We can perform a few transformations on a value but -have the variable be immutable after those transformations have been completed. - -The other difference between `mut` and shadowing is that because we’re -effectively creating a new variable when we use the `let` keyword again, we can -change the type of the value, but reuse the same name. For example, say our -program asks a user to show how many spaces they want between some text by -inputting space characters, but we really want to store that input as a number: - -```rust -let spaces = " "; -let spaces = spaces.len(); -``` - -This construct is allowed because the first `spaces` variable is a string type, -and the second `spaces` variable, which is a brand-new variable that happens to -have the same name as the first one, is a number type. Shadowing thus spares us -from having to come up with different names, like `spaces_str` and -`spaces_num`; instead, we can reuse the simpler `spaces` name. However, if we -try to use `mut` for this, as shown here: - -```rust,ignore -let mut spaces = " "; -spaces = spaces.len(); -``` - -we’ll get a compile-time error because we’re not allowed to mutate a variable’s -type: - -```bash -error[E0308]: mismatched types - --> src/main.rs:3:14 - | -3 | spaces = spaces.len(); - | ^^^^^^^^^^^^ expected &str, found usize - | - = note: expected type `&str` - = note: found type `usize` -``` - -Now that we’ve explored how variables work, let’s look at more data types they -can have. - -## Data Types - -Every value in Rust is of a certain *type*, which tells Rust what kind of data -is being specified so it knows how to work with that data. In this section, -we’ll look at a number of types that are built into the language. We split the -types into two subsets: scalar and compound. - -Throughout this section, keep in mind that Rust is a *statically typed* -language, which means that it must know the types of all variables at compile -time. The compiler can usually infer what type we want to use based on the -value and how we use it. In cases when many types are possible, such as when we -converted a `String` to a numeric type using `parse` in Chapter 2, we must add -a type annotation, like this: - -```rust -let guess: u32 = "42".parse().unwrap(); -``` - -If we don’t add the type annotation here, Rust will display the following -error, which means the compiler needs more information from us to know which -possible type we want to use: - -```bash -error[E0282]: unable to infer enough type information about `_` - --> src/main.rs:2:5 - | -2 | let guess = "42".parse().unwrap(); - | ^^^^^ cannot infer type for `_` - | - = note: type annotations or generic parameter binding required -``` - -You’ll see different type annotations as we discuss the various data types. - -### Scalar Types - -A *scalar* type represents a single value. Rust has four primary scalar types: -integers, floating-point numbers, booleans, and characters. You’ll likely -recognize these from other programming languages, but let’s jump into how they -work in Rust. - -#### Integer Types - -An *integer* is a number without a fractional component. We used one integer -type earlier in this chapter, the `i32` type. This type declaration indicates -that the value it’s associated with should be a signed integer (hence the `i`, -as opposed to a `u` for unsigned) for a 32-bit system. Table 3-1 shows the -built-in integer types in Rust. Each variant in the Signed and Unsigned columns -(for example, *i32*) can be used to declare the type of an integer value. - - -Table 3-1: Integer Types in Rust - - -| Length | Signed | Unsigned | -|--------|--------|----------| -| 8-bit | i8 | u8 | -| 16-bit | i16 | u16 | -| 32-bit | i32 | u32 | -| 64-bit | i64 | u64 | -| arch | isize | usize | - -Each variant can be either signed or unsigned and has an explicit size. -Signed and unsigned refers to whether it’s possible for the number to be -negative or positive; in other words, whether the number needs to have a sign -with it (signed) or whether it will only ever be positive and can therefore be -represented without a sign (unsigned). It’s like writing numbers on paper: when -the sign matters, a number is shown with a plus sign or a minus sign; however, -when it’s safe to assume the number is positive, it’s shown with no sign. -Signed numbers are stored using two’s complement representation (if you’re -unsure what this is, you can search for it online; an explanation is outside -the scope of this book). - -Each signed variant can store numbers from -(2n - 1) to 2n - -1 - 1 inclusive, where `n` is the number of bits that variant uses. So an -`i8` can store numbers from -(27) to 27, which equals --128 to 127. Unsigned variants can store numbers from 0 to 2n - 1, -so a `u8` can store numbers from 0 to 28 - 1, which equals 0 to 255. - -Additionally, the `isize` and `usize` types depend on the kind of computer your -program is running on: 64-bits if you’re on a 64-bit architecture and 32-bits -if you’re on a 32-bit architecture. - -You can write integer literals in any of the forms shown in Table 3-2. Note -that all number literals except the byte literal allow a type suffix, such as -`57u8`, and `_` as a visual separator, such as `1_000`. - - -Table 3-2: Integer Literals in Rust - - -| Number literals | Example | -|------------------|---------------| -| Decimal | `98_222` | -| Hex | `0xff` | -| Octal | `0o77` | -| Binary | `0b1111_0000` | -| Byte (`u8` only) | `b'A'` | - -So how do you know which type of integer to use? If you’re unsure, Rust’s -defaults are generally good choices, and integer types default to `i32`: it’s -generally the fastest, even on 64-bit systems. The primary situation in which -you’d use `isize` or `usize` is when indexing some sort of collection. - -#### Floating-Point Types - -Rust also has two primitive types for *floating-point numbers*, which are -numbers with decimal points. Rust’s floating-point types are `f32` and `f64`, -which are 32 bits and 64 bits in size, respectively. The default type is `f64` -because it’s roughly the same speed as `f32` but is capable of more precision. -It’s possible to use an `f64` type on 32-bit systems, but it will be slower -than using an `f32` type on those systems. Most of the time, trading potential -worse performance for better precision is a reasonable initial choice, and you -should benchmark your code if you suspect floating-point size is a problem in -your situation. - -Here’s an example that shows floating-point numbers in action: - -Filename: src/main.rs - -```rust -fn main() { - let x = 2.0; // f64 - - let y: f32 = 3.0; // f32 -} -``` - -Floating-point numbers are represented according to the IEEE-754 standard. The -`f32` type is a single-precision float, and `f64` has double precision. - -#### Numeric Operations - -Rust supports the usual basic mathematic operations you’d expect for all of the -number types: addition, subtraction, multiplication, division, and remainder. -The following code shows how you’d use each one in a `let` statement: - -Filename: src/main.rs - -```rust -fn main() { - // addition - let sum = 5 + 10; - - // subtraction - let difference = 95.5 - 4.3; - - // multiplication - let product = 4 * 30; - - // division - let quotient = 56.7 / 32.2; - - // remainder - let remainder = 43 % 5; -} -``` - -Each expression in these statements uses a mathematical operator and evaluates -to a single value, which is then bound to a variable. Appendix B contains a -list of all operators that Rust provides. - -#### The Boolean Type - -As in most other programming languages, a boolean type in Rust has two possible -values: `true` and `false`. The boolean type in Rust is specified using `bool`. -For example: - -Filename: src/main.rs - -```rust -fn main() { - let t = true; - - let f: bool = false; // with explicit type annotation -} -``` - -The main way to consume boolean values is through conditionals, such as an `if` -statement. We’ll cover how `if` statements work in Rust in the “Control Flow” -section. - -#### The Character Type - -So far we’ve only worked with numbers, but Rust supports letters too. Rust’s -`char` type is the language’s most primitive alphabetic type, and the following -code shows one way to use it: - -Filename: src/main.rs - -```rust -fn main() { - let c = 'z'; - let z = 'ℤ'; - let heart_eyed_cat = '😻'; -} -``` - -Rust’s `char` type represents a Unicode Scalar Value, which means it can -represent a lot more than just ASCII. Accented letters, Chinese/Japanese/Korean -ideographs, emoji, and zero width spaces are all valid `char` types in Rust. -Unicode Scalar Values range from `U+0000` to `U+D7FF` and `U+E000` to -`U+10FFFF` inclusive. However, a “character” isn’t really a concept in Unicode, -so your human intuition for what a “character” is may not match up with what a -`char` is in Rust. We’ll discuss this topic in detail in the “Strings” section -in Chapter 8. - -### Compound Types - -*Compound types* can group multiple values of other types into one type. Rust -has two primitive compound types: tuples and arrays. - -#### Grouping Values into Tuples - -A tuple is a general way of grouping together some number of other values with -a variety of types into one compound type. - -We create a tuple by writing a comma-separated list of values inside -parentheses. Each position in the tuple has a type, and the types of the -different values in the tuple don’t have to be the same. We’ve added optional -type annotations in this example: - -Filename: src/main.rs - -```rust -fn main() { - let tup: (i32, f64, u8) = (500, 6.4, 1); -} -``` - -The variable `tup` binds to the entire tuple, since a tuple is considered a -single compound element. To get the individual values out of a tuple, we can -use pattern matching to destructure a tuple value, like this: - -Filename: src/main.rs - -```rust -fn main() { - let tup = (500, 6.4, 1); - - let (x, y, z) = tup; - - println!("The value of y is: {}", y); -} -``` - -This program first creates a tuple and binds it to the variable `tup`. It then -uses a pattern with `let` to take `tup` and turn it into three separate -variables, `x`, `y`, and `z`. This is called *destructuring*, because it breaks -the single tuple into three parts. Finally, the program prints the value of -`y`, which is `6.4`. - -In addition to destructuring through pattern matching, we can also access a -tuple element directly by using a period (`.`) followed by the index of the -value we want to access. For example: - -Filename: src/main.rs - -```rust -fn main() { - let x: (i32, f64, u8) = (500, 6.4, 1); - - let five_hundred = x.0; - - let six_point_four = x.1; - - let one = x.2; -} -``` - -This program creates a tuple, `x`, and then makes new variables for each -element by using their index. As with most programming languages, the first -index in a tuple is 0. - -#### Arrays - -Another way to have a collection of multiple values is with an *array*. Unlike -a tuple, every element of an array must have the same type. Arrays in Rust are -different than arrays in some other languages because arrays in Rust have a -fixed length: once declared, they cannot grow or shrink in size. - -In Rust, the values going into an array are written as a comma-separated list -inside square brackets: - -Filename: src/main.rs - -```rust -fn main() { - let a = [1, 2, 3, 4, 5]; -} -``` - -Arrays are useful when you want your data allocated on the stack rather than -the heap (we will discuss the stack and the heap more in Chapter 4), or when -you want to ensure you always have a fixed number of elements. They aren’t as -flexible as the vector type, though. The vector type is a similar collection -type provided by the standard library that *is* allowed to grow or shrink in -size. If you’re unsure whether to use an array or a vector, you should probably -use a vector: Chapter 8 discusses vectors in more detail. - -An example of when you might want to use an array rather than a vector is in a -program that needs to know the names of the months of the year. It’s very -unlikely that such a program will need to add or remove months, so you can use -an array because you know it will always contain 12 items: - -```rust -let months = ["January", "February", "March", "April", "May", "June", "July", - "August", "September", "October", "November", "December"]; -``` - -##### Accessing Array Elements - -An array is a single chunk of memory allocated on the stack. We can access -elements of an array using indexing, like this: - -Filename: src/main.rs - -```rust -fn main() { - let a = [1, 2, 3, 4, 5]; - - let first = a[0]; - let second = a[1]; -} -``` - -In this example, the variable named `first` will get the value `1`, because -that is the value at index `[0]` in the array. The variable named `second` will -get the value `2` from index `[1]` in the array. - -##### Invalid Array Element Access - -What happens if we try to access an element of an array that is past the end of -the array? Say we change the example to the following: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let a = [1, 2, 3, 4, 5]; - - let element = a[10]; - - println!("The value of element is: {}", element); -} -``` - -Running this code using `cargo run` produces the following result: - -```bash -$ cargo run - Compiling arrays v0.1.0 (file:///projects/arrays) - Running `target/debug/arrays` -thread '
' panicked at 'index out of bounds: the len is 5 but the index is - 10', src/main.rs:4 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/arrays` (exit code: 101) -``` - -The compilation didn’t produce any errors, but the program results in a -*runtime* error and didn’t exit successfully. When you attempt to access an -element using indexing, Rust will check that the index you’ve specified is less -than the array length. If the index is greater than the length, Rust will -*panic*, which is the term Rust uses when a program exits with an error. - -This is the first example of Rust’s safety principles in action. In many -low-level languages, this kind of check is not done, and when you provide an -incorrect index, invalid memory can be accessed. Rust protects you against this -kind of error by immediately exiting instead of allowing the memory access and -continuing. Chapter 9 discusses more of Rust’s error handling. - -## How Functions Work - -Functions are pervasive in Rust code. You’ve already seen one of the most -important functions in the language: the `main` function, which is the entry -point of many programs. You’ve also seen the `fn` keyword, which allows you to -declare new functions. - -Rust code uses *snake case* as the conventional style for function and variable -names. In snake case, all letters are lowercase and underscores separate words. -Here’s a program that contains an example function definition: - -Filename: src/main.rs - -```rust -fn main() { - println!("Hello, world!"); - - another_function(); -} - -fn another_function() { - println!("Another function."); -} -``` - -Function definitions in Rust start with `fn` and have a set of parentheses -after the function name. The curly braces tell the compiler where the function -body begins and ends. - -We can call any function we’ve defined by entering its name followed by a set -of parentheses. Because `another_function` is defined in the program, it can be -called from inside the `main` function. Note that we defined `another_function` -*after* the `main` function in the source code; we could have defined it before -as well. Rust doesn’t care where you define your functions, only that they’re -defined somewhere. - -Let’s start a new binary project named *functions* to explore functions -further. Place the `another_function` example in *src/main.rs* and run it. You -should see the following output: - -```bash -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -Hello, world! -Another function. -``` - -The lines execute in the order in which they appear in the `main` function. -First, the “Hello, world!” message prints, and then `another_function` is -called and its message is printed. - -### Function Arguments - -Functions can also take arguments. The following rewritten version of -`another_function` shows what arguments look like in Rust: - -Filename: src/main.rs - -```rust -fn main() { - another_function(5); -} - -fn another_function(x: i32) { - println!("The value of x is: {}", x); -} -``` - -Try running this program; you should get the following output: - -```bash -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -The value of x is: 5 -``` - -The declaration of `another_function` has one argument named `x`. The type of -`x` is specified as `i32`. When `5` is passed to `another_function`, the -`println!` macro puts `5` where the pair of curly braces were in the format -string. - -In function signatures, you *must* declare the type. This is a deliberate -decision in Rust’s design: requiring type annotations in function definitions -means the compiler almost never needs you to use them elsewhere in the code to -figure out what you mean. - -When you want a function to have multiple arguments, separate them inside the -function signature with commas, like this: - -Filename: src/main.rs - -```rust -fn main() { - another_function(5, 6); -} - -fn another_function(x: i32, y: i32) { - println!("The value of x is: {}", x); - println!("The value of y is: {}", y); -} -``` - -This example creates a function with two arguments, both of which are `i32` -types. If your function has multiple arguments, the arguments don’t need to be -the same type, but they just happen to be in this example. The function then -prints out the values of both of its arguments. - -Let’s try running this code. Replace the program currently in your *function* -project’s *src/main.rs* file with the preceding example, and run it using -`cargo run`: - -```bash -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -The value of x is: 5 -The value of y is: 6 -``` - -Because `5` is passed as the `x` argument and `6` is passed as the `y` -argument, the two strings are printed with these values. - -### Function Bodies - -Function bodies are made up of a series of statements optionally ending in an -expression. So far, we’ve only covered functions without an ending expression, -but we have seen expressions as parts of statements. Because Rust is an -expression-based language, this is an important distinction to understand. -Other languages don’t have the same distinctions, so let’s look at what -statements and expressions are and how their differences affect the bodies of -functions. - -### Statements and Expressions - -We’ve actually already used statements and expressions. *Statements* are -instructions that perform some action and do not return a value. *Expressions* -evaluate to a resulting value. Let’s look at some examples. - -Creating a variable and assigning a value to it with the `let` keyword is a -statement. In Listing 3-3, `let y = 6;` is a statement: - -Filename: src/main.rs - -```rust -fn main() { - let y = 6; -} -``` - - -Listing 3-3: A `main` function declaration containing one statement. - - -Function definitions are also statements; the entire preceding example is a -statement in itself. - -Statements do not return values. Therefore, you can’t assign a `let` statement -to another variable, as the following code tries to do: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let x = (let y = 6); -} -``` - -When you run this program, you’ll get an error like this: - -```bash -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) -error: expected expression, found statement (`let`) - --> src/main.rs:2:14 - | -2 | let x = (let y = 6); - | ^^^ - | - = note: variable declaration using `let` is a statement -``` - -The `let y = 6` statement does not return a value, so there isn’t anything for -`x` to bind to. This is different than in other languages, such as C and Ruby, -where the assignment returns the value of the assignment. In those languages, -you can write `x = y = 6` and have both `x` and `y` have the value `6`; that is -not the case in Rust. - -Expressions evaluate to something and make up most of the rest of the code that -you’ll write in Rust. Consider a simple math operation, such as `5 + 6`, which -is an expression that evaluates to the value `11`. Expressions can be part of -statements: in Listing 3-3 that had the statement `let y = 6;`, `6` is an -expression that evaluates to the value `6`. Calling a function is an -expression. Calling a macro is an expression. The block that we use to create -new scopes, `{}`, is an expression, for example: - -Filename: src/main.rs - -```rust -fn main() { - let x = 5; - - let y = { - let x = 3; - x + 1 - }; - - println!("The value of y is: {}", y); -} -``` - -This expression: - -```rust,ignore -{ - let x = 3; - x + 1 -} -``` - -is a block that, in this case, evaluates to `4`. That value gets bound to `y` -as part of the `let` statement. Note the line without a semicolon at the end, -unlike most of the lines you’ve seen so far. Expressions do not include ending -semicolons. If you add a semicolon to the end of an expression, you turn it -into a statement, which will then not return a value. Keep this in mind as you -explore function return values and expressions next. - -### Functions with Return Values - -Functions can return values to the code that calls them. We don’t name return -values, but we do declare their type after an arrow (`->`). In Rust, the return -value of the function is synonymous with the value of the final expression in -the block of the body of a function. Here’s an example of a function that -returns a value: - -Filename: src/main.rs - -```rust -fn five() -> i32 { - 5 -} - -fn main() { - let x = five(); - - println!("The value of x is: {}", x); -} -``` - -There are no function calls, macros, or even `let` statements in the `five` -function—just the number `5` by itself. That’s a perfectly valid function in -Rust. Note that the function’s return type is specified, too, as `-> i32`. Try -running this code; the output should look like this: - -```bash -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -The value of x is: 5 -``` - -The `5` in `five` is the function’s return value, which is why the return type -is `i32`. Let’s examine this in more detail. There are two important bits: -first, the line `let x = five();` shows that we’re using the return value of a -function to initialize a variable. Because the function `five` returns a `5`, -that line is the same as the following: - -```rust -let x = 5; -``` - -Second, the `five` function requires no arguments and defines the type of the -return value, but the body of the function is a lonely `5` with no semicolon -because it’s an expression whose value we want to return. Let’s look at another -example: - -Filename: src/main.rs - -```rust -fn main() { - let x = plus_one(5); - - println!("The value of x is: {}", x); -} - -fn plus_one(x: i32) -> i32 { - x + 1 -} -``` - -Running this code will print `The value of x is: 6`. What happens if we place a -semicolon at the end of the line containing `x + 1`, changing it from an -expression to a statement? - -Filename: src/main.rs - -```rust,ignore -fn main() { - let x = plus_one(5); - - println!("The value of x is: {}", x); -} - -fn plus_one(x: i32) -> i32 { - x + 1; -} -``` - -Running this code produces an error, as follows: - -```bash -error[E0269]: not all control paths return a value - --> src/main.rs:7:1 - | -7 | fn plus_one(x: i32) -> i32 { - | ^ - | -help: consider removing this semicolon: - --> src/main.rs:8:10 - | -8 | x + 1; - | ^ -``` - -The main error message, “not all control paths return a value,” reveals the -core issue with this code. The definition of the function `plus_one` says that -it will return an `i32`, but statements don’t evaluate to a value. Therefore, -nothing is returned, which contradicts the function definition and results in -an error. In this output, Rust provides a message to possibly help rectify this -issue: it suggests removing the semicolon, which would fix the error. - -## Comments - -All programmers strive to make their code easy to understand, but sometimes -extra explanation is warranted. In these cases, programmers leave notes, or -*comments*, in their source code that the compiler will ignore but people -reading the source code may find useful. - -Here’s a simple comment: - -```rust -// Hello, world. -``` - -In Rust, comments must start with two slashes and continue until the end of the -line. For comments that extend beyond a single line, you’ll need to include -`//` on each line, like this: - -```rust -// So we’re doing something complicated here, long enough that we need -// multiple lines of comments to do it! Whew! Hopefully, this comment will -// explain what’s going on. -``` - -Comments can also be placed at the end of lines containing code: - -Filename: src/main.rs - -```rust -fn main() { - let lucky_number = 7; // I’m feeling lucky today. -} -``` - -But you’ll more often see them used in this format, with the comment on a -separate line above the code it's annotating: - -Filename: src/main.rs - -```rust -fn main() { - // I’m feeling lucky today. - let lucky_number = 7; -} -``` - -That’s all there is to comments. They’re not particularly complicated. - -## Control Flow - -Deciding whether or not to run some code depending on if a condition is true or -deciding to run some code repeatedly while a condition is true are basic -building blocks in most programming languages. The most common constructs that -let you control the flow of execution of Rust code are `if` expressions and -loops. - -### `if` Expressions - -An `if` expression allows us to branch our code depending on conditions. We -provide a condition and then state, “If this condition is met, run this block -of code. If the condition is not met, do not run this block of code.” - -Create a new project called *branches* in your *projects* directory to explore -the `if` expression. In the *src/main.rs* file, input the following: - -Filename: src/main.rs - -```rust -fn main() { - let number = 3; - - if number < 5 { - println!("condition was true"); - } else { - println!("condition was false"); - } -} -``` - -All `if` expressions start with the keyword `if`, which is followed by a -condition. In this case, the condition checks whether or not the variable -`number` has a value less than 5. The block of code we want to execute if the -condition is true is placed immediately after the condition inside curly -braces. Blocks of code associated with the conditions in `if` expressions are -sometimes called *arms*, just like the arms in `match` expressions that we -discussed in the “Comparing the Guess to the Secret Number” section of Chapter -2. Optionally, we can also include an `else` expression, which we chose to do -here, to give the program an alternative block of code to execute should the -condition evaluate to false. If you don’t provide an `else` expression and the -condition is false, the program will just skip the `if` block and move on to -the next bit of code. - -Try running this code; you should see the following output: - -```bash -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -condition was true -``` - -Let’s try changing the value of `number` to a value that makes the condition -`false` to see what happens: - -```rust,ignore -let number = 7; -``` - -Run the program again, and look at the output: - -```bash -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -condition was false -``` - -It’s also worth noting that the condition in this code *must* be a `bool`. To -see what happens if the condition isn’t a `bool`, try running the following -code: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let number = 3; - - if number { - println!("number was three"); - } -} -``` - -The `if` condition evaluates to a value of `3` this time, and Rust throws an -error: - -```bash - Compiling branches v0.1.0 (file:///projects/branches) -error[E0308]: mismatched types - --> src/main.rs:4:8 - | -4 | if number { - | ^^^^^^ expected bool, found integral variable - | - = note: expected type `bool` - = note: found type `{integer}` - -error: aborting due to previous error -Could not compile `branches`. -``` - -The error indicates that Rust expected a `bool` but got an integer. Rust will -not automatically try to convert non-boolean types to a boolean, unlike -languages such as Ruby and JavaScript. You must be explicit and always provide -`if` with a `boolean` as its condition. If we want the `if` code block to run -only when a number is not equal to `0`, for example, we can change the `if` -expression to the following: - -Filename: src/main.rs - -```rust -fn main() { - let number = 3; - - if number != 0 { - println!("number was something other than zero"); - } -} -``` - -Running this code will print `number was something other than zero`. - -#### Multiple Conditions with `else if` - -We can have multiple conditions by combining `if` and `else` in an `else if` -expression. For example: - -Filename: src/main.rs - -```rust -fn main() { - let number = 6; - - if number % 4 == 0 { - println!("number is divisible by 4"); - } else if number % 3 == 0 { - println!("number is divisible by 3"); - } else if number % 2 == 0 { - println!("number is divisible by 2"); - } else { - println!("number is not divisible by 4, 3, or 2"); - } -} -``` - -This program has four possible paths it can take. After running it, you should -see the following output: - -```bash -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -number is divisible by 3 -``` - -When this program executes, it checks each `if` expression in turn and executes -the first body for which the condition holds true. Note that even though 6 is -divisible by 2, we don’t see the output `number is divisible by 2`, nor do we -see the `number is not divisible by 4, 3, or 2` text from the `else` block. The -reason is that Rust will only execute the block for the first true condition, -and once it finds one, it won’t even check the rest. - -Using too many `else if` expressions can clutter your code, so if you have more -than one, you might want to refactor your code. Chapter 6 describes a powerful -Rust branching construct called `match` for these cases. - -#### Using `if` in a `let` statement - -Because `if` is an expression, we can use it on the right side of a `let` -statement, for instance in Listing 3-4: - -Filename: src/main.rs - -```rust -fn main() { - let condition = true; - let number = if condition { - 5 - } else { - 6 - }; - - println!("The value of number is: {}", number); -} -``` - - -Listing 3-4: Assigning the result of an `if` expression to a variable - - -The `number` variable will be bound to a value based on the outcome of the `if` -expression. Run this code to see what happens: - -```bash -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -The value of number is: 5 -``` - -Remember that blocks of code evaluate to the last expression in them, and -numbers by themselves are also expressions. In this case, the value of the -whole `if` expression depends on which block of code executes. This means the -values that have the potential to be results from each arm of the `if` must be -the same type; in Listing 3-4, the results of both the `if` arm and the `else` -arm were `i32` integers. But what happens if the types are mismatched, as in -the following example? - -Filename: src/main.rs - -```rust,ignore -fn main() { - let condition = true; - - let number = if condition { - 5 - } else { - "six" - }; - - println!("The value of number is: {}", number); -} -``` - -When we run this code, we’ll get an error. The `if` and `else` arms have value -types that are incompatible, and Rust indicates exactly where to find the -problem in the program: - -```bash - Compiling branches v0.1.0 (file:///projects/branches) -error[E0308]: if and else have incompatible types - --> src/main.rs:4:18 - | -4 | let number = if condition { - | ^ expected integral variable, found reference - | - = note: expected type `{integer}` - = note: found type `&’static str` -``` - -The expression in the `if` block evaluates to an integer, and the expression in -the `else` block evaluates to a string. This won’t work because variables must -have a single type. Rust needs to know at compile time what type the `number` -variable is, definitively, so it can verify at compile time that its type is -valid everywhere we use `number`. Rust wouldn’t be able to do that if the type -of `number` was only determined at runtime; the compiler would be more complex -and would make fewer guarantees about the code if it had to keep track of -multiple hypothetical types for any variable. - -### Repetition with Loops - -It’s often useful to execute a block of code more than once. For this task, -Rust provides several *loops*. A loop runs through the code inside the loop -body to the end and then starts immediately back at the beginning. To -experiment with loops, let’s make a new project called *loops*. - -Rust has three kinds of loops: `loop`, `while`, and `for`. Let’s try each one. - -#### Repeating Code with `loop` - -The `loop` keyword tells Rust to execute a block of code over and over again -forever or until you explicitly tell it to stop. - -As an example, change the *src/main.rs* file in your *loops* directory to look -like this: - -Filename: src/main.rs - -```rust,ignore -fn main() { - loop { - println!("again!"); - } -} -``` - -When we run this program, we’ll see `again!` printed over and over continuously -until we stop the program manually. Most terminals support a keyboard shortcut, - ctrl-C, to halt a program that is stuck in a continual loop. Give it a try: - -```bash -$ cargo run - Compiling loops v0.1.0 (file:///projects/loops) - Running `target/debug/loops` -again! -again! -again! -again! -^Cagain! -``` - -The symbol `^C` represents where you pressed ctrl-C. You may or may not see the -word `again!` printed after the `^C`, depending on where the code was in the -loop when it received the halt signal. - -Fortunately, Rust provides another, more reliable way to break out of a loop. -You can place the `break` keyword within the loop to tell the program when to -stop executing the loop. Recall that we did this in the guessing game in the -“Quitting After a Correct Guess” section of Chapter 2 to exit the -program when the user won the game by guessing the correct number. - -#### Conditional Loops with `while` - -It’s often useful for a program to evaluate a condition within a loop. While -the condition is true, the loop runs. When the condition ceases to be true, you -call `break`, stopping the loop. This loop type could be implemented using a -combination of `loop`, `if`, `else`, and `break`; you could try that now in a -program, if you’d like. - -However, this pattern is so common that Rust has a built-in language construct -for it, and it’s called a `while` loop. The following example uses `while`: the -program loops three times, counting down each time. Then, after the loop, it -prints another message and exits: - -Filename: src/main.rs - -```rust -fn main() { - let mut number = 3; - - while number != 0 { - println!("{}!", number); - - number = number - 1; - } - - println!("LIFTOFF!!!"); -} -``` - -This construct eliminates a lot of nesting that would be necessary if you used -`loop`, `if`, `else`, and `break`, and it’s clearer. While a condition holds -true, the code runs; otherwise, it exits the loop. - -#### Looping Through a Collection with `for` - -You could use the `while` construct to loop over the elements of a collection, -such as an array. For example: - -Filename: src/main.rs - -```rust -fn main() { - let a = [10, 20, 30, 40, 50]; - let mut index = 0; - - while index < 5 { - println!("the value is: {}", a[index]); - - index = index + 1; - } -} -``` - - -Listing 3-5: Looping through each element of a collection using a `while` loop - - -Here, the code counts up through the elements in the array. It starts at index -`0`, and then loops until it reaches the final index in the array (that is, -when `index < 5` is no longer true). Running this code will print out every -element in the array: - -```bash -$ cargo run - Compiling loops v0.1.0 (file:///projects/loops) - Running `target/debug/loops` -the value is: 10 -the value is: 20 -the value is: 30 -the value is: 40 -the value is: 50 -``` - -All five array values appear in the terminal, as expected. Even though `index` -will reach a value of `6` at some point, the loop stops executing before trying -to fetch a sixth value from the array. - -But this approach is error prone; we could cause the program to panic if the -index length is incorrect. It’s also slow, because the compiler needs to -perform the conditional check on every element on every iteration through the -loop. - -As a more efficient alternative, you can use a `for` loop and execute some code -for each item in a collection. A `for` loop looks like this: - -Filename: src/main.rs - -```rust -fn main() { - let a = [10, 20, 30, 40, 50]; - - for element in a.iter() { - println!("the value is: {}", element); - } -} -``` - - -Listing 3-6: Looping through each element of a collection using a `for` loop - - -When we run this code, we’ll see the same output as in Listing 3-5. More -importantly, we’ve now increased the safety of the code and eliminated the -chance of bugs that might result from going beyond the end of the array or not -going far enough and missing some items. - -For example, in the code in Listing 3-5, if you removed an item from the `a` -array but forgot to update the condition to `while index < 4`, the code would -panic. Using the `for` loop, you don’t need to remember to change any other -code if you changed the number of values in the array. - -The safety and conciseness of `for` loops make them the most commonly used loop -construct in Rust. Even in situations in which you want to run some code a -certain number of times, as in the countdown example that used a `while` loop -in Listing 3-5, most Rustaceans would use a `for` loop. The way to do that -would be to use a `Range`, which is a type provided by the standard library -that generates all numbers in sequence starting from one number and ending -before another number. - -Here’s what the countdown would look like using a `for` loop and another method -we’ve not yet talked about, `rev`, to reverse the range: - -Filename: src/main.rs - -```rust -fn main() { - for number in (1..4).rev() { - println!("{}!", number); - } - println!("LIFTOFF!!!"); -} -``` - -This code is a bit nicer, isn’t it? - -## Summary - -You made it! That was a sizable chapter: you learned about variables, scalar -and`if` expressions, and loops! If you want to practice with the concepts -discussed in this chapter, try building programs to do the following: - -* Convert temperatures between Fahrenheit and Celsius. -* Generate the nth Fibonacci number. -* Print the lyrics to the Christmas carol “The Twelve Days of Christmas,” -taking advantage of the repetition in the song. - -When you’re ready to move on, we’ll talk about a concept in Rust that *doesn’t* -commonly exist in other programming languages: ownership. diff --git a/nostarch/chapter04.md b/nostarch/chapter04.md deleted file mode 100644 index aa92aa7..0000000 --- a/nostarch/chapter04.md +++ /dev/null @@ -1,1244 +0,0 @@ - -[TOC] - -# Understanding Ownership - -Ownership is Rust’s most unique feature, and it enables Rust to make memory -safety guarantees without needing a garbage collector. Therefore, it’s -important to understand how ownership works in Rust. In this chapter we’ll talk -about ownership as well as several related features: borrowing, slices, and how -Rust lays data out in memory. - -## What Is Ownership? - -Rust’s central feature is *ownership*. Although the feature is straightforward -to explain, it has deep implications for the rest of the language. - -All programs have to manage the way they use a computer’s memory while running. -Some languages have garbage collection that constantly looks for no longer used -memory as the program runs; in other languages, the programmer must explicitly -allocate and free the memory. Rust uses a third approach: memory is managed -through a system of ownership with a set of rules that the compiler checks at -compile time. No run-time costs are incurred for any of the ownership features. - -Because ownership is a new concept for many programmers, it does take some time -to get used to. The good news is that the more experienced you become with Rust -and the rules of the ownership system, the more you’ll be able to naturally -develop code that is safe and efficient. Keep at it! - -When you understand ownership, you’ll have a solid foundation for understanding -the features that make Rust unique. In this chapter, you’ll learn ownership by -working through some examples that focus on a very common data structure: -strings. - -PROD: START BOX - -### The Stack and the Heap - -In many programming languages, we don’t have to think about the stack and the -heap very often. But in a systems programming language like Rust, whether a -value is on the stack or the heap has more of an effect on how the language -behaves and why we have to make certain decisions. We’ll describe parts of -ownership in relation to the stack and the heap later in this chapter, so here -is a brief explanation in preparation. - -Both the stack and the heap are parts of memory that is available to your code -to use at runtime, but they are structured in different ways. The stack stores -values in the order it gets them and removes the values in the opposite order. -This is referred to as *last in, first out*. Think of a stack of plates: when -you add more plates, you put them on top of the pile, and when you need a -plate, you take one off the top. Adding or removing plates from the middle or -bottom wouldn’t work as well! Adding data is called *pushing onto the stack*, -and removing data is called *popping off the stack*. - -The stack is fast because of the way it accesses the data: it never has to -search for a place to put new data or a place to get data from because that -place is always the top. Another property that makes the stack fast is that all -data on the stack must take up a known, fixed size. - -For data with a size unknown to us at compile time or a size that might change, -we can store data on the heap instead. The heap is less organized: when we put -data on the heap, we ask for some amount of space. The operating system finds -an empty spot somewhere in the heap that is big enough, marks it as being in -use, and returns to us a pointer to that location. This process is called -*allocating on the heap*, and sometimes we abbreviate the phrase as just -“allocating.” Pushing values onto the stack is not considered allocating. -Because the pointer is a known, fixed size, we can store the pointer on the -stack, but when we want the actual data, we have to follow the pointer. - -Think of being seated at a restaurant. When you enter, you state the number of -people in your group, and the staff finds an empty table that fits everyone and -leads you there. If someone in your group comes late, they can ask where you’ve -been seated to find you. - -Accessing data in the heap is slower than accessing data on the stack because -we have to follow a pointer to get there. Contemporary processors are faster if -they jump around less in memory. Continuing the analogy, consider a server at a -restaurant taking orders from many tables. It’s most efficient to get all the -orders at one table before moving on to the next table. Taking an order from -table A, then an order from table B, then one from A again, and then one from B -again would be a much slower process. By the same token, a processor can do its -job better if it works on data that’s close to other data (as it is on the -stack) rather than farther away (as it can be on the heap). Allocating a large -amount of space on the heap can also take time. - -When our code calls a function, the values passed into the function (including, -potentially, pointers to data on the heap) and the function’s local variables -get pushed onto the stack. When the function is over, those values get popped -off the stack. - -Keeping track of what parts of code are using what data on the heap, minimizing -the amount of duplicate data on the heap, and cleaning up unused data on the -heap so we don’t run out of space are all problems that ownership addresses. -Once you understand ownership, you won’t need to think about the stack and the -heap very often, but knowing that managing heap data is why ownership exists -can help explain why it works the way it does. - -PROD: END BOX - -### Ownership Rules - -First, let’s take a look at the ownership rules. Keep these rules in mind as we -work through the examples that illustrate the rules: - -1. Each value in Rust has a variable that’s called its *owner*. -2. There can only be one owner at a time. -3. When the owner goes out of scope, the value will be dropped. - -### Variable Scope - -We’ve walked through an example of a Rust program already in Chapter 2. Now -that we’re past basic syntax, we won’t include all the `fn main() {` code in -examples, so if you’re following along, you’ll have to put the following -examples inside a `main` function manually. As a result, our examples will be a -bit more concise, letting us focus on the actual details rather than -boilerplate code. - -As a first example of ownership, we’ll look at the *scope* of some variables. A -scope is the range within a program for which an item is valid. Let’s say we -have a variable that looks like this: - -```rust -let s = "hello"; -``` - -The variable `s` refers to a string literal, where the value of the string is -hardcoded into the text of our program. The variable is valid from the point at -which it’s declared until the end of the current *scope*. Listing 4-1 has -comments annotating where the variable `s` is valid: - -```rust -{ // s is not valid here, it’s not yet declared - let s = "hello"; // s is valid from this point forward - - // do stuff with s -} // this scope is now over, and s is no longer valid -``` - - -Listing 4-1: A variable and the scope in which it is valid - - -In other words, there are two important points in time here: - -1. When `s` comes *into scope*, it is valid. -1. It remains so until it goes *out of scope*. - -At this point, the relationship between scopes and when variables are valid is -similar to other programming languages. Now we’ll build on top of this -understanding by introducing the `String` type. - -### The `String` Type - -To illustrate the rules of ownership, we need a data type that is more complex -than the ones we covered in Chapter 3. All the data types we’ve looked at -previously are stored on the stack and popped off the stack when their scope is -over, but we want to look at data that is stored on the heap and explore how -Rust knows when to clean up that data. - -We’ll use `String` as the example here and concentrate on the parts of `String` -that relate to ownership. These aspects also apply to other complex data types -provided by the standard library and that you create. We’ll discuss `String` in -more depth in Chapter 8. - -We’ve already seen string literals, where a string value is hardcoded into our -program. String literals are convenient, but they aren’t always suitable for -every situation in which you want to use text. One reason is that they’re -immutable. Another is that not every string value can be known when we write -our code: for example, what if we want to take user input and store it? For -these situations, Rust has a second string type, `String`. This type is -allocated on the heap and as such is able to store an amount of text that is -unknown to us at compile time. You can create a `String` from a string literal -using the `from` function, like so: - -```rust -let s = String::from("hello"); -``` - -The double colon (`::`) is an operator that allows us to namespace this -particular `from` function under the `String` type rather than using some sort -of name like `string_from`. We’ll discuss this syntax more in the “Method -Syntax” section of Chapter 5 and when we talk about namespacing with modules in -Chapter 7. - -This kind of string *can* be mutated: - -```rust -let mut s = String::from("hello"); - -s.push_str(", world!"); // push_str() appends a literal to a String - -println!("{}", s); // This will print `hello, world!` -``` - -So, what’s the difference here? Why can `String` be mutated but literals -cannot? The difference is how these two types deal with memory. - -### Memory and Allocation - -In the case of a string literal, we know the contents at compile time so the -text is hardcoded directly into the final executable, making string literals -fast and efficient. But these properties only come from its immutability. -Unfortunately, we can’t put a blob of memory into the binary for each piece of -text whose size is unknown at compile time and whose size might change while -running the program. - -With the `String` type, in order to support a mutable, growable piece of text, -we need to allocate an amount of memory on the heap, unknown at compile time, -to hold the contents. This means: - -1. The memory must be requested from the operating system at runtime. -2. We need a way of returning this memory to the operating system when we’re -done with our `String`. - -That first part is done by us: when we call `String::from`, its implementation -requests the memory it needs. This is pretty much universal in programming -languages. - -However, the second part is different. In languages with a *garbage collector -(GC)*, the GC keeps track and cleans up memory that isn’t being used anymore, -and we, as the programmer, don’t need to think about it. Without a GC, it’s the -programmer’s responsibility to identify when memory is no longer being used and -call code to explicitly return it, just as we did to request it. Doing this -correctly has historically been a difficult programming problem. If we forget, -we’ll waste memory. If we do it too early, we’ll have an invalid variable. If -we do it twice, that’s a bug too. We need to pair exactly one `allocate` with -exactly one `free`. - -Rust takes a different path: the memory is automatically returned once the -variable that owns it goes out of scope. Here’s a version of our scope example -from Listing 4-1 using a `String` instead of a string literal: - -```rust -{ - let s = String::from("hello"); // s is valid from this point forward - - // do stuff with s -} // this scope is now over, and s is no - // longer valid -``` - -There is a natural point at which we can return the memory our `String` needs -to the operating system: when `s` goes out of scope. When a variable goes out -of scope, Rust calls a special function for us. This function is called `drop`, -and it’s where the author of `String` can put the code to return the memory. -Rust calls `drop` automatically at the closing `}`. - -> Note: In C++, this pattern of deallocating resources at the end of an item's -lifetime is sometimes called *Resource Acquisition Is Initialization (RAII)*. -The `drop` function in Rust will be familiar to you if you’ve used RAII -patterns. - -This pattern has a profound impact on the way Rust code is written. It may seem -simple right now, but the behavior of code can be unexpected in more -complicated situations when we want to have multiple variables use the data -we’ve allocated on the heap. Let’s explore some of those situations now. - -#### Ways Variables and Data Interact: Move - -Multiple variables can interact with the same data in different ways in Rust. -Let’s look at an example using an integer in Listing 4-2: - -```rust -let x = 5; -let y = x; -``` - - -Listing 4-2: Assigning the integer value of variable `x` to `y` - - -We can probably guess what this is doing based on our experience with other -languages: “Bind the value `5` to `x`; then make a copy of the value in `x` and -bind it to `y`.” We now have two variables, `x` and `y`, and both equal `5`. -This is indeed what is happening because integers are simple values with a -known, fixed size, and these two `5` values are pushed onto the stack. - -Now let’s look at the `String` version: - -```rust -let s1 = String::from("hello"); -let s2 = s1; -``` - -This looks very similar to the previous code, so we might assume that the way -it works would be the same: that is, the second line would make a copy of the -value in `s1` and bind it to `s2`. But this isn’t quite what happens. - -To explain this more thoroughly, let’s look at what `String` looks like under -the covers in Figure 4-3. A `String` is made up of three parts, shown on the -left: a pointer to the memory that holds the contents of the string, a length, -and a capacity. This group of data is stored on the stack. On the right is the -memory on the heap that holds the contents. - -String in memory - - -Figure 4-3: Representation in memory of a `String` holding the value `"hello"` -bound to `s1` - - -The length is how much memory, in bytes, the contents of the `String` is -currently using. The capacity is the total amount of memory, in bytes, that the -`String` has received from the operating system. The difference between length -and capacity matters, but not in this context, so for now, it’s fine to ignore -the capacity. - -When we assign `s1` to `s2`, the `String` data is copied, meaning we copy the -pointer, the length, and the capacity that are on the stack. We do not copy the -data on the heap that the pointer refers to. In other words, the data -representation in memory looks like Figure 4-4. - -s1 and s2 pointing to the same value - - -Figure 4-4: Representation in memory of the variable `s2` that has a copy of -the pointer, length, and capacity of `s1` - - -The representation does *not* look like Figure 4-5, which is what memory would -look like if Rust instead copied the heap data as well. If Rust did this, the -operation `s2 = s1` could potentially be very expensive in terms of runtime -performance if the data on the heap was large. - -s1 and s2 to two places - - -Figure 4-5: Another possibility of what `s2 = s1` might do if Rust copied the -heap data as well - - -Earlier, we said that when a variable goes out of scope, Rust automatically -calls the `drop` function and cleans up the heap memory for that variable. But -Figure 4-4 shows both data pointers pointing to the same location. This is a -problem: when `s2` and `s1` go out of scope, they will both try to free the -same memory. This is known as a *double free* error and is one of the memory -safety bugs we mentioned previously. Freeing memory twice can lead to memory -corruption, which can potentially lead to security vulnerabilities. - -To ensure memory safety, there’s one more detail to what happens in this -situation in Rust. Instead of trying to copy the allocated memory, Rust -considers `s1` to no longer be valid and therefore, Rust doesn’t need to free -anything when `s1` goes out of scope. Check out what happens when you try to -use `s1` after `s2` is created: - -```rust,ignore -let s1 = String::from("hello"); -let s2 = s1; - -println!("{}", s1); -``` - -You’ll get an error like this because Rust prevents you from using the -invalidated reference: - -```text -5:22 error: use of moved value: `s1` [E0382] -println!("{}", s1); - ^~ -5:24 note: in this expansion of println! (defined in ) -3:11 note: `s1` moved here because it has type `collections::string::String`, -which is moved by default - let s2 = s1; - ^~ -``` - -If you’ve heard the terms “shallow copy” and “deep copy” while working with -other languages, the concept of copying the pointer, length, and capacity -without copying the data probably sounds like a shallow copy. But because Rust -also invalidates the first variable, instead of calling this a shallow copy, -it’s known as a *move*. Here we would read this by saying that `s1` was *moved* -into `s2`. So what actually happens is shown in Figure 4-6. - -s1 moved to s2 - - -Figure 4-6: Representation in memory after `s1` has been invalidated - - -That solves our problem! With only `s2` valid, when it goes out of scope, it -alone will free the memory, and we’re done. - -In addition, there’s a design choice that’s implied by this: Rust will never -automatically create “deep” copies of your data. Therefore, any *automatic* -copying can be assumed to be inexpensive in terms of runtime performance. - -#### Ways Variables and Data Interact: Clone - -If we *do* want to deeply copy the heap data of the `String`, not just the -stack data, we can use a common method called `clone`. We’ll discuss method -syntax in Chapter 5, but because methods are a common feature in many -programming languages, you’ve probably seen them before. - -Here’s an example of the `clone` method in action: - -```rust -let s1 = String::from("hello"); -let s2 = s1.clone(); - -println!("s1 = {}, s2 = {}", s1, s2); -``` - -This works just fine and is how you can explicitly produce the behavior shown -in Figure 4-4, where the heap data *does* get copied. - -When you see a call to `clone`, you know that some arbitrary code is being -executed and that code may be expensive. It’s a visual indicator that something -different is going on. - -#### Stack-Only Data: Copy - -There’s another wrinkle we haven’t talked about yet. This code using integers, -part of which was shown earlier in Listing 4-2, works and is valid: - -```rust -let x = 5; -let y = x; - -println!("x = {}, y = {}", x, y); -``` - -But this code seems to contradict what we just learned: we don’t have a call to -`clone`, but `x` is still valid and wasn’t moved into `y`. - -The reason is that types like integers that have a known size at compile time -are stored entirely on the stack, so copies of the actual values are quick to -make. That means there’s no reason we would want to prevent `x` from being -valid after we create the variable `y`. In other words, there’s no difference -between deep and shallow copying here, so calling `clone` wouldn’t do anything -differently from the usual shallow copying and we can leave it out. - -Rust has a special annotation called the `Copy` trait that we can place on -types like integers that are stored on the stack (we’ll talk more about traits -in Chapter 10). If a type has the `Copy` trait, an older variable is still -usable after assignment. Rust won’t let us annotate a type with the `Copy` -trait if the type, or any of its parts, has implemented the `D``rop` trait. If -the type needs something special to happen when the value goes out of scope and -we add the `Copy` annotation to that type, we’ll get a compile time error. - -So what types are `Copy`? You can check the documentation for the given type to -be sure, but as a general rule, any group of simple scalar values can be -`Copy`, and nothing that requires allocation or is some form of resource is -`Copy`. Here are some of the types that are `Copy`: - -* All the integer types, like `u32`. -* The boolean type, `bool`, with values `true` and `false`. -* All the floating point types, like `f64`. -* Tuples, but only if they contain types that are also `Copy`. `(i32, i32)` is -`Copy`, but `(i32, String)` is not. - -### Ownership and Functions - -The semantics for passing a value to a function are similar to assigning a -value to a variable. Passing a variable to a function will move or copy, just -like assignment. Listing 4-7 has an example with some annotations showing where -variables go into and out of scope: - -Filename: src/main.rs - -```rust -fn main() { - let s = String::from("hello"); // s comes into scope. - - takes_ownership(s); // s's value moves into the function... - // ... and so is no longer valid here. - let x = 5; // x comes into scope. - - makes_copy(x); // x would move into the function, - // but i32 is Copy, so it’s okay to still - // use x afterward. - -} // Here, x goes out of scope, then s. But since s's value was moved, nothing - // special happens. - -fn takes_ownership(some_string: String) { // some_string comes into scope. - println!("{}", some_string); -} // Here, some_string goes out of scope and `drop` is called. The backing - // memory is freed. - -fn makes_copy(some_integer: i32) { // some_integer comes into scope. - println!("{}", some_integer); -} // Here, some_integer goes out of scope. Nothing special happens. -``` - - -Listing 4-7: Functions with ownership and scope annotated - - -If we tried to use `s` after the call to `takes_ownership`, Rust would throw a -compile time error. These static checks protect us from mistakes. Try adding -code to `main` that uses `s` and `x` to see where you can use them and where -the ownership rules prevent you from doing so. - -### Return Values and Scope - -Returning values can also transfer ownership. Here’s an example with similar -annotations to those in Listing 4-7: - -Filename: src/main.rs - -```rust -fn main() { - let s1 = gives_ownership(); // gives_ownership moves its return - // value into s1. - - let s2 = String::from("hello"); // s2 comes into scope. - - let s3 = takes_and_gives_back(s2); // s2 is moved into - // takes_and_gives_back, which also - // moves its return value into s3. -} // Here, s3 goes out of scope and is dropped. s2 goes out of scope but was - // moved, so nothing happens. s1 goes out of scope and is dropped. - -fn gives_ownership() -> String { // gives_ownership will move its - // return value into the function - // that calls it. - - let some_string = String::from("hello"); // some_string comes into scope. - - some_string // some_string is returned and - // moves out to the calling - // function. -} - -// takes_and_gives_back will take a String and return one. -fn takes_and_gives_back(a_string: String) -> String { // a_string comes into -scope. - - a_string // a_string is returned and moves out to the calling function. -} -``` - -The ownership of variables follows the same pattern every time: assigning a -value to another variable moves it, and when heap data values’ variables go out -of scope, if the data hasn’t been moved to be owned by another variable, the -value will be cleaned up by `drop`. - -Taking ownership and then returning ownership with every function is a bit -tedious. What if we want to let a function use a value but not take ownership? -It’s quite annoying that anything we pass in also needs to be passed back if we -want to use it again, in addition to any data resulting from the body of the -function that we might want to return as well. - -It’s possible to return multiple values using a tuple, like this: - -Filename: src/main.rs - -```rust -fn main() { - let s1 = String::from("hello"); - - let (s2, len) = calculate_length(s1); - - println!("The length of '{}' is {}.", s2, len); -} - -fn calculate_length(s: String) -> (String, usize) { - let length = s.len(); // len() returns the length of a String. - - (s, length) -} -``` - -But this is too much ceremony and a lot of work for a concept that should be -common. Luckily for us, Rust has a feature for this concept, and it’s called -*references*. - -## References and Borrowing - -The issue with the tuple code at the end of the preceding section is that we -have to return the `String` to the calling function so we can still use the -`String` after the call to `calculate_length`, because the `String` was moved -into `calculate_length`. - -Here is how you would define and use a `calculate_length` function that takes a -*reference* to an object as an argument instead of taking ownership of the -argument: - -Filename: src/main.rs - -```rust -fn main() { - let s1 = String::from("hello"); - - let len = calculate_length(&s1); - - println!("The length of '{}' is {}.", s1, len); -} - -fn calculate_length(s: &String) -> usize { - s.len() -} -``` - -First, notice that all the tuple code in the variable declaration and the -function return value is gone. Second, note that we pass `&s1` into -`calculate_length`, and in its definition, we take `&String` rather than -`String`. - -These ampersands are *references*, and they allow you to refer to some value -without taking ownership of it. Figure 4-8 shows a diagram. - -&String s pointing at String s1 - - -Figure 4-8: `&String s` pointing at `String s1` - - -Let’s take a closer look at the function call here: - -```rust -let s1 = String::from("hello"); - -let len = calculate_length(&s1); -``` - -The `&s1` syntax lets us create a reference that *refers* to the value of `s1` -but does not own it. Because it does not own it, the value it points to will -not be dropped when the reference goes out of scope. - -Likewise, the signature of the function uses `&` to indicate that it takes a -reference as an argument. Let’s add some explanatory annotations: - -```rust -fn calculate_length(s: &String) -> usize { // s is a reference to a String - s.len() -} // Here, s goes out of scope. But because it does not have ownership of what - // it refers to, nothing happens. -``` - -The scope in which the variable `s` is valid is the same as any function -argument's scope, but we don’t drop what the reference points to when it goes -out of scope because we don’t have ownership. Functions that take references as -arguments instead of the actual values mean we won’t need to return the values -in order to give back ownership, since we never had ownership. - -We call taking references as function arguments *borrowing*. As in real life, -if a person owns something, you can borrow it from them. When you’re done, you -have to give it back. - -So what happens if we try to modify something we’re borrowing? Try the code in -Listing 4-9. Spoiler alert: it doesn’t work! - -Filename: src/main.rs - -```rust,ignore -fn main() { - let s = String::from("hello"); - - change(&s); -} - -fn change(some_string: &String) { - some_string.push_str(", world"); -} -``` - - -Listing 4-9: Attempting to modify a borrowed value - - -Here’s the error: - -```text -error: cannot borrow immutable borrowed content `*some_string` as mutable - --> error.rs:8:5 - | -8 | some_string.push_str(", world"); - | ^^^^^^^^^^^ -``` - -Just as variables are immutable by default, so are references. We’re not -allowed to modify something we have a reference to. - -### Mutable References - -We can fix the error in the code from Listing 4-9 with just a small tweak: - -Filename: src/main.rs - -```rust -fn main() { - let mut s = String::from("hello"); - - change(&mut s); -} - -fn change(some_string: &mut String) { - some_string.push_str(", world"); -} -``` - -First, we had to change `s` to be `mut`. Then we had to create a mutable -reference with `&mut s` and accept a mutable reference with `some_string: &mut -String`. - -But mutable references have one big restriction: you can only have one mutable -reference to a particular piece of data in a particular scope. This code will -fail: - -Filename: src/main.rs - -```rust,ignore -let mut s = String::from("hello"); - -let r1 = &mut s; -let r2 = &mut s; -``` - -Here’s the error: - -```text -error[E0499]: cannot borrow `s` as mutable more than once at a time - --> borrow_twice.rs:5:19 - | -4 | let r1 = &mut s; - | - first mutable borrow occurs here -5 | let r2 = &mut s; - | ^ second mutable borrow occurs here -6 | } - | - first borrow ends here -``` - -This restriction allows for mutation but in a very controlled fashion. It’s -something that new Rustaceans struggle with, because most languages let you -mutate whenever you’d like. The benefit of having this restriction is that Rust -can prevent data races at compile time. - -A *data race* is a particular type of race condition in which these three -behaviors occur: - -1. Two or more pointers access the same data at the same time. -1. At least one of the pointers is being used to write to the data. -1. There’s no mechanism being used to synchronize access to the data. - -Data races cause undefined behavior and can be difficult to diagnose and fix -when you’re trying to track them down at runtime; Rust prevents this problem -from happening because it won’t even compile code with data races! - -As always, we can use curly brackets to create a new scope, allowing for -multiple mutable references, just not *simultaneous* ones: - -```rust -let mut s = String::from("hello"); - -{ - let r1 = &mut s; - -} // r1 goes out of scope here, so we can make a new reference with no problems. - -let r2 = &mut s; -``` - -A similar rule exists for combining mutable and immutable references. This code -results in an error: - -```rust,ignore -let mut s = String::from("hello"); - -let r1 = &s; // no problem -let r2 = &s; // no problem -let r3 = &mut s; // BIG PROBLEM -``` - -Here’s the error: - -```text -error[E0502]: cannot borrow `s` as mutable because it is also borrowed as -immutable - --> borrow_thrice.rs:6:19 - | -4 | let r1 = &s; // no problem - | - immutable borrow occurs here -5 | let r2 = &s; // no problem -6 | let r3 = &mut s; // BIG PROBLEM - | ^ mutable borrow occurs here -7 | } - | - immutable borrow ends here -``` - -Whew! We *also* cannot have a mutable reference while we have an immutable one. -Users of an immutable reference don’t expect the values to suddenly change out -from under them! However, multiple immutable references are okay because no one -who is just reading the data has the ability to affect anyone else’s reading of -the data. - -Even though these errors may be frustrating at times, remember that it’s the -Rust compiler pointing out a potential bug early (at compile time rather than -at runtime) and showing you exactly where the problem is instead of you having -to track down why sometimes your data isn’t what you thought it should be. - -### Dangling References - -In languages with pointers, it’s easy to erroneously create a *dangling -pointer*, a pointer that references a location in memory that may have been -given to someone else, by freeing some memory while preserving a pointer to -that memory. In Rust, by contrast, the compiler guarantees that references will -never be dangling references: if we have a reference to some data, the compiler -will ensure that the data will not go out of scope before the reference to the -data does. - -Let’s try to create a dangling reference: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let reference_to_nothing = dangle(); -} - -fn dangle() -> &String { - let s = String::from("hello"); - - &s -} -``` - -Here’s the error: - -```text -error[E0106]: missing lifetime specifier - --> dangle.rs:5:16 - | -5 | fn dangle() -> &String { - | ^^^^^^^ - | - = help: this function's return type contains a borrowed value, but there is no - value for it to be borrowed from - = help: consider giving it a 'static lifetime - -error: aborting due to previous error -``` - -This error message refers to a feature we haven’t covered yet: *lifetimes*. -We’ll discuss lifetimes in detail in Chapter 10. But, if you disregard the -parts about lifetimes, the message does contain the key to why this code is a -problem: - -``` -this function's return type contains a borrowed value, but there is no value -for it to be borrowed from. -``` - -Let’s take a closer look at exactly what’s happening at each stage of our -`dangle` code: - -```rust,ignore -fn dangle() -> &String { // dangle returns a reference to a String - - let s = String::from("hello"); // s is a new String - - &s // we return a reference to the String, s -} // Here, s goes out of scope, and is dropped. Its memory goes away. - // Danger! -``` - -Because `s` is created inside `dangle`, when the code of `dangle` is finished, -`s` will be deallocated. But we tried to return a reference to it. That means -this reference would be pointing to an invalid `String`! That’s no good. Rust -won’t let us do this. - -The correct code here is to return the `String` directly: - -```rust -fn no_dangle() -> String { - let s = String::from("hello"); - - s -} -``` - -This works without any problems. Ownership is moved out, and nothing is -deallocated. - -### The Rules of References - -Let’s recap what we’ve discussed about references: - -1. At any given time, you can have *either* but not both of: - * One mutable reference. - * Any number of immutable references. -2. References must always be valid. - -Next, we’ll look at a different kind of reference: slices. - -## Slices - -Another data type that does not have ownership is the *slice*. Slices let you -reference a contiguous sequence of elements in a collection rather than the -whole collection. - -Here’s a small programming problem: write a function that takes a string and -returns the first word it finds in that string. If the function doesn’t find a -space in the string, it means the whole string is one word, so the entire -string should be returned. - -Let’s think about the signature of this function: - -```rust,ignore -fn first_word(s: &String) -> ? -``` - -This function, `first_word`, takes a `&String` as an argument. We don’t want -ownership, so this is fine. But what should we return? We don’t really have a -way to talk about *part* of a string. However, we could return the index of the -end of the word. Let’s try that as shown in Listing 4-10: - -Filename: src/main.rs - -```rust -fn first_word(s: &String) -> usize { - let bytes = s.as_bytes(); - - for (i, &item) in bytes.iter().enumerate() { - if item == b' ' { - return i; - } - } - - s.len() -} -``` - - -Listing 4-10: The `first_word` function that returns a byte index value into -the `String` argument - - -Let’s break down this code a bit: - -```rust,ignore -let bytes = s.as_bytes(); -``` - -Because we need to go through the `String` element by element and check whether -a value is a space, we’ll convert our `String` to an array of bytes using the -`as_bytes` method: - -```rust,ignore -for (i, &item) in bytes.iter().enumerate() { -``` - -We’ll discuss iterators in more detail in Chapter 16. For now, know that `iter` -is a method that returns each element in a collection, and `enumerate` wraps -the result of `iter` and returns each element as part of a tuple instead. The -first element of the returned tuple is the index, and the second element is a -reference to the element. This is a bit more convenient than calculating the -index ourselves. - -Because the method returns a tuple, we can use patterns, just like everywhere -else in Rust. So we match against the tuple with `i` for the index and `&item` -for a single byte. Because we get a reference from `.iter().enumerate()`, we -use `&` in the pattern: - -```rust,ignore - if item == b' ' { - return i; - } -} -s.len() -``` - -We search for the byte that represents the space by using the byte literal -syntax. If we find a space, we return the position. Otherwise, we return the -length of the string by using `s.len()`. - -We now have a way to find out the index of the end of the first word in the -string, but there’s a problem. We’re returning a `usize` on its own, but it’s -only a meaningful number in the context of the `&String`. In other words, -because it’s a separate value from the `String`, there’s no guarantee that it -will still be valid in the future. Consider the program in Listing 4-11 that -uses the `first_word` function from Listing 4-10: - -Filename: src/main.rs - -```rust -fn main() { - let mut s = String::from("hello world"); - - let word = first_word(&s); // word will get the value 5. - - s.clear(); // This empties the String, making it equal to "". - - // word still has the value 5 here, but there's no more string that - // we could meaningfully use the value 5 with. word is now totally invalid! -} -``` - - -Listing 4-11: Storing the result from calling the `first_word` function then -changing the `String` contents - - -This program compiles without any errors and also would if we used `word` after -calling `s.clear()`. `word` isn’t connected to the state of `s` at all, so -`word` still contains the value `5`. We could use that value `5` with the -variable `s` to try to extract the first word out, but this would be a bug -because the contents of `s` have changed since we saved `5` in `word`. - -Having to worry about the index in `word` getting out of sync with the data in -`s` is tedious and error prone! Managing these indices is even more brittle if -we write a `second_word` function. Its signature would have to look like this: - -```rust,ignore -fn second_word(s: &String) -> (usize, usize) { -``` - -Now we’re tracking a start *and* an ending index, and we have even more values -that were calculated from data in a particular state but aren’t tied to that -state at all. We now have three unrelated variables floating around that need -to be kept in sync. - -Luckily, Rust has a solution to this problem: string slices. - -### String Slices - -A *string slice* is a reference to part of a `String`, and looks like this: - -```rust -let s = String::from("hello world"); - -let hello = &s[0..5]; -let world = &s[6..11]; -``` - -This is similar to taking a reference to the whole `String` but with the extra -`[0..5]` bit. Rather than a reference to the entire `String`, it’s a reference -to an internal position in the `String` and the number of elements that it -refers to. - -We create slices with a range of `[starting_index..ending_index]`, but the -slice data structure actually stores the starting position and the length of -the slice. So in the case of `let world = &s[6..11];`, `world` would be a slice -that contains a pointer to the 6th byte of `s` and a length value of 5. - -Figure 4-12 shows this in a diagram. - -world containing a pointer to the 6th byte of String s and a length 5 - - -Figure 4-12: String slice referring to part of a `String` - - -With Rust’s `..` range syntax, if you want to start at the first index (zero), -you can drop the value before the two periods. In other words, these are equal: - -```rust -let s = String::from("hello"); - -let slice = &s[0..2]; -let slice = &s[..2]; -``` - -By the same token, if your slice includes the last byte of the `String`, you -can drop the trailing number. That means these are equal: - -```rust -let s = String::from("hello"); - -let len = s.len(); - -let slice = &s[3..len]; -let slice = &s[3..]; -``` - -You can also drop both values to take a slice of the entire string. So these -are equal: - -```rust -let s = String::from("hello"); - -let len = s.len(); - -let slice = &s[0..len]; -let slice = &s[..]; -``` - -With all this information in mind, let’s rewrite `first_word` to return a -slice. The type that signifies “string slice” is written as `&str`: - -Filename: src/main.rs - -```rust -fn first_word(s: &String) -> &str { - let bytes = s.as_bytes(); - - for (i, &item) in bytes.iter().enumerate() { - if item == b' ' { - return &s[0..i]; - } - } - - &s[..] -} -``` - -We get the index for the end of the word in the same way as we did in Listing -4-10, by looking for the first occurrence of a space. When we find a space, we -return a string slice using the start of the string and the index of the space -as the starting and ending indices. - -Now when we call `first_word`, we get back a single value that is tied to the -underlying data. The value is made up of a reference to the starting point of -the slice and the number of elements in the slice. - -Returning a slice would also work for a `second_word` function: - -```rust,ignore -fn second_word(s: &String) -> &str { -``` - -We now have a straightforward API that’s much harder to mess up, since the -compiler will ensure the references into the `String` remain valid. Remember -the bug in the program in Listing 4-11, when we got the index to the end of the -first word but then cleared the string so our index was invalid? That code was -logically incorrect but didn’t show any immediate errors. The problems would -show up later if we kept trying to use the first word index with an emptied -string. Slices make this bug impossible and let us know we have a problem with -our code much sooner. Using the slice version of `first_word` will throw a -compile time error: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let mut s = String::from("hello world"); - - let word = first_word(&s); - - s.clear(); // Error! -} -``` - -Here’s the compiler error: - -```text -17:6 error: cannot borrow `s` as mutable because it is also borrowed as - immutable [E0502] - s.clear(); // Error! - ^ -15:29 note: previous borrow of `s` occurs here; the immutable borrow prevents - subsequent moves or mutable borrows of `s` until the borrow ends - let word = first_word(&s); - ^ -18:2 note: previous borrow ends here -fn main() { - -} -^ -``` - -Recall from the borrowing rules that if we have an immutable reference to -something, we cannot also take a mutable reference. Because `clear` needs to -truncate the `String`, it tries to take a mutable reference, which fails. Not -only has Rust made our API easier to use, but it has also eliminated an entire -class of errors at compile time! - -#### String Literals Are Slices - -Recall that we talked about string literals being stored inside the binary. Now -that we know about slices, we can properly understand string literals: - -```rust -let s = "Hello, world!"; -``` - -The type of `s` here is `&str`: it’s a slice pointing to that specific point of -the binary. This is also why string literals are immutable; `&str` is an -immutable reference. - -#### String Slices as Arguments - -Knowing that you can take slices of literals and `String`s leads us to one more -improvement on `first_word`, and that’s its signature: - -```rust,ignore -fn first_word(s: &String) -> &str { -``` - -A more experienced Rustacean would write the following line instead because it -allows us to use the same function on both `String`s and `&str`s: - -```rust,ignore -fn first_word(s: &str) -> &str { -``` - -If we have a string slice, we can pass that as the argument directly. If we -have a `String`, we can pass a slice of the entire `String`. Defining a -function to take a string slice argument instead of a reference to a String -makes our API more general and useful without losing any functionality: - -Filename: src/main.rs - -```rust -fn main() { - let my_string = String::from("hello world"); - - // first_word works on slices of `String`s - let word = first_word(&my_string[..]); - - let my_string_literal = "hello world"; - - // first_word works on slices of string literals - let word = first_word(&my_string_literal[..]); - - // since string literals *are* string slices already, - // this works too, without the slice syntax! - let word = first_word(my_string_literal); -} -``` - -### Other Slices - -String slices, as you might imagine, are specific to strings. But there’s a -more general slice type, too. Consider this array: - -```rust -let a = [1, 2, 3, 4, 5]; -``` - -Just like we might want to refer to a part of a string, we might want to refer -to part of an array and would do so like this: - -```rust -let a = [1, 2, 3, 4, 5]; - -let slice = &a[1..3]; -``` - -This slice has the type `&[i32]`. It works the same way as string slices do, by -storing a reference to the first element and a length. You’ll use this kind of -slice for all sorts of other collections. We’ll discuss these collections in -detail when we talk about vectors in Chapter 8. - -## Summary - -The concepts of ownership, borrowing, and slices are what ensure memory safety -in Rust programs at compile time. The Rust language gives you control over your -memory usage like other systems programming languages, but having the owner of -data automatically clean up that data when the owner goes out of scope means -you don’t have to write and debug extra code to get this control. - -Ownership affects how lots of other parts of Rust work, so we’ll talk about -these concepts further throughout the rest of the book. Let’s move on to the -next chapter and look at grouping pieces of data together in a `struct`. diff --git a/nostarch/chapter05.md b/nostarch/chapter05.md deleted file mode 100644 index 18094bd..0000000 --- a/nostarch/chapter05.md +++ /dev/null @@ -1,615 +0,0 @@ - -[TOC] - -# Structs - -A `struct`, short for *structure*, is a custom data type that lets us name and -package together multiple related values that make up a meaningful group. If -you come from an object-oriented language, a `struct` is like an object’s data -attributes. In the next section of this chapter, we’ll talk about how to define -methods on our structs; methods are how you specify the *behavior* that goes -along with a struct’s data. The `struct` and `enum` (that we will talk about in -Chapter 6) concepts are the building blocks for creating new types in your -program’s domain in order to take full advantage of Rust’s compile-time type -checking. - -One way of thinking about structs is that they are similar to tuples, which we -talked about in Chapter 3. Like tuples, the pieces of a struct can be different -types. Unlike tuples, we name each piece of data so that it’s clearer what the -values mean. Structs are more flexible as a result of these names: we don’t -have to rely on the order of the data to specify or access the values of an -instance. - -To define a struct, we enter the keyword `struct` and give the whole struct a -name. A struct’s name should describe what the significance is of these pieces -of data being grouped together. Then, inside curly braces, we define the names -of the pieces of data, which we call *fields*, and specify each field’s type. -For example, Listing 5-1 shows a struct to store information about a user -account: - -```rust -struct User { - username: String, - email: String, - sign_in_count: u64, - active: bool, -} -``` - - -Listing 5-1: A `User` struct definition - - -To use a struct once we've defined it, we create an *instance* of that struct -by specifying concrete values for each of the fields. Creating an instance is -done by stating the name of the struct, then curly braces with `key: value` -pairs inside it where the keys are the names of the fields and the values are -the data we want to store in those fields. The fields don’t have to be -specified in the same order in which the struct declared them. In other words, -the struct definition is like a general template for the type, and instances -fill in that template with particular data to create values of the type. For -example, we can declare a particular user like this: - -```rust -let user1 = User { - email: String::from("someone@example.com"), - username: String::from("someusername123"), - active: true, - sign_in_count: 1, -}; -``` - -To get a particular value out of a struct, we can use dot notation. If we -wanted just this user’s email address, we can say `user1.email`. - -## Ownership of Struct Data - -In the `User` struct definition in Listing 5-1, we used the owned `String` type -rather than the `&str` string slice type. This is a deliberate choice because -we want instances of this struct to own all of its data, and for that data to -be valid for as long as the entire struct is valid. - -It is possible for structs to store references to data owned by something else, -but to do so requires the use of *lifetimes*, a feature of Rust that we'll -discuss in Chapter 10. Lifetimes ensure that the data a struct references is -valid for as long as the struct is. If you try to store a reference in a struct -without specifying lifetimes, like this: - -Filename: src/main.rs - -```rust,ignore -struct User { - username: &str, - email: &str, - sign_in_count: u64, - active: bool, -} - -fn main() { - let user1 = User { - email: "someone@example.com", - username: "someusername123", - active: true, - sign_in_count: 1, - }; -} -``` - -The compiler will complain that it needs lifetime specifiers: - -```text -error[E0106]: missing lifetime specifier - --> - | -2 | username: &str, - | ^ expected lifetime parameter - -error[E0106]: missing lifetime specifier - --> - | -3 | email: &str, - | ^ expected lifetime parameter -``` - -We will talk about how to fix these errors in order to store references in -structs in Chapter 10, but for now, fix errors like these by switching to owned -types like `String` instead of references like `&str`. - -## An Example Program - -To understand when we might want to use structs, let’s write a program that -calculates the area of a rectangle. We’ll start off with single variables, then -refactor our program until we’re using structs instead. - -Let’s make a new binary project with Cargo called *rectangles* that will take -the length and width of a rectangle specified in pixels and will calculate the -area of the rectangle. Listing 5-2 has a short program with one way of doing -just that in our project’s *src/main.rs*: - -Filename: src/main.rs - -```rust -fn main() { - let length1 = 50; - let width1 = 30; - - println!( - "The area of the rectangle is {} square pixels.", - area(length1, width1) - ); -} - -fn area(length: u32, width: u32) -> u32 { - length * width -} -``` - - -Listing 5-2: Calculating the area of a rectangle specified by its length and -width in separate variables - - -Let’s try running this program with `cargo run`: - -```text -The area of the rectangle is 1500 square pixels. -``` - -### Refactoring with Tuples - -Our little program works okay; it figures out the area of the rectangle by -calling the `area` function with each dimension. But we can do better. The -length and the width are related to each other since together they describe one -rectangle. - -The issue with this method is evident in the signature of `area`: - -```rust,ignore -fn area(length: u32, width: u32) -> u32 { -``` - -The `area` function is supposed to calculate the area of one rectangle, but our -function takes two arguments. The arguments are related, but that’s not -expressed anywhere in our program itself. It would be more readable and more -manageable to group length and width together. - -We’ve already discussed one way we might do that in Chapter 3: tuples. Listing -5-3 has a version of our program which uses tuples: - -Filename: src/main.rs - -```rust -fn main() { - let rect1 = (50, 30); - - println!( - "The area of the rectangle is {} square pixels.", - area(rect1) - ); -} - -fn area(dimensions: (u32, u32)) -> u32 { - dimensions.0 * dimensions.1 -} -``` - - -Listing 5-3: Specifying the length and width of the rectangle with a tuple - - - - -In one way, this is a little better. Tuples let us add a bit of structure, and -we’re now passing just one argument. But in another way this method less clear: -tuples don’t give names to their elements, so our calculation has gotten more -confusing because we have to index into the parts of the tuple: - - - -```rust,ignore -dimensions.0 * dimensions.1 -``` - -It doesn’t matter if we mix up length and width for the area calculation, but -if we were to draw the rectangle on the screen it would matter! We would have -to remember that `length` was the tuple index `0` and `width` was the tuple -index `1`. If someone else was to work on this code, they would have to figure -this out and remember it as well. It would be easy to forget or mix these -values up and cause errors, since we haven’t conveyed the meaning of our data -in our code. - -### Refactoring with Structs: Adding More Meaning - -Here is where we bring in structs. We can transform our tuple into a data type -with a name for the whole as well as names for the parts, as shown in Listing -5-4: - -Filename: src/main.rs - -```rust -struct Rectangle { - length: u32, - width: u32, -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!( - "The area of the rectangle is {} square pixels.", - area(&rect1) - ); -} - -fn area(rectangle: &Rectangle) -> u32 { - rectangle.length * rectangle.width -} -``` - - -Listing 5-4: Defining a `Rectangle` struct - - - - -Here we’ve defined a struct and given it the name `Rectangle`. Inside the `{}` -we defined the fields to be `length` and `width`, both of which have type -`u32`. Then in `main`, we create a particular instance of a `Rectangle` that -has a length of 50 and a width of 30. - -Our `area` function now takes one argument that we’ve named `rectangle` whose -type is an immutable borrow of a struct `Rectangle` instance. As we covered in -Chapter 4, we want to borrow the struct rather than take ownership of it so -that `main` keeps its ownership and can continue using `rect1`, so that’s why -we have the `&` in the function signature and at the call site. - -The `area` function accesses the `length` and `width` fields of the `Rectangle` -instance it got as an argument. Our function signature for `area` now says -exactly what we mean: calculate the area of a `Rectangle`, using its `length` -and `width` fields. This conveys that the length and width are related to each -other, and gives descriptive names to the values rather than using the tuple -index values of `0` and `1`. This is a win for clarity. - -### Adding Useful Functionality with Derived Traits - -It’d be nice to be able to print out an instance of our `Rectangle` while we’re -debugging our program and see the values for all its fields. Listing 5-5 tries -using the `println!` macro as we have been: - -Filename: src/main.rs - -```rust,ignore -struct Rectangle { - length: u32, - width: u32, -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!("rect1 is {}", rect1); -} -``` - - -Listing 5-5: Attempting to print a `Rectangle` instance - - -If we run this, we get an error with this core message: - -```text -error[E0277]: the trait bound `Rectangle: std::fmt::Display` is not satisfied -``` - -The `println!` macro can do many kinds of formatting, and by default, `{}` -tells `println!` to use formatting known as `Display`: output intended for -direct end-user consumption. The primitive types we’ve seen so far implement -`Display` by default, as there’s only one way you’d want to show a `1` or any -other primitive type to a user. But with structs, the way `println!` should -format the output is less clear as there are more display possibilities: Do you -want commas or not? Do you want to print the struct `{}`s? Should all the -fields be shown? Because of this ambiguity, Rust doesn’t try to guess what we -want and structs do not have a provided implementation of `Display`. - -If we keep reading the errors, though, we’ll find this helpful note: - -```text -note: `Rectangle` cannot be formatted with the default formatter; try using -`:?` instead if you are using a format string -``` - -Let’s try it! The `println!` will now look like -`println!("rect1 is {:?}", rect1);`. Putting the specifier `:?` inside -the `{}` tells `println!` we want to use an output format called `Debug`. -`Debug` is a trait that enables us to print out our struct in a way that is -useful for developers so that we can see its value while we are debugging our -code. - -Let’s try running with this change and… drat. We still get an error: - -```text -error: the trait bound `Rectangle: std::fmt::Debug` is not satisfied -``` - -Again, though, the compiler has given us a helpful note! - -```text -note: `Rectangle` cannot be formatted using `:?`; if it is defined in your -crate, add `#[derive(Debug)]` or manually implement it -``` - -Rust *does* include functionality to print out debugging information, but we -have to explicitly opt-in to having that functionality be available for our -struct. To do that, we add the annotation `#[derive(Debug)]` just before our -struct definition, as shown in Listing 5-6: - -```rust -#[derive(Debug)] -struct Rectangle { - length: u32, - width: u32, -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!("rect1 is {:?}", rect1); -} -``` - - -Listing 5-6: Adding the annotation to derive the `Debug` trait and printing the -`Rectangle` instance using debug formatting - - -At this point, if we run this program, we won’t get any errors and we’ll see -the following output: - -```text -rect1 is Rectangle { length: 50, width: 30 } -``` - -Nice! It’s not the prettiest output, but it shows the values of all the fields -for this instance, which would definitely help during debugging. If we want -output that is a bit prettier and easier to read, which can be helpful with -larger structs, we can use `{:#?}` in place of `{:?}` in the `println!` string. -If we use the pretty debug style in this example, the output will look like: - -``` -rect1 is Rectangle { - length: 50, - width: 30 -} -``` - -There are a number of traits Rust has provided for us to use with the `derive` -annotation that can add useful behavior to our custom types. Those traits and -their behaviors are listed in Appendix C. We’ll be covering how to implement -these traits with custom behavior, as well as creating your own traits, in -Chapter 10. - -Our `area` function is pretty specific—it only computes the area of rectangles. -It would be nice to tie this behavior together more closely with our -`Rectangle` struct, since it’s behavior that our `Rectangle` type has -specifically. Let’s now look at how we can continue to refactor this code by -turning the `area` function into an `area` *method* defined on our `Rectangle` -type. - -## Method Syntax - -*Methods* are similar to functions: they’re declared with the `fn` keyword and -their name, they can take arguments and return values, and they contain some -code that gets run when they’re called from somewhere else. Methods are -different from functions, however, because they’re defined within the context -of a struct (or an enum or a trait object, which we will cover in Chapters 6 -and 13, respectively), and their first argument is always `self`, which -represents the instance of the struct that the method is being called on. - -### Defining Methods - -Let’s change our `area` function that takes a `Rectangle` instance as an -argument and instead make an `area` method defined on the `Rectangle` struct, -as shown in Listing 5-7: - -Filename: src/main.rs - -```rust -#[derive(Debug)] -struct Rectangle { - length: u32, - width: u32, -} - -impl Rectangle { - fn area(&self) -> u32 { - self.length * self.width - } -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!( - "The area of the rectangle is {} square pixels.", - rect1.area() - ); -} -``` - - -Listing 5-7: Defining an `area` method on the `Rectangle` struct - - - - -In order to make the function be defined within the context of `Rectangle`, we -start an `impl` block (`impl` is short for *implementation*). Then we move the -function within the `impl` curly braces, and change the first (and in this -case, only) argument to be `self` in the signature and everywhere within the -body. Then in `main` where we called the `area` function and passed `rect1` as -an argument, we can instead use *method syntax* to call the `area` method on -our `Rectangle` instance. Method syntax is taking an instance and adding a dot -followed by the method name, parentheses, and any arguments. - -In the signature for `area`, we get to use `&self` instead of `rectangle: -&Rectangle` because Rust knows the type of `self` is `Rectangle` due to this -method being inside the `impl Rectangle` context. Note we still need to have -the `&` before `self`, just like we had `&Rectangle`. Methods can choose to -take ownership of `self`, borrow `self` immutably as we’ve done here, or borrow -`self` mutably, just like any other argument. - -We’ve chosen `&self` here for the same reason we used `&Rectangle` in the -function version: we don’t want to take ownership, and we just want to be able -to read the data in the struct, not write to it. If we wanted to be able to -change the instance that we’ve called the method on as part of what the method -does, we’d put `&mut self` as the first argument instead. Having a method that -takes ownership of the instance by having just `self` as the first argument is -rarer; this is usually used when the method transforms `self` into something -else and we want to prevent the caller from using the original instance after -the transformation. - -The main benefit of using methods over functions, in addition to getting to use -method syntax and not having to repeat the type of `self` in every method’s -signature, is for organization. We’ve put all the things we can do with an -instance of a type together in one `impl` block, rather than make future users -of our code search for capabilities of `Rectangle` all over the place. - -PROD: START BOX - -### Where’s the `->` Operator? - -In languages like C++, there are two different operators for calling methods: -`.` if you’re calling a method on the object directly, and `->` if you’re -calling the method on a pointer to the object and thus need to dereference the -pointer first. In other words, if `object` is a pointer, `object->something()` -is like `(*object).something()`. - -Rust doesn’t have an equivalent to the `->` operator; instead, Rust has a -feature called *automatic referencing and dereferencing*. Calling methods is -one of the few places in Rust that has behavior like this. - -Here’s how it works: when you call a method with `object.something()`, Rust -will automatically add in `&`, `&mut`, or `*` so that `object` matches the -signature of the method. In other words, these are the same: - -```rust -p1.distance(&p2); -(&p1).distance(&p2); -``` - -The first one looks much, much cleaner. This automatic referencing behavior -works because methods have a clear receiver — the type of `self`. Given the -receiver and name of a method, Rust can figure out definitively whether the -method is just reading (so needs `&self`), mutating (so `&mut self`), or -consuming (so `self`). The fact that Rust makes borrowing implicit for method -receivers is a big part of making ownership ergonomic in practice. - -PROD: END BOX - -### Methods with More Arguments - -Let’s practice some more with methods by implementing a second method on our -`Rectangle` struct. This time, we’d like for an instance of `Rectangle` to take -another instance of `Rectangle` and return `true` if the second rectangle could -fit completely within `self` and `false` if it would not. That is, if we run -the code in Listing 5-8, once we've defined the `can_hold` method: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - let rect2 = Rectangle { length: 40, width: 10 }; - let rect3 = Rectangle { length: 45, width: 60 }; - - println!("Can rect1 hold rect2? {}", rect1.can_hold(&rect2)); - println!("Can rect1 hold rect3? {}", rect1.can_hold(&rect3)); -} -``` - - -Listing 5-8: Demonstration of using the as-yet-unwritten `can_hold` method - - -We want to see this output, since both of `rect2`’s dimensions are smaller than -`rect1`’s, but `rect3` is wider than `rect1`: - -```text -Can rect1 hold rect2? true -Can rect1 hold rect3? false -``` - -We know we want to define a method, so it will be within the `impl Rectangle` -block. The method name will be `can_hold`, and it will take an immutable borrow -of another `Rectangle` as an argument. We can tell what the type of the -argument will be by looking at a call site: `rect1.can_hold(&rect2)` passes in -`&rect2`, which is an immutable borrow to `rect2`, an instance of `Rectangle`. -This makes sense, since we only need to read `rect2` (rather than write, which -would mean we’d need a mutable borrow) and we want `main` to keep ownership of -`rect2` so that we could use it again after calling this method. The return -value of `can_hold` will be a boolean, and the implementation will check to see -if `self`’s length and width are both greater than the length and width of the -other `Rectangle`, respectively. Let’s add this new method to the `impl` block -from Listing 5-7: - -Filename: src/main.rs - -```rust -impl Rectangle { - fn area(&self) -> u32 { - self.length * self.width - } - - fn can_hold(&self, other: &Rectangle) -> bool { - self.length > other.length && self.width > other.width - } -} -``` - - - -If we run this with the `main` from Listing 5-8, we will get our desired output! -Methods can take multiple arguments that we add to the signature after the -`self` parameter, and those arguments work just like arguments in functions do. - -### Associated Functions - -One more useful feature of `impl` blocks: we’re allowed to define functions -within `impl` blocks that *don’t* take `self` as a parameter. These are called -*associated functions*, since they’re associated with the struct. They’re still -functions though, not methods, since they don’t have an instance of the struct -to work with. You’ve already used an associated function: `String::from`. - -Associated functions are often used for constructors that will return a new -instance of the struct. For example, we could provide an associated function -that would take one dimension argument and use that as both length and width, -thus making it easier to create a square `Rectangle` rather than having to -specify the same value twice: - -Filename: src/main.rs - -```rust -impl Rectangle { - fn square(size: u32) -> Rectangle { - Rectangle { length: size, width: size } - } -} -``` - -To call this associated function, we use the `::` syntax with the struct name: -`let sq = Rectange::square(3);`, for example. This function is namespaced by -the struct: the `::` syntax is used for both associated functions and -namespaces created by modules, which we’ll learn about in Chapter 7. - -## Summary - -Structs let us create custom types that are meaningful for our domain. By using -structs, we can keep associated pieces of data connected to each other and name -each piece to make our code clear. Methods let us specify the behavior that -instances of our structs have, and associated functions let us namespace -functionality that is particular to our struct without having an instance -available. - -Structs aren’t the only way we can create custom types, though; let’s turn to -the `enum` feature of Rust and add another tool to our toolbox. diff --git a/nostarch/chapter06.md b/nostarch/chapter06.md deleted file mode 100644 index 914fe3d..0000000 --- a/nostarch/chapter06.md +++ /dev/null @@ -1,772 +0,0 @@ - -[TOC] - -# Enums and Pattern Matching - -In this chapter we’ll look at *enumerations*, also referred to as *enums*. -Enums allow you to define a type by enumerating its possible values. First, -we’ll define and use an enum to show how an enum can encode meaning along with -data. Next, we’ll explore a particularly useful enum, called `Option`, which -expresses that a value can be either something or nothing. Then we’ll look at -how pattern matching in the `match` expression makes it easy to run different -code for different values of an enum. Finally, we’ll cover how the `if let` -construct is another convenient and concise idiom available to you to handle -enums in your code. - -Enums are a feature in many languages, but their capabilities differ in each -language. Rust’s enums are most similar to *algebraic data types* in functional -languages like F#, OCaml, and Haskell. - -## Defining an Enum - -Let’s look at a situation we might want to express in code and see why enums -are useful and more appropriate than structs in this case. Say we need to work -with IP addresses. Currently, two major standards are used for IP addresses: -version four and version six. These are the only possibilities for an IP -address that our program will come across: we can *enumerate* all possible -values, which is where enumeration gets its name. - -Any IP address can be either a version four or a version six address but not -both at the same time. That property of IP addresses makes the enum data -structure appropriate for this case, because enum values can only be one of the -variants. Both version four and version six addresses are still fundamentally -IP addresses, so they should be treated as the same type when the code is -handling situations that apply to any kind of IP address. - -We can express this concept in code by defining an `IpAddrKind` enumeration and -listing the possible kinds an IP address can be, `V4` and `V6`. These are known -as the *variants* of the enum: - -```rust -enum IpAddrKind { - V4, - V6, -} -``` - -`IpAddrKind` is now a custom data type that we can use elsewhere in our code. - -### Enum Values - -We can create instances of each of the two variants of `IpAddrKind` like this: - -```rust -let four = IpAddrKind::V4; -let six = IpAddrKind::V6; -``` - -Note that the variants of the enum are namespaced under its identifier, and we -use a double colon to separate the two. The reason this is useful is that now -both values `IpAddrKind::V4` and `IpAddrKind::V6` are of the same type: -`IpAddrKind`. We can then, for instance, define a function that takes any -`IpAddrKind`: - -```rust -fn route(ip_type: IpAddrKind) { } -``` - -And we can call this function with either variant: - -```rust -route(IpAddrKind::V4); -route(IpAddrKind::V6); -``` - -Using enums has even more advantages. Thinking more about our IP address type, -at the moment we don’t have a way to store the actual IP address *data*; we -only know what *kind* it is. Given that you just learned about structs in -Chapter 5, you might tackle this problem as shown in Listing 6-1: - -```rust -enum IpAddrKind { - V4, - V6, -} - -struct IpAddr { - kind: IpAddrKind, - address: String, -} - -let home = IpAddr { - kind: IpAddrKind::V4, - address: String::from("127.0.0.1"), -}; - -let loopback = IpAddr { - kind: IpAddrKind::V6, - address: String::from("::1"), -}; -``` - - -Listing 6-1: Storing the data and `IpAddrKind` variant of an IP address using a -`struct` - - -Here, we’ve defined a struct `IpAddr` that has two fields: a `kind` field that -is of type `IpAddrKind` (the enum we defined previously) and an `address` field -of type `String`. We have two instances of this struct. The first, `home`, has -the value `IpAddrKind::V4` as its `kind` with associated address data of -`127.0.0.1`. The second instance, `loopback`, has the other variant of -`IpAddrKind` as its `kind` value, `V6`, and has address `::1` associated with -it. We’ve used a struct to bundle the `kind` and `address` values together, so -now the variant is associated with the value. - -We can represent the same concept in a more concise way using just an enum -rather than an enum as part of a struct by putting data directly into each enum -variant. This new definition of the `IpAddr` enum says that both `V4` and `V6` -variants will have associated `String` values: - -```rust -enum IpAddr { - V4(String), - V6(String), -} - -let home = IpAddr::V4(String::from("127.0.0.1")); - -let loopback = IpAddr::V6(String::from("::1")); -``` - -We attach data to each variant of the enum directly, so there is no need for an -extra struct. - -There’s another advantage to using an enum rather than a struct: each variant -can have different types and amounts of associated data. Version four type IP -addresses will always have four numeric components that will have values -between 0 and 255. If we wanted to store `V4` addresses as four `u8` values but -still express `V6` addresses as one `String` value, we wouldn’t be able to with -a struct. Enums handle this case with ease: - -```rust -enum IpAddr { - V4(u8, u8, u8, u8), - V6(String), -} - -let home = IpAddr::V4(127, 0, 0, 1); - -let loopback = IpAddr::V6(String::from("::1")); -``` - -We’ve shown several different possibilities that we could define in our code -for storing IP addresses of the two different varieties using an enum. However, -as it turns out, wanting to store IP addresses and encode which kind they are -is so common that the standard library has a definition we can use! Let’s look -at how the standard library defines `IpAddr`: it has the exact enum and -variants that we’ve defined and used, but it embeds the address data inside the -variants in the form of two different structs, which are defined differently -for each variant: - -```rust -struct Ipv4Addr { - // details elided -} - -struct Ipv6Addr { - // details elided -} - -enum IpAddr { - V4(Ipv4Addr), - V6(Ipv6Addr), -} -``` - -This code illustrates that you can put any kind of data inside an enum variant: -strings, numeric types, or structs, for example. You can even include another -enum! Also, standard library types are often not much more complicated than -what you might come up with. - -Note that even though the standard library contains a definition for `IpAddr`, -we can still create and use our own definition without conflict because we -haven’t brought the standard library’s definition into our scope. We’ll talk -more about importing types in Chapter 7. - -Let’s look at another example of an enum in Listing 6-2: this one has a wide -variety of types embedded in its variants: - -```rust -enum Message { - Quit, - Move { x: i32, y: i32 }, - Write(String), - ChangeColor(i32, i32, i32), -} -``` - - -Listing 6-2: A `Message` enum whose variants each store different amounts and -types of values - - -This enum has four variants with different types: - -* `Quit` has no data associated with it at all. -* `Move` includes an anonymous struct inside it. -* `Write` includes a single `String`. -* `ChangeColor` includes three `i32`s. - -Defining an enum with variants like the ones in Listing 6-2 is similar to -defining different kinds of struct definitions except the enum doesn’t use the -`struct` keyword and all the variants are grouped together under the `Message` -type. The following structs could hold the same data that the preceding enum -variants hold: - -```rust -struct QuitMessage; // unit struct -struct MoveMessage { - x: i32, - y: i32, -} -struct WriteMessage(String); // tuple struct -struct ChangeColorMessage(i32, i32, i32); // tuple struct -``` - -But if we used the different structs, which each have their own type, we -wouldn’t be able to as easily define a function that could take any of these -kinds of messages as we could with the `Message` enum defined in Listing 6-2, -which is a single type. - -There is one more similarity between enums and structs: just as we’re able to -define methods on structs using `impl`, we’re also able to define methods on -enums. Here’s a method named `call` that we could define on our `Message` enum: - -```rust -impl Message { - fn call(&self) { - // method body would be defined here - } -} - -let m = Message::Write(String::from("hello")); -m.call(); -``` - -The body of the method would use `self` to get the value that we called the -method on. In this example, we’ve created a variable `m` that has the value -`Message::Write("hello")`, and that is what `self` will be in the body of the -`call` method when `m.call()` runs. - -Let’s look at another enum in the standard library that is very common and -useful: `Option`. - -### The `Option` Enum and Its Advantages Over Null Values - -In the previous section, we looked at how the `IpAddr` enum let us use Rust’s -type system to encode more information than just the data into our program. -This section explores a case study of `Option`, which is another enum defined -by the standard library. The `Option` type is used in many places because it -encodes the very common scenario in which a value could be something or it -could be nothing. Expressing this concept in terms of the type system means the -compiler can check that you’ve handled all the cases you should be handling, -which can prevent bugs that are extremely common in other programming languages. - -Programming language design is often thought of in terms of which features you -include, but the features you exclude are important too. Rust doesn’t have the -null feature that many other languages have. *Null* is a value that means there -is no value there. In languages with null, variables can always be in one of -two states: null or not-null. - -In “Null References: The Billion Dollar Mistake,” Tony Hoare, the inventor of -null, has this to say: - -> I call it my billion-dollar mistake. At that time, I was designing the first -> comprehensive type system for references in an object-oriented language. My -> goal was to ensure that all use of references should be absolutely safe, with -> checking performed automatically by the compiler. But I couldn't resist the -> temptation to put in a null reference, simply because it was so easy to -> implement. This has led to innumerable errors, vulnerabilities, and system -> crashes, which have probably caused a billion dollars of pain and damage in -> the last forty years. - -The problem with null values is that if you try to actually use a value that’s -null as if it is a not-null value, you’ll get an error of some kind. Because -this null or not-null property is pervasive, it’s extremely easy to make this -kind of error. - -However, the concept that null is trying to express is still a useful one: a -null is a value that is currently invalid or absent for some reason. - -The problem isn’t with the actual concept but with the particular -implementation. As such, Rust does not have nulls, but it does have an enum -that can encode the concept of a value being present or absent. This enum is -`Option`, and it is defined by the standard library as follows: - -```rust -enum Option { - Some(T), - None, -} -``` - -The `Option` enum is so useful that it’s even included in the prelude; you -don’t need to import it explicitly. In addition, so are its variants: you can -use `Some` and `None` directly without prefixing them with `Option::`. -`Option` is still just a regular enum, and `Some(T)` and `None` are still -variants of type `Option`. - -The `` syntax is a feature of Rust we haven’t talked about yet. It’s a -generic type parameter, and we’ll cover generics in more detail in Chapter 10. -For now, all you need to know is that `` means the `Some` variant of the -`Option` enum can hold one piece of data of any type. Here are some examples of -using `Option` values to hold number types and string types: - -```rust -let some_number = Some(5); -let some_string = Some("a string"); - -let absent_number: Option = None; -``` - -If we use `None` rather than `Some`, we need to tell Rust what type of -`Option` we have, because the compiler can't infer the type that the `Some` -variant will hold by looking only at a `None` value. - -When we have a `Some` value, we know that a value is present, and the value is -held within the `Some`. When we have a `None` value, in some sense, it means -the same thing as null: we don’t have a valid value. So why is having -`Option` any better than having null? - -In short, because `Option` and `T` (where `T` can be any type) are different -types, the compiler won’t let us use an `Option` value as if it was -definitely a valid value. For example, this code won’t compile because it’s -trying to compare an `Option` to an `i8`: - -```rust,ignore -let x: i8 = 5; -let y: Option = Some(5); - -let sum = x + y; -``` - -If we run this code, we get an error message like this: - -```text -error[E0277]: the trait bound `i8: std::ops::Add>` is -not satisfied - --> - | -7 | let sum = x + y; - | ^^^^^ - | -``` - -Intense! In effect, this error message means that Rust doesn’t understand how -to add an `Option` and an `i8`, because they’re different types. When we -have a value of a type like `i8` in Rust, the compiler will ensure that we -always have a valid value. We can proceed confidently without having to check -for null before using that value. Only when we have an `Option` (or -whatever type of value we’re working with) do we have to worry about possibly -not having a value, and the compiler will make sure we handle that case before -using the value. - -In other words, you have to convert an `Option` to a `T` before you can -perform `T` operations with it. Generally, this helps catch one of the most -common issues with null: assuming that something isn’t null when it actually -is. - -Not having to worry about missing an assumption of having a not-null value -helps you to be more confident in your code. In order to have a value that can -possibly be null, you must explicitly opt in by making the type of that value -`Option`. Then, when you use that value, you are required to explicitly -handle the case when the value is null. Everywhere that a value has a type that -isn’t an `Option`, you *can* safely assume that the value isn’t null. This -was a deliberate design decision for Rust to limit null’s pervasiveness and -increase the safety of Rust code. - -So, how do you get the `T` value out of a `Some` variant when you have a value -of type `Option` so you can use that value? The `Option` enum has a large -number of methods that are useful in a variety of situations; you can check -them out in its documentation. Becoming familiar with the methods on -`Option` will be extremely useful in your journey with Rust. - -In general, in order to use an `Option` value, we want to have code that -will handle each variant. We want some code that will run only when we have a -`Some(T)` value, and this code is allowed to use the inner `T`. We want some -other code to run if we have a `None` value, and that code doesn’t have a `T` -value available. The `match` expression is a control flow construct that does -just this when used with enums: it will run different code depending on which -variant of the enum it has, and that code can use the data inside the matching -value. - -## The `match` Control Flow Operator - -Rust has an extremely powerful control-flow operator called `match` that allows -us to compare a value against a series of patterns and then execute code based -on which pattern matches. Patterns can be made up of literal values, variable -names, wildcards, and many other things; Chapter 18 will be about all the -different kinds of patterns and what they do. The power of `match` comes from -the expressiveness of the patterns and the compiler checks that make sure all -possible cases are handled. - -Think of a `match` expression kind of like a coin sorting machine: coins slide -down a track with variously sized holes along it, and each coin falls through -the first hole it encounters that it fits into. In the same way, values go -through each pattern in a `match`, and at the first pattern the value “fits,” -the value will fall into the associated code block to be used during execution. - -Because we just mentioned coins, let’s use them as an example using `match`! We -can write a function that can take an unknown United States coin and, in a -similar way as the counting machine, determine which coin it is and return its -value in cents, as shown here in Listing 6-3: - -```rust -enum Coin { - Penny, - Nickel, - Dime, - Quarter, -} - -fn value_in_cents(coin: Coin) -> i32 { - match coin { - Coin::Penny => 1, - Coin::Nickel => 5, - Coin::Dime => 10, - Coin::Quarter => 25, - } -} -``` - - -Listing 6-3: An enum and a `match` expression that has the variants of the enum -as its patterns. - - -Let’s break down the `match` in the `value_in_cents` function. First, we list -the `match` keyword followed by an expression, which in this case is the value -`coin`. This seems very similar to an expression used with `if`, but there’s a -big difference: with `if`, the expression needs to return a boolean value. -Here, it can be any type. The type of `coin` in this example is the `Coin` enum -that we defined in Listing 6-3. - -Next are the `match` arms. An arm has two parts: a pattern and some code. The -first arm here has a pattern that is the value `Coin::Penny` and then the `=>` -operator that separates the pattern and the code to run. The code in this case -is just the value `1`. Each arm is separated from the next with a comma. - -When the `match` expression executes, it compares the resulting value against -the pattern of each arm, in order. If a pattern matches the value, the code -associated with that pattern is executed. If that pattern doesn’t match the -value, execution continues to the next arm, much like a coin sorting machine. -We can have as many arms as we need: in Listing 6-3, our `match` has four arms. - -The code associated with each arm is an expression, and the resulting value of -the expression in the matching arm is the value that gets returned for the -entire `match` expression. - -Curly braces typically aren’t used if the match arm code is short, as it is in -Listing 6-3 where each arm just returns a value. If you want to run multiple -lines of code in a match arm, you can use curly braces. For example, the -following code would print out “Lucky penny!” every time the method was called -with a `Coin::Penny` but would still return the last value of the block, `1`: - -```rust -fn value_in_cents(coin: Coin) -> i32 { - match coin { - Coin::Penny => { - println!("Lucky penny!"); - 1 - }, - Coin::Nickel => 5, - Coin::Dime => 10, - Coin::Quarter => 25, - } -} -``` - -### Patterns that Bind to Values - -Another useful feature of match arms is that they can bind to parts of the -values that match the pattern. This is how we can extract values out of enum -variants. - -As an example, let’s change one of our enum variants to hold data inside it. -From 1999 through 2008, the United States printed quarters with different -designs for each of the 50 states on one side. No other coins got state -designs, so only quarters have this extra value. We can add this information to -our `enum` by changing the `Quarter` variant to include a `State` value stored -inside it, which we've done here in Listing 6-4: - -```rust -#[derive(Debug)] // So we can inspect the state in a minute -enum UsState { - Alabama, - Alaska, - // ... etc -} - -enum Coin { - Penny, - Nickel, - Dime, - Quarter(UsState), -} -``` - - -Listing 6-4: A `Coin` enum where the `Quarter` variant also holds a `UsState` -value - - -Let’s imagine that a friend of ours is trying to collect all 50 state quarters. -While we sort our loose change by coin type, we’ll also call out the name of -the state associated with each quarter so if it’s one our friend doesn’t have, -they can add it to their collection. - -In the match expression for this code, we add a variable called `state` to the -pattern that matches values of the variant `Coin::Quarter`. When a -`Coin::Quarter` matches, the `state` variable will bind to the value of that -quarter’s state. Then we can use `state` in the code for that arm, like so: - -```rust -fn value_in_cents(coin: Coin) -> i32 { - match coin { - Coin::Penny => 1, - Coin::Nickel => 5, - Coin::Dime => 10, - Coin::Quarter(state) => { - println!("State quarter from {:?}!", state); - 25 - }, - } -} -``` - -If we were to call `value_in_cents(Coin::Quarter(UsState::Alaska))`, `coin` -would be `Coin::Quarter(UsState::Alaska)`. When we compare that value with each -of the match arms, none of them match until we reach `Coin::Quarter(state)`. At -that point, the binding for `state` will be the value `UsState::Alaska`. We can -then use that binding in the `println!` expression, thus getting the inner -state value out of the `Coin` enum variant for `Quarter`. - -### Matching with `Option` - -In the previous section we wanted to get the inner `T` value out of the `Some` -case when using `Option`; we can also handle `Option` using `match` as we -did with the `Coin` enum! Instead of comparing coins, we’ll compare the -variants of `Option`, but the way that the `match` expression works remains -the same. - -Let’s say we want to write a function that takes an `Option`, and if -there’s a value inside, adds one to that value. If there isn’t a value inside, -the function should return the `None` value and not attempt to perform any -operations. - -This function is very easy to write, thanks to `match`, and will look like -Listing 6-5: - -```rust -fn plus_one(x: Option) -> Option { - match x { - None => None, - Some(i) => Some(i + 1), - } -} - -let five = Some(5); -let six = plus_one(five); -let none = plus_one(None); -``` - - -Listing 6-5: A function that uses a `match` expression on an `Option` - - -#### Matching `Some(T)` - -Let’s examine the first execution of `plus_one` in more detail. When we call -`plus_one(five)` w, the variable `x` in the body of `plus_one` will have the -value `Some(5)`. We then compare that against each match arm. - -```rust,ignore -None => None, -``` - -The `Some(5)` value doesn’t match the pattern `None` u, so we continue to the -next arm. - -```rust,ignore -Some(i) => Some(i + 1), -``` - -Does `Some(5)` match `Some(i)` v? Why yes it does! We have the same variant. -The `i` binds to the value contained in `Some`, so `i` takes the value `5`. The -code in the match arm is then executed, so we add one to the value of `i` and -create a new `Some` value with our total `6` inside. - -#### Matching `None` - -Now let’s consider the second call of `plus_one` in Listing 6-5 where `x` is -`None` x. We enter the `match` and compare to the first arm u. - -```rust,ignore -None => None, -``` - -It matches! There’s no value to add to, so the program stops and returns the -`None` value on the right side of `=>`. Because the first arm matched, no other -arms are compared. - -Combining `match` and enums is useful in many situations. You’ll see this -pattern a lot in Rust code: `match` against an enum, bind a variable to the -data inside, and then execute code based on it. It’s a bit tricky at first, but -once you get used to it, you’ll wish you had it in all languages. It’s -consistently a user favorite. - -### Matches Are Exhaustive - -There’s one other aspect of `match` we need to discuss. Consider this version -of our `plus_one` function: - -```rust,ignore -fn plus_one(x: Option) -> Option { - match x { - Some(i) => Some(i + 1), - } -} -``` - -We didn’t handle the `None` case, so this code will cause a bug. Luckily, it’s -a bug Rust knows how to catch. If we try to compile this code, we’ll get this -error: - -```text -error[E0004]: non-exhaustive patterns: `None` not covered - --> - | -6 | match x { - | ^ pattern `None` not covered -``` - -Rust knows that we didn’t cover every possible case and even knows which -pattern we forgot! Matches in Rust are *exhaustive*: we must exhaust every last -possibility in order for the code to be valid. Especially in the case of -`Option`, when Rust prevents us from forgetting to explicitly handle the -`None` case, it protects us from assuming that we have a value when we might -have null, thus making the billion dollar mistake discussed earlier. - -### The `_` Placeholder - -Rust also has a pattern we can use in situations when we don’t want to list all -possible values. For example, a `u8` can have valid values of 0 through 255. If -we only care about the values 1, 3, 5, and 7, we don’t want to have to list out -0, 2, 4, 6, 8, 9 all the way up to 255. Fortunately, we don’t have to: we can -use the special pattern `_` instead: - -```rust -let some_u8_value = 0u8; -match some_u8_value { - 1 => println!("one"), - 3 => println!("three"), - 5 => println!("five"), - 7 => println!("seven"), - _ => (), -} -``` - -The `_` pattern will match any value. By putting it after our other arms, the -`_` will match all the possible cases that aren’t specified before it. The `()` -is just the unit value, so nothing will happen in the `_` case. As a result, we -can say that we want to do nothing for all the possible values that we don’t -list before the `_` placeholder. - -However, the `match` expression can be a bit wordy in a situation in which we -only care about *one* of the cases. For this situation, Rust provides `if let`. - -## Concise Control Flow with `if let` - -The `if let` syntax lets you combine `if` and `let` into a less verbose way to -handle values that match one pattern and ignore the rest. Consider the program -in Listing 6-6 that matches on an `Option` value but only wants to execute -code if the value is three: - -```rust -let some_u8_value = Some(0u8); -match some_u8_value { - Some(3) => println!("three"), - _ => (), -} -``` - - -Listing 6-6: A `match` that only cares about executing code when the value is -`Some(3)` - - -We want to do something with the `Some(3)` match but do nothing with any other -`Some` value or the `None` value. To satisfy the `match` expression, we -have to add `_ => ()` after processing just one variant, which is a lot of -boilerplate code to add. - -Instead, we could write this in a shorter way using `if let`. The following -code behaves the same as the `match` in Listing 6-6: - -```rust -if let Some(3) = some_u8_value { - println!("three"); -} -``` - -`if let` takes a pattern and an expression separated by an `=`. It works the -same way as a `match`, where the expression is given to the `match` and the -pattern is its first arm. - -Using `if let` means you have less to type, less indentation, and less -boilerplate code. However, we’ve lost the exhaustive checking that `match` -enforces. Choosing between `match` and `if let` depends on what you’re doing in -your particular situation and if gaining conciseness is an appropriate -trade-off for losing exhaustive checking. - -In other words, you can think of `if let` as syntax sugar for a `match` that -runs code when the value matches one pattern and then ignores all other values. - -We can include an `else` with an `if let`. The block of code that goes with the -`else` is the same as the block of code that would go with the `_` case in the -`match` expression that is equivalent to the `if let` and `else`. Recall the -`Coin` enum definition in Listing 6-4, where the `Quarter` variant also held a -`UsState` value. If we wanted to count all non-quarter coins we see while also -announcing the state of the quarters, we could do that with a `match` -expression like this: - -```rust -let mut count = 0; -match coin { - Coin::Quarter(state) => println!("State quarter from {:?}!", state), - _ => count += 1, -} -``` - -Or we could use an `if let` and `else` expression like this: - -```rust -let mut count = 0; -if let Coin::Quarter(state) = coin { - println!("State quarter from {:?}!", state); -} else { - count += 1; -} -``` - -If you have a situation in which your program has logic that is too verbose to -express using a `match`, remember that `if let` is in your Rust toolbox as well. - -## Summary - -We’ve now covered how to use enums to create custom types that can be one of a -set of enumerated values. We’ve shown how the standard library’s `Option` -type helps you use the type system to prevent errors. When enum values have -data inside them, you can use `match` or `if let` to extract and use those -values, depending on how many cases you need to handle. - -Your Rust programs can now express concepts in your domain using structs and -enums. Creating custom types to use in your API ensures type safety: the -compiler will make certain your functions only get values of the type each -function expects. - -In order to provide a well-organized API to your users that is straightforward -to use and only exposes exactly what your users will need, let’s now turn to -Rust’s modules. - diff --git a/nostarch/chapter07.md b/nostarch/chapter07.md deleted file mode 100644 index 8a89bb0..0000000 --- a/nostarch/chapter07.md +++ /dev/null @@ -1,1055 +0,0 @@ - -[TOC] - -# Modules - -When you start writing programs in Rust, your code might live solely in the -`main` function. As your code grows, you’ll eventually move functionality out -into other functions, both for re-use and for better organization. By splitting -your code up into smaller chunks, each chunk is easier to understand on its -own. But what happens if find yourself with too many functions? Rust has a -module system that handles the problem of wanting to to re-use code while -keeping your code organized. - -In the same way that you extract lines of code into a function, you can extract -functions (and other code like structs and enums too) into different modules. A -*module* is a namespace that contains definitions of functions or types, and -you can choose whether those definitions are visible outside their module -(public) or not (private). Here’s an overview of how modules work: - -* You declare a new module with the keyword `mod` -* By default, everything is set as private, but you can use the `pub` keyword - to make the module public, and therefore visible outside of the namespace. -* The `use` keyword allows you to bring modules, or the definitions inside - modules, into scope so that it’s easier to refer to them. - -We’ll take a look at each of these parts and see how they fit into the whole. - -## `mod` and the Filesystem - -We’ll start our module example by making a new project with Cargo, but instead -of creating a binary crate, we’re going to make a library crate: a project that -other people can pull into their projects as a dependency. We saw this with the -`rand` crate in Chapter 2. - -We’ll create a skeleton of a library that provides some general networking -functionality; we’re going to concentrate on the organization of the modules -and functions, but not worry about what code goes in the function bodies. We’ll -call our library `communicator`. By default, cargo will create a library unless -another type of project is specified, so if we leave off the `--bin` option -that we’ve been using so far our project will be a library: - -```bash -$ cargo new communicator -$ cd communicator -``` - -Notice that Cargo generated *src/lib.rs* instead of *src/main.rs*. Inside -*src/lib.rs* we’ll find this: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} -``` - -Cargo creates an empty test to help us get our library started, rather -than the “Hello, world!” binary that we get with the `--bin` option. We’ll look -at the `#[]` and `mod tests` syntax a little later, but for now just make sure -to leave it in your *src/lib.rs*. - -Since we don’t have a *src/main.rs*, there’s nothing for Cargo to execute with -the `cargo run` command. Therefore, we will be using the `cargo build` command -to only compile our library crate’s code. - -We’re going to look at different options for organizing your library’s code -which will be suitable in a variety of situations, depending on the intentions -you have for your code. - -### Module Definitions - -For our `communicator` networking library, we’re first going to define a module -named `network` that contains the definition of a function called `connect`. -Every module definition in Rust starts with the `mod` keyword. Add this code to -the beginning of the *lib.rs* file, above the test code: - -Filename: src/lib.rs - -```rust -mod network { - fn connect() { - } -} -``` - -After the `mod` keyword, we put the name of the module, `network`, then a block -of code in curly braces. Everything inside this block is inside the namespace -`network`. In this case, we have a single function, `connect`. If we wanted to -call this function from a script outside the `network` module, we would need to -specify the module and use the namespace syntax `::`, like so: -`network::connect()`, rather than just `connect()`. - -We can also have multiple modules, side-by-side, in the same *src/lib.rs* file. -For example, to have a `client` module too, that also has a function named -`connect`, we can add: - -Filename: src/lib.rs - -```rust -mod network { - fn connect() { - } -} - -mod client { - fn connect() { - } -} -``` - - -Listing 7-1: The `network` module and the `client` module defined side-by-side -in *src/lib.rs* - - -Now we have a `network::connect` function and a `client::connect` function. -These can have completely different functionality, and the function names do -not conflict with each other since they’re in different modules. - -We can also put modules inside of modules. This can be useful as your modules -grow to keep related functionality organized together and separate -functionality apart. The choice of how you organize your code depends on how -you think about the relationship between the parts of your code. For instance, -the `client` code and its `connect` function might make more sense to users of -our library if it was inside the `network` namespace instead, like so: - -Filename: src/lib.rs - -```rust -mod network { - fn connect() { - } - - mod client { - fn connect() { - } - } -} -``` - - -Listing 7-2: Moving the `client` module inside of the `network` module - - -In your *src/lib.rs* file, replace the existing `mod network` and `mod client` -definitions with this one that has the `client` module as an inner module of -`network`. Now we have the functions `network::connect` and -`network::client::connect`: again, the two functions named `connect` don’t -conflict with each other since they’re in different namespaces. - -In this way, modules form a hierarchy. The contents of `src/lib.rs` are at the -topmost level, and the submodules are at lower levels. Here’s what the -organization of our example from Listing 7-1 looks like when thought of this -way: - -```text -communicator - ├── network - └── client -``` - -And here’s the example from Listing 7-2: - -```text -communicator - └── network - └── client -``` - -You can see that in Listing 7-2, `client` is a child of the `network` module, -rather than a sibling. More complicated projects can have a lot of modules, and -they’ll need to be orgnaized logically in order to keep track of them. What -“logically” means in your project is up to you and depends on how you and users -of your library think about your project’s domain. Use the techniques we’ve -shown here to create side-by-side modules and nested modules in whatever -structure you would like. - -### Moving Modules to Other Files - -Modules form a hierarchical structure, much like another structure in computing -that you’re used to: file systems! We can use Rust’s module system along with -multiple files to split Rust projects up so that not everything lives in -*src/lib.rs*. For this example, we will start with this code in *src/lib.rs*: - -File: src/lib.rs - -```rust -mod client { - fn connect() { - } -} - -mod network { - fn connect() { - } - - mod server { - fn connect() { - } - } -} -``` - - -Listing 7-3: Three modules, `client`, `network`, and `network::server` all -defined in *src/lib.rs* - - -which has this module hierarchy: - -```text -communicator - ├── client - └── network - └── server -``` - -If these modules had many functions, and each function was getting long, we -would have to scroll through this file to find the code we wanted to work with. -This would be a good reason to pull each of the `client`, `network`, and -`server` modules out of *src/lib.rs* and into their own files. Let’s start by -extracting the `client` module into another file. First, replace the `client` -module code in *src/lib.rs* with the following: - -File: src/lib.rs - -```rust,ignore -mod client; - -mod network { - fn connect() { - } - - mod server { - fn connect() { - } - } -} -``` - - - -We’re still *defining* the `client` module here, but by removing the curly -braces and definitions inside the `client` module and replacing them with a -semicolon, we’re letting Rust know to look in another location for the code -defined inside that module. - -So now we need to create the external file with that module name. Create a -`client.rs` file in your *src/* directory, then open it up and enter the -following, which is the `connect` function in the `client` module that we -removed in the previous step: - -File: src/client.rs - -```rust -fn connect() { -} -``` - -Note that we don’t need a `mod` declaration in this file; that’s because we -already declared the `client` module with `mod` in `src/lib.rs`. This file just -provides the *contents* of the `client` module. If we put a `mod client` here, -we’d be giving the `client` module its own submodule named `client`! - -Rust only knows to look in *src/lib.rs* by default. If we want to add more -files to our project, we need to tell Rust in *src/lib.rs* to look in other -files; this is why `mod client` needs to be defined in *src/lib.rs* and can’t -be defined in *src/client.rs*. - -Now, everything should compile successfully, though you’ll get a few warnings. -Remember to use `cargo build` instead of `cargo run` since we have a library -crate rather than a binary crate: - -```bash -$ cargo build - Compiling communicator v0.1.0 (file:///projects/communicator) - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/client.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/lib.rs:4:5 - | -4 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/lib.rs:8:9 - | -8 | fn connect() { - | ^ -``` - -These warnings tell us that we have functions that are never used. Don’t worry -about those warnings for now; we’ll address them later in the chapter. The good -news is that they’re just warnings; our project was built successfully! - -Let’s extract the `network` module into its own file next, using the same -pattern. In `src/lib.rs`, delete the body of the `network` module and add a -semicolon to the declaration, like so: - -Filename: src/lib.rs - -```rust,ignore -mod client; - -mod network; -``` - -Then create a new `src/network.rs` file and enter the following: - -Filename: src/network.rs - -```rust -fn connect() { -} - -mod server { - fn connect() { - } -} -``` - -Notice that we still have a `mod` declaration within this module file; -this is because we still want `server` to be a sub-module of `network`. - -Now run `cargo build` again. Success! We have one more module to extract: -`server`. Because it’s a sub-module—that is, a module within a module—our -current tactic of extracting a module into a file named after that module won’t -work. We’re going to try anyway so that we can see the error. First change -*src/network.rs* to have `mod server;` instead of the `server` module’s -contents: - -Filename: src/network.rs - -```rust,ignore -fn connect() { -} - -mod server; -``` - -Then create a `src/server.rs` file and enter the contents of the `server` -module that we extracted: - -Filename: src/server.rs - -```rust -fn connect() { -} -``` - -When we try to `cargo build`, we’ll get this error: - -```bash -$ cargo build - Compiling communicator v0.1.0 (file:///projects/communicator) -error: cannot declare a new module at this location - --> src/network.rs:4:5 - | -4 | mod server; - | ^^^^^^ - | -note: maybe move this module `network` to its own directory via `network/mod.rs` - --> src/network.rs:4:5 - | -4 | mod server; - | ^^^^^^ -note: ... or maybe `use` the module `server` instead of possibly redeclaring it - --> src/network.rs:4:5 - | -4 | mod server; - | ^^^^^^ -``` - - -Listing 7-4: Error when trying to extract the `server` submodule into -*src/server.rs* - - -The error says we `cannot declare a new module at this location` and is -pointing to the `mod server;` line in `src/network.rs`. So `src/network.rs` is -different than `src/lib.rs` somehow; let’s keep reading to understand why. - -The note in the middle of Listing 7-4 is actually pretty helpful, as it points -out something we haven’t yet talked about doing: - -> note: maybe move this module `network` to its own directory via -`network/mod.rs` - -Instead of continuing to follow the same file naming pattern we used -previously, we can do what the note suggests: - -1. Make a new *directory* named *network*, the parent module’s name -2. Move the *src/network.rs* file into the new *network* directory and rename - it so that it is now *src/network/mod.rs* -3. Move the submodule file *src/server.rs* into the *network* directory - -Here are commands to carry out these steps: - -```bash -$ mkdir src/network -$ mv src/network.rs src/network/mod.rs -$ mv src/server.rs src/network -``` - -Now if we try to `cargo build`, compilation will work (we’ll still have -warnings though). Our module layout still looks like this, which is exactly the -same as it did when we had all the code in *src/lib.rs* in Listing 7-3: - -```text -communicator - ├── client - └── network - └── server -``` - -The corresponding file layout now looks like this: - -```text -├── src -│   ├── client.rs -│   ├── lib.rs -│   └── network -│   ├── mod.rs -│   └── server.rs -``` - -So when we wanted to extract the `network::server` module, why did we have to -also change the *src/network.rs* file into the *src/network/mod.rs* file, and -also put the code for `network::server` in the `network` directory in -*src/network/server.rs*, instead of just being able to extract the -*network::server* into *src/server.rs*? The reason is that Rust wouldn’t be -able to tell that `server` was supposed to be a submodule of `network` if the -*server.rs* file was in the *src* directory. To make it clearer why Rust can’t -tell, let’s consider a different example where we have this module hierarchy -with all the definitions in *src/lib.rs*: - -```text -communicator - ├── client - └── network - └── client -``` - -In this example, we have three modules again, `client`, `network`, and -`network::client`. If we follow the same steps we originally did above for -extracting modules into files, for the `client` module we would create -*src/client.rs*. For the `network` module, we would create *src/network.rs*. -Then we wouldn’t be able to extract the `network::client` module into a -*src/client.rs* file, because that already exists for the top-level `client` -module! If we put the code in both the `client` and `network::client` modules -in the *src/client.rs* file, Rust would not have any way to know whether the -code was for `client` or for `network::client`. - -Therefore, once we wanted to extract a file for the `network::client` submodule -of the `network` module, we needed to create a directory for the `network` -module instead of a *src/network.rs* file. The code that is in the `network` -module then goes into the *src/network/mod.rs* file, and the submodule -`network::client` can have its own *src/network/client.rs* file. Now the -top-level *src/client.rs* is unambiguously the code that belongs to the -`client` module. - -### Rules of Module File Systems - -In summary, these are the rules of modules with regards to files: - -* If a module named `foo` has no submodules, you should put the declarations - for `foo` in a file named `foo.rs`. -* If a module named `foo` does have submodules, you should put the declarations - for `foo` in a file named `foo/mod.rs`. -* The first two rules apply recursively, so that if a module named `foo` has a - submodule named `bar` and `bar` does not have submodules, you should have the - following files in your `src` directory: - - ```text - ├── foo - │   ├── bar.rs (contains the declarations in `foo::bar`) - │   └── mod.rs (contains the declarations in `foo`, including `mod bar`) - ``` - -* The modules themselves should be declared in their parent module’s file using - the `mod` keyword. - -Next, we’ll talk about the `pub` keyword, and get rid of those warnings! - -## Controlling Visibility with `pub` - -We resolved the error messages shown in Listing 7-4 by moving the `network` and -`network::server` code into the *src/network/mod.rs* and -*src/network/server.rs* files, respectively. At that point, `cargo build` was -able to build our project, but we still get some warning messages about the -`client::connect`, `network::connect`, and `network::server::connect` functions -not being used: - -```bash -warning: function is never used: `connect`, #[warn(dead_code)] on by default -src/client.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/mod.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -So why are we receiving these warnings? After all, we’re building a library -with functions that are intended to be used by our *users*, and not necessarily -by us within our own project, so it shouldn’t matter that these `connect` -functions go unused. The point of creating them is that they will be used by -another project and not our own. - -To understand why this program invokes these warnings, let’s try using the -`connect` library as if we were another project, calling it externally. We can -do that by creating a binary crate in the same directory as our library crate, -by making a `src/main.rs` file containing this code: - -Filename: src/main.rs - -```rust,ignore -extern crate communicator; - -fn main() { - communicator::client::connect(); -} -``` - -We use the `extern crate` command to bring the `communicator` library crate -into scope, because our package actually now contains *two* crates. Cargo -treats *src/main.rs* as the root file of a binary crate, which is separate from -the existing library crate whose root file is *src/lib.rs*. This pattern is -quite common for executable projects: most functionality is in a library crate, -and the binary crate uses that library crate. This way, other programs can also -use the library crate, and it’s a nice separation of concerns. - -Our binary crate right now just calls our library’s `connect` function from the -`client` module. However, invoking `cargo build` will now give us an error -after the warnings: - -```bash -error: module `client` is private - --> src/main.rs:4:5 - | -4 | communicator::client::connect(); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -``` - -Ah ha! This tells us that the `client` module is private, and this is the crux -of the warnings. It’s also the first time we’ve run into the concepts of -*public* and *private* in the context of Rust. The default state of all code in -Rust is private: no one else is allowed to use the code. If you don’t use a -private function within your own program, since your own program is the only -code allowed to use that function, Rust will warn you that the function has -gone unused. - -Once we specify that a function like `client::connect` is public, not only will -our call to that function from our binary crate be allowed, the warning that -the function is unused will go away. Marking something public lets Rust know -that we intend for the function to be used by code outside of our program. Rust -considers the theoretical external usage that’s now possible as the function -“being used.” Thus, when something is marked as public, Rust will not require -that it’s used in our own program and will stop warning that the item is -unused. - -### Making a Function Public - -To tell Rust to make something public, we add the `pub` keyword to the start of -the declaration of the item we want to make public. We’ll focus on fixing the -warning that tells us that `client::connect` has gone unused for now, as well -as the “module `client` is private” error from our binary crate. Modify -`src/lib.rs` to make the `client` module public, like so: - -Filename: src/lib.rs - -```rust,ignore -pub mod client; - -mod network; -``` - -The `pub` goes right before `mod`. Let’s try building again: - -```bash - -error: function `connect` is private - --> src/main.rs:4:5 - | -4 | communicator::client::connect(); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -``` - -Hooray! We have a different error! Yes, different error messages are a cause -for celebration. The new error says “function `connect` is private”, so let’s -edit `src/client.rs` to make `client::connect` public too: - -Filename: src/client.rs - -```rust -pub fn connect() { -} -``` - -And run `cargo build` again: - -```bash -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/mod.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -It compiled, and the warning about `client::connect` not being used is gone! - -Unused code warnings don’t always indicate that something needs to be made -public: if you *didn’t* want these functions to be part of your public API, -unused code warnings could be alerting you to code you no longer needed and can -safely delete. They could also be alerting you to a bug, if you had just -accidentally removed all places within your library where this function is -called. - -In our case though, we *do* want the other two functions to be part of our -crate’s public API, so let’s mark them as `pub` as well to try to get rid of -the remaining warnings. Modify `src/network/mod.rs` to be: - -Filename: src/network/mod.rs - -```rust,ignore -pub fn connect() { -} - -mod server; -``` - -And compile: - -```bash -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/mod.rs:1:1 - | -1 | pub fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -Hmmm, we’re still getting an unused function warning even though -`network::connect` is set to `pub`. This is because the function is public -within the module, but the `network` module that the function resides in is not -public. We’re working from the interior of the library out this time, where -with `client::connect` we worked from the outside in. We need to change -`src/lib.rs` to make `network` public too: - -Filename: src/lib.rs - -```rust,ignore -pub mod client; - -pub mod network; -``` - -Now if we compile, that warning is gone: - -```bash -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -Only one warning left! Try to fix this one on your own! - -### Privacy Rules - -Overall, these are the rules for item visibility: - -1. If an item is public, it can be accessed through any of its - parent modules. -2. If an item is private, it may be accessed only by the current module and its - child modules. - -### Privacy Examples - -Let’s look at a few more examples to get some practice. Create a new library -project and enter the code in Listing 7-5 into your new project’s `src/lib.rs`: - -Filename: src/lib.rs - -```rust,ignore -mod outermost { - pub fn middle_function() {} - - fn middle_secret_function() {} - - mod inside { - pub fn inner_function() {} - - fn secret_function() {} - } -} - -fn try_me() { - outermost::middle_function(); - outermost::middle_secret_function(); - outermost::inside::inner_function(); - outermost::inside::secret_function(); -} -``` - -Before you try to compile this code, make a guess about which lines in `try_me` -function will have errors. Then try compiling to see if you were right, and read -on for discussion of the errors! - -#### Looking at the Errors - -The `try_me` function is in the root module of our project. The module named -`outermost` is private, but the second privacy rule says the `try_me` function -is allowed to access the `outermost` module since `outermost` is in the current -(root) module, as is `try_me`. - -The call to `outermost::middle_function` will work. This is because -`middle_function` is public, and `try_me` is accessing `middle_function` -through its parent module, `outermost` We determined in the previous paragraph -that this module is accessible. - -The call to `outermost::middle_secret_function` will cause a compilation error. -`middle_secret_function` is private, so the second rule applies. The root -module is neither the current module of `middle_secret_function` (`outermost` -is), nor is it a child module of the current module of `middle_secret_function`. - -The module named `inside` is private and has no child modules, so it can only -be accessed by its current module, `outermost`. That means the `try_me` -function is not allowed to call `outermost::inside::inner_function` or -`outermost::inside::secret_function` either. - -#### Fixing the Errors - -Here are some suggestions for changing the code in an attempt to fix the -errors. Before you try each one, make a guess as to whether it will fix the -errors, then compile to see if you’re right and use the privacy rules to -understand why. - -* What if the `inside` module was public? -* What if `outside` was public and `inside` was private? -* What if, in the body of `inner_function`, you called - `::outermost::middle_secret_function()`? (The two colons at the beginning - mean that we want to refer to the namespaces starting from the root - namespace.) - -Feel free to design more experiments and try them out! - -Next, let’s talk about bringing items into a scope with the `use` keyword. - -## Importing Names - -We’ve covered how to call functions defined within a module using the module -name as part of the call, as in the call to the `namespaces` function shown -here in Listing 7-6. - -Filename: src/main.rs - -```rust -pub mod a { - pub mod series { - pub mod of { - pub fn namespaces() {} - } - } -} - -fn main() { - a::series::of::namespaces(); -} -``` - - -Listing 7-6: Calling a function by fully specifying its enclosing module’s -namespaces - - -As you can see, referring to the fully qualified name can get quite lengthy. -Luckily, Rust has a keyword to make these calls more concise. - -### Concise Imports with `use` - -Rust’s `use` keyword works to shorten lengthy function calls by bringing the -modules of the function you want to call into a scope. Here’s an example of -bringing the `a::series::of` namespace into a binary crate’s root scope: - -Filename: src/main.rs - -```rust -pub mod a { - pub mod series { - pub mod of { - pub fn namespaces() {} - } - } -} - -use a::series::of; - -fn main() { - of::namespaces(); -} -``` - -The line `use a::series::of;` has made it so that anywhere in this scope that -we would want to refer to the `of` namespace, instead of having to say -`a::series::of`, we can replace that with `of`. - -The `use` keyword brings only what we have specified into scope; it does not -bring children of modules into scope. That’s why we still have to say -`of::namespaces` when we want to call the `namespaces` function. - -We could have chosen to bring the function itself into scope, by instead -specifying the function in the `use` as follows: - -```rust -pub mod a { - pub mod series { - pub mod of { - pub fn namespaces() {} - } - } -} - -use a::series::of::namespaces; - -fn main() { - namespaces(); -} -``` - -This allows us to exclude any of the modules and just reference the function at -the callsite. - -Since enums also form this kind of namespace, we can import an enum’s variants -with `use` as well. For any kind of `use` statement, if you’re importing -multiple items from one namespace, you can list them using curly braces and -commas in the last position, like so: - -```rust -enum TrafficLight { - Red, - Yellow, - Green, -} - -use TrafficLight::{Red, Yellow}; - -fn main() { - let red = Red; - let yellow = Yellow; - let green = TrafficLight::Green; // because we didn’t `use` TrafficLight::Green -} -``` - -### Glob Imports with `*` - -To import all the items in a namespace at once, we can use the `*` syntax. For -example: - -```rust -enum TrafficLight { - Red, - Yellow, - Green, -} - -use TrafficLight::*; - -fn main() { - let red = Red; - let yellow = Yellow; - let green = Green; -} -``` - -The `*` is called a *glob*, and it will import everything that’s visible inside -of the namespace. Globs should be used sparingly: they are convenient, but you -might also pull in more things than you expected and cause naming conflicts. - -### Using `super` to Access a Parent Module - -As you now know, when you create a library crate, Cargo makes a `tests` module -for you. Let’s go into more detail about that now. In your `communicator` -project, open `src/lib.rs`. - -Filename: src/lib.rs - -```rust,ignore -pub mod client; - -pub mod network; - -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} -``` - -We’ll explain more about testing in Chapter 12, but parts of this should make -sense now: we have a module named `tests` that lives next to our other modules -and contains one function named `it_works`. Even though there are special -annotations, the `tests` module is just another module! So our module hierarchy -looks like this: - -```text -communicator - ├── client - ├── network - | └── client - └── tests -``` - - -Tests are for exercising the code within our library, so let’s try to call -our `client::connect` function from this `it_works` function, even though -we’re not going to be checking any functionality right now: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - client::connect(); - } -} -``` - -Run the tests by invoking the `cargo test` command: - -```bash -$ cargo test - Compiling communicator v0.1.0 (file:///projects/communicator) -error[E0433]: failed to resolve. Use of undeclared type or module `client` - --> src/lib.rs:9:9 - | -9 | client::connect(); - | ^^^^^^^^^^^^^^^ Use of undeclared type or module `client` - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -The compilation failed, but why? We don’t need to place `communicator::` in -front of the function like we did in `src/main.rs` because we are definitely -within the `communicator` library crate here. The reason is that paths are -always relative to the current module, which here is `tests`. The only -exception is in a `use` statement, where paths are relative to the crate root -by default. Our `tests` module needs the `client` module in its scope! - -So how do we get back up one module in the module hierarchy to be able to call -the `client::connect` function in the `tests` module? In the `tests` module, we -can either use leading colons to let Rust know that we want to start from the -root and list the whole path: - -```rust,ignore -::client::connect(); -``` - -Or we can use `super` to move up one module in the hierarchy from our current -module: - -```rust,ignore -super::client::connect(); -``` - -These two options don’t look all that different in this example, but if you’re -deeper in a module hierarchy, starting from the root every time would get long. -In those cases, using `super` to get from the current module to sibling modules -is a good shortcut. Plus, if you’ve specified the path from the root in many -places in your code and then you rearrange your modules by moving a subtree to -another place, you’d end up needing to update the path in a lot of places, -which would be tedious. - -It would also be annoying to have to type `super::` all the time in each test, -but you’ve already seen the tool for that solution: `use`! The `super::` -functionality changes the path you give to `use` so that it is relative to the -parent module instead of to the root module. - -For these reasons, in the `tests` module especially, `use super::something` is -usually the way to go. So now our test looks like this: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - use super::client; - - #[test] - fn it_works() { - client::connect(); - } -} -``` - -If we run `cargo test` again, the test will pass and the first part of the test -result output will be: - -```bash -$ cargo test - Compiling communicator v0.1.0 (file:///projects/communicator) - Running target/debug/communicator-92007ddb5330fa5a - -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -## Summary - -Now you know techniques for organizing your code! Use these to group related -functionality together, keep files from getting too long, and present a tidy -public API to users of your library. - -Next, let’s look at some collection data structures in the standard library -that you can make use of in your nice, neat code! diff --git a/nostarch/chapter08.md b/nostarch/chapter08.md deleted file mode 100644 index c651818..0000000 --- a/nostarch/chapter08.md +++ /dev/null @@ -1,973 +0,0 @@ - -[TOC] - -# Fundamental Collections - -Rust's standard library includes a number of really useful data structures -called *collections*. Most other data types represent one specific value, but -collections can contain multiple values. Unlike the built-in array and tuple -types, the data these collections point to is stored on the heap, which means -the amount of data does not need to be known at compile time and can grow or -shrink as the program runs. Each kind of collection has different capabilities -and costs, and choosing an appropriate one for the situation you're in is a -skill you'll develop over time. In this chapter, we'll go over three -collections which are used very often in Rust programs: - -* A *vector* allows us to store a variable number of values next to each other. -* A *string* is a collection of characters. We've seen the `String` type - before, but we'll talk about it in depth now. -* A *hash map* allows us to associate a value with a particular key. - -There are more specialized variants of each of these data structures for -particular situations, but these are the most fundamental and common. We're -going to discuss how to create and update each of the collections, as well as -what makes each special. - -## Vectors - -The first type we'll look at is `Vec`, also known as a *vector*. Vectors -allow us to store more than one value in a single data structure that puts all -the values next to each other in memory. Vectors can only store values of the -same type. They are useful in situations where you have a list of items, such -as the lines of text in a file or the prices of items in a shopping cart. - -### Creating a New Vector - -To create a new, empty vector, we can call the `Vec::new` function: - -```rust -let v: Vec = Vec::new(); -``` - -Note that we added a type annotation here. Since we aren't inserting any values -into this vector, Rust doesn't know what kind of elements we intend to store. -This is an important point. Vectors are homogenous: they may store many values, -but those values must all be the same type. Vectors are implemented using -generics, which Chapter 10 will cover how to use in your own types. For now, -all you need to know is that the `Vec` type provided by the standard library -can hold any type, and when a specific `Vec` holds a specific type, the type -goes within angle brackets. We've told Rust that the `Vec` in `v` will hold -elements of the `i32` type. - -In real code, Rust can infer the type of value we want to store once we insert -values, so you rarely need to do this type annotation. It's more common to -create a `Vec` that has initial values, and Rust provides the `vec!` macro for -convenience. The macro will create a new `Vec` that holds the values we give -it. This will create a new `Vec` that holds the values `1`, `2`, and `3`: - -```rust -let v = vec![1, 2, 3]; -``` - -Because we've given initial `i32` values, Rust can infer that the type of `v` -is `Vec`, and the type annotation isn't necessary. Let's look at how to -modify a vector next. - -### Updating a Vector - -To create a vector then add elements to it, we can use the `push` method: - -```rust -let mut v = Vec::new(); - -v.push(5); -v.push(6); -v.push(7); -v.push(8); -``` - -As with any variable as we discussed in Chapter 3, if we want to be able to -change its value, we need to make it mutable with the `mut` keyword. The -numbers we place inside are all `i32`s, and Rust infers this from the data, so -we don't need the `Vec` annotation. - -### Dropping a Vector Drops its Elements - -Like any other `struct`, a vector will be freed when it goes out of scope: - -```rust -{ - let v = vec![1, 2, 3, 4]; - - // do stuff with v - -} // <- v goes out of scope and is freed here -``` - -When the vector gets dropped, all of its contents will also be dropped, meaning -those integers it holds will be cleaned up. This may seem like a -straightforward point, but can get a little more complicated once we start to -introduce references to the elements of the vector. Let's tackle that next! - -### Reading Elements of Vectors - -Now that you know how to create, update, and destroy vectors, knowing how to -read their contents is a good next step. There are two ways to reference a -value stored in a vector. In the examples, we've annotated the types of the -values that are returned from these functions for extra clarity. - -This example shows both methods of accessing a value in a vector either with -indexing syntax or the `get` method: - -```rust -let v = vec![1, 2, 3, 4, 5]; - -let third: &i32 = &v[2]; -let third: Option<&i32> = v.get(2); -``` - -There are a few things to note here. First, that we use the index value of `2` -to get the third element: vectors are indexed by number, starting at zero. -Second, the two different ways to get the third element are: using `&` and -`[]`s, which gives us a reference, or using the `get` method with the index -passed as an argument, which gives us an `Option<&T>`. - -The reason Rust has two ways to reference an element is so that you can choose -how the program behaves when you try to use an index value that the vector -doesn't have an element for. As an example, what should a program do if it has -a vector that holds five elements then tries to access an element at index 100 -like this: - -```rust,should_panic -let v = vec![1, 2, 3, 4, 5]; - -let does_not_exist = &v[100]; -let does_not_exist = v.get(100); -``` - -When you run this, you will find that with the first `[]` method, Rust will -cause a `panic!` when a non-existent element is referenced. This method would -be preferable if you want your program to consider an attempt to access an -element past the end of the vector to be a fatal error that should crash the -program. - -When the `get` method is passed an index that is outside the array, it will -return `None` without `panic!`ing. You would use this if accessing an element -beyond the range of the vector will happen occasionally under normal -circumstances. Your code can then have logic to handle having either -`Some(&element)` or `None`, as we discussed in Chapter 6. For example, the -index could be coming from a person entering a number. If they accidentally -enter a number that's too large and your program gets a `None` value, you could -tell the user how many items are in the current `Vec` and give them another -chance to enter a valid value. That would be more user-friendly than crashing -the program for a typo! - -#### Invalid References - -Once the program has a valid reference, the borrow checker will enforce the -ownership and borrowing rules covered in Chapter 4 to ensure this reference and -any other references to the contents of the vector stay valid. Recall the rule -that says we can't have mutable and immutable references in the same scope. -That rule applies in this example, where we hold an immutable reference to the -first element in a vector and try to add an element to the end: - -```rust,ignore -let mut v = vec![1, 2, 3, 4, 5]; - -let first = &v[0]; - -v.push(6); -``` - -Compiling this will give us this error: - -```text -error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable - | -4 | let first = &v[0]; - | - immutable borrow occurs here -5 | -6 | v.push(6); - | ^ mutable borrow occurs here -7 | } - | - immutable borrow ends here -``` - -This code might look like it should work: why should a reference to the first -element care about what changes about the end of the vector? The reason why -this code isn't allowed is due to the way vectors work. Adding a new element -onto the end of the vector might require allocating new memory and copying the -old elements over to the new space, in the circumstance that there isn't enough -room to put all the elements next to each other where the vector was. In that -case, the reference to the first element would be pointing to deallocated -memory. The borrowing rules prevent programs from ending up in that situation. - -> Note: For more on this, see The Nomicon at *https://doc.rust-lang.org/stable/nomicon/vec.html*. - - -### Using an Enum to Store Multiple Types - -At the beginning of this chapter, we said that vectors can only store values -that are all the same type. This can be inconvenient; there are definitely use -cases for needing to store a list of things of different types. Luckily, the -variants of an enum are all defined under the same enum type. When we need to -store elements of a different type in a vector this scenario, we can define and -use an enum! - -For example, let's say we want to get values from a row in a spreadsheet, where -some of the columns in the row contain integers, some floating point numbers, -and some strings. We can define an enum whose variants will hold the different -value types, and then all of the enum variants will be considered the same -type, that of the enum. Then we can create a vector that holds that enum and -so, ultimately, holds different types: - -```rust -enum SpreadsheetCell { - Int(i32), - Float(f64), - Text(String), -} - -let row = vec![ - SpreadsheetCell::Int(3), - SpreadsheetCell::Text(String::from("blue")), - SpreadsheetCell::Float(10.12), -]; -``` - -The reason Rust needs to know exactly what types will be in the vector at -compile time is so that it knows exactly how much memory on the heap will be -needed to store each element. A secondary advantage to this is that we can be -explicit about what types are allowed in this vector. If Rust allowed a vector -to hold any type, there would be a chance that one or more of the types would -cause errors with the operations performed on the elements of the vector. Using -an enum plus a `match` means that Rust will ensure at compile time that we -always handle every possible case, as we discussed in Chapter 6. - - - - -If you don't know at the time that you're writing a program the exhaustive set -of types the program will get at runtime to store in a vector, the enum -technique won't work. Insetad, you can use a trait object, which we'll cover in -Chapter 13. - -Now that we've gone over some of the most common ways to use vectors, be sure -to take a look at the API documentation for all of the many useful methods -defined on `Vec` by the standard library. For example, in addition to `push` -there's a `pop` method that will remove and return the last element. Let's move -on to the next collection type: `String`! - - - - - -## Strings - -We've already talked about strings a bunch in Chapter 4, but let's take a more -in-depth look at them now. Strings are an area that new Rustaceans commonly get -stuck on. This is due to a combination of three things: Rust's propensity for -making sure to expose possible errors, strings being a more complicated data -structure than many programmers give them credit for, and UTF-8. These things -combine in a way that can seem difficult when coming from other languages. - -The reason Strings are in the collections chapter is that strings are -implemented as a collection of bytes plus some methods to provide useful -functionality when those bytes are interpreted as text. In this section, we'll -talk about the operations on `String` that every collection type has, like -creating, updating, and reading. We'll also discuss the ways in which `String` -is different than the other collections, namely how indexing into a `String` is -complicated by the differences in which people and computers interpret `String` -data. - -### What is a String? - -Before we can dig into those aspects, we need to talk about what exactly we -mean by the term 'string'. Rust actually only has one string type in the core -language itself: `str`, the string slice, which is usually seen in its borrowed -form, `&str`. We talked about *string slices* in Chapter 4: these are a -reference to some UTF-8 encoded string data stored elsewhere. String literals, -for example, are stored in the binary output of the program, and are therefore -string slices. - -The type called `String` is provided in Rust's standard library rather than -coded into the core language, and is a growable, mutable, owned, UTF-8 encoded -string type. When Rustaceans talk about 'strings' in Rust, they usually mean -both the `String` and the string slice `&str` types, not just one of those. -This section is largely about `String`, but both these types are used heavily -in Rust's standard library. Both `String` and string slices are UTF-8 encoded. - -Rust's standard library also includes a number of other string types, such as -`OsString`, `OsStr`, `CString`, and `CStr`. Library crates may provide even -more options for storing string data. Similar to the `*String`/`*Str` naming, -they often provide an owned and borrowed variant, just like `String`/`&str`. -These string types may store different encodings or be represented in memory in -a different way, for example. We won't be talking about these other string -types in this chapter; see their API documentation for more about how to use -them and when each is appropriate. - -### Creating a New String - -Many of the same operations available with `Vec` are available with `String` as -well, starting with the `new` function to create a string, like so: - -```rust -let s = String::new(); -``` - -This creates a new empty string called `s` that we can then load data into. - -Often, we'll have some initial data that we'd like to start the string off -with. For that, we use the `to_string` method, which is available on any type -that implements the `Display` trait, which string literals do: - -```rust -let data = "initial contents"; - -let s = data.to_string(); - -// the method also works on a literal directly: -let s = "initial contents".to_string(); -``` - -This creates a string containing `initial contents`. - -We can also use the function `String::from` to create a `String` from a string -literal. This is equivalent to using `to_string`: - -```rust -let s = String::from("initial contents"); -``` - -Because strings are used for so many things, there are many different generic -APIs that can be used for strings, so there are a lot of options. Some of them -can feel redundant, but they all have their place! In this case, `String::from` -and `.to_string` end up doing the exact same thing, so which you choose is a -matter of style. - -Remember that strings are UTF-8 encoded, so we can include any properly encoded -data in them: - -```rust -let hello = "السلام عليكم"; -let hello = "Dobrý den"; -let hello = "Hello"; -let hello = "שָׁלוֹם"; -let hello = "नमस्ते"; -let hello = "こんにちは"; -let hello = "안녕하세요"; -let hello = "你好"; -let hello = "Olá"; -let hello = "Здравствуйте"; -let hello = "Hola"; -``` - -### Updating a String - -A `String` can can grow in size and its contents can change just like the -contents of a `Vec`, by pushing more data into it. In addition, `String` has -concatenation operations implemented with the `+` operator for convenience. - -#### Appending to a String with Push - -We can grow a `String` by using the `push_str` method to append a string slice: - -```rust -let mut s = String::from("foo"); -s.push_str("bar"); -``` - -`s` will contain "foobar" after these two lines. The `push_str` method takes a -string slice because we don't necessarily want to take ownership of the -argument. For example, it would be unfortunate if we weren't able to use `s2` -after appending its contents to `s1`: - -```rust -let mut s1 = String::from("foo"); -let s2 = String::from("bar"); -s1.push_str(&s2); -``` - -The `push` method is defined to take a single character as an argument and add -it to the `String`: - -```rust -let mut s = String::from("lo"); -s.push('l'); -``` - -After this, `s` will contain "lol". - -#### Concatenation with the + Operator or the `format!` Macro - -Often, we'll want to combine two existing strings together. One way is to use -the `+` operator like this: - -```rust -let s1 = String::from("Hello, "); -let s2 = String::from("world!"); -let s3 = s1 + &s2; // Note that s1 has been moved here and can no longer be used -``` - -After this code the String `s3` will contain `Hello, world!`. The reason that -`s1` is no longer valid after the addition and the reason that we used a -reference to `s2` has to do with the signature of the method that gets called -when we use the `+` operator. The `+` operator uses the `add` method, whose -signature looks something like this: - -```rust,ignore -fn add(self, s: &str) -> String { -``` - -This isn't the exact signature that's in the standard library; there `add` is -defined using generics. Here, we're looking at the signature of `add` with -concrete types substituted for the generic ones, which is what happens when we -call this method with `String` values. This signature gives us the clues we -need to understand the tricky bits of the `+` operator. - -First of all, `s2` has an `&`, meaning that we are adding a *reference* of the -second string to the first string. This is because of the `s` argument in the -`add` function: we can only add a `&str` to a `String`, we can't add two -`String`s together. Remember back in Chapter 4 when we talked about how -`&String` will coerce to `&str`: we write `&s2` so that the `String` will -coerce to the proper type, `&str`. Because this method does not take ownership -of the argument, `s2` will still be valid after this operation. - -Second, we can see in the signature that `add` takes ownership of `self`, -because `self` does *not* have an `&`. This means `s1` in the above example -will be moved into the `add` call and no longer be valid after that. So while -`let s3 = s1 + &s2;` looks like it will copy both strings and create a new one, -this statement actually takes ownership of `s1`, appends a copy of `s2`'s -contents, then returns ownership of the result. In other words, it looks like -it's making a lot of copies, but isn't: the implementation is more efficient -than copying. - -If we need to concatenate multiple strings, the behavior of `+` gets unwieldy: - -```rust -let s1 = String::from("tic"); -let s2 = String::from("tac"); -let s3 = String::from("toe"); - -let s = s1 + "-" + &s2 + "-" + &s3; -``` - -`s` will be "tic-tac-toe" at this point. With all of the `+` and `"` -characters, it gets hard to see what's going on. For more complicated string -combining, we can use the `format!` macro: - -```rust -let s1 = String::from("tic"); -let s2 = String::from("tac"); -let s3 = String::from("toe"); - -let s = format!("{}-{}-{}", s1, s2, s3); -``` - - - - - -This code will also set `s` to "tic-tac-toe". The `format!` macro works in the -same way as `println!`, but instead of printing the output to the screen, it -returns a `String` with the contents. This version is much easier to read, and -also does not take ownership of any of its arguments. - -### Indexing into Strings - -In many other languages, accessing individual characters in a string by -referencing them by index is a valid and common operation. In Rust, however, if -we try to access parts of a `String` using indexing syntax, we'll get an error. -That is, this code: - -```rust,ignore -let s1 = String::from("hello"); -let h = s1[0]; -``` - -will result in this error: - -```text -error: the trait bound `std::string::String: std::ops::Index<_>` is not -satisfied [--explain E0277] - |> - |> let h = s1[0]; - |> ^^^^^ -note: the type `std::string::String` cannot be indexed by `_` -``` - -The error and the note tell the story: Rust strings don't support indexing. So -the follow-up question is, why not? In order to answer that, we have to talk a -bit about how Rust stores strings in memory. - -#### Internal Representation - -A `String` is a wrapper over a `Vec`. Let's take a look at some of our -properly-encoded UTF-8 example strings from before. First, this one: - -```rust -let len = "Hola".len(); -``` - -In this case, `len` will be four, which means the `Vec` storing the string -"Hola" is four bytes long: each of these letters takes one byte when encoded in -UTF-8. What about this example, though? - -```rust -let len = "Здравствуйте".len(); -``` - -A person asked how long the string is might say 12. However, Rust's answer -is 24. This is the number of bytes that it takes to encode "Здравствуйте" in -UTF-8, since each character takes two bytes of storage. Therefore, an index -into the string's bytes will not always correlate to a valid character. - -To demonstrate, consider this invalid Rust code: - -```rust,ignore -let hello = "Здравствуйте"; -let answer = &hello[0]; -``` - -What should the value of `answer` be? Should it be `З`, the first letter? When -encoded in UTF-8, the first byte of `З` is `208`, and the second is `151`, so -`answer` should in fact be `208`, but `208` is not a valid character on its -own. Returning `208` is likely not what a person would want if they asked for -the first letter of this string, but that's the only data that Rust has at byte -index 0. Returning the byte value is probably not what people want, even with -only latin letters: `&"hello"[0]` would return `104`, not `h`. To avoid -returning an unexpected value and causing bugs that might not be discovered -immediately, Rust chooses to not compile this code at all and prevent -misunderstandings earlier. - -#### Bytes and Scalar Values and Grapheme Clusters! Oh my! - -This leads to another point about UTF-8: there are really three relevant ways -to look at strings, from Rust's perspective: as bytes, scalar values, and -grapheme clusters (the closest thing to what people would call 'letters'). - -If we look at the Hindi word "नमस्ते" written in the Devanagari script, it is -ultimately stored as a `Vec` of `u8` values that looks like this: - -```text -[224, 164, 168, 224, 164, 174, 224, 164, 184, 224, 165, 141, 224, 164, 164, 224, 165, 135] -``` - -That's 18 bytes, and is how computers ultimately store this data. If we look at -them as Unicode scalar values, which are what Rust's `char` type is, those -bytes look like this: - -```text -['न', 'म', 'स', '्', 'त', 'े'] -``` - -There are six `char` values here, but the fourth and sixth are not letters, -they're diacritics that don't make sense on their own. Finally, if we look at -them as grapheme clusters, we'd get what a person would call the four letters -that make up this word: - -```text -["न", "म", "स्", "ते"] -``` - -Rust provides different ways of interpreting the raw string data that computers -store so that each program can choose the interpretation it needs, no matter -what human language the data is in. - -A final reason Rust does not allow you to index into a `String` to get a -character is that indexing operations are expected to always take constant time -(O(1)). It isn't possible to guarantee that performance with a `String`, -though, since Rust would have to walk through the contents from the beginning -to the index to determine how many valid characters there were. - -All of these problems mean that Rust does not implement `[]` for `String`, so -we cannot directly do this. - -### Slicing Strings - -However, indexing the *bytes* of a string is very useful, and is not expected -to be fast. While we can't use `[]` with a single number, we _can_ use `[]` -with a range to create a string slice containing particular bytes: - -```rust -let hello = "Здравствуйте"; - -let s = &hello[0..4]; -``` - -Here, `s` will be a `&str` that contains the first four bytes of the string. -Earlier, we mentioned that each of these characters was two bytes, so that -means that `s` will be "Зд". - -What would happen if we did `&hello[0..1]`? The answer: it will panic at -runtime, in the same way that accessing an invalid index in a vector does: - -```text -thread 'main' panicked at 'index 0 and/or 1 in `Здравствуйте` do not lie on -character boundary', ../src/libcore/str/mod.rs:1694 -``` - -You should use this with caution, since it can cause your program to crash. - -### Methods for Iterating Over Strings - -Luckily, there are other ways we can access elements in a String. - -If we need to perform operations on individual characters, the best way to do -so is to use the `chars` method. Calling `chars` on "नमस्ते" separates out and -returns six values of type `char`, and you can iterate over the result in order -to access each element: - -```rust -for c in "नमस्ते".chars() { - println!("{}", c); -} -``` - -This code will print: - -```text -न -म -स -् -त -े -``` - -The `bytes` method returns each raw byte, which might be appropriate for your -domain: - -```rust -for b in "नमस्ते".bytes() { - println!("{}", b); -} -``` - -This code will print the 18 bytes that make up this `String`, starting with: - -```text -224 -164 -168 -224 -// ... etc -``` - -But make sure to remember that valid UTF-8 characters may be made up of more -than one byte. - -Getting grapheme clusters from `String`s is complex, so this functionality is -not provided by the standard library. There are crates available on crates.io -if this is the functionality you need. - - - - - -### Strings are Not so Simple - -To summarize, strings are complicated. Different programming languages make -different choices about how to present this complexity to the programmer. Rust -has chosen to make the correct handling of `String` data the default behavior -for all Rust programs, which does mean programmers have to put more thought -into handling UTF-8 data upfront. This tradeoff exposes more of the complexity -of strings than other programming languages do, but this will prevent you from -having to handle errors involving non-ASCII characters later in your -development lifecycle. - -Let's switch to something a bit less complex: Hash Map! - -## Hash Maps - -The last of our fundamental collections is the *hash map*. The type `HashMap` stores a mapping of keys of type `K` to values of type `V`. It does this -via a *hashing function*, which determines how it places these keys and values -into memory. Many different programming languages support this kind of data -structure, but often with a different name: hash, map, object, hash table, or -associative array, just to name a few. - -Hash maps are useful for when you want to be able to look up data not by an -index, as you can with vectors, but by using a key that can be of any type. For -example, in a game, you could keep track of each team's score in a hash map -where each key is a team's name and the values are each team's score. Given a -team name, you can retrieve their score. - -We'll go over the basic API of hash maps in this chapter, but there are many -more goodies hiding in the functions defined on `HashMap` by the standard -library. As always, check the standard library documentation for more -information. - -### Creating a New Hash Map - -We can create an empty `HashMap` with `new`, and add elements with `insert`. -Here we're keeping track of the scores of two teams whose names are Blue and -Yellow. The Blue team will start with 10 points and the Yellow team starts with -50: - -```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Yellow"), 50); -``` - -Note that we need to first `use` the `HashMap` from the collections portion of -the standard library. Of our three fundamental collections, this one is the -least often used, so it's not included in the features imported automatically -in the prelude. Hash maps also have less support from the standard library; -there's no built-in macro to construct them, for example. - -Just like vectors, hash maps store their data on the heap. This `HashMap` has -keys of type `i32` and values of type `&str`. Like vectors, hash maps are -homogenous: all of the keys must have the same type, and all of the values must -have the same type. - -Another way of constructing a hash map is by using the `collect` method on a -vector of tuples, where each tuple consists of a key and its value. The -`collect` method gathers up data into a number of collection types, including -`HashMap`. For example, if we had the team names and initial scores in two -separate vectors, we can use the `zip` method to create a vector of tuples -where "Blue" is paired with 10, and so forth. Then we can use the `collect` -method to turn that vector of tuples into a `HashMap`: - -```rust -use std::collections::HashMap; - -let teams = vec![String::from("Blue"), String::from("Yellow")]; -let initial_scores = vec![10, 50]; - -let scores: HashMap<_, _> = teams.iter().zip(initial_scores.iter()).collect(); -``` - -The type annotation `HashMap<_, _>` is needed here because it's possible to -`collect` into many different data structures, and Rust doesn't know which you -want unless you specify. For the type parameters for the key and value types, -however, we use underscores and Rust can infer the types that the hash map -contains based on the types of the data in the vector. - -### Hashmaps and Ownership - -For types that implement the `Copy` trait, like `i32`, the values are copied -into the hash map. For owned values like `String`, the values will be moved and -the hash map will be the owner of those values: - -```rust -use std::collections::HashMap; - -let field_name = String::from("Favorite color"); -let field_value = String::from("Blue"); - -let mut map = HashMap::new(); -map.insert(field_name, field_value); -// field_name and field_value are invalid at this point -``` - -We would not be able to use the bindings `field_name` and `field_value` after -they have been moved into the hash map with the call to `insert`. - -If we insert references to values into the hash map, the values themselves will -not be moved into the hash map. The values that the references point to must be -valid for at least as long as the hash map is valid, though. We will talk more -about these issues in the Lifetimes section of Chapter 10. - -### Accessing Values in a Hash Map - -We can get a value out of the hash map by providing its key to the `get` method: - -```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Yellow"), 50); - -let team_name = String::from("Blue"); -let score = scores.get(&team_name); -``` - -Here, `score` will have the value that's associated with the Blue team, and the -result will be `Some(10)`. The result is wrapped in `Some` because `get` -returns an `Option`; if there's no value for that key in the hash map, `get` -will return `None`. The program will need to handle the `Option` in one of -the ways that we covered in Chapter 6. - -We can iterate over each key/value pair in a hash map in a similar manner as we -do with vectors, using a `for` loop: - -```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Yellow"), 50); - -for (key, value) in &scores { - println!("{}: {}", key, value); -} -``` - -This will print each pair, in an arbitrary order: - -```text -Yellow: 50 -Blue: 10 -``` - -### Updating a Hash Map - - - - -While the number of keys and values is growable, each individual key can only -have one value associated with it at a time. When we want to change the data in -a hash map, we have to decide how to handle the case when a key already has a -value assigned. We could choose to replace the old value with the new value, -completely disregarding the old value. We could choose to keep the old value -and ignore the new value, and only add the new value if the key *doesn't* -already have a value. Or we could combine the old value and the new value. -Let's look at how to do each of these! - -#### Overwriting a Value - -If we insert a key and a value into a hashmap, then insert that same key with a -different value, the value associated with that key will be replaced. Even -though this following code calls `insert` twice, the hash map will only contain -one key/value pair because we're inserting the value for the Blue team's key -both times: - -```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Blue"), 25); - -println!("{:?}", scores); -``` - -This will print `{"Blue": 25}`. The original value of 25 has been overwritten. - - -#### Only Insert If the Key Has No Value - -It's common to want to check if a particular key has a value and, if it does -not, insert a value for it. Hash maps have a special API for this, called -`entry`, that takes the key we want to check as an argument. The return value -of the `entry` function is an enum, `Entry`, that represents a value that might -or might not exist. Let's say that we want to check if the key for the Yellow -team has a value associated with it. If it doesn't, we want to insert the value -50, and the same for the Blue team. With the entry API, the code for this -looks like: - -```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); -scores.insert(String::from("Blue"), 10); - -scores.entry(String::from("Yellow")).or_insert(50); -scores.entry(String::from("Blue")).or_insert(50); - -println!("{:?}", scores); -``` - -The `or_insert` method on `Entry` returns the value for the `Entry`'s key if it -exists, and if not, inserts its argument as the new value for the `Entry`'s key -and returns that. This is much cleaner than writing the logic ourselves, and in -addition, plays more nicely with the borrow checker. - -This code will print `{"Yellow": 50, "Blue": 10}`. The first call to `entry` -will insert the key for the Yellow team with the value 50, since the Yellow -team doesn't have a value already. The second call to `entry` will not change -the hash map since the Blue team already has the value 10. - -#### Update a Value Based on the Old Value - -Another common use case for hash maps is to look up a key's value then update -it, based on the old value. For instance, if we wanted to count how many times -each word appeared in some text, we could use a hash map with the words as keys -and increment the value to keep track of how many times we've seen that word. -If this is the first time we've seen a word, we'll first insert the value `0`. - -```rust -use std::collections::HashMap; - -let text = "hello world wonderful world"; - -let mut map = HashMap::new(); - -for word in text.split_whitespace() { - let count = map.entry(word).or_insert(0); - *count += 1; -} - -println!("{:?}", map); -``` - -This will print `{"world": 2, "hello": 1, "wonderful": 1}`. The `or_insert` -method actually returns a mutable reference (`&mut V`) to the value for this -key. Here we store that mutable reference in the `count` variable, so in order -to assign to that value we must first dereference `count` using the asterisk -(`*`). The mutable reference goes out of scope at the end of the `for` loop, so -all of these changes are safe and allowed by the borrowing rules. - -### Hashing Function - -By default, `HashMap` uses a cryptographically secure hashing function that can -provide resistance to Denial of Service (DoS) attacks. This is not the fastest -hashing algorithm out there, but the tradeoff for better security that comes -with the drop in performance is worth it. If you profile your code and find -that the default hash function is too slow for your purposes, you can switch to -another function by specifying a different *hasher*. A hasher is a type that -implements the `BuildHasher` trait. We'll be talking about traits and how to -implement them in Chapter 10. - -## Summary - -Vectors, strings, and hash maps will take you far in programs where you need to -store, access, and modify data. Here are some exercises you should now be -equipped to solve: - -1. Given a list of integers, use a vector and return the mean (average), median - (when sorted, the value in the middle position), and mode (the value that - occurs most often; a hash map will be helpful here) of the list. -2. Convert strings to Pig Latin, where the first consonant of each word is - moved to the end of the word with an added "ay", so "first" becomes - "irst-fay". Words that start with a vowel get "hay" added to the end instead - ("apple" becomes "apple-hay"). Remember about UTF-8 encoding! -3. Using a hash map and vectors, create a text interface to allow a user to add - employee names to a department in the company. For example, "Add Sally to - Engineering" or "Add Amir to Sales". Then let the user retrieve a list of all - people in a department or all people in the company by department, sorted - alphabetically. - -The standard library API documentation describes methods these types have that -will be helpful for these exercises! - -We're getting into more complex programs where operations can fail, which means -it's a perfect time to go over error handling next! diff --git a/nostarch/chapter09.md b/nostarch/chapter09.md deleted file mode 100644 index 8660d63..0000000 --- a/nostarch/chapter09.md +++ /dev/null @@ -1,1072 +0,0 @@ - -[TOC] - -# Error Handling - -Rust's commitment to reliability extends to error handling. Errors are a fact -of life in software, so Rust has a number of features for handling situations -in which something goes wrong. In many cases, Rust will require you to -acknowledge the possibility of an error occurring and take some action before -your code will compile. This makes your program more robust by ensuring that you -won't only discover errors after you've deployed your code to production. - -Rust groups errors into two major categories: *recoverable* and *unrecoverable* -errors. Recoverable errors are situations when it's usually reasonable to -report the problem to the user and retry the operation, like a file not being -found. Unrecoverable errors are always symptoms of bugs, like trying to access -a location beyond the end of an array. - -Most languages don't distinguish between the two kinds of errors, and handle -both in the same way using mechanisms like exceptions. Rust doesn't have -exceptions. Instead, it has the value `Result` for recoverable errors and -the `panic!` macro that stops execution when it encounters unrecoverable -errors. This chapter will cover calling `panic!` first, then talk about -returning `Result` values. Finally, we'll discuss considerations to take -into account when deciding whether to try to recover from an error or to stop -execution. - -## Unrecoverable Errors with `panic!` - -Sometimes, bad things happen, and there's nothing that you can do about it. For -these cases, Rust has the `panic!` macro. When this macro executes, your -program will print a failure message, unwind and clean up the stack, and then -quit. The most common situation this occurs in is when a bug of some kind has -been detected and it's not clear to the programmer how to handle the error. - - - -> #### Unwinding -> By default, when a `panic!` occurs, the program starts -> *unwinding*, which means Rust walks back up the stack and cleans up the data -> from each function it encounters, but this walking and cleanup is a lot of -> work. The alternative is to immediately `abort`, which ends the program -> without cleaning up. Memory that the program was using will then need to be -> cleaned up by the operating system. If in your program you need to make -> the resulting binary as small as possible, you can switch from unwinding to -> aborting on panic by adding `panic = 'abort'` to the appropriate `[profile]` -> sections in your `Cargo.toml`. For example, if you want to abort on panic in -> release mode: -> -> ```toml -> profile.release -> panic = 'abort' -> ``` - - - -Let's try calling `panic!()` with a simple program: - -Filename: src/main.rs - -```rust,should_panic -fn main() { - panic!("crash and burn"); -} -``` - -If you run it, you'll see something like this: - -```text -$ cargo run - Compiling panic v0.1.0 (file:///projects/panic) - Finished debug [unoptimized + debuginfo] target(s) in 0.25 secs - Running `target/debug/panic` -thread 'main' panicked at 'crash and burn', src/main.rs:2 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/panic` (exit code: 101) -``` - -The last three lines contain the error message caused by the call to `panic!`. -The first line shows our panic message and the place in our source code where -the panic occurred: `src/main.rs:2` indicates that it's the second like of our -*main.rs* file. - -In this case, the line indicated is part of our code, and if we go to that line -we see the `panic!` macro call. In other cases, the `panic!` call might be in -code that our code calls. The filename and line number reported by the error -message will be someone else's code where the `panic!` macro is called, not the -line of our code that eventually led to the `panic!`. We can use the backtrace -of the functions the `panic!` call came from to figure this out. - -### Using a `panic!` Backtrace - -Let's look at another example to see what it's like when a `panic!` call comes -from a library because of a bug in our code instead of from our code calling -the macro directly: - -Filename: src/main.rs - -```rust,should_panic -fn main() { - let v = vec![1, 2, 3]; - - v[100]; -} -``` - -We're attempting to access the hundredth element of our vector, but it only has -three elements. In this situation, Rust will panic. Using `[]` is supposed to -return an element, but if you pass an invalid index, there's no element that -Rust could return here that would be correct. - -Other languages like C will attempt to give you exactly what you asked for in -this situation, even though it isn't what you want: you'll get whatever is at -the location in memory that would correspond to that element in the vector, -even though the memory doesn't belong to the vector. This is called a *buffer -overread*, and can lead to security vulnerabilities if an attacker can -manipulate the index in such a way as to read data they shouldn't be allowed to -that is stored after the array. - -In order to protect your program from this sort of vulnerability, if you try to -read an element at an index that doesn't exist, Rust will stop execution and -refuse to continue. Let's try it and see: - -```text -$ cargo run - Compiling panic v0.1.0 (file:///projects/panic) - Finished debug [unoptimized + debuginfo] target(s) in 0.27 secs - Running `target/debug/panic` -thread 'main' panicked at 'index out of bounds: the len is 3 but the index is -100', ../src/libcollections/vec.rs:1265 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/panic` (exit code: 101) -``` - -This points at a file we didn't write, *../src/libcollections/vec.rs*. That's -the implementation of `Vec` in the standard library. The code that gets run -when we use `[]` on our vector `v` is in *../src/libcollections/vec.rs*, and -that is where the `panic!` is actually happening. - -The next `note` line tells us that we can set the `RUST_BACKTRACE` environment -variable to get a backtrace of exactly what happened to cause the error. Let's -try that. Listing 9-1 shows the output: - -
- -```text -$ RUST_BACKTRACE=1 cargo run - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target/debug/panic` -thread 'main' panicked at 'index out of bounds: the len is 3 but the index is -100', ../src/libcollections/vec.rs:1265 -stack backtrace: - 1: 0x560956150ae9 - -std::sys::backtrace::tracing::imp::write::h482d45d91246faa2 - 2: 0x56095615345c - -std::panicking::default_hook::_{{closure}}::h89158f66286b674e - 3: 0x56095615291e - std::panicking::default_hook::h9e30d428ee3b0c43 - 4: 0x560956152f88 - -std::panicking::rust_panic_with_hook::h2224f33fb7bf2f4c - 5: 0x560956152e22 - std::panicking::begin_panic::hcb11a4dc6d779ae5 - 6: 0x560956152d50 - std::panicking::begin_panic_fmt::h310416c62f3935b3 - 7: 0x560956152cd1 - rust_begin_unwind - 8: 0x560956188a2f - core::panicking::panic_fmt::hc5789f4e80194729 - 9: 0x5609561889d3 - -core::panicking::panic_bounds_check::hb2d969c3cc11ed08 - 10: 0x56095614c075 - _ as -core..ops..Index>::index::hb9f10d3dadbe8101 - at ../src/libcollections/vec.rs:1265 - 11: 0x56095614c134 - panic::main::h2d7d3751fb8705e2 - at /projects/panic/src/main.rs:4 - 12: 0x56095615af46 - __rust_maybe_catch_panic - 13: 0x560956152082 - std::rt::lang_start::h352a66f5026f54bd - 14: 0x56095614c1b3 - main - 15: 0x7f75b88ed72f - __libc_start_main - 16: 0x56095614b3c8 - _start - 17: 0x0 - -error: Process didn't exit successfully: `target/debug/panic` (exit code: 101) -``` - -
- -Listing 9-1: The backtrace generated by a call to `panic!` displayed when -the environment variable `RUST_BACKTRACE` is set - -
-
- -That's a lot of output! Line 11 of the backtrace points to the line in our -project causing the problem: `src/main.rs`, line four. A backtrace is a list of -all the functions that have been called to get to this point. Backtraces in -Rust work like they do in other languages: the key to reading the backtrace is -to start from the top and read until you see files you wrote. That's the spot -where the problem originated. The lines above the lines mentioning your files -are code that your code called; the lines below are code that called your code. -These lines might include core Rust code, standard library code, or crates that -you're using. - -If we don't want our program to panic, the location pointed to by the first -line mentioning a file we wrote is where we should start investigating in order -to figure out how we got to this location with values that caused the panic. In -our example where we deliberately wrote code that would panic in order to -demonstrate how to use backtraces, the way to fix the panic is to not try to -request an element at index 100 from a vector that only contains three items. -When your code panics in the future, you'll need to figure out for your -particular case what action the code is taking with what values that causes the -panic and what the code should do instead. - -We'll come back to `panic!` and when we should and should not use these methods -later in the chapter. Next, we'll now look at how to recover from an error with -`Result`. - -## Recoverable Errors with `Result` - -Most errors aren't serious enough to require the program to stop entirely. -Sometimes, when a function fails, it's for a reason that we can easily -interpret and respond to. For example, if we try to open a file and that -operation fails because the file doesn't exist, we might want to create the -file instead of terminating the process. - -Recall from Chapter 2 the section on "Handling Potential Failure with the -`Result` Type" that the `Result` enum is defined as having two variants, `Ok` -and `Err`, as follows: - -```rust -enum Result { - Ok(T), - Err(E), -} -``` - - - - -The `T` and `E` are generic type parameters; we'll go into generics in more -detail in Chapter 10. What you need to know right now is that `T` represents -the type of the value that will be returned in a success case within the `Ok` -variant, and `E` represents the type of the error that will be returned in a -failure case within the `Err` variant. Because `Result` has these generic type -parameters, we can use the `Result` type and the functions that the standard -library has defined on it in many different situations where the successful -value and error value we want to return may differ. - -Let's call a function that returns a `Result` value because the function could -fail: opening a file, shown in Listing 9-2. - -
-Filename: src/main.rs - -```rust -use std::fs::File; - -fn main() { - let f = File::open("hello.txt"); -} -``` - -
- -Listing 9-2: Opening a file - -
-
- -How do we know `File::open` returns a `Result`? We could look at the standard -library API documentation. We could ask the compiler! If we give `f` a type -annotation of some type that we know the return type of the function is *not*, -then we try to compile the code, the compiler will tell us that the types don't -match. The error message will then tell us what the type of `f` *is*! Let's try -it: we know that the return type of `File::open` isn't of type `u32`, so let's -change the `let f` statement to: - -```rust,ignore -let f: u32 = File::open("hello.txt"); -``` - -Attempting to compile now gives us: - -```text -error[E0308]: mismatched types - --> src/main.rs:4:18 - | -4 | let f: u32 = File::open("hello.txt"); - | ^^^^^^^^^^^^^^^^^^^^^^^ expected u32, found enum `std::result::Result` - | - = note: expected type `u32` - = note: found type `std::result::Result` -``` - -This tells us the return type of the `File::open` function is a `Result`. -The generic parameter `T` has been filled in here with the type of the success -value, `std::fs::File`, which is a file handle. The type of `E` used in the -error value is `std::io::Error`. - -This return type means the call to `File::open` might succeed and return to us -a file handle that we can read from or write to. The function call also might -fail: for example, the file might not exist, or we might not have permission to -access the file. The `File::open` function needs to have a way to tell us -whether it succeeded or failed, and at the same time give us either the file -handle or error information. This information is exactly what the `Result` enum -conveys. - -In the case where `File::open` succeeds, the value we will have in the variable -`f` will be an instance of `Ok` that contains a file handle. In the case where -it fails, the value in `f` will be an instance of `Err` that contains more -information about the kind of error that happened. - - - - -We need to add to the code from Listing 9-2 to take different actions depending -on the value `File::open` returned. Listing 9-3 shows one way to handle the -`Result` with a basic tool: the `match` expression that we learned about in -Chapter 6. - - - -
-Filename: src/main.rs - -```rust,should_panic -use std::fs::File; - -fn main() { - let f = File::open("hello.txt"); - - let f = match f { - Ok(file) => file, - Err(error) => panic!("There was a problem opening the file: {:?}", -error), - }; -} -``` - -
- -Listing 9-3: Using a `match` expression to handle the `Result` variants we -might have - -
-
- - - - -Note that, like the `Option` enum, the `Result` enum and its variants have been -imported in the prelude, so we don't need to specify `Result::` before the `Ok` -and `Err` variants in the `match` arms. - -Here we tell Rust that when the result is `Ok`, return the inner `file` value -out of the `Ok` variant, and we then assign that file handle value to the -variable `f`. After the `match`, we can then use the file handle for reading or -writing. - -The other arm of the `match` handles the case where we get an `Err` value from -`File::open`. In this example, we've chosen to call the `panic!` macro. If -there's no file named `hello.txt` in our current directory and we run this -code, we'll see the following output from the `panic!` macro: - -```text -thread 'main' panicked at 'There was a problem opening the file: Error { repr: -Os { code: 2, message: "No such file or directory" } }', src/main.rs:8 -``` - - - - -### Matching on Different Errors - -The code in Listing 9-3 will `panic!` no matter the reason that `File::open` -failed. What we'd really like to do instead is take different actions for -different failure reasons: if `File::open` failed because the file doesn't -exist, we want to create the file and return the handle to the new file. If -`File::open` failed for any other reason, for example because we didn't have -permission to open the file, we still want to `panic!` in the same way as we -did in Listing 9-3. Let's look at Listing 9-4, which adds another arm to the -`match`: - -
-Filename: src/main.rs - -```rust,ignore -use std::fs::File; -use std::io::ErrorKind; - -fn main() { - let f = File::open("hello.txt"); - - let f = match f { - Ok(file) => file, - Err(ref error) if error.kind() == ErrorKind::NotFound => { - match File::create("hello.txt") { - Ok(fc) => fc, - Err(e) => panic!("Tried to create file but there was a problem: {:?}", e), - } - }, - Err(error) => panic!("There was a problem opening the file: {:?}", -error), - }; -} -``` - -
- -Listing 9-4: Handling different kinds of errors in different ways - -
-
- - - -The type of the value that `File::open` returns inside the `Err` variant is -`io::Error`, which is a struct provided by the standard library. This struct -has a method `kind` that we can call to get an `io::ErrorKind` value. -`io::ErrorKind` is an enum provided by the standard library that has variants -representing the different kinds of errors that might result from an `io` -operation. The variant we're interested in is `ErrorKind::NotFound`, which -indicates the file we're trying to open doesn't exist yet. - -The condition `if error.kind() == ErrorKind::NotFound` is called a *match -guard*: it's an extra condition on a `match` arm that further refines the arm's -pattern. This condition must be true in order for that arm's code to get run; -otherwise, the pattern matching will move on to consider the next arm in the -`match`. The `ref` in the pattern is needed so that the `error` is not moved -into the guard condition but is merely referenced by it. The reason `ref` is -used to take a reference in a pattern instead of `&` will be covered in detail -in Chapter XX. In short, in the context of a pattern, `&` matches a reference -and give us its value, but `ref` matches a value and gives us a reference to it. - -The condition we want to check in the match guard is whether the value returned -by `error.kind()` is the `NotFound` variant of the `ErrorKind` enum. If it is, -we try to create the file with 'File::create'. However, since `File::create` -could also fail, we need to add an inner `match` statement as well! When the -file can't be opened, a different error message will be printed. The last arm -of the outer `match` stays the same so that the program panics on any error -besides the missing file error. - -### Shortcuts for Panic on Error: `unwrap` and `expect` - -Using `match` works well enough, but it can be a bit verbose and doesn't always -communicate intent well. The `Result` type has many helper methods -defined on it to do various things. One of those methods, called `unwrap`, is -a shortcut method that is implemented just like the `match` statement we wrote -in Listing 9-3. If the `Result` value is the `Ok` variant, `unwrap` will return -the value inside the `Ok`. If the `Result` is the `Err` variant, `unwrap` will -call the `panic!` macro for us. - - - - - - -```rust,should_panic -use std::fs::File; - -fn main() { - let f = File::open("hello.txt").unwrap(); -} -``` - - - - -If we run this code without a *hello.txt* file, we'll see an error message from -the `panic` call that the `unwrap` method makes: - -```text -thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error { -repr: Os { code: 2, message: "No such file or directory" } }', -../src/libcore/result.rs:837 -``` - -There's another method similar to `unwrap` that lets us also choose the -`panic!` error message: `expect`. Using `expect` instead of `unwrap` and -providing good error messages can convey your intent and make tracking down the -source of a panic easier. The syntax of`expect` looks like this: - - - -```rust,should_panic -use std::fs::File; - -fn main() { - let f = File::open("hello.txt").expect("Failed to open hello.txt"); -} -``` - -We use `expect` in the same way as `unwrap`: to return the file handle or call -the `panic!` macro. The error message that `expect` uses in its call to -`panic!` will be the parameter that we pass to `expect` instead of the default -`panic!` message that `unwrap` uses. Here's what it looks like: - -```text -thread 'main' panicked at 'Failed to open hello.txt: Error { repr: Os { code: -2, message: "No such file or directory" } }', ../src/libcore/result.rs:837 -``` - - - - - - - -### Propagating Errors - -When writing a function whose implementation calls something that might fail, -instead of handling the error within this function, you can choose to let your -caller know about the error so they can decide what to do. This is known as -*propagating* the error, and gives more control to the calling code where there -might be more information or logic that dictates how the error should be -handled than what you have available in the context of your code. - - - - -For example, Listing 9-5 shows a function that reads a username from a file. If -the file doesn't exist or can't be read, this function will return those errors -to the code that called this function: - -
- -```rust -use std::io; -use std::fs::File; - -fn read_username_from_file() -> Result { - let f = File::open("hello.txt"); - - let mut f = match f { - Ok(file) => file, - Err(e) => return Err(e), - }; - - let mut s = String::new(); - - match f.read_to_string(&mut s) { - Ok(_) => Ok(s), - Err(e) => Err(e), - } -} -``` - -
- -Listing 9-5: A function that returns errors to the calling code using `match` - -
-
- -Let's look at the return type of the function first: `Result`. This means that the function is returning a value of the type -`Result` where the generic parameter `T` has been filled in with the -concrete type `String`, and the generic type `E` has been filled in with the -concrete type `io::Error`. If this function succeeds without any problems, the -caller of this function will receive an `Ok` value that holds a `String` -- the -username that this function read from the file. If this function encounters any -problems, the caller of this function will receive an `Err` value that holds an -instance of `io::Error` that contains more information about what the problems -were. We chose `io::Error` as the return type of this function because that -happens to be the type of the error value returned from both of the operations -we're calling in this function's body that might fail: the `File::open` -function and the `read_to_string` method. - -The body of the function starts by calling the `File::open` function. Then we -handle the `Result` value returned with a `match` similar to the `match` in -Listing 9-3, only instead of calling `panic!` in the `Err` case, we return -early from this function and pass the error value from `File::open` back to the -caller as this function's error value. If `File::open` succeeds, we store the -file handle in the variable `f` and continue. - -Then we create a new `String` in variable `s` and call the `read_to_string` -method on the file handle in `f` in order to read the contents of the file into -`s`. The `read_to_string` method also returns a `Result` because it might fail, -even though `File::open` succeeded. So we need another `match` to handle that -`Result`: if `read_to_string` succeeds, then our function has succeeded, and we -return the username from the file that's now in `s` wrapped in an `Ok`. If -`read_to_string` fails, we return the error value in the same way that we -returned the error value in the `match` that handled the return value of -`File::open`. We don't need to explicitly say `return`, however, since this is -the last expression in the function. - -The code that calls this code will then handle getting either an `Ok` value -that contains a username or an `Err` value that contains an `io::Error`. We -don't know what the caller will do with those values. If they get an `Err` -value, they could choose to call `panic!` and crash their program, use a -default username, or look up the username from somewhere other than a file, for -example. We don't have enough information on what the caller is actually trying -to do, so we propagate all the success or error information upwards for them to -handle as they see fit. - -This pattern of propagating errors is so common in Rust that there is dedicated -syntax to make this easier: `?`. - -### A Shortcut for Propagating Errors: `?` - - - -Listing 9-6 shows an implementation of `read_username_from_file` that has the -same functionality as it had in Listing 9-5, but this implementation uses the -question mark: - - - -
- -```rust -use std::io; -use std::fs::File; - -fn read_username_from_file() -> Result { - let mut f = File::open("hello.txt")?; - let mut s = String::new(); - f.read_to_string(&mut s)?; - Ok(s) -} -``` - -
- -Listing 9-6: A function that returns errors to the calling code using `?` - -
-
- - - - -The `?` placed after a `Result` value is defined to work the exact same way as -the`match` expressions we defined to handle the `Result` values in Listing 9-5. -If the value of the `Result` is an `Ok`, the value inside the `Ok` will get -returned from this expression and the program will continue. If the value is an -`Err`, the value inside the `Err` will be returned from the whole function as -if we had used the `return` keyword so that the error value gets propagated to -the caller. - -In the context of Listing 9-6, the `?` at the end of the `File::open` call will -return the value inside an `Ok` to the binding `f`. If an error occurs, `?` -will return early out of the whole function and give any `Err` value to our -caller. The same thing applies to the `?` at the end of the `read_to_string` -call. - -The `?` eliminates a lot of boilerplate and makes this function's -implementation simpler. We could even shorten this code further by chaining -method calls immediately after the `?`: - -```rust -use std::io; -use std::io::Read; -use std::fs::File; - -fn read_username_from_file() -> Result { - let mut s = String::new(); - - File::open("hello.txt")?.read_to_string(&mut s)?; - - Ok(s) -} -``` - - - - -We've moved the creation of the new `String` in `s` to the beginning of the -function; that part hasn't changed. Instead of creating a variable `f`, we've -chained the call to `read_to_string` directly onto the result of -`File::open("hello.txt")?`. We still have a `?` at the end of the -`read_to_string` call, and we still return an `Ok` value containing the -username in `s` when both `File::open` and `read_to_string` succeed rather than -returning errors. The functionality is again the same as in Listing 9-5 and -Listing 9-6, this is just a different, more ergonomic way to write it. - -#### `?` Can Only Be Used in Functions That Return `Result` - - - - -The `?` can only be used in functions that have a return type of `Result`, -since it is defined to work in exactly the same way as the `match` expression -we defined in Listing 9-5. The part of the `match` that requires a return type -of `Result` is `return Err(e)`, so the return type of the function must be a -`Result` to be compatible with this `return`. - - - - -Let's look at what happens if use `try!` in the `main` function, which you'll -recall has a return type of `()`: - -```rust,ignore -fn main() { - let f = File::open("hello.txt")?; -} -``` - - - -When we compile this, we get the following error message: - -```bash -error[E0308]: mismatched types - --> - | -3 | let f = File::open("hello.txt")?; - | ^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found enum `std::result::Result` - | - = note: expected type `()` - = note: found type `std::result::Result<_, _>` -``` - -This error is pointing out that we have mismatched types: the `main()` function -has a return type of `()`, but the `?` might return a `Result`. In functions -that don't return `Result`, when you call other functions that return `Result`, -you'll need to use a `match` or one of the `Result` methods to handle it, -instead of using `?` to potentially propagate the error to the caller. - -Now that we've discussed the details of calling `panic!` or returning `Result`, -let's return to the topic of how to decide which is appropriate to use in which -cases. - -## To `panic!` or Not To `panic!` - -So how do you decide when you should `panic!` and when you should return -`Result`? When code panics, there's no way to recover. You could choose to call -`panic!` for any error situation, whether there's a possible way to recover or -not, but then you're making the decision for your callers that a situation is -unrecoverable. When you choose to return a `Result` value, you give your caller -options, rather than making the decision for them. They could choose to attempt -to recover in a way that's appropriate for their situation, or they could -decide that actually, an `Err` value in this case is unrecoverable, so they can -call `panic!` and turn your recoverable error into an unrecoverable one. -Therefore, returning `Result` is a good default choice when you're defining a -function that might fail. - -There are a few situations in which it's more appropriate to write code that -panics instead of returning a `Result`, but they are less common. Let's discuss -why it's appropriate to panic in examples, prototype code, and tests, then -situations where you as a human can know a method won't fail that the compiler -can't reason about, and conclude with some general guidelines on how to decide -whether to panic in library code. - -### Examples, Prototype Code, and Tests: Perfectly Fine to Panic - -When you're writing an example to illustrate some concept, having robust error -handling code in the example as well can make the example less clear. In -examples, it's understood that a call to a method like `unwrap` that could -`panic!` is meant as a placeholder for the way that you'd actually like your -application to handle errors, which can differ based on what the rest of your -code is doing. - -Similarly, the `unwrap` and `expect` methods are very handy when prototyping, -before you're ready to decide how to handle errors. They leave clear markers in -your code for when you're ready to make your program more robust. - -If a method call fails in a test, we'd want the whole test to fail, even if that -method isn't the functionality under test. Because `panic!` is how a test gets -marked as a failure, calling `unwrap` or `expect` is exactly what makes sense to -do. - -### Cases When You Have More Information Than The Compiler - -It would also be appropriate to call `unwrap` when you have some other logic -that ensures the `Result` will have an `Ok` value, but the logic isn't -something the compiler understands. You'll still have a `Result` value that you -need to handle: whatever operation you're calling still has the possibility of -failing in general, even though it's logically impossible in your particular -situation. If you can ensure by manually inspecting the code that you'll never -have an `Err` variant, it is perfectly acceptable to call `unwrap`. Here's an -example: - - - - -```rust -use std::net::IpAddr; - -let home = "127.0.0.1".parse::().unwrap(); -``` - -We're creating an `IpAddr` instance by parsing a hardcoded string. We can see -that `"127.0.0.1"` is a valid IP address, so it's acceptable to use `unwrap` -here. However, having a hardcoded, valid string doesn't change the return type -of the `parse` method: we still get a `Result` value, and the compiler will -still make us handle the `Result` as if the `Err` variant is still a possibility -since the compiler isn't smart enough to see that this string is always a -valid IP address. If the IP address string came from a user instead of being -hardcoded into the program, and therefore *did* have a possibility of failure, -we'd definitely want to handle the `Result` in a more robust way instead. - -### Guidelines for Error Handling - -It's advisable to have your code `panic!` when it's possible that you could end -up in a *bad state*---in this context, *bad state* is when some assumption, -guarantee, contract, or invariant has been broken, such as when invalid values, -contradictory values, or missing values are passed to your code---plus one or -more of the following: - -* The bad state is not something that's *expected* to happen occasionally -* Your code after this point needs to rely on not being in this bad state -* There's not a good way to encode this information in the types you use - -If someone calls your code and passes in values that don't make sense, the best -thing might be to `panic!` and alert the person using your library to the bug -in their code so that they can fix it during development. Similarly, `panic!` -is often appropriate if you're calling external code that is out of your -control, and it returns an invalid state that you have no way of fixing. - -When a bad state is reached, but it's expected to happen no matter how well you -write your code, it's still more appropriate to return a `Result` rather than -calling `panic!`. Examples of this include a parser being given malformed data, -or an HTTP request returning a status that indicates you have hit a rate limit. -In these cases, you should indicate that failure is an expected possibility by -returning a `Result` in order to propagate these bad states upwards so that the -caller can decide how they would like to handle the problem. To `panic!` -wouldn't be the best way to handle these cases. - -When your code performs operations on values, your code should verify the -values are valid first, and `panic!` if the values aren't valid. This is mostly -for safety reasons: attempting to operate on invalid data can expose your code -to vulnerabilities. This is the main reason that the standard library will -`panic!` if you attempt an out-of-bounds array access: trying to access memory -that doesn't belong to the current data structure is a common security problem. -Functions often have *contracts*: their behavior is only guaranteed if the -inputs meet particular requirements. Panicking when the contract is violated -makes sense because a contract violation always indicates a caller-side bug, -and it is not a kind of error you want callers to have to explicitly handle. In -fact, there's no reasonable way for calling code to recover: the calling -*programmers* need to fix the code. Contracts for a function, especially when a -violation will cause a `panic`, should be explained in the API documentation -for the function. - -Having lots of error checks in all of your functions would be verbose and -annoying, though. Luckily, you can use Rust's type system (and thus the type -checking the compiler does) to do a lot of the checks for you. If your function -takes a particular type as an argument, you can proceed with your code's logic -knowing that the compiler has already ensured you have a valid value. For -example, if you have a type rather than an `Option`, your program expects to -have *something* rather than *nothing*. Your code then doesn't have to handle -two cases for the `Some` and `None` variants, it will only have one case for -definitely having a value. Code trying to pass nothing to your function won't -even compile, so your function doesn't have to check for that case at runtime. -Another example is using an unsigned integer type like `u32`, which ensures the -argument value is never negative. - - - - -### Creating Custom Types for Validation - -Let's take the idea of using Rust's type system to ensure we have a valid value -one step further, and look at creating a custom type for validation. Recall the -guessing game in Chapter 2, where our code asked the user to guess a number -between 1 and 100. We actually never validated that the user's guess was -between those numbers before checking it against our secret number, only that -it was positive. In this case, the consequences were not very dire: our output -of "Too high" or "Too low" would still be correct. It would be a useful -enhancement to guide the user towards valid guesses, though, and have different -behavior when a user guesses a number that's out of range versus when a user -types, for example, letters instead. - -One way to do this would be to parse the guess as an `i32` instead of only a -`u32`, to allow potentially negative numbers, then add a check for the number -being in range: - -```rust,ignore -loop { - // snip - - let guess: i32 = match guess.trim().parse() { - Ok(num) => num, - Err(_) => continue, - }; - - if guess < 1 || guess > 100 { - println!("The secret number will be between 1 and 100."); - continue; - } - - match guess.cmp(&secret_number) { - // snip -} -``` - - - -The `if` expression checks to see if our value is out of range, tells the user -about the problem, and calls `continue` to start the next iteration of the loop -and ask for another guess. After the `if` expression, we can proceed with the -comparisons between `guess` and the secret number knowing that guess is between -1 and 100. - -However, this is not an ideal solution: if it was absolutely critical that the -program only operated on values between 1 and 100, and it had many functions -with this requirement, it would be tedious (and potentially impact performance) -to have a check like this in every function. - -Instead, we can make a new type and put the validations in the type's -constructor rather than repeating them. That way, it's safe for functions to -use the new type in their signatures and confidently use the values they -receive. Listing 9-8 shows one way to define a `Guess` type that will only -create an instance of `Guess` if the `new` function receives a value between 1 -and 100: - -
- -```rust -struct Guess { - value: u32, -} - -impl Guess { - pub fn new(value: u32) -> Guess { - if value < 1 || value > 100 { - panic!("Guess value must be between 1 and 100, got {}.", value); - } - - Guess { - value: value, - } - } - - pub fn value(&self) -> u32 { - self.value - } -} -``` - -
- -Listing 9-8: A `Guess` type that will only continue with values between 1 and -100 - -
-
- - - -First, we define a struct named `Guess` that has a field named `value` that -holds a `u32`. This is where the number will be stored. - -Then we implement an associated function named `new` on `Guess` that is a -constructor of `Guess` values. The `new` function takes one argument named -`value` of type `u32` and returns a `Guess`. The code in the body of the `new` -function tests the `value` argument to make sure it is between 1 and 100. If -`value` doesn't pass this test, we call `panic!`, which will alert the -programmer who is calling this code that they have a bug they need to fix, -since creating a `Guess` with a `value` outside this range would violate the -contract that `Guess::new` is relying on. The conditions in which `Guess::new` -might panic should be discussed in its public-facing API documentation; we'll -cover documentation conventions around indicating the possibility of a `panic!` -in the API documentation that you create in Chapter 14. If `value` does pass -the test, we create a new `Guess` with its `value` field set to the `value` -argument, and return the `Guess`. - - - - -Next, we implement a method named `value` that borrows `self`, doesn't take any -other arguments, and returns a `u32`. This is a kind of method sometimes called -a *getter*, since its purpose is to get some data from its fields and return -it. This public method is necessary because the `value` field of the `Guess` -struct is private. It's important that the `value` field is private so that -code using the `Guess` struct is not allowed to set `value` directly: callers -*must* use the `Guess::new` constructor function to create an instance of -`Guess`, which ensures there's no way for a `Guess` to have a `value` that -hasn't been checked by the conditions in the constructor. - -A function that takes as an argument or returns only numbers between 1 and 100 -could then declare in its signature that it takes a `Guess` rather than a -`u32`, and wouldn't need to do any additional checks in its body. - -## Summary - -Rust's error handling features are designed to help you write more robust code. -The `panic!` macro signals that your program is in a state it can't handle, and -lets you tell the process to stop instead of trying to proceed with invalid or -incorrect values. The `Result` enum uses Rust's type system to indicate that -operations might fail in a way that your code could recover from. You can use -`Result` to tell code that calls your code that it needs to handle potential -success or failure as well. Using `panic!` and `Result` in the appropriate -situations will make your code more reliable in the face of inevitable problems. - -Now that we've seen useful ways that the standard library uses generics with -the `Option` and `Result` enums, let's talk about how generics work and how you -can make use of them in your code. diff --git a/nostarch/chapter10.md b/nostarch/chapter10.md deleted file mode 100644 index f44af6c..0000000 --- a/nostarch/chapter10.md +++ /dev/null @@ -1,1215 +0,0 @@ - -[TOC] - -# Generics - -One of the core tools a programming language gives you is the ability to deal -effectively with duplication of code. It's important to minimize the amount of -code that is duplicated throughout a program to make maintenace easier and -minimize logic errors. Maintenance will be easier if there's only one place -that you need to change the code if you change your mind about how the program -should work, rather than multiple places in the code. If your program's logic -is duplicated in different places and those places don't match, you'll get -errors or unexpected and undesired behavior from your program that could be -hard to track down. Rust has the concept of *generics* as one way to eliminate -duplicate code. Generics come in the form of generic types, traits that those -generic types have, and generic lifetimes. We'll cover how to use all of these -in this chapter. - -## Removing Duplication by Extracting a Function - -Let's first go through a technique for dealing with duplication that you're -probably familiar with: extracting a function. Consider a small program that -finds the largest number in a list, shown in Listing 10-1: - -Filename: src/main.rs - -```rust -fn main() { - let numbers = vec![34, 50, 25, 100, 65]; - - let mut largest = numbers[0]; - - for number in numbers { - if largest > number { - largest = number; - } - } - - println!("The largest number is {}", largest); -} -``` - - -Listing 10-1: Code to find the largest number in a list of numbers - - -If we needed to find the largest number in two different lists of numbers, we -could duplicate the code in Listing 10-1 and have the same logic exist in two -places in the program: - -Filename: src/main.rs - -```rust -fn main() { - let numbers = vec![34, 50, 25, 100, 65]; - - let mut largest = numbers[0]; - - for number in numbers { - if largest > number { - largest = number; - } - } - - println!("The largest number is {}", largest); - - let numbers = vec![102, 34, 6000, 89, 54, 2, 43, 8]; - - let mut largest = numbers[0]; - - for number in numbers { - if largest > number { - largest = number; - } - } - - println!("The largest number is {}", largest); -} -``` - -Copying code is tedious and error-prone, plus now we have two places to update -the logic if we need it to change. Rust, like many languages, gives us a way to -deal with this duplication by creating an abstraction, and in this case the -abstraction we'll use is a function. Here's a program where we've extracted the -code in Listing 10-1 that finds the largest number into a function named -`largest`. This program can find the largest number in two different lists of -numbers, but the code from Listing 10-1 only exists in one spot: - -Filename: src/main.rs - -```rust -fn largest(numbers: Vec) { - let mut largest = numbers[0]; - - for number in numbers { - if largest > number { - largest = number; - } - } - - println!("The largest number is {}", largest); -} - -fn main() { - let numbers = vec![34, 50, 25, 100, 65]; - - largest(numbers); - - let numbers = vec![102, 34, 6000, 89, 54, 2, 43, 8]; - - largest(numbers); -} -``` - -The function takes an argument, `numbers`, which represents any concrete -`Vec` that we might pass into the function. The code in the function -definition operates on the `numbers` representation of any `Vec`. When -we call the `largest` function, the code actually runs on the specific values -that we pass in. - -Functions aren't the only way to eliminate duplication. For example, our -`largest` function only works for vectors of `i32`. What if we wanted to find -the largest number in a list of floats? Or the largest value in some sort of -custom `struct` or `enum`? We can't solve those kinds of duplication with -regular functions. - -To solve these kinds of problems, Rust provides a feature called *generics*. In -the same way that functions allow us to abstract over common code, generics -allow us to abstract over types. This ability gives us tremendous power to -write code that works in a large number of situations. First, we'll examine the -syntax of generics. Then, we'll talk about another feature that's used to -augment generics: traits. Finally, we'll discuss one of Rust's most unique uses -of generics: lifetimes. - -## Generics Syntax - -We've already hinted at the idea of generics in previous chapters, but we -never dug into what exactly they are or how to use them. In places where we -specify a type, like function signatures or structs, instead we can use -*generics*. Generics are stand-ins that represent an abstract set instead of something concrete. In this section, we're going to cover generic *data types*. - -You can recognize when any kind of generics are used by the way that they fit -into Rust's syntax: any time you see angle brackets, `<>`, you're dealing with -generics. Types we've seen before, like in Chapter 8 where we discussed vectors -with types like `Vec`, employ generics. The type that the standard library -defines for vectors is `Vec`. That `T` is called a *type parameter*, and it -serves a similar function as parameters to functions: you fill in the parameter -with a concrete type, and that determines how the overall type works. In the -same way that a function like `foo(x: i32)` can be called with a specific value -such as `foo(5)`, a `Vec` can be created with a specific type, like -`Vec`. - -### Duplicated Enum Definitions - -Let's dive into generic data types in more detail. We learned about how to use -the `Option` enum in Chapter 6, but we never examined its definition. Let's -try to imagine how we'd write it! We'll start from duplicated code like we did -in the "Removing Duplication by Extracting a Function" section. This time, -we'll remove the duplication by extracting a generic data type instead of -extracting a function, but the mechanics of doing the extraction will be -similar. First, let's consider an `Option` enum with a `Some` variant that can -only hold an `i32`. We'll call this enum `OptionalNumber`: - -Filename: src/main.rs - -```rust -enum OptionalNumber { - Some(i32), - None, -} - -fn main() { - let number = OptionalNumber::Some(5); - let no_number = OptionalNumber::None; -} -``` - -This works just fine for `i32`s. But what if we also wanted to store `f64`s? We -would have to duplicate code to define a separate `Option` enum type for each -type we wanted to be able to hold in the `Some` variants. For example, here is -how we could define and use `OptionalFloatingPointNumber`: - -Filename: src/main.rs - -```rust -enum OptionalFloatingPointNumber { - Some(f64), - None, -} - -fn main() { - let number = OptionalFloatingPointNumber::Some(5.0); - let no_number = OptionalFloatingPointNumber::None; -} -``` - -We've made the enum's name a bit long in order to drive the point home. With -what we currently know how to do in Rust, we would have to write a unique type -for every single kind of value we wanted to have either `Some` or `None` of. In -other words, the idea of "an optional value" is a more abstract concept than one -specific type. We want it to work for any type at all. - -### Removing Duplication by Extracting a Generic Data Type - -Let's see how to get from duplicated types to the generic type. Here are the -definitions of our two enums side-by-side: - -```text -enum OptionalNumber { enum OptionalFloatingPointNumber { - Some(i32), Some(f64), - None, None, -} } -``` - -Aside from the names, we have one line where the two definitions are very -close, but still different: the line with the `Some` definitions. The only -difference is the type of the data in that variant, `i32` and `f64`. - -Just like we can parameterize arguments to a function by choosing a name, we -can parameterize the type by choosing a name. In this case, we've chosen the -name `T`. We could choose any identifier here, but Rust style has type -parameters follow the same style as types themselves: CamelCase. In addition, -they tend to be short, often one letter. `T` is the traditional default choice, -short for 'type'. Let's use that name in our `Some` variant definitions where -the `i32` and `f64` types were: - -```text -enum OptionalNumber { enum OptionalFloatingPointNumber { - Some(T), Some(T), - None, None, -} } -``` - -There's one problem, though: we've *used* `T`, but not defined it. This would -be similar to using an argument to a function in the body without declaring it -in the signature. We need to tell Rust that we've introduced a generic -parameter. The syntax to do that is the angle brackets, like this: - -```text -enum OptionalNumber { enum OptionalFloatingPointNumber { - Some(T), Some(T), - None, None, -} } -``` - -The `<>`s after the enum name indicate a list of type parameters, just like -`()` after a function name indicates a list of value parameters. Now the only -difference between our two `enum`s is the name. Since we've made them generic, -they're not specific to integers or floating point numbers anymore, so they can -have the same name: - -```text -enum Option { enum Option { - Some(T), Some(T), - None, None, -} } -``` - -Now they're identical! We've made our type fully generic. This definition is -also how `Option` is defined in the standard library. If we were to read this -definition aloud, we'd say, "`Option` is an `enum` with one type parameter, -`T`. It has two variants: `Some`, which has a value with type `T`, and `None`, -which has no value." We can now use the same `Option` type whether we're holding an `i32` or an `f64`: - -```rust -let integer = Option::Some(5); -let float = Option::Some(5.0); -``` - -We've left in the `Option::` namespace for consistency with the previous -examples, but since `use Option::*` is in the prelude, it's not needed. Usually -using `Option` looks like this: - -```rust -let integer = Some(5); -let float = Some(5.0); -``` - -When you recognize situations with almost-duplicate types like this in your -code, you can follow this process to reduce duplication using generics. - -### Monomorphization at Compile Time - -Understanding this refactoring process is also useful in understanding how -generics work behind the scenes: the compiler does the exact opposite of this -process when compiling your code. *Monomorphization* means taking code that -uses generic type parameters and generating code that is specific for each -concrete type that is used with the generic code. Monomorphization is why -Rust's generics are extremely efficient at runtime. Consider this code that -uses the standard library's `Option`: - -```rust -let integer = Some(5); -let float = Some(5.0); -``` - -When Rust compiles this code, it will perform monomorphization. What this means -is the compiler will see that we've used two kinds of `Option`: one where -`T` is `i32`, and one where `T` is `f64`. As such, it will expand the generic -definition of `Option` into `Option_i32` and `Option_f64`, thereby replacing -the generic definition with the specific ones. The more specific version looks -like the duplicated code we started with at the beginning of this section: - -Filename: src/main.rs - -```rust -enum Option_i32 { - Some(i32), - None, -} - -enum Option_f64 { - Some(f64), - None, -} - -fn main() { - let integer = Option_i32::Some(5); - let float = Option_f64::Some(5.0); -} -``` - -In other words, we can write the non-duplicated form that uses generics in our -code, but Rust will compile that into code that acts as though we wrote the -specific type out in each instance. This means we pay no runtime cost for using -generics; it's just like we duplicated each particular definition. - -### Generic Structs - -In a similar fashion as we did with enums, we can use `<>`s with structs as -well in order to define structs that have a generic type parameter in one or -more of their fields. Generic structs also get monomorphized into specialized -types at compile time. Listing 10-2 shows the definition and use of a `Point` -struct that could hold `x` and `y` coordinate values that are any type: - -Filename: src/main.rs - -```rust -struct Point { - x: T, - y: T, -} - -fn main() { - let integer = Point { x: 5, y: 10 }; - let float = Point { x: 1.0, y: 4.0 }; -} -``` - - -Listing 10-2: A `Point` struct that holds `x` and `y` values of type `T` - - -The syntax is the same with structs: add a `` after the name of the struct, -then use `T` in the definition where you want to use that generic type instead -of a specific type. - -### Multiple Type Parameters - -Note that in the `Point` definition in Listing 10-2, we've used the same `T` -parameter for both fields. This means `x` and `y` must always be values of the -same type. Trying to instantiate a `Point` that uses an `i32` for `x` and an -`f64` for `y`, like this: - -```rust,ignore -let p = Point { x: 5, y: 20.0 }; -``` - -results in a compile-time error that indicates the type of `y` must match the -type of `x`: - -```bash -error[E0308]: mismatched types - | -7 | let p = Point { x: 5, y: 20.0 }; - | ^^^^ expected integral variable, found floating-point variable - | - = note: expected type `{integer}` - = note: found type `{float}` -``` - -If we need to be able to have fields with generic but different types, we can -declare multiple type parameters within the angle brackets, separated by a -comma. Listing 10-3 shows how to define a `Point` that can have different types -for `x` and `y`: - -Filename: src/main.rs - -```rust -struct Point { - x: X, - y: Y, -} - -fn main() { - let integer = Point { x: 5, y: 10 }; - let float = Point { x: 1.0, y: 4.0 }; - let p = Point { x: 5, y: 20.0 }; -} -``` - - -Listing 10-2: A `Point` struct that holds an `x` value of type `X` and a `y` -value of type `Y` - - -Now `x` will have the type of `X`, and `y` will have the type of `Y`, and we -can instantiate a `Point` with an `i32` for `x` and an `f64` for `y`. - -We can make `enum`s with multiple type parameters as well. Recall the enum -`Result` from Chapter 9 that we used for recoverable errors. Here's its -definition: - -```rust -enum Result { - Ok(T), - Err(E), -} -``` - -Each variant stores a different kind of information, and they're both generic. - -You can have as many type parameters as you'd like. Similarly to parameters of -values in function signatures, if you have a lot of parameters, the code can -get quite confusing, so try to keep the number of parameters defined in any one -type small if you can. - -### Generic Functions and Methods - -In a similar way to data structures, we can use the `<>` syntax in function or -method definitions. The angle brackets for type parameters go after the -function or method name and before the argument list in parentheses: - -```rust -fn generic_function(value: T) { - // code goes here -} -``` - -We can use the same process that we used to refactor duplicated type -definitions using generics to refactor duplicated function definitions using -generics. Consider these two side-by-side function signatures that differ in -the type of `value`: - -```text -fn takes_integer(value: i32) { fn takes_float(value: f64) { - // code goes here // code goes here -} } -``` - -We can add a type parameter list that declares the generic type `T` after the -function names, then use `T` where the specific `i32` and `f64` types were: - -```text -fn takes_integer(value: T) { fn takes_float(value: T) { - // code goes here // code goes here -} } -``` - -At this point, only the names differ, so we could unify the two functions into -one: - -```rust,ignore -fn takes(value: T) { - // code goes here -} -``` - -There's one problem though. We've got some function *definitions* that work, -but if we try to use `value` in code in the function body, we'll get an -error. For example, the function definition in Listing 10-3 tries to print out -`value` in its body: - -Filename: src/lib.rs - -```rust,ignore -fn show_anything(value: T) { - println!("I have something to show you!"); - println!("It's: {}", value); -} -``` - - -Listing 10-3: A `show_anything` function definition that does not yet compile - - -Compiling this definition results in an error: - -```bash - error[E0277]: the trait bound `T: std::fmt::Display` is not satisfied - --> :3:37 - | -3 | println!("It's: {}", value); - | ^^^^^ trait `T: std::fmt::Display` not satisfied - | - = help: consider adding a `where T: std::fmt::Display` bound - = note: required by `std::fmt::Display::fmt` - -error: aborting due to previous error(s) -``` - -This error mentions something we haven't learned about yet: traits. In the next -section, we'll learn how to make this compile. - -## Traits - -*Traits* are similar to a feature often called 'interfaces' in other languages, -but are also different. Traits let us do another kind of abstraction: they let -us abstract over *behavior* that types can have in common. - -When we use a generic type parameter, we are telling Rust that any type is -valid in that location. When other code *uses* a value that could be of any -type, we need to also tell Rust that the type has the functionality that we -need. Traits let us specify that, for example, we need any type `T` that has -methods defined on it that allow us to print a value of that type. This is -powerful because we can still leave our definitions generic to allow use of -many different types, but we can constrain the type at compile-time to types -that have the behavior we need to be able to use. - -Here's an example definition of a trait named `Printable` that has a method -named `print`: - -Filename: src/lib.rs - -```rust -trait Printable { - fn print(&self); -} -``` - - -Listing 10-4: A `Printable` trait definition with one method, `print` - - -We declare a trait with the `trait` keyword, then the trait's name. In this -case, our trait will describe types which can be printed. Inside of curly -braces, we declare a method signature, but instead of providing an -implementation inside curly braces, we put a semicolon after the signature. A -trait can have multiple methods in its body, with the method signatures listend one per line and each line ending in a semicolon. - -Implementing a trait for a particular type looks similar to implementing -methods on a type since it's also done with the `impl` keyword, but we specify -the trait name as well. Inside the `impl` block, we specify definitions for the -trait's methods in the context of the specific type. Listing 10-5 has an -example of implementing the `Printable` trait from Listing 10-4 (that only has -the `print` method) for a `Temperature` enum: - -Filename: src/lib.rs - -```rust -enum Temperature { - Celsius(i32), - Fahrenheit(i32), -} - -impl Printable for Temperature { - fn print(&self) { - match *self { - Temperature::Celsius(val) => println!("{}°C", val), - Temperature::Fahrenheit(val) => println!("{}°F", val), - } - } -} -``` - - -Listing 10-5: Implementing the `Printable` trait on a `Temperature` enum - - -In the same way `impl` lets us define methods, we've used it to define methods -that pertain to our trait. We can call methods that our trait has defined just -like we can call other methods: - -Filename: src/main.rs - -```rust -fn main() { - let t = Temperature::Celsius(37); - - t.print(); -} -``` - -Note that in order to use a trait's methods, the trait itself must be in scope. -If the definition of `Printable` was in a module, the definition would need to -be defined as `pub` and we would need to `use` the trait in the scope where we -wanted to call the `print` method. This is because it's possible to have two -traits that both define a method named `print`, and our `Temperature` enum might -implement both. Rust wouldn't know which `print` method we wanted unless we -brought the trait we wanted into our current scope with `use`. - -### Trait Bounds - -Defining traits with methods and implementing the trait methods on a particular -type gives Rust more information than just defining methods on a type directly. -The information Rust gets is that the type that implements the trait can be -used in places where the code specifies that it needs some type that implements -a trait. To illustrate this, Listing 10-6 has a `print_anything` function -definition. This is similar to the `show_anything` function from Listing 10-3, -but this function has a *trait bound* on the generic type `T` and uses the -`print` function from the trait. A trait bound constrains the generic type to -be any type that implements the trait specified, instead of any type at all. -With the trait bound, we're then allowed to use the trait method `print` in the -function body: - -Filename: src/lib.rs - -```rust -fn print_anything(value: T) { - println!("I have something to print for you!"); - value.print(); -} -``` - - -Listing 10-6: A `print_anything` function that uses the trait bound `Printable` -on type `T` - - -Trait bounds are specified in the type name declarations within the angle -brackets. After the name of the type that you want to apply the bound to, add a -colon (`:`) and then specify the name of the trait. This function now specifies -that it takes a `value` parameter that can be of any type, as long as that type -implements the trait `Printable`. We need to specify the `Printable` trait in -the type name declarations because we want to be able to call the `print` -method that is part of the `Printable` trait. - -Now we are able to call the `print_anything` function from Listing 10-6 and -pass it a `Temperature` instance as the `value` parameter, since we implemented -the trait `Printable` on `Temperature` in Listing 10-5: - -Filename: src/main.rs - -```rust -fn main() { - let temperature = Temperature::Fahrenheit(98); - print_anything(temperature); -} -``` - -If we implement the `Printable` trait on other types, we can use them with the -`print_anything` method too. If we try to call `print_anything` with an `i32`, -which does *not* implement the `Printable` trait, we get a compile-time error -that looks like this: - -```bash -error[E0277]: the trait bound `{integer}: Printable` is not satisfied - | -29 | print_anything(3); - | ^^^^^^^^^^^^^^ trait `{integer}: Printable` not satisfied - | - = help: the following implementations were found: - = help: - = note: required by `print_anything` -``` - -Traits are an extremely useful feature of Rust. You'll almost never see generic -functions without an accompanying trait bound. There are many traits in the -standard library, and they're used for many, many different things. For -example, our `Printable` trait is similar to one of those traits, `Display`. -And in fact, that's how `println!` decides how to format things with `{}`. The -`Display` trait has a `fmt` method that determines how to format something. - -Listing 10-7 shows our original example from Listing 10-3, but this time using -the standard library's `Display` trait in the trait bound on the generic type -in the `show_anything` function: - -Filename: src/lib.rs - -```rust -use std::fmt::Display; - -fn show_anything(value: T) { - println!("I have something to show you!"); - println!("It's: {}", value); -} -``` - - -Listing 10-7: The `show_anything` function with trait bounds - - -Now that this function specifies that `T` can be any type as long as that type -implements the `Display` trait, this code will compile. - -### Multiple Trait Bounds and `where` Syntax - -Each generic type can have its own trait bounds. The signature for a function -that takes a type `T` that implements `Display` and a type `U` that implements -`Printable` looks like: - -```rust,ignore -fn some_function(value: T, other_value: U) { -``` - -To specify multiple trait bounds on one type, list the trait bounds in a list -with a `+` between each trait. For example, here's the signature of a function -that takes a type `T` that implements `Display` and `Clone` (which is another -standard library trait we have mentioned): - -```rust,ignore -fn some_function(value: T) { -``` - -When trait bounds start getting complicated, there is another syntax that's a -bit cleaner: `where`. And in fact, the error we got when we ran the code from -Listing 10-3 referred to it: - -```bash -help: consider adding a `where T: std::fmt::Display` bound -``` - -The `where` syntax moves the trait bounds after the function arguments list. -This definition of `show_anything` means the exact same thing as the definition -in Listing 10-7, just said a different way: - -Filename: src/lib.rs - -```rust -use std::fmt::Display; - -fn show_anything(value: T) where T: Display { - println!("I have something to show you!"); - println!("It's: {}", value); -} -``` - -Instead of `T: Display` going inside the angle brackets, they go after the -`where` keyword at the end of the function signature. This can make complex -signatures easier to read. The `where` clause and its parts can also go on new -lines. Here's the signature of a function that takes three generic type -parameters that each have multiple trait bounds: - -```rust,ignore -fn some_function(t: T, u: U, v: V) - where T: Display + Clone, - U: Printable + Debug, - V: Clone + Printable -{ -``` - -Generic type parameters and trait bounds are part of Rust's rich type system. -Another important kind of generic in Rust interacts with Rust's ownership and -references features, and they're called *lifetimes*. - -## Lifetime Syntax - -Generic type parameters let us abstract over types, and traits let us abstract -over behavior. There's one more way that Rust allows us to do something -similar: *lifetimes* allow us to be generic over scopes of code. - -Scopes of code? Yes, it's a bit unusual. Lifetimes are, in some ways, Rust's -most distinctive feature. They are a bit different than the tools you have used -in other programming languages. Lifetimes are a big topic, so we're not going -to cover everything about them in this chapter. What we *are* going to do is -talk about the very basics of lifetimes, so that when you see the syntax in -documentation or other places, you'll be familiar with the concepts. Chapter 20 -will contain more advanced information about everything lifetimes can do. - -### Core Syntax - -We talked about references in Chapter 4, but we left out an important detail. -As it turns out, every reference in Rust has a *lifetime*, which is the scope -for which that reference is valid. Most of the time, lifetimes are implicit, -but just like we can choose to annotate types everywhere, we can choose to -annotate lifetimes. - -Lifetimes have a slightly unusual syntax: - -```rust,ignore -&i32 // a reference -&'a i32 // a reference with an explicit lifetime -``` - -The `'a` there is a *lifetime* with the name `a`. A single apostrophe indicates -that this name is for a lifetime. Lifetime names need to be declared before -they're used. Here's a function signature with lifetime declarations and -annotations: - -```rust,ignore -fn some_function<'a>(argument: &'a i32) { -``` - -Notice anything? In the same way that generic type declarations go inside angle -brackets after the function name, lifetime declarations also go inside those -same angle brackets. We can even write functions that take both a lifetime -declaration and a generic type declaration: - -```rust,ignore -fn some_function<'a, T>(argument: &'a T) { -``` - -This function takes one argument, a reference to some type, `T`, and the -reference has the lifetime `'a`. In the same way that we parameterize functions -that take generic types, we parameterize references with lifetimes. - -So, that's the syntax, but *why*? What does a lifetime do, anyway? - -### Lifetimes Prevent Dangling References - -Consider the program in listing 10-8. There's an outer scope and an inner -scope. The outer scope declares a variable named `r` with no initial value, and -the inner scope declares a variable named `x` with the initial value of 5. -Inside the inner scope, we attempt to set the value of `r` to a reference to -`x`. Then the inner scope ends and we attempt to print out the value in `r`: - -```rust,ignore -{ - let r; - - { - let x = 5; - r = &x; - } - - println!("r: {}", r); -} -``` - - -Listing 10-8: An attempt to use a reference whose value has gone out of scope - - -If we compile this code, we get an error: - -```text - error: `x` does not live long enough - --> :6:10 - | -6 | r = &x; - | ^ does not live long enough -7 | } - | - borrowed value only lives until here -... -10 | } - | - borrowed value needs to live until here -``` - -The variable `x` doesn't "live long enough." Why not? Well, `x` is going to go -out of scope when we hit the closing curly brace on line 7, ending the inner -scope. But `r` is valid for the outer scope; its scope is larger and we say -that it "lives longer." If Rust allowed this code to work, `r` would be -referencing memory that was deallocated when `x` went out of scope. That'd be -bad! Once it's deallocated, it's meaningless. - -So how does Rust determine that this code should not be allowed? Part of the -compiler called the *borrow checker* compares scopes to determine that all -borrows are valid. Here's the same example from Listing 10-8 with some -annotations: - -```rust,ignore -{ - let r; // -------+-- 'a - // | - { // | - let x = 5; // -+-----+-- 'b - r = &x; // | | - } // -+ | - // | - println!("r: {}", r); // | - // | - // -------+ -} -``` - -Here, we've annotated the lifetime of `r` with `'a` and the lifetime of `x` -with `'b`. Rust looks at these lifetimes and sees that `r` has a lifetime of -`'a`, but that it refers to something with a lifetime of `'b`. It rejects the -program because the lifetime `'b` is shorter than the lifetime of `'a`-- the -value that the reference is referring to does not live as long as the reference -does. - -Let's look at a different example that compiles because it does not try to make -a dangling reference, and see what the lifetimes look like: - -```rust -{ - let x = 5; // -----+-- 'b - // | - let r = &x; // --+--+-- 'a - // | | - println!("r: {}", r); // | | - // --+ | - // -----+ -} -``` - -Here, `x` lives for `'b`, which in this case is larger than `'a`. This is -allowed: Rust knows that the reference in `r` will always be valid, as it has a -smaller scope than `x`, the value it refers to. - -Note that we didn't have to name any lifetimes in the code itself; Rust figured -it out for us. One situation in which Rust can't figure out the lifetimes is -for a function or method when one of the arguments or return values is a -reference, except for a few scenarios we'll discuss in the lifetime elision -section. - -### Lifetime Annotations in Struct Definitions - -Another time that Rust can't figure out the lifetimes is when structs have a -field that holds a reference. In that case, naming the lifetimes looks like -this: - -```rust -struct Ref<'a> { - x: &'a i32, -} -``` - -Again, the lifetime names are declared in the angle brackets where generic type -parameters are declared, and this is because lifetimes are a form of generics. -In the examples above, `'a` and `'b` were concrete lifetimes: we knew about `r` -and `x` and how long they would live exactly. However, when we write a -function, we can't know beforehand exactly all of the arguments that it could -be called with and how long they will be valid for. We have to explain to Rust -what we expect the lifetime of the argument to be (we'll learn about how -to know what you expect the lifetime to be in a bit). This is similar to -writing a function that has an argument of a generic type: we don't know what -type the arguments will actually end up being when the function gets called. -Lifetimes are the same idea, but they are generic over the scope of a -reference, rather than a type. - -### Lifetime Annotations in Function Signatures - -Lifetime annotations for functions go on the function signature, but we don't -have to annotate any of the code in the function body with lifetimes. That's -because Rust can analyze the specific code inside the function without any -help. When a function interacts with references that come from or go to code -outside that function, however, the lifetimes of those arguments or return -values will potentially be different each time that function gets called. Rust -would have to analyze every place the function is called to determine that -there were no dangling references. That would be impossible because a library -that you provide to someone else might be called in code that hasn't been -written yet, at the time that you're compiling your library. - -Lifetime parameters specify generic lifetimes that will apply to any specific -lifetimes the function gets called with. The annotation of lifetime parameters -tell Rust what it needs to know in order to be able to analyze a function -without knowing about all possible calling code. Lifetime annotations do not -change how long any of the references involved live. In the same way that -functions can accept any type when the signature specifies a generic type -parameter, functions can accept references with any lifetime when the signature -specifies a generic lifetime parameter. - -To understand lifetime annotations in context, let's write a function that will -return the longest of two string slices. The way we want to be able to call -this function is by passing two string slices, and we want to get back a string -slice. The code in Listing 10-9 should print `The longest string is abcd` once -we've implemented the `longest` function: - -Filename: src/main.rs - -```rust -fn main() { - let a = String::from("abcd"); - let b = "xyz"; - - let c = longest(a.as_str(), b); - println!("The longest string is {}", c); -} -``` - - -Listing 10-9: A `main` function that demonstrates how we'd like to use the -`longest` function - - -Note that we want the function to take string slices because we don't want the -`longest` function to take ownership of its arguments, and we want the function -to be able to accept slices of a `String` (like `a`) is as well as string -literals (`b`). Refer back to the "String Slices as Arguments" section of -Chapter 4 for more discussion about why these are the arguments we want. - -Here's the start of an implementation of the `longest` function that won't -compile yet: - -```rust,ignore -fn longest(x: &str, y: &str) -> &str { - if x.len() > y.len() { - x - } else { - y - } -} -``` - -If we try to compile this, we get an error that talks about lifetimes: - -```text -error[E0106]: missing lifetime specifier - | -1 | fn longest(x: &str, y: &str) -> &str { - | ^ expected lifetime parameter - | - = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `x` or `y` -``` - -The help text is telling us that the return type needs a generic lifetime -parameter on it because this function is returning a reference and Rust can't -tell if the reference being returned refers to `x` or `y`. Actually, we don't -know either, since in the `if` block in the body of this function returns a -reference to `x` and the `else` block returns a reference to `y`! The way to -specify the lifetime parameters in this case is to have the same lifetime for -all of the input parameters and the return type: - -Filename: src/main.rs - -```rust -fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { - if x.len() > y.len() { - x - } else { - y - } -} -``` - -This will compile and will produce the result we want with the `main` function -in Listing 10-9. This function signature is now saying that for some lifetime -named `'a`, it will get two arguments, both which are string slices that live -at least as long as the lifetime `'a`. The function will return a string slice -that also will last at least as long as the lifetime `'a`. This is the contract -we are telling Rust we want it to enforce. By specifying the lifetime -parameters in this function signature, we are not changing the lifetimes of any -values passed in or returned, but we are saying that any values that do not -adhere to this contract should be rejected by the borrow checker. This function -does not know (or need to know) exactly how long `x` and `y` will live since it -knows that there is some scope that can be substituted for `'a` that will -satisfy this signature. - -The exact way to specify lifetime parameters depends on what your function is -doing. If the function didn't actually return the longest string slice but -instead always returned the first argument, we wouldn't need to specify a -lifetime on `y`. This code compiles: - -Filename: src/main.rs - -```rust -fn longest<'a>(x: &'a str, y: &str) -> &'a str { - x -} -``` - -The lifetime parameter for the return type needs to be specified and needs to -match one of the arguments' lifetime parameters. If the reference returned does -*not* refer to one of the arguments, the only other possibility is that it -refers to a value created within this function, and that would be a dangling -reference since the value will go out of scope at the end of the function. -Consider this attempted implementation of `longest`: - -Filename: src/main.rs - -```rust,ignore -fn longest<'a>(x: &str, y: &str) -> &'a str { - let result = String::from("really long string"); - result.as_str() -} -``` - -Even though we've specified a lifetime for the return type, this function fails -to compile with the following error message: - -```text -error: `result` does not live long enough - | -3 | result.as_str() - | ^^^^^^ does not live long enough -4 | } - | - borrowed value only lives until here - | -note: borrowed value must be valid for the lifetime 'a as defined on the block at 1:44... - | -1 | fn longest<'a>(x: &str, y: &str) -> &'a str { - | ^ -``` - -The problem is that `result` will go out of scope and get cleaned up at the end -of the `longest` function, and we're trying to return a reference to `result` -from the function. There's no way we can specify lifetime parameters that would -change the dangling reference, and Rust won't let us create a dangling -reference. In this case, the best fix would be to return an owned data type -rather than a reference so that the calling function is then responsible for -cleaning up the value. - -Ultimately, lifetime syntax is about connecting the lifetimes of various -arguments and return values of functions. Once they're connected, Rust has -enough information to allow memory-safe operations and disallow operations that -would create dangling pointers or otherwise violate memory safety. - -### Lifetime Elision - -If every reference has a lifetime, and we need to provide them for functions -that use references as arguments or return values, then why did this function -from the "String Slices" section of Chapter 4 compile? We haven't annotated any -lifetimes here, yet Rust happily compiles this function: - -Filename: src/lib.rs - -```rust -fn first_word(s: &str) -> &str { - let bytes = s.as_bytes(); - - for (i, &item) in bytes.iter().enumerate() { - if item == b' ' { - return &s[0..i]; - } - } - - &s[..] -} -``` - -The answer is historical: in early versions of pre-1.0 Rust, this would not -have compiled. Every reference needed an explicit lifetime. At that time, the -function signature would have been written like this: - -```rust,ignore -fn first_word<'a>(s: &'a str) -> &'a str { -``` - -After writing a lot of Rust code, some patterns developed. The Rust team -noticed that the vast majority of code followed the pattern, and being forced -to use explicit lifetime syntax on every reference wasn't a very great -developer experience. - -To make it so that lifetime annotations weren't needed as often, they added -*lifetime elision rules* to Rust's analysis of references. This feature isn't -full inference: Rust doesn't try to guess what you meant in places where there -could be ambiguity. The rules are a very basic set of particular cases, and if -your code fits one of those cases, you don't need to write the lifetimes -explicitly. Here are the rules: - -Lifetimes on function arguments are called *input lifetimes*, and lifetimes on -return values are called *output lifetimes*. There's one rule related to how -Rust infers input lifetimes in the absence of explicit annotations: - -1. Each argument that is a reference and therefore needs a lifetime parameter - gets its own. In other words, a function with one argument gets one lifetime - parameter: `fn foo<'a>(x: &'a i32)`, a function with two arguments gets two - separate lifetime parameters: `fn foo<'a, 'b>(x: &'a i32, y: &'b i32)`, and - so on. - -And two rules related to output lifetimes: - -2. If there is exactly one input lifetime parameter, that lifetime is assigned - to all output lifetime parameters: `fn foo<'a>(x: &'a i32) -> &'a i32`. -3. If there are multiple input lifetime parameters, but one of them is `&self` - or `&mut self`, then the lifetime of `self` is the lifetime assigned to all - output lifetime parameters. This makes writing methods much nicer. - -If none of these three rules apply, then you must explicitly annotate input and -output lifetimes. These rules do apply in the `first_word` function, which is -why we didn't have to specify any lifetimes. - -These rules cover the vast majority of cases, allowing you to write a lot of -code without needing to specify explicit lifetimes. However, Rust is always -checking these rules and the lifetimes in your program, and cases in which the -lifetime elision rules do not apply are cases where you'll need to add lifetime -parameters to help Rust understand the contracts of your code. - -### Lifetime Annotations in Method Definitions - -Now that we've gone over the lifetime elision rules, defining methods on -structs that hold references will make more sense. The lifetime name needs to -be declared after the `impl` keyword and then used after the struct's name, -since the lifetime is part of the struct's type. The lifetimes can be elided in -any methods where the output type's lifetime is the same as that of the -struct's because of the third elision rule. Here's a struct called `App` that -holds a reference to another struct, `Config`, defined elsewhere. The -`append_to_name` method does not need lifetime annotations even though the -method has a reference as an argument and is returning a reference; the -lifetime of the return value will be the lifetime of `self`: - -Filename: src/lib.rs - -```rust -struct App<'a> { - name: String, - config: &'a Config, -} - -impl<'a> App<'a> { - fn append_to_name(&mut self, suffix: &str) -> &str { - self.name.push_str(suffix); - self.name.as_str() - } -} -``` - -### The Static Lifetime - -There is *one* special lifetime that Rust knows about: `'static`. The `'static` -lifetime is the entire duration of the program. All string literals have the -`'static` lifetime: - -```rust -let s: &'static str = "I have a static lifetime."; -``` - -The text of this string is stored directly in the binary of your program and -the binary of your program is always available. Therefore, the lifetime of all -string literals is `'static`. You may see suggestions to use the `'static` -lifetime in error message help text, but before adding it, think about whether -the reference you have is one that actually lives the entire lifetime of your -program or not (or even if you want it to live that long, if it could). Most of -the time, the problem in the code is an attempt to create a dangling reference -or a mismatch of the available lifetimes, and the solution is fixing those -problems, not specifying the `'static` lifetime. - -## Summary - -We've covered the basics of Rust's system of generics. Generics are the core to -building good abstractions, and can be used in a number of ways. There's more -to learn about them, particularly lifetimes, but we'll cover those in later -chapters. Let's move on to I/O functionality. diff --git a/nostarch/chapter11.md b/nostarch/chapter11.md deleted file mode 100644 index 64582c7..0000000 --- a/nostarch/chapter11.md +++ /dev/null @@ -1,887 +0,0 @@ - -[TOC] - -# Testing - -> Program testing can be a very effective way to show the presence of bugs, but -> it is hopelessly inadequate for showing their absence. -> -> Edsger W. Dijkstra, "The Humble Programmer" (1972) - -Rust is a programming language that cares a lot about correctness, but -correctness is a complex topic and isn't easy to prove. Rust places a lot of -weight on its type system to help ensure that our programs do what we intend, -but it cannot help with everything. As such, Rust also includes support for -writing software tests in the language itself. - -For example, we can write a function called `add_two` with a signature that -accepts an integer as an argument and returns an integer as a result. We can -implement and compile that function, and Rust can do all the type checking and -borrow checking that we've seen it's capable of doing. What Rust *can't* check -for us is that we've implemented this function to return the argument plus two -and not the argument plus 10 or the argument minus 50! That's where tests come -in. We can write tests that, for example, pass `3` to the `add_two` function -and check that we get `5` back. We can run the tests whenever we make changes -to our code to make sure we didn't change any existing behavior from what the -tests specify it should be. - -Testing is a skill, and we cannot hope to cover everything about how to write -good tests in one chapter of a book. What we can discuss, however, are the -mechanics of Rust's testing facilities. We'll talk about the annotations and -macros available to you when writing your tests, the default behavior and -options provided for running your tests, and how to organize tests into unit -tests and integration tests. - -## Writing Tests - -Tests are Rust functions that use particular features and are written in such a -way as to verify that non-test code is functioning in the expected manner. -Everything we've discussed about Rust code applies to Rust tests as well! Let's -look at the features Rust provides specifically for writing tests: the `test` -attribute, a few macros, and the `should_panic` attribute. - -### The `test` attribute - -At its simplest, a test in Rust is a function that's annotated with the `test` -attribute. Let's make a new library project with Cargo called `adder`: - -```text -$ cargo new adder - Created library `adder` project -$ cd adder -``` - -Cargo will automatically generate a simple test when you make a new library -project. Here's the contents of `src/lib.rs`: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} -``` - -For now, let's ignore the `tests` module and the `#[cfg(test)]` annotation in -order to focus on just the function. Note the `#[test]` before it: this -attribute indicates this is a test function. The function currently has no -body; that's good enough to pass! We can run the tests with `cargo test`: - -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.22 secs - Running target/debug/deps/adder-ce99bcc2479f4607 - -running 1 test -test it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests adder - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Cargo compiled and ran our tests. There are two sets of output here; we're -going to focus on the first set in this chapter. The second set of output is -for documentation tests, which we'll talk about in Chapter 14. For now, note -this line: - -```text -test it_works ... ok -``` - -The `it_works` text comes from the name of our function. - -We also get a summary line that tells us the aggregate results of all the -tests that we have: - -```text -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -### The `assert!` macro - -The empty test function passes because any test which doesn't `panic!` passes, -and any test that does `panic!` fails. Let's make the test fail by using the -`assert!` macro: - -Filename: src/lib.rs - -```rust -#[test] -fn it_works() { - assert!(false); -} -``` - -The `assert!` macro is provided by the standard library, and it takes one -argument. If the argument is `true`, nothing happens. If the argument is -`false`, the macro will `panic!`. Let's run our tests again: - -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.22 secs - Running target/debug/deps/adder-ce99bcc2479f4607 - -running 1 test -test it_works ... FAILED - -failures: - ----- it_works stdout ---- - thread 'it_works' panicked at 'assertion failed: false', src/lib.rs:5 -note: Run with `RUST_BACKTRACE=1` for a backtrace. - - -failures: - it_works - -test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured - -error: test failed -``` - -Rust indicates that our test failed: - -```text -test it_works ... FAILED -``` - -And shows that the test failed because the `assert!` macro in `src/lib.rs` on -line 5 got a `false` value: - -```text -thread 'it_works' panicked at 'assertion failed: false', src/lib.rs:5 -``` - -The test failure is also reflected in the summary line: - -```text -test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured -``` - -### Testing equality with the `assert_eq!` and `assert_ne!` macros - -A common way to test functionality is to compare the result of the code under -test to the value you expect it to be, and check that they're equal. You can do -this using the `assert!` macro by passing it an expression using the `==` -macro. This is so common, though, that the standard library provides a pair of -macros to do this for convenience: `assert_eq!` and `assert_ne!`. These macros -compare two arguments for equality or inequality, respectively. The other -advantage of using these macros is they will print out what the two values -actually are if the assertion fails so that it's easier to see *why* the test -failed, whereas the `assert!` macro would just print out that it got a `false` -value for the `==` expression. - -Here's an example test that uses each of these macros and will pass: - -Filename: src/lib.rs - -```rust -#[test] -fn it_works() { - assert_eq!("Hello", "Hello"); - - assert_ne!("Hello", "world"); -} -``` - -You can also specify an optional third argument to each of these macros, which -is a custom message that you'd like to be added to the failure message. The -macros expand to logic similar to this: - -```rust,ignore -// assert_eq! - panic if the values aren't equal -if left_val != right_val { - panic!( - "assertion failed: `(left == right)` (left: `{:?}`, right: `{:?}`): {}" - left_val, - right_val, - optional_custom_message - ) -} - -// assert_ne! - panic if the values are equal -if left_val == right_val { - panic!( - "assertion failed: `(left != right)` (left: `{:?}`, right: `{:?}`): {}" - left_val, - right_val, - optional_custom_message - ) -} -``` - -Let's take a look at a test that will fail becasue `hello` is not equal to -`world`. We've also added a custom error message, `greeting operation failed`: - -Filename: src/lib.rs - -```rust -#[test] -fn a_simple_case() { - let result = "hello"; // this value would come from running your code - assert_eq!(result, "world", "greeting operation failed"); -} -``` - -Running this indeed fails, and the output we get explains why the test failed -and includes the custom error message we specified: - -```text ----- a_simple_case stdout ---- - thread 'a_simple_case' panicked at 'assertion failed: `(left == right)` - (left: `"hello"`, right: `"world"`): greeting operation failed', - src/main.rs:4 -``` - -The two arguments to `assert_eq!` are named "left" and "right" rather than -"expected" and "actual"; the order of the value that comes from your code and -the value hardcoded into your test isn't important. - -Since these macros use the operators `==` and `!=` and print the values using -debug formatting, the values being compared must implement the `PartialEq` and -`Debug` traits. Types provided by Rust implement these traits, but for structs -and enums that you define, you'll need to add `PartialEq` in order to be able -to assert that values of those types are equal or not equal and `Debug` in -order to be able to print out the values in the case that the assertion fails. -Because both of these traits are derivable traits that we mentioned in Chapter -5, usually this is as straightforward as adding the `#[derive(PartialEq, -Debug)]` annotation to your struct or enum definition. See Appendix C for more -details about these and other derivable traits. - -## Test for failure with `should_panic` - -We can invert our test's failure with another attribute: `should_panic`. This -is useful when we want to test that calling a particular function will cause an -error. For example, let's test something that we know will panic from Chapter -8: attempting to create a slice using range syntax with byte indices that -aren't on character boundaries. Add the `#[should_panic]` attribute before the -function like the `#[test]` attribute, as shown in Listing 11-1: - -
-Filename: src/lib.rs - -```rust -#[test] -#[should_panic] -fn slice_not_on_char_boundaries() { - let s = "Здравствуйте"; - &s[0..1]; -} -``` - -
- -Listing 11-1: A test expecting a `panic!` - -
-
- -This test will succeed, since the code panics and we said that it should. If -this code happened to run and did not cause a `panic!`, this test would fail. - -`should_panic` tests can be fragile, as it's hard to guarantee that the test -didn't fail for a different reason than the one you were expecting. To help -with this, an optional `expected` parameter can be added to the `should_panic` -attribute. The test harness will make sure that the failure message contains -the provided text. A more robust version of Listing 11-1 would be the -following, in Listing 11-2: - -
-Filename: src/lib.rs - -```rust -#[test] -#[should_panic(expected = "do not lie on character boundary")] -fn slice_not_on_char_boundaries() { - let s = "Здравствуйте"; - &s[0..1]; -} -``` - - - -
- -Listing 11-2: A test expecting a `panic!` with a particular message - -
-
- -Try on your own to see what happens when a `should_panic` test panics but -doesn't match the expected message: cause a `panic!` that happens for a -different reason in this test, or change the expected panic message to -something that doesn't match the character boundary panic message. - -## Running tests - -Just like `cargo run` compiles your code and then runs the resulting binary, -`cargo test` compiles your code in test mode and runs the resulting test -binary. The default behavior of the binary that `cargo test` produces is to run -all the tests in parallel and to capture output generated during test runs so -that it's easier to read the output about the test results. - -The default behavior of running tests can be changed by specifying command line -options. Some of these options can be passed to `cargo test`, and some need to -be passed instead to the resulting test binary. The way to separate these -arguments is with `--`: after `cargo test`, list the arguments that go to -`cargo test`, then the separator `--`, and then the arguments that go to the -test binary. - -### Tests Run in Parallel - -Tests are run in parallel using threads. For this reason, you should take care -that your tests are written in such a way as to not depend on each other or on -any shared state. Shared state can also include the environment, such as the -current working directory or environment variables. - -If you don't want this behavior, or if you want more fine-grained control over -the number of threads used, you can send the `--test-threads` flag and the -number of threads to the test binary. Setting the number of test threads to 1 -means to not use any parallelism: - -```text -$ cargo test -- --test-threads=1 -``` - -### Tests Capture Output - -By default, Rust's test library captures and discards output to standard out -and standard error, unless the test fails. For example, if you call `println!` -in a test and the test passes, you won't see the `println!` output in your -terminal. This behavior can be disabled by sending the `--nocapture` flag to -the test binary: - -```text -$ cargo test -- --nocapture -``` - -### Running a Subset of Tests by Name - -Sometimes, running a full test suite can take a long time. If you're only -working on code in a particular area, you might want to only run the tests -having to do with that code. `cargo test` takes an argument that allows you to -only run certain tests, specified by name. - -Let's create three tests with the following names as shown in Listing 11-3: - -
-Filename: src/lib.rs - -```rust -#[test] -fn add_two_and_two() { - assert_eq!(4, 2 + 2); -} - -#[test] -fn add_three_and_two() { - assert_eq!(5, 3 + 2); -} - -#[test] -fn one_hundred() { - assert_eq!(102, 100 + 2); -} -``` - -
- -Listing 11-3: Three tests with a variety of names - -
-
- -Running with different arguments will run different subsets of the tests. No -arguments, as we've already seen, runs all the tests: - -```text -$ cargo test - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-06a75b4a1f2515e9 - -running 3 tests -test add_three_and_two ... ok -test one_hundred ... ok -test add_two_and_two ... ok - -test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured -``` - -We can pass the name of any test function to run only that test: - -```text -$ cargo test one_hundred - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-06a75b4a1f2515e9 - -running 1 test -test one_hundred ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -We can also pass part of a name, and `cargo test` will run all tests that match: - -```text -$ cargo test add - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-06a75b4a1f2515e9 - -running 2 tests -test add_three_and_two ... ok -test add_two_and_two ... ok - -test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured -``` - -Module names become part of the test name, so module names can be used in a -similar way to run just the tests for a particular module. For example, if our -code was organized into a module named `adding` and a module named -`subtracting` with tests in each, as in Listing 11-4: - -
-Filename: src/lib.rs - -```rust -mod adding { - #[test] - fn add_two_and_two() { - assert_eq!(4, 2 + 2); - } - - #[test] - fn add_three_and_two() { - assert_eq!(5, 3 + 2); - } - - #[test] - fn one_hundred() { - assert_eq!(102, 100 + 2); - } -} - -mod subtracting { - #[test] - fn subtract_three_and_two() { - assert_eq!(1, 3 - 2); - } -} -``` - -
- -Listing 11-4: Tests in two modules named `adding` and `subtracting` - -
-
- -Running `cargo test` will run all of the tests, and the module names will -appear in the test names in the output: - -```text -$ cargo test - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-d84f1c6cb24adeb4 - -running 4 tests -test adding::add_two_and_two ... ok -test adding::add_three_and_two ... ok -test subtracting::subtract_three_and_two ... ok -test adding::one_hundred ... ok -``` - -Running `cargo test adding` would run just the tests in that module and not any -of the tests in the subtracting module: - -```text -$ cargo test adding - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-d84f1c6cb24adeb4 - -running 3 tests -test adding::add_three_and_two ... ok -test adding::one_hundred ... ok -test adding::add_two_and_two ... ok - -test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured -``` - -### Ignore Some Tests Unless Specifically Requested - -Sometimes a few specific tests can be very time-consuming to execute, so during -most runs of `cargo test`, we'd like to exclude them. Instead of having to -construct an argument to `cargo test` to run all tests except these and -remember to use that argument every time, we can annotate these tests with the -`ignore` attribute: - -Filename: src/lib.rs - -```rust -#[test] -fn it_works() { - assert!(true); -} - -#[test] -#[ignore] -fn expensive_test() { - // code that takes an hour to run -} -``` - -Now if we run our tests, we'll see `it_works` is run, but `expensive_test` is -not: - -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.24 secs - Running target/debug/deps/adder-ce99bcc2479f4607 - -running 2 tests -test expensive_test ... ignored -test it_works ... ok - -test result: ok. 1 passed; 0 failed; 1 ignored; 0 measured - - Doc-tests adder - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -We can run only the expensive tests by explicitly asking to run them using -`cargo test -- --ignored`: - -```text -$ cargo test -- --ignored - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-ce99bcc2479f4607 - -running 1 test -test expensive_test ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -This way, most of the time that you run `cargo test` the results would be fast. -When you're at a point that it makes sense to check the results of the -`ignored` tests and you have time to wait for the results, you can choose to -run `cargo test -- --ignored` instead. - -## Test Organization - -As mentioned before, testing is a large discipline, and different people -sometimes use different terminology and organization. The Rust community tends -to think about tests in terms of two main categories: *unit tests* and -*integration tests*. Unit tests tend to be smaller and more focused, testing -one module in isolation at a time. They can also test private interfaces. -Integration tests are entirely external to your library. They use your code in -the same way any other code would, using only the public interface and -exercising multiple modules per test. Both kinds of tests are important to -ensure that the pieces of your library are doing what you expect them to -separately and together. - -### Unit Tests - -The purpose of unit tests is to test each unit of code in isolation from the -rest of the code, in order to be able to quickly pinpoint where code is working -as expected or not. Unit tests live in the *src* directory, in the same files -as the code they are testing. They are separated into their own `tests` module -in each file. - -#### The Tests Module and `cfg(test)` - -By placing tests in their own module and using the `cfg` annotation on the -module, we can tell Rust to only compile and run the test code when we run -`cargo test`. This saves compile time when we only want to build the library -code with `cargo build`, and saves space in the resulting compiled artifact -since the tests are not included. - -Remember when we generated the new `adder` project in the last section? Cargo -generated this code for us: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} -``` - -We ignored the module stuff so we could concentrate on the mechanics of the -test code inside the module, but now let's focus on the code surrounding our -tests. - -First of all, there's a new attribute, `cfg`. The `cfg` attribute lets us -declare that something should only be included given a certain *configuration*. -Rust provides the `test` configuration for compiling and running tests. By -using this attribute, Cargo only compiles our test code if we're currently -trying to run the tests. - -Next, the `tests` module holds all of our test functions, while our code is -outside of the `tests` module. The name of the `tests` module is a convention; -otherwise this is a regular module that follows the usual visibility rules we -covered in Chapter 7. Because we're in an inner module, we need to bring the -code under test into scope. This can be annoying if you have a large module, so -this is a common use of globs. - -Up until now in this chapter, we've been writing tests in our `adder` project -that don't actually call any code we've written. Let's change that now! In -*src/lib.rs*, place this `add_two` function and `tests` module that has a test -function to exercise the code, as shown in Listing 11-5: - -
-Filename: src/lib.rs - -```rust -pub fn add_two(a: i32) -> i32 { - a + 2 -} - -#[cfg(test)] -mod tests { - use add_two; - - #[test] - fn it_works() { - assert_eq!(4, add_two(2)); - } -} -``` - -
- -Listing 11-5: Testing the function `add_two` in a child `tests` module - -
-
- -Notice in addition to the test function, we also added `use add_two;` within -the `tests` module. This brings the code we want to test into the scope of the -inner `tests` module, just like we'd need to do for any inner module. If we run -this test now with `cargo test`, it will pass: - -```text -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -If we had forgotten to bring the `add_two` function into scope, we would get an -unresolved name error since the `tests` module wouldn't know anything about the -`add_two` function: - -```text -error[E0425]: unresolved name `add_two` - --> src/lib.rs:9:23 - | -9 | assert_eq!(4, add_two(2)); - | ^^^^^^^ unresolved name -``` - -If this module contained lots of code we wanted to test, it would be annoying -to list everything in the `use` statement in the tests. It's common instead to -put `use super::*;` within a module's `test` submodule in order to bring -everything into the `test` module scope at once. - -#### Testing Private Functions - -There's controversy within the testing community about whether you should write -unit tests for private functions or not. Regardless of which testing ideology -you adhere to, Rust does allow you to test private functions due to the way -that the privacy rules work. Consider the code in Listing 11-6 with the private -function `internal_adder`: - -
-Filename: src/lib.rs - -```rust -pub fn add_two(a: i32) -> i32 { - internal_adder(a, 2) -} - -fn internal_adder(a: i32, b: i32) -> i32 { - a + b -} - -#[cfg(test)] -mod tests { - use internal_adder; - - #[test] - fn internal() { - assert_eq!(4, internal_adder(2, 2)); - } -} -``` - -
- -Listing 11-6: Testing a private function - -
-
- -Because tests are just Rust code and the `tests` module is just another module, -we can import and call `internal_adder` in a test just fine. If you don't think -private functions should be tested, there's nothing in Rust that will compel -you to do so. - -### Integration Tests - -In Rust, integration tests are tests that are entirely external to your -library. They use your library in the same way any other code would. Their -purpose is to test that many parts of your library work correctly together. -Units of code that work correctly by themselves could have problems when -integrated, so test coverage of the integrated code is important as well. - -#### The *tests* Directory - -Cargo has support for integration tests in the *tests* directory. If you make -one and put Rust files inside, Cargo will compile each of the files as an -individual crate. Let's give it a try! - -First, make a *tests* directory at the top level of your project directory, -next to *src*. Then, make a new file, *tests/integration_test.rs*, and put the -code in Listing 11-7 inside: - -
-Filename: tests/integration_test.rs - -```rust,ignore -extern crate adder; - -#[test] -fn it_adds_two() { - assert_eq!(4, adder::add_two(2)); -} -``` - -
- -Listing 11-7: An integration test of a function in the `adder` crate - -
-
- -We now have `extern crate adder` at the top, which we didn't need in the unit -tests. Each test in the `tests` directory is an entirely separate crate, so we -need to import our library into each of them. This is also why `tests` is a -suitable place to write integration-style tests: they use the library like any -other consumer of it would, by importing the crate and using only the public -API. - -We also don't need a `tests` module in this file. The whole directory won't be -compiled unless we're running the tests, so we don't need to annotate any part -of it with `#[cfg(test)]`. Also, each test file is already isolated into its -own crate, so we don't need to separate the test code further. - -Let's run the integration tests, which also get run when we run `cargo test`: - -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Running target/debug/deps/adder-91b3e234d4ed382a - -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Running target/debug/integration_test-952a27e0126bb565 - -running 1 test -test it_adds_two ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests adder - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Now we have three sections of output: the unit tests, the integration test, and -the doc tests. Note that adding more unit tests in any *src* file will add more -lines to the unit tests section. Adding more test functions to the integration -test file we created will add more lines to that section. If we add more -integration test *files* in the *tests* directory, there will be more -integration test sections: one for each file. - -Specifying a test function name argument with `cargo test` will also match -against test function names in any integration test file. To run all of the -tests in only one particular integration test file, use the `--test` argument -of `cargo test`: - -```text -$ cargo test --test integration_test - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/integration_test-952a27e0126bb565 - -running 1 test -test it_adds_two ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -#### Submodules in Integration Tests - -As you add more integration tests, you may want to make more than one file in -the `tests` directory in order to group the test functions by the functionality -they're testing, for example. As we mentioned before, that will work fine, -given that Cargo treats every file as its own crate. - -Eventually, you may have a set of helper functions that are common to all -integration tests, for example, functions that set up common scenarios. If you -extract these into a file in the *tests* directory, like *tests/common.rs* for -example, this file will be compiled into a separate crate just like the Rust -files in this directory that contain test functions are. There will be a -separate section in the test output for this file. Since this is probably not -what you want, it's recommended to instead use a *mod.rs* file in a -subdirectory, like *tests/common/mod.rs*, for helper functions. Files in -subdirectories of the *tests* directory do not get compiled as separate crates -or have sections in the test output. - -#### Integration Tests for Binary Crates - -If your project is a binary crate that only contains a *src/main.rs* and does -not have a *src/lib.rs*, it is not possible to create integration tests in the -*tests* directory and use `extern crate` to import the functions in -*src/main.rs*. This is one of the reasons Rust projects that provide a binary -have a straightforward *src/main.rs* that calls logic that lives in -*src/lib.rs*. With that structure, integration tests *can* test the library -crate by using `extern crate` to cover the important functionality, and if that -works, the small amount of code in *src/main.rs* will work as well and does not -need to be tested. - -## Summary - -Rust's testing features provide a way to specify how code should function to -ensure the code continues to work in the specified ways even as we make -changes. Unit tests exercise different parts of a library separately and can -test private implementation details. Integration tests cover the use of many -parts of the library working together, and use the library's public API to test -the code in the same way other code will use it. Rust's type system and -ownership rules help prevent some kinds of bugs, but tests are an important -part of reducing logic bugs having to do with how your code is expected to -behave. - -Let's put together the knowledge from this chapter and other previous chapters -and work on a project in the next chapter! diff --git a/nostarch/chapter12.md b/nostarch/chapter12.md deleted file mode 100644 index 349582b..0000000 --- a/nostarch/chapter12.md +++ /dev/null @@ -1,1580 +0,0 @@ - -[TOC] - -# An I/O Project - -We've learned a lot over the last few chapters. Let's take that new knowledge -and apply it by building a project together. Along the way, we'll learn a bit -more about Rust's standard library. - -So what should we build? One that uses Rust's strengths. A great use of Rust is -for command line tools: Rust's speed, safety, 'single binary' output, and -cross-platform support make it a good language choice for this kind of task. So -we'll make our own version of a classic command line tool: `grep`. `grep` is -short for "Globally search a Regular Expression and Print." In the -simplest use case, it does this: - -- Takes a filename and a string as arguments. -- Reads the file. -- Finds lines in the file that contain the string argument. -- Prints out those lines. - -In addition, we'll add one extra feature: an environment variable that will -allow us to search for the string argument in a case-insensitive way. - -There's another great reason to use `grep` as an example project: a very -fully-featured version of `grep` has already been created in Rust by a -community member, Andrew Gallant. It's called `ripgrep`, and it's very, -very fast. While our version of `grep` will be fairly simple, you'll have -some of the background knowledge to understand that project if you want to see -something more real-world. - -This project will bring together a number of things we learned previously: - -- Organize code (using what we learned in modules, Chapter 7) -- Use vectors and strings (collections, Chapter 8) -- Handle errors (Chapter 9) -- Use traits and lifetimes where appropriate (Chapter 10) -- Have tests (Chapter 11) - -Additionally, we'll briefly introduce closures, iterators, and trait objects, -which Chapters XX, YY, and ZZ respectively are about to cover in detail. - -Let's create a new project with, as always, `cargo new`: - -```text -$ cargo new --bin greprs - Created binary (application) `greprs` project -$ cd greprs -``` - -We're calling our version of `grep` 'greprs', so that we don't confuse any of -our users into thinking that it's the more fully-featured version of `grep` -they may already have installed on their system. - -## Accepting Command Line Arguments - -Our first task is to have `greprs` accept its two command line arguments. There -are some existing libraries on crates.io that can help us do this, but since -we're learning, we'll implement this ourselves. - -We'll need to call a function provided in Rust's standard library: -`std::env::args`. This function returns an *iterator* of the command line -arguments that were given to our program. We haven't discussed iterators yet; -Chapter 16 will cover them fully. For our purposes, though, we don't need to -understand much about how they work in order to use them. We only need to -understand two things: - -1. Iterators produce a series of values. -2. We can call the `collect` function on an iterator to turn it into a vector - containing all of the elements the iterator produces. - -Let's give it a try as shown in Listing 12-1: - -
-Filename: src/main.rs - -```rust -use std::env; - -fn main() { - let args: Vec = env::args().collect(); - println!("{:?}", args); -} -``` - -
- -Listing 12-1: Collect the command line arguments into a vector and print them out - -
-
- - - -First, we have a `use` statement to bring the `std::env` module into scope. -When using a function that's nested in more than one level of module, like -`std::env::args` is, it's conventional to use `use` to bring the parent module -into scope, rather than the function itself. `env::args` is less ambiguous than -a lone `args`. Also, if we end up using more than one function in `std::env`, -we only need a single `use`. - -On the first line of `main`, we call `env::args`, and immediately use `collect` -to create a vector out of it. We're also explicitly annotating the type of -`args` here: `collect` can be used to create many kinds of collections. Rust -won't be able to infer what kind of type we want, so the annotation is -required. We very rarely need to annotate types in Rust, but `collect` is one -function where you often need to. - -Finally, we print out the vector with the debug formatter, `:?`. Let's try -running our code with no arguments, and then with two arguments: - -```text -$ cargo run -["target/debug/greprs"] - -$ cargo run needle haystack -...snip... -["target/debug/greprs", "needle", "haystack"] -``` - -You'll notice one interesting thing: the name of the binary is the first -argument. The reasons for this are out of the scope of this chapter, but it's -something we'll have to remember to account for. - -Now that we have a way to access all of the arguments, let's find the ones we -care about and save them in variables as shown in Listing 12-2: - -
-Filename: src/main.rs - -```rust -use std::env; - -fn main() { - let args: Vec = env::args().collect(); - - let search = &args[1]; - let filename = &args[2]; - - println!("Searching for {}", search); - println!("In file {}", filename); -} -``` - -
- -Listing 12-2: Create variables to hold the search argument and filename argument - -
-
- - - -Remember, the program's name is the first argument, so we don't need `args[0]`. -We've decided that the first argument will be the string we're searching for, -so we put a reference to the first argument in the variable `search`. The -second argument will be the filename, so we put a reference to the second -argument in the variable `filename`. Let's try running this program again: - -```text -$ cargo run test sample.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe test sample.txt` -Searching for test -In file sample.txt -``` - -Great! There's one problem, though. Let's try giving it no arguments: - -```text -$ cargo run - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe` -thread 'main' panicked at 'index out of bounds: the len is 1 -but the index is 1', ../src/libcollections\vec.rs:1307 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -``` - -Because our vector only has one element, the program's name, but we tried to -access the second element, our program panics with a message about the -out-of-bound access. While this error message is _accurate_, it's not -meaningful to users of our program at all. We could fix this problem right now, -but let's push forward: we'll improve this situation before we're finished. - -## Reading a File - -Now that we have some variables containing the information that we need, let's -try using them. The next step is to open the file that we want to search. To do -that, we need a file. Create one called `poem.txt` at the root level of your -project, and fill it up with some Emily Dickinson: - -Filename: poem.txt - -```text -I'm nobody! Who are you? -Are you nobody, too? -Then there's a pair of us — don't tell! -They'd banish us, you know. - -How dreary to be somebody! -How public, like a frog -To tell your name the livelong day -To an admiring bog! -``` - - - -With that in place, let's edit *src/main.rs* and add code to open the file as -shown in Listing 12-3: - -
-Filename: src/main.rs - -```rust -use std::env; -use std::fs::File; -use std::io::prelude::*; - -fn main() { - let args: Vec = env::args().collect(); - - let search = &args[1]; - let filename = &args[2]; - - println!("Searching for {}", search); - println!("In file {}", filename); - - let mut f = File::open(filename).expect("file not found"); - - let mut contents = String::new(); - f.read_to_string(&mut contents).expect("something went wrong reading the file"); - - println!("With text:\n{}", contents); -} -``` - -
- -Listing 12-3: Read the contents of the file specified by the second argument - -
-
- - - -We've added a few things. First of all, we need some more `use` statements to -bring in the relevant parts of the standard library: we need `std::fs::File` -for dealing with files, and `std::io::prelude::*` contains various traits that -are useful when doing I/O, including file I/O. In the same way that Rust has a -general prelude that brings certain things into scope automatically, the -`std::io` module has its own prelude of common things you'll need when working -with I/O. Unlike the default prelude, we must explicitly `use` the prelude in -`std::io`. - -In `main`, we've added three things: first, we get a handle to the file and -open it by using the `File::open` function and passing it the name of the file -specified in the second argument. Second, we create a mutable, empty `String` -in the variable `contents`, then call `read_to_string` on our file handle with -our `contents` string as the argument; `contents` is where `read_to_string` -will place the data it reads. Finally, we print out the entire file contents, -which is a way for us to be sure our program is working so far. - -Let's try running this code, specifying any string for the first argument (since -we haven't implemented the searching part yet) and our *poem.txt* file as the -second argument: - -```text -$ cargo run the poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe the poem.txt` -Searching for the -In file poem.txt -With text: -I'm nobody! Who are you? -Are you nobody, too? -Then there's a pair of us — don't tell! -They'd banish us, you know. - -How dreary to be somebody! -How public, like a frog -To tell your name the livelong day -To an admiring bog! -``` - -Great! Our code is working. However, it's got a few flaws. Because our program -is still small, these flaws aren't a huge deal, but as our program grows, it -will be harder and harder to fix them in a clean way. Let's do the refactoring -now, instead of waiting. The refactoring will be much easier to do with only -this small amount of code. - -## Improving Error Handling and Modularity - -There are four problems that we'd like to fix to improve our program, and they -all have to do with potential errors and the way the program is structured. The -first problem is where we open the file: we've used `expect` to print out an -error message if opening the file fails, but the error message only says "file -not found". There are a number of ways that opening a file can fail, but we're -always assuming that it's due to the file being missing. For example, the file -could exist, but we might not have permission to open it: right now, we print -an error message that says the wrong thing! - -Secondly, our use of `expect` over and over is similar to the earlier issue we -noted with the `panic!` on indexing if we don't pass any command line -arguments: while it _works_, it's a bit unprincipled, and we're doing it all -throughout our program. It would be nice to put our error handling in one spot. - -The third problem is that our `main` function now does two things: it parses -arguments, and it opens up files. For such a small function, this isn't a huge -problem. However, as we keep growing our program inside of `main`, the number of -separate tasks in the `main` function will get larger and larger. As one -function gains many responsibilities, it gets harder to reason about, harder to -test, and harder to change without breaking one of its parts. - -This also ties into our fourth problem: while `search` and `filename` are -configuration variables to our program, variables like `f` and `contents` are -used to perform our program's logic. The longer `main` gets, the more variables -we're going to bring into scope, and the more variables we have in scope, the -harder it is to keep track of which ones we need for which purpose. It would be -better if we grouped the configuration variables into one structure to make -their purpose clear. - -Let's address these problems by restructuring our project. - -### Separation of Concerns for Binary Projects - -These kinds of organizational problems are common to many similar kinds of -projects, so the Rust community has developed a pattern for organizing the -separate concerns. This pattern is useful for organizing any binary project -you'll build in Rust, so we can justify doing this refactoring a bit earlier, -since we know that our project fits the pattern. The pattern looks like this: - -1. Split your program into both a *main.rs* and a *lib.rs*. -2. Place your command line parsing logic into *main.rs*. -3. Place your program's logic into *lib.rs*. -4. The job of the `main` function is: - * parse arguments - * set up any other configuration - * call a `run` function in *lib.rs* - * if `run` returns an error, handle that error - -Whew! The pattern sounds more complicated than it is, honestly. It's all about -separating concerns: *main.rs* handles actually running the program, and -*lib.rs* handles all of the actual logic of the task at hand. Let's re-work our -program into this pattern. First, let's extract a function whose purpose is -only to parse arguments. Listing 12-4 shows the new start of `main` that calls -a new function `parse_config`, which we're still going to define in -*src/main.rs*: - -
-Filename: src/main.rs - -```rust,ignore -fn main() { - let args: Vec = env::args().collect(); - - let (search, filename) = parse_config(&args); - - // ...snip... -} - -fn parse_config(args: &[String]) -> (&str, &str) { - let search = &args[1]; - let filename = &args[2]; - - (search, filename) -} -``` - -
- -Listing 12-4: Extract a `parse_config` function from `main` - -
-
- - - -This may seem like overkill, but we're working in small steps. After making -this change, run the program again to verify that the argument parsing still -works. It's good to check your progress often, so that you have a better idea -of which change caused a problem, should you encounter one. - -### Grouping Configuration Values - -Now that we have a function, let's improve it. Our code still has an indication -that there's a better design possible: we return a tuple, but then immediately -break that tuple up into individual parts again. This code isn't bad on its -own, but there's one other sign we have room for improvement: we called our -function `parse_config`. The `config` part of the name is saying the two values -we return should really be bound together, since they're both part of one -configuration value. - -> Note: some people call this anti-pattern of using primitive values when a -> complex type would be more appropriate *primitive obsession*. - -Let's introduce a struct to hold all of our configuration. Listing 12-5 shows -the addition of the `Config` struct definition, the refactoring of -`parse_config`, and updates to `main`: - -
-Filename: src/main.rs - -```rust -# use std::env; -# -fn main() { - let args: Vec = env::args().collect(); - - let config = parse_config(&args); - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - // ...snip... -} - -struct Config { - search: String, - filename: String, -} - -fn parse_config(args: &[String]) -> Config { - let search = args[1].clone(); - let filename = args[2].clone(); - - Config { - search: search, - filename: filename, - } -} -``` - -
- -Listing 12-5: Refactoring `parse_config` to return an instance of a `Config` -struct - -
-
- - - -The signature of `parse_config` now indicates that it returns a `Config` value. -In the body of `parse_config`, we used to be returning string slices that were -references to `String` values in `args`, but we've defined `Config` to contain -owned `String` values. Because the argument to `parse_config` is a slice of -`String` values, the `Config` instance can't take ownership of the `String` -values: that violates Rust's borrowing rules, since the `args` variable in -`main` owns the `String` values and is only letting the `parse_config` function -borrow them. - -There are a number of different ways we could manage the `String` data; for -now, we'll take the easy but less efficient route, and call the `clone` method -on the string slices. The call to `clone` will make a full copy of the string's -data for the `Config` instance to own, which does take more time and memory -than storing a reference to the string data, but cloning the data makes our -code very straightforward. - - - -> #### The Tradeoffs of Using `clone` -> -> There's a tendency amongst many Rustaceans to prefer not to use `clone` to fix -> ownership problems due to its runtime cost. In Chapter XX on iterators, we'll -> learn how to make this situation more efficient. For now, it's okay to copy a -> few strings to keep making progress. We're only going to be making these -> copies once, and our filename and search string are both very small. It's -> better to have a working program that's a bit inefficient than try to -> hyper-optimize code on your first pass. As you get more experienced with Rust, -> it'll be easier to skip this step, but for now, it's perfectly acceptable to -> call `clone`. - - - -We've updated `main` to put the instance of `Config` that `parse_config` -returns in a variable named `config`, and we've updated the code that was using -the separate `search` and `filename` variables to use the fields on the -`Config` struct instead. - -### Creating a Constructor for `Config` - -Let's now think about the purpose of `parse_config`: it's a function that -creates a `Config` instance. We've already seen a convention for functions that -create instances: a `new` function, like `String::new`. Listing 12-6 shows the -result of transforming `parse_config` into a `new` function associated with our -`Config` struct: - -
-Filename: src/main.rs - -```rust - -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args); - - // ...snip... -} - -// ...snip... - -impl Config { - fn new(args: &[String]) -> Config { - let search = args[1].clone(); - let filename = args[2].clone(); - - Config { - search: search, - filename: filename, - } - } -} -``` - -
- -Listing 12-6: Changing `parse_config` into `Config::new` - -
-
- - - -We've changed the name of `parse_config` to `new` and moved it within an `impl` -block. We've also updated the callsite in `main`. Try compiling this again to -make sure it works. - -### Returning a `Result` from the Constructor - -Here's our last refactoring of this method: remember how accessing the vector -with indices 1 and 2 panics when it contains fewer than 3 items and gives a bad -error message? Let's fix that! Listing 12-7 shows how we can check that our -slice is long enough before accessing those locations, and panic with a better -error message: - -
-Filename: src/main.rs - -```rust,ignore -// ...snip... -fn new(args: &[String]) -> Config { - if args.len() < 3 { - panic!("not enough arguments"); - } - // ...snip... -``` - -
- -Listing 12-7: Adding a check for the number of arguments - -
-
- - - -With these extra few lines of code in `new`, let's try running our program -without any arguments: - -```bash -$ cargo run - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe` -thread 'main' panicked at 'not enough arguments', src\main.rs:29 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -``` - -This is a bit better! We at least have a reasonable error message here. -However, we also have a bunch of extra information that we don't want to give -to our users. We can do better by changing the type signature of `new`. Right -now, it returns only a `Config`, so there's no way to indicate that an error -happened while creating our `Config`. Instead, we can return a `Result`, as -shown in Listing 12-8: - -
-Filename: src/main.rs - -```rust,ignore -impl Config { - fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - Ok(Config { - search: search, - filename: filename, - }) - } -} -``` - -
- -Listing 12-8: Return a `Result` from `Config::new` - -
-
- - - -Our `new` function now returns a `Result`, with a `Config` instance in the -success case and a `&'static str` when an error happens. Recall from "The -Static Lifetime" section in Chapter 10 `&'static str` is the type of string -literals, which is what our error message is for now. - -We've made two changes in the body of the `new` function: instead of calling -`panic!` if there aren't enough arguments, we now return an `Err` value. We -wrapped the `Config` return value in an `Ok`. These changes make the function -conform to its new type signature. - -### Calling `Config::new` and Handling Errors - -Now we need to make some changes to `main` as shown in Listing 12-9: - -
-Filename: src/main.rs - -```rust,ignore -use std::process; - -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args).unwrap_or_else(|err| { - println!("Problem parsing arguments: {}", err); - process::exit(1); - }); - - // ...snip... -``` - -
- -Listing 12-9: Exiting with an error code if creating a new `Config` fails - -
-
- - - -We've added a new `use` line to import `process` from the standard library. -In the `main` function itself, we'll handle the `Result` value returned -from the `new` function and exit the process in a cleaner way if `Config::new` -returns an `Err` value. - -We're using a method we haven't covered before that's defined on `Result` -by the standard library: `unwrap_or_else`. This method has similar behavior as -`unwrap` if the `Result` is an `Ok` value: it returns the inner value `Ok` is -wrapping. Unlike `unwrap`, if the value is an `Err` value, this method calls a -*closure* which is an anonymous function that we define and pass as an argument -to `unwrap_or_else`. We'll be covering closures in more detail in Chapter XX; -the important part to understand in this case is that `unwrap_or_else` will -pass the inner value of the `Err` to our closure in the argument `err` that -appears between the vertical pipes. Using `unwrap_or_else` lets us do some -custom, non-`panic!` error handling. - -Said error handling is only two lines: we print out the error, then call -`std::process::exit`. That function will stop our program's execution -immediately and return the number passed to it as a return code. By convention, -a zero means success and any other value means failure. In the end, this has -similar characteristics to our `panic!`-based handling we had in Listing 12-7, -but we no longer get all the extra output. Let's try it: - -```bash -$ cargo run - Compiling greprs v0.1.0 (file:///projects/greprs) - Finished debug [unoptimized + debuginfo] target(s) in 0.48 secs - Running `target\debug\greprs.exe` -Problem parsing arguments: not enough arguments -``` - -Great! This output is much friendlier for our users. - -### Handling Errors from the `run` Function - -Now that we're done refactoring our configuration parsing, let's improve our -program's logic. Listing 12-10 shows the code after extracting a function named -`run` that we'll call from `main`. The `run` function contains the code that -was in `main`: - -
-Filename: src/main.rs - -```rust,ignore -fn main() { - // ...snip... - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - run(config); -} - -fn run(config: Config) { - let mut f = File::open(config.filename).expect("file not found"); - - let mut contents = String::new(); - f.read_to_string(&mut contents).expect("something went wrong reading the file"); - - println!("With text:\n{}", contents); -} - -// ...snip... -``` - -
- -Listing 12-10: Extracting a `run` functionality for the rest of the program logic - -
-
- - - -The contents of `run` are the previous lines that were in `main`, and the `run` -function takes a `Config` as an argument. Now that we have a separate function, -we can make a similar improvement to the one we made to `Config::new` in -Listing 12-8: let's return a `Result` instead of calling `panic!` via -`expect`. Listing 12-11 shows the addition of a `use` statement to bring -`std::error::Error` struct into scope and the changes to the `run` function -to return a `Result`: - -
-Filename: src/main.rs - -```rust,ignore -use std::error::Error; - -// ...snip... - -fn run(config: Config) -> Result<(), Box> { - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - println!("With text:\n{}", contents); - - Ok(()) -} -``` - -
- -Listing 12-11: Changing the `run` function to return `Result` - -
-
- - - -We've made three big changes here. The first is the return type of the `run` -function is now `Result<(), Box>`. Previously, our function returned the -unit type, `()`, so that's still the value returned in the `Ok` case. For our -error type, we're going to use `Box`. This is called a *trait object*, -which we'll be covering in Chapter XX. For now, think of it like this: -`Box` means the function will return some kind of type that implements -the `Error` trait, but we're not specifying what particular type the return -value will be. This gives us flexibility to return error values that may be of -different types in different error cases. `Box` is a smart pointer to heap -data, and we'll be going into detail about `Box` in Chapter YY. - -The second change is that we've removed our calls to `expect` in favor of `?`, -like we talked about in Chapter 9. Rather than `panic!` on an error, this will -return the error value from the function we're in for the caller to handle. - -The third change is that we're now returning an `Ok` value from this function -in the success case. Because we've declared the `run` function's success type -as `()` in the signature, we need to wrap the unit type value in the `Ok` -value. `Ok(())` looks a bit strange at first, but using `()` in this way is the -idiomatic way to indicate that we're calling `run` for its side effects only; -it doesn't return anything interesting. - -This will compile, but with a warning: - -```text -warning: unused result which must be used, #[warn(unused_must_use)] on by default - --> src\main.rs:39:5 - | -39 | run(config); - | ^^^^^^^^^^^^ -``` - -Rust is trying to tell us that we're ignoring our `Result`, which might be an -error value. Let's handle that now. We'll use a similar technique as the way we -handled failure with `Config::new` in Listing 12-9, but with a slight -difference: - -Filename: src/main.rs - -```rust,ignore -fn main() { - // ...snip... - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - if let Err(e) = run(config) { - println!("Application error: {}", e); - - process::exit(1); - } -} -``` - - - -Instead of `unwrap_or_else`, we use `if let` to see if `run` returns an `Err` -value and call `process::exit(1)` if so. Why? The distinction between this case -and the `Config::new` case is a bit subtle. With `Config::new`, we cared about -two things: - -1. Detecting any errors that happen -2. Getting a `Config` if no errors happened - -In this case, because `run` returns a `()` in the success case, the only thing -we care about is the first case: detecting an error. If we used -`unwrap_or_else`, we'd get its return value, which would be `()`. That's not -very useful. - -The bodies of the `if let` and of the `unwrap_or_else` are the same in both -cases though: we print out an error and exit. - -### Split Code into a Library Crate - -This is looking pretty good! There's one more thing we haven't done yet: split -the *src/main.rs* up and put some code into *src/lib.rs* Let's do that now: -move the `run` function from *src/main.rs* to a new file, *src/lib.rs*. You'll -also need to move the relevant `use` statements and the definition of `Config` -and its `new` method as well. Your *src/lib.rs* should now look like Listing -12-12: - -
-Filename: src/lib.rs - -```rust,ignore -use std::error::Error; -use std::fs::File; -use std::io::prelude::*; - -pub struct Config { - pub search: String, - pub filename: String, -} - -impl Config { - pub fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - Ok(Config { - search: search, - filename: filename, - }) - } -} - -pub fn run(config: Config) -> Result<(), Box>{ - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - println!("With text:\n{}", contents); - - Ok(()) -} -``` - -
- -Listing 12-12: Moving `Config` and `run` into *src/lib.rs* - -
-
- - - -Notice we also made liberal use of `pub`: on `Config`, its fields and its `new` -method, and on the `run` function. - -Now in *src/main.rs*, we need to bring in the code that's now in *src/lib.rs* -through `extern crate greprs`. Then we need to add a `use greprs::Config` line -to bring `Config` into scope, and prefix the `run` function with our crate name -as shown in Listing 12-13: - -
-Filename: src/main.rs - -```rust,ignore -extern crate greprs; - -use std::env; -use std::process; - -use greprs::Config; - -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args).unwrap_or_else(|err| { - println!("Problem parsing arguments: {}", err); - process::exit(1); - }); - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - if let Err(e) = greprs::run(config) { - println!("Application error: {}", e); - - process::exit(1); - } -} -``` - -
- -Listing 12-13: Bringing the `greprs` crate into the scope of *src/main.rs* - -
-
- - - -With that, everything should work again. Give it a few `cargo run`s and make -sure you haven't broken anything. Whew! That all was a lot of work, but we've -set ourselves up for success in the future. We've set up a way to handle errors -in a much nicer fashion, and we've made our code slightly more modular. Almost -all of our work will be done in *src/lib.rs* from here on out. - -Let's take advantage of this newfound modularity by doing something that would -have been hard with our old code, but is easy with our new code: write some -tests! - -## Testing the Library's Functionality - -Writing tests for the core functionality of our code is now easier since we -extracted the logic into *src/lib.rs* and left all the argument parsing and -error handling in *src/main.rs*. We can now call our code directly with various -arguments and check return values without having to call our binary from the -command line. - -We're going to write a function named `grep` that takes our search term and the -text to search and produces a list of search results. Let's remove that -`println!` from `run` (and from *src/main.rs* as well, as we don't really need -those anymore either), and call the new `grep` function with the options we've -collected. We'll add a placeholder implementation of the function for now, and -a test that specifies the behavior we'd like the `grep` function to have. The -test will fail with our placeholder implementation, of course, but we can make -sure the code compiles and that we get the failure message we expect. Listing -12-14 shows these modifications: - -
-Filename: src/lib.rs - -```rust -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - vec![] -} - -pub fn run(config: Config) -> Result<(), Box>{ - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - grep(&config.search, &contents); - - Ok(()) -} - -#[cfg(test)] -mod test { - use grep; - - #[test] - fn one_result() { - let search = "duct"; - let contents = "\ -Rust: -safe, fast, productive. -Pick three."; - - assert_eq!( - vec!["safe, fast, productive."], - grep(search, contents) - ); - } -} -``` - -
- -Listing 12-14: Creating a function where our logic will go and a failing test -for that function - -
-
- - - -Notice that we need an explicit lifetime `'a` declared in the signature of -`grep` and used with the `contents` argument and the return value. Remember, -lifetime parameters are used to specify which arguments' lifetimes connect to -the lifetime of the return value. In this case, we're indicating that the -vector we're returning is going to contain string slices that reference slices -of the argument `contents`, as opposed to referencing slices of the argument -`search`. Another way to think about what we're telling Rust is that the data -returned by the `grep` function will live as long as the data passed into this -function in the `contents` argument. This is important! Given that the data a -slice references needs to be valid in order for the reference to be valid, if -the compiler thought that we were making string slices of `search` rather than -`contents`, it would do its safety checking incorrectly. If we tried to compile -this function without lifetimes, we would get this error: - -```text -error[E0106]: missing lifetime specifier - --> src\lib.rs:37:46 - | -37 | fn grep(search: &str, contents: &str) -> Vec<&str> { - | ^ expected lifetime parameter - | - = help: this function's return type contains a borrowed value, but the - signature does not say whether it is borrowed from `search` or - `contents` -``` - -Rust can't possibly know which of the two arguments we need, so it needs us to -tell it. Because `contents` is the argument that contains all of our text and -we want to return the parts of that text that match, we know `contents` is the -argument that should be connected to the return value using the lifetime syntax. - -Connecting arguments to return values in the signature is something that other -programming languages don't make you do, so don't worry if this still feels -strange! Knowing how to specify lifetimes gets easier over time, and practice -makes perfect. You may want to re-read the above section or go back and compare -this example with the Lifetime Syntax section in Chapter 10. - -Now let's try running our test: - -```text -$ cargo test -...warnings... - Finished debug [unoptimized + debuginfo] target(s) in 0.43 secs - Running target/debug/deps/greprs-abcabcabc - -running 1 test -test test::one_result ... FAILED - -failures: - ----- test::one_result stdout ---- - thread 'test::one_result' panicked at 'assertion failed: `(left == right)` -(left: `["safe, fast, productive."]`, right: `[]`)', src/lib.rs:16 -note: Run with `RUST_BACKTRACE=1` for a backtrace. - - -failures: - test::one_result - -test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured - -error: test failed -``` - -Great, our test fails, exactly as we expected. Let's get the test to pass! It's -failing because we always return an empty vector. Here's what we're going to do -to implement `grep`: - -1. Iterate through each line of the contents. -2. Check if the line contains our search string. - * If it does, add it to the list of values we're returning. - * If not, do nothing. -3. Return the list of results that match. - -Let's take each step at a time, starting with iterating through lines. Strings -have a helpful method to handle this, conveniently named `lines`: - -Filename: src/lib.rs - -```rust,ignore -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - for line in contents.lines() { - // do something with line - } -} -``` - - - -We're using a `for` loop along with the `lines` method to get each line in turn. -Next, let's see if our line contains the search string. Luckily, strings have a -helpful method named `contains` that does this for us! Using the `contains` -method looks like this: - -Filename: src/lib.rs - -```rust,ignore -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - for line in contents.lines() { - if line.contains(search) { - // do something with line - } - } -} -``` - - - -Finally, we need a way to store the lines that contain our search string. For -that, we can make a mutable vector before the `for` loop and call the `push` -method to store a `line` in the vector. After the `for` loop, we return the -vector: - -Filename: src/lib.rs - -```rust,ignore -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let mut results = Vec::new(); - - for line in contents.lines() { - if line.contains(search) { - results.push(line); - } - } - - results -} -``` - - - -Let's give it a try: - -```text -$ cargo test -running 1 test -test test::one_result ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Running target/debug/greprs-2f55ee8cd1721808 - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests greprs - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Great! It works. Now that our test is passing, we could consider opportunities -for refactoring the implementation of `grep` and be certain we maintain the -same functionality while we do so. This code isn't bad, but it isn't taking -advantage of some useful features of iterators. We'll be coming back to this -example in Chapter 13 where we'll explore iterators in detail and see how to -improve it. - -Now that the `grep` function is working, we need to do one last thing inside of -the `run` function: we never printed out the results! We'll do that by adding -a `for` loop that prints each line returned from the `grep` function: - -Filename: src/lib.rs - -```rust,ignore -pub fn run(config: Config) -> Result<(), Box> { - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - for line in grep(&config.search, &contents) { - println!("{}", line); - } - - Ok(()) -} -``` - - - -Now our whole program should be working! Let's try it out: - -```text -$ cargo run the poem.txt - Compiling greprs v0.1.0 (file:///projects/greprs) - Finished debug [unoptimized + debuginfo] target(s) in 0.38 secs - Running `target\debug\greprs.exe the poem.txt` -Then there's a pair of us - don't tell! -To tell your name the livelong day - -$ cargo run a poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe a poem.txt` -I'm nobody! Who are you? -Then there's a pair of us - don't tell! -They'd banish us, you know. -How dreary to be somebody! -How public, like a frog -To tell your name the livelong day -To an admiring bog! -``` - -Excellent! We've built our own version of a classic tool, and learned a lot -about how to structure applications. We've also learned a bit about file input -and output, lifetimes, testing, and command line parsing. - -## Working with Environment Variables - -Let's add one more feature: case insensitive searching. In addition, this -setting won't be a command line option: it'll be an environment variable -instead. We could choose to make case insensitivity a command line option, but -our users have requested an environment variable that they could set once and -make all their searches case insensitive in that terminal session. - -### Implement and Test a Case-Insensitive `grep` Function - -First, let's add a new function that we will call when the environment variable -is on. Let's start by adding a new test and re-naming our existing one: - -```rust,ignore -#[cfg(test)] -mod test { - use {grep, grep_case_insensitive}; - - #[test] - fn case_sensitive() { - let search = "duct"; - let contents = "\ -Rust: -safe, fast, productive. -Pick three. -Duct tape."; - - assert_eq!( - vec!["safe, fast, productive."], - grep(search, contents) - ); - } - - #[test] - fn case_insensitive() { - let search = "rust"; - let contents = "\ -Rust: -safe, fast, productive. -Pick three. -Trust me."; - - assert_eq!( - vec!["Rust:", "Trust me."], - grep_case_insensitive(search, contents) - ); - } -} -``` - - - -We're going to define a new function named `grep_case_insensitive`. Its -implementation will be almost the same as the `grep` function, but with some -minor changes: - -Filename: src/lib.rs - -```rust -fn grep_case_insensitive<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let search = search.to_lowercase(); - let mut results = Vec::new(); - - for line in contents.lines() { - if line.to_lowercase().contains(&search) { - results.push(line); - } - } - - results -} -``` - - - -First, we lowercase the `search` string, and store it in a shadowed variable -with the same name. Note that `search` is now a `String` rather than a string -slice, so we need to add an ampersand when we pass `search` to `contains` since -`contains` takes a string slice. - -Second, we add a call to `to_lowercase` each `line` before we check if it -contains `search`. Since we've converted both `line` and `search` into all -lowercase, we'll find matches no matter what case they used in the file and the -command line arguments, respectively. Let's see if this passes the tests: - -```text - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target\debug\deps\greprs-e58e9b12d35dc861.exe - -running 2 tests -test test::case_insensitive ... ok -test test::case_sensitive ... ok - -test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured - - Running target\debug\greprs-8a7faa2662b5030a.exe - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests greprs - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Great! Now, we have to actually use the new `grep_case_insensitive` function. -First, let's add a configuration option for it to the `Config` struct: - -Filename: src/lib.rs - -```rust -pub struct Config { - pub search: String, - pub filename: String, - pub case_sensitive: bool, -} -``` - - - -And then check for that option inside of the `run` function, and decide which -function to call based on the value of the `case_sensitive` function: - -Filename: src/lib.rs - -```rust,ignore -pub fn run(config: Config) -> Result<(), Box>{ - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - let results = if config.case_sensitive { - grep(&config.search, &contents) - } else { - grep_case_insensitive(&config.search, &contents) - }; - - for line in results { - println!("{}", line); - } - - Ok(()) -} -``` - - - -Finally, we need to actually check the environment for the variable. To bring -the `env` module from the standard library into our project, we add a `use` line -at the top of *src/lib.rs*: - -Filename: src/lib.rs - -```rust -use std::env; -``` - -And then use the `vars` method from the `env` module inside of `Config::new`: - -Filename: src/lib.rs - -```rust -impl Config { - pub fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - let mut case_sensitive = true; - - for (name, _) in env::vars() { - if name == "CASE_INSENSITIVE" { - case_sensitive = false; - } - } - - Ok(Config { - search: search, - filename: filename, - case_sensitive: case_sensitive, - }) - } -} -``` - - - -Here, we call `env::vars`, which works in a similar way as `env::args`. The -difference is `env::vars` returns an iterator of environment variables rather -than command line arguments. Instead of using `collect` to create a vector of -all of the environment variables, we're using a `for` loop. `env::vars` returns -tuples: the name of the environment variable and its value. We never care about -the values, only if the variable is set at all, so we use the `_` placeholder -instead of a name to let Rust know that it shouldn't warn us about an unused -variable. Finally, we have a `case_sensitive` variable, which is set to true by -default. If we ever find a `CASE_INSENSITIVE` environment variable, we set the -`case_sensitive` variable to false instead. Then we return the value as part of -the `Config`. - -Let's give it a try! - -```text -$ cargo run to poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe to poem.txt` -Are you nobody, too? -How dreary to be somebody! -``` - -```text -$ CASE_INSENSITIVE=1 cargo run to poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe to poem.txt` -Are you nobody, too? -How dreary to be somebody! -To tell your name the livelong day -To an admiring bog! -``` - -Excellent! Our `greprs` program can now do case insensitive searching controlled -by an environment variable. Now you know how to manage options set using -either command line arguments or environment variables! - -Some programs allow both arguments _and_ environment variables for the same -configuration. In those cases, the programs decide that one or the other of -arguments or environment variables take precedence. For another exercise on -your own, try controlling case insensitivity through a command line argument as -well, and decide which should take precedence if you run the program with -contradictory values. - -The `std::env` module contains many more useful features for dealing with -environment variables; check out its documentation to see what's available. - -## Write to `stderr` Instead of `stdout` - -Right now, we're writing all of our output to the terminal with `println!`. -This works, but most terminals provide two kinds of output: "standard out" is -used for most information, but "standard error" is used for error messages. This -makes it easier to do things like "Print error messages to my terminal, but -write other output to a file." - -We can see that our program is only capable of printing to `stdout` by -redirecting it to a file using `>` on the command line, and running our program -without any arguments, which causes an error: - -```text -$ cargo run > output.txt -``` - -The `>` syntax tells the shell to write the contents of standard out to -*output.txt* instead of the screen. However, if we open *output.txt* after -running we'll see our error message: - -```text -Application error: No search string or filename found -``` - -We'd like this to be printed to the screen instead, and only have the output -from a successful run end up in the file if we run our program this way. Let's -change how error messages are printed as shown in Listing 12-15: - -
-Filename: src/main.rs - -```rust,ignore -extern crate greprs; - -use std::env; -use std::process; - -use greprs::Config; - -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args).unwrap_or_else(|err| { - println!("Problem parsing arguments: {}", err); - process::exit(1); - }); - - if let Err(e) = greprs::run(config) { - let mut stderr = std::io::stderr(); - - writeln!( - &mut stderr, - "Application error: {}", - e - ).expect("Could not write to stderr"); - - process::exit(1); - } -} -``` - -
- -Listing 12-15: Writing error messages to `stderr` instead of `stdout` - -
-
- - - -Rust does not have a convenient function like `println!` for writing to -standard error. Instead, we use the `writeln!` macro, which is sort of like -`println!`, but it takes an extra argument. The first thing we pass to it is -what to write to. We can acquire a handle to standard error through the -`std::io::stderr` function. We give a mutable reference to `stderr` to -`writeln!`; we need it to be mutable so we can write to it! The second and -third arguments to `writeln!` are like the first and second arguments to -`println!`: a format string and any variables we're interpolating. - -Let's try running the program again in the same way, without any arguments and -redirecting `stdout` with `>`: - -```text -$ cargo run > output.txt -Application error: No search string or filename found -``` - -Now we see our error on the screen, but `output.txt` contains nothing. If we -try it again with arguments that work: - -```text -$ cargo run to poem.txt > output.txt -``` - -We'll see no output to our terminal, but `output.txt` will contain -our results: - -Filename: output.txt - -```text -Are you nobody, too? -How dreary to be somebody! -``` - -## Summary - -In this chapter, we've covered how to do common I/O operations in a Rust -context. By using command line arguments, files, environment variables, and the -ability to write to `stderr`, you're now prepared to write command line -applications. By using the concepts from previous chapters, your code will be -well-organized, be able to store data effectively in the appropriate data -structures, handle errors nicely, and be well tested. We also saw a real-world -scenario where lifetime annotations are needed to ensure references are -always valid. - -Next, let's explore how to make use of some features of Rust that were -influenced by functional languages: closures and iterators. diff --git a/nostarch/chapter13.md b/nostarch/chapter13.md deleted file mode 100644 index c7d647f..0000000 --- a/nostarch/chapter13.md +++ /dev/null @@ -1,799 +0,0 @@ - -[TOC] - -# Functional Language features in Rust - Iterators and Closures - -Rust's design has taken inspiration from a lot of previous work. One of Rust's -influences is functional programming, where functions are values that can be -used as arguments or return values to other functions, assigned to variables, -and so forth. We're going to sidestep the issue of what, exactly, functional -programming is or is not, and instead show off some features of Rust that -are similar to features in many languages referred to as functional. - -More specifically, we're going to cover: - -* *Closures*, a function-like construct you can store in a variable. -* *Iterators*, a way of processing series of elements. -* How to use these features to improve upon the project from the last chapter. -* The performance of these features. Spoiler alert: they're faster than you - might think! - -This is not a complete list of Rust's influence from the functional style: -pattern matching, enums, and many other features are too. But mastering -closures and iterators are an important part of writing idiomatic, fast Rust -code. - -## Closures - -Rust gives you the ability to define *closures*, which are similar to -functions. Instead of starting with a technical definition, let's see what -closures look like, syntactically, and then we'll return to defining what they -are. Listing 13-1 shows a small closure whose definition is assigned to the -variable `add_one`, which we can then use to call the closure: - -
-Filename: src/main.rs - -```rust -fn main() { - let add_one = |x| x + 1; - - let five = add_one(4); - - assert_eq!(5, five); -} -``` - -
- -Listing 13-1: A closure that takes one parameter and adds one to it, assigned to -the variable `add_one` - -
-
- -The closure definition, on the first line, shows that the closure takes one -parameter named `x`. Parameters to closures go in between vertical pipes (`|`). - -This is a minimal closure with only one expression as its body. Listing 13-2 has -a closure with a bit more complexity: - -
-Filename: src/main.rs - -```rust -fn main() { - let calculate = |a, b| { - let mut result = a * 2; - - result += b; - - result - }; - - assert_eq!(7, calculate(2, 3)); // 2 * 2 + 3 == 7 - assert_eq!(13, calculate(4, 5)); // 4 * 2 + 5 == 13 -} -``` - -
- -Listing 13-2: A closure with two parameters and multiple expressions in its body - -
-
- -We can use curly brackets to define a closure body with more than one -expression. - -You'll notice a few things about closures that are different from functions -defined with the `fn` keyword. The first difference is that we did not need to -annotate the types of the parameters the closure takes or the value it returns. -We can choose to add type annotations if we want; Listing 13-3 shows the -closure from Listing 13-1 with annotations for the parameter's and return -value's types: - -
-Filename: src/main.rs - -```rust -fn main() { - let add_one = |x: i32| -> i32 { x + 1 }; - - assert_eq!(2, add_one(1)); -} -``` - -
- -Listing 13-3: A closure definition with optional parameter and return value -type annotations - -
-
- -The syntax of closures and functions looks more similar with type annotations. -Let's compare the different ways we can specify closures with the syntax for -defining a function more directly. We've added some spaces here to line up the -relevant parts: - -```rust,ignore -fn add_one_v1 (x: i32) -> i32 { x + 1 } // a function -let add_one_v2 = |x: i32| -> i32 { x + 1 }; // the full syntax for a closure -let add_one_v3 = |x| { x + 1 }; // a closure eliding types -let add_one_v4 = |x| x + 1 ; // without braces -``` - -The reason type annotations are not required for defining a closure but are -required for defining a function is that functions are part of an explicit -interface exposed to your users, so defining this interface rigidly is -important for ensuring that everyone agrees on what types of values a function -uses and returns. Closures aren't used in an exposed interface like this, -though: they're stored in bindings and called directly. Being forced to -annotate the types would be a significant ergonomic loss for little advantage. - -Closure definitions do have one type inferred for each of their parameters and -for their return value. For instance, if we call the closure without type -annotations from Listing 13-1 using an `i8`, we'll get an error if we then try -to call the same closure with an `i32`: - -Filename: src/main.rs - -```rust,ignore -let add_one = |x| x + 1; - -let five = add_one(4i8); -assert_eq!(5i8, five); - -let three = add_one(2i32); -``` - -The compiler gives us this error: - -```text -error[E0308]: mismatched types - --> - | -7 | let three = add_one(2i32); - | ^^^^ expected i8, found i32 -``` - -Since closures' types can be inferred reliably since they're called directly, -it would be tedious if we were required to annotate their types. - -Another reason to have a different syntax from functions for closures is that -they have different behavior than functions: closures possess an *environment*. - -### Closures Can Reference Their Environment - -We've learned that functions can only use variables that are in scope, either -by being `const` or being declared as parameters. Closures can do more: they're -allowed to access variables from their enclosing scope. Listing 13-4 has an -example of a closure in the variable `equal_to_x` that uses the variable `x` -from the closure's surrounding environment: - -
-Filename: src/main.rs - -```rust -fn main() { - let x = 4; - - let equal_to_x = |z| z == x; - - let y = 4; - - assert!(equal_to_x(y)); -} -``` - -
- -Listing 13-4: Example of a closure that refers to a variable in its enclosing -scope - -
-
- -Here, even though `x` is not one of the parameters of `equal_to_x`, the -`equal_to_x` closure is allowed to use `x`, since `x` is a variable defined in -the scope that `equal_to_x` is defined. We aren't allowed to do the same thing -that Listing 13-4 does with functions; let's see what happens if we try: - -Filename: src/main.rs - -```rust,ignore -fn main() { - let x = 4; - - fn equal_to_x(z: i32) -> bool { z == x } - - let y = 4; - - assert!(equal_to_x(y)); -} -``` - -We get an error: - -```text -error[E0434]: can't capture dynamic environment in a fn item; use the || { ... } -closure form instead - --> - | -4 | fn equal_to_x(z: i32) -> bool { z == x } - | ^ -``` - -The compiler even reminds us that this only works with closures! - -Creating closures that capture values from their environment is mostly used in -the context of starting new threads. We'll show some more examples and explain -more detail about this feature of closures in Chapter 16 when we talk about -concurrency. - -### Closures as Function Parameters Using the `Fn` Traits - -While we can bind closures to variables, that's not the most useful thing we -can do with them. We can also define functions that have closures as parameters -by using the `Fn` traits. Here's an example of a function named `call_with_one` -whose signature has a closure as a parameter: - -```rust -fn call_with_one(some_closure: F) -> i32 - where F: Fn(i32) -> i32 { - - some_closure(1) -} - -let answer = call_with_one(|x| x + 2); - -assert_eq!(3, answer); -``` - -We pass the closure `|x| x + 2`, to `call_with_one`, and `call_with_one` calls -that closure with `1` as an argument. The return value of the call to -`some_closure` is then returned from `call_with_one`. - -The signature of `call_with_one` is using the `where` syntax discussed in the -Traits section of Chapter 10. The `some_closure` parameter has the generic type -`F`, which in the `where` clause is defined as having the trait bounds -`Fn(i32) -> i32`. The `Fn` trait represents a closure, and we can add types to -the `Fn` trait to represent a specific type of closure. In this case, our -closure has a parameter of type `i32` and returns an `i32`, so the generic bound -we specify is `Fn(i32) -> i32`. - -Specifying a function signature that contains a closure requires the use of -generics and trait bounds. Each closure has a unique type, so we can't write -the type of a closure directly, we have to use generics. - -`Fn` isn't the only trait bound available for specifying closures, however. -There are three: `Fn`, `FnMut`, and `FnOnce`. This continues the patterns of -threes we've seen elsewhere in Rust: borrowing, borrowing mutably, and -ownership. Using `Fn` specifies that the closure used may only borrow values in -its environment. To specify a closure that mutates the environment, use -`FnMut`, and if the closure takes ownership of the environment, `FnOnce`. Most -of the time, you can start with `Fn`, and the compiler will tell you if you -need `FnMut` or `FnOnce` based on what happens when the function calls the -closure. - -To illustrate a situation where it's useful for a function to have a parameter -that's a closure, let's move on to our next topic: iterators. - -## Iterators - -Iterators are a pattern in Rust that allows you to do some processing on a -sequence of items. For example, the code in Listing 13-5 adds one to each -number in a vector: - -
- -```rust -let v1 = vec![1, 2, 3]; - -let v2: Vec = v1.iter().map(|x| x + 1).collect(); - -assert_eq!(v2, [2, 3, 4]); -``` - -
- -Listing 13-5: Using an iterator, `map`, and `collect` to add one to each number -in a vector - -
-
- - - -The `iter` method on vectors allows us to produce an *iterator* from the -vector. Next, the `map` method called on the iterator allows us to process each -element: in this case, we've passed a closure to `map` that specifies for every -element `x`, add one to it. `map` is one of the most basic ways of interacting -with an iterator, as processing each element in turn is very useful! Finally, -the `collect` method consumes the iterator and puts the iterator's elements -into a new data structure. In this case, since we've said that `v2` has the -type `Vec`, `collect` will create a new vector out of the `i32` values. - -Methods on iterators like `map` are sometimes called *iterator adaptors* -because they take one iterator and produce a new iterator. That is, `map` -builds on top of our previous iterator and produces another iterator by calling -the closure it's passed to create the new sequence of values. - -So, to recap, this line of code does the following: - -1. Creates an iterator from the vector. -2. Uses the `map` adaptor with a closure argument to add one to each element. -3. Uses the `collect` adaptor to consume the iterator and make a new vector. - -That's how we end up with `[2, 3, 4]`. As you can see, closures are a very -important part of using iterators: they provide a way of customizing the -behavior of an iterator adaptor like `map`. - -### Iterators are Lazy - -In the previous section, you may have noticed a subtle difference in wording: -we said that `map` *adapts* an iterator, but `collect` *consumes* one. That was -intentional. By themselves, iterators won't do anything; they're lazy. That is, -if we write code like Listing 13-5 except we don't call `collect`: - -```rust -let v1: Vec = vec![1, 2, 3]; - -v1.iter().map(|x| x + 1); // without collect -``` - -It will compile, but it will give us a warning: - -```text -warning: unused result which must be used: iterator adaptors are lazy and do -nothing unless consumed, #[warn(unused_must_use)] on by default - --> src/main.rs:4:1 - | -4 | v1.iter().map(|x| x + 1); // without collect - | ^^^^^^^^^^^^^^^^^^^^^^^^^ -``` - -We get this warning because iterator adaptors won't start actually doing the -processing on their own. They need some other method that causes the iterator -chain to evaluate. We call those *consuming adaptors*, and `collect` is one of -them. - -So how do we tell which iterator methods consume the iterator or not? And what -adaptors are available? For that, let's look at the `Iterator` trait. - -### The `Iterator` trait - -Iterators all implement a trait named `Iterator` that is defined in the standard -library. The definition of the trait looks like this: - -```rust -trait Iterator { - type Item; - - fn next(&mut self) -> Option; -} -``` - -There's some new syntax that we haven't covered here yet: `type Item` and -`Self::Item` are defining an *associated type* with this trait, and we'll talk -about associated types in depth in Chapter XX. For now, all you need to know is -that this code says the `Iterator` trait requires that you also define an -`Item` type, and this `Item` type is used in the return type of the `next` -method. In other words, the `Item` type will be the type of element that's -returned from the iterator. - -Let's make an iterator named `Counter` that will count from `1` to `5`, using -the `Iterator` trait. First, we need to create a struct that holds the current -state of the iterator, which is one field named `count` that will hold a `u32`. -We'll also define a `new` method, which isn't strictly necessary. We want our -`Counter` to go from one to five, though, so we're always going to have it -holding a zero to start: - -```rust -struct Counter { - count: u32, -} - -impl Counter { - fn new() -> Counter { - Counter { count: 0 } - } -} -``` - -Next, we're going to implement the `Iterator` trait for our `Counter` type by -defining the body of the `next` method. The way we want our iterator to work -is to add one to the state (which is why we initialized `count` to 0, since we -want our iterator to return one first). If `count` is still less than six, we'll -return the current value, but if `count` is six or higher, our iterator will -return `None`, as shown in Listing 13-6: - -
- -```rust -impl Iterator for Counter { - // Our iterator will produce u32s - type Item = u32; - - fn next(&mut self) -> Option { - // increment our count. This is why we started at zero. - self.count += 1; - - // check to see if we've finished counting or not. - if self.count < 6 { - Some(self.count) - } else { - None - } - } -} -``` - -
- -Listing 13-6: Implementing the `Iterator` trait on our `Counter` struct - -
-
- - - -The `type Item = u32` line is saying that the associated `Item` type will be -a `u32` for our iterator. Again, don't worry about associated types yet, because -we'll be covering them in Chapter XX. - -The `next` method is the main interface into an iterator, and it returns an -`Option`. If the option is `Some(value)`, we have gotten another value from the -iterator. If it's `None`, iteration is finished. Inside of the `next` method, -we do whatever kind of calculation our iterator needs to do. In this case, we -add one, then check to see if we're still below six. If we are, we can return -`Some(self.count)` to produce the next value. If we're at six or more, -iteration is over, so we return `None`. - -The iterator trait specifies that when an iterator returns `None`, that -indicates iteration is finished. The trait does not mandate anything about the -behavior an iterator must have if the `next` method is called again after -having returned one `None` value. In this case, every time we call `next` after -getting the first `None` value will still return `None`, but the internal -`count` field will continue to be incremented by one each time. If we call -`next` as many times as the maximum value a `u32` value can hold, `count` will -overflow (which will `panic!` in debug mode and wrap in release mode). Other -iterator implementations choose to start iterating again. If you need to be -sure to have an iterator that will always return `None` on subsequent calls to -the `next` method after the first `None` value is returned, you can use the -`fuse` method to create an iterator with that characteristic out of any other -iterator. - -Once we've implemented the `Iterator` trait, we have an iterator! We can use -the iterator functionality that our `Counter` struct now has by calling the -`next` method on it repeatedly: - -```rust,ignore -let mut counter = Counter::new(); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); -``` - -This will print `Some(1)` through `Some(5)` and then `None`, each on their own -line. - -### All Sorts of `Iterator` Adaptors - -In Listing 13-5, we had iterators and we called methods like `map` and -`collect` on them. In Listing 13-6, however, we only implemented the `next` -method on our `Counter`. How do we get methods like `map` and `collect` on our -`Counter`? - -Well, when we told you about the definition of `Iterator`, we committed a small -lie of omission. The `Iterator` trait has a number of other useful methods -defined on it that come with default implementations that call the `next` -method. Since `next` is the only method of the `Iterator` trait that does not -have a default implementation, once you've done that, you get all of the other -`Iterator` adaptors for free. There are a lot of them! - -For example, if for some reason we wanted to take the first five values that -an instance of `Counter` produces, pair those values with values produced by -another `Counter` instance after skipping the first value that instance -produces, multiply each pair together, keep only those results that are -divisible by three, and add all the resulting values together, we could do: - -```rust,ignore -let sum: u32 = Counter::new().take(5) - .zip(Counter::new().skip(1)) - .map(|(a, b)| a * b) - .filter(|x| x % 3 == 0) - .sum(); -assert_eq!(48, sum); -``` - -All of these method calls are possible because we implemented the `Iterator` -trait by specifying how the `next` method works. Use the standard library -documentation to find more useful methods that will come in handy when you're -working with iterators. - -## Improving our I/O Project - -In our I/O project implementing `grep` in the last chapter, there are some -places where the code could be made clearer and more concise using iterators. -Let's take a look at how iterators can improve our implementation of the -`Config::new` function and the `grep` function. - -### Removing a `clone` by Using an Iterator - -Back in listing 12-8, we had this code that took a slice of `String` values and -created an instance of the `Config` struct by checking for the right number of -arguments, indexing into the slice, and cloning the values so that the `Config` -struct could own those values: - -```rust,ignore -impl Config { - fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - Ok(Config { - search: search, - filename: filename, - }) - } -} -``` - -At the time, we said not to worry about the `clone` calls here, and that we -could remove them in the future. Well, that time is now! So, why do we need -`clone` here? The issue is that we have a slice with `String` elements in the -parameter `args`, and the `new` function does not own `args`. In order to be -able to return ownership of a `Config` instance, we need to clone the values -that we put in the `search` and `filename` fields of `Config`, so that the -`Config` instance can own its values. - -Now that we know more about iterators, we can change the `new` function to -instead take ownership of an iterator as its argument. We'll use the iterator -functionality instead of having to check the length of the slice and index into -specific locations. Since we've taken ownership of the iterator, and we won't be -using indexing operations that borrow anymore, we can move the `String` values -from the iterator into `Config` instead of calling `clone` and making a new -allocation. - -First, let's take `main` as it was in Listing 12-6, and change it to pass the -return value of `env::args` to `Config::new`, instead of calling `collect` and -passing a slice: - -```rust,ignore -fn main() { - let config = Config::new(env::args()); - // ...snip... -``` - - - -If we look in the standard library documentation for the `env::args` function, -we'll see that its return type is `std::env::Args`. So next we'll update the -signature of the `Config::new` function so that the parameter `args` has the -type `std::env::Args` instead of `&[String]`: - - -```rust,ignore -impl Config { - fn new(args: std::env::Args) -> Result { - // ...snip... -``` - - - -Next, we'll fix the body of `Config::new`. As we can also see in the standard -library documentation, `std::env::Args` implements the `Iterator` trait, so we -know we can call the `next` method on it! Here's the new code: - -```rust -impl Config { - fn new(mut args: std::env::Args) -> Result { - args.next(); - - let search = match args.next() { - Some(arg) => arg, - None => return Err("Didn't get a search string"), - }; - - let filename = match args.next() { - Some(arg) => arg, - None => return Err("Didn't get a file name"), - }; - - Ok(Config { - search: search, - filename: filename, - }) - } -} -``` - - - -Remember that the first value in the return value of `env::args` is the name of -the program. We want to ignore that, so first we'll call `next` and not do -anything with the return value. The second time we call `next` should be the -value we want to put in the `search` field of `Config`. We use a `match` to -extract the value if `next` returns a `Some`, and we return early with an `Err` -value if there weren't enough arguments (which would cause this call to `next` -to return `None`). - -We do the same thing for the `filename` value. It's slightly unfortunate that -the `match` expressions for `search` and `filename` are so similar. It would be -nice if we could use `?` on the `Option` returned from `next`, but `?` only -works with `Result` values currently. Even if we could use `?` on `Option` like -we can on `Result`, the value we would get would be borrowed, and we want to -move the `String` from the iterator into `Config`. - -### Making Code Clearer with Iterator Adaptors - -The other bit of code where we could take advantage of iterators was in the -`grep` function as implemented in Listing 12-15: - - - -```rust -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let mut results = Vec::new(); - - for line in contents.lines() { - if line.contains(search) { - results.push(line); - } - } - - results -} -``` - -We can write this code in a much shorter way, and avoiding having to have a -mutable intermediate `results` vector, by using iterator adaptor methods like -this instead: - -```rust -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - contents.lines() - .filter(|line| line.contains(search)) - .collect() -} -``` - -Here, we use the `filter` adaptor to only keep the lines that -`line.contains(search)` returns true for. We then collect them up into another -vector with `collect`. Much simpler! - -We can use the same technique in the `grep_case_insensitive` function that we -defined in Listing 12-16 as follows: - - - -```rust -fn grep_case_insensitive<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - contents.lines() - .filter(|line| { - line.to_lowercase().contains(&search) - }).collect() -} -``` - -Not too bad! So which style should you choose? Most Rust programmers prefer to -use the iterator style. It's a bit tougher to understand at first, but once you -gain an intuition for what the various iterator adaptors do, this is much -easier to understand. Instead of fiddling with the various bits of looping -and building a new vector, the code focuses on the high-level objective of the -loop, abstracting some of the commonplace code so that it's easier to see the -concepts that are unique to this usage of the code, like the condition on which -the code is filtering each element in the iterator. - -But are they truly equivalent? Surely the more low-level loop will be faster. -Let's talk about performance. - -## Performance - -Which version of our `grep` functions is faster: the version with an explicit -`for` loop or the version with iterators? We ran a benchmark by loading the -entire contents of "The Adventures of Sherlock Holmes" by Sir Arthur Conan -Doyle into a `String` and looking for the word "the" in the contents. Here were -the results of the benchmark on the version of grep using the `for` loop and the -version using iterators: - -```text -test bench_grep_for ... bench: 19,620,300 ns/iter (+/- 915,700) -test bench_grep_iter ... bench: 19,234,900 ns/iter (+/- 657,200) -``` - -The iterator version ended up slightly faster! We're not going to go through -the benchmark code here, as the point is not to prove that they're exactly -equivalent, but to get a general sense of how these two implementations -compare. For a *real* benchmark, you'd want to check various texts of various -sizes, different words, words of different lengths, and all kinds of other -variations. The point is this: iterators, while a high-level abstraction, get -compiled down to roughly the same code as if you'd written the lower-level code -yourself. Iterators are one of Rust's *zero-cost abstractions*, by which we mean -using the abstraction imposes no additional runtime overhead in the same way -that Bjarne Stroustrup, the original designer and implementer of C++, defines -*zero-overhead*: - -> In general, C++ implementations obey the zero-overhead principle: What you -> don’t use, you don’t pay for. And further: What you do use, you couldn’t hand -> code any better. -> -> - Bjarne Stroustrup "Foundations of C++" - -As another example, here is some code taken from an audio decoder. This code -uses an iterator chain to do some math on three variables in scope: a `buffer` -slice of data, an array of 12 `coefficients`, and an amount by which to shift -data in `qlp_shift`. We've declared the variables within this example but not -given them any values; while this code doesn't have much meaning outside of its -context, it's still a concise, real-world example of how Rust translates -high-level ideas to low-level code: - -```rust,ignore -let buffer: &mut [i32]; -let coefficients: [i64; 12]; -let qlp_shift: i16; - -for i in 12..buffer.len() { - let prediction = coefficients.iter() - .zip(&buffer[i - 12..i]) - .map(|(&c, &s)| c * s as i64) - .sum::() >> qlp_shift; - let delta = buffer[i]; - buffer[i] = prediction as i32 + delta; -} -``` - -In order to calculate the value of `prediction`, this code iterates through -each of the 12 values in `coefficients`, uses the `zip` method to pair the -coefficient values with the previous 12 values in `buffer`. Then for each pair, -multiply the values together, sum all the results, and shift the bits in the -sum `qlp_shift` bits to the right - -Calculations in applications like audio decoders often prioritize performance -most highly. Here, we're creating an iterator, using two adaptors, then -consuming the value. What assembly code would this Rust code compile to? Well, -as of this writing, it compiles down to the same assembly you'd write by hand. -There's no loop at all corresponding to the iteration over the values in -`coefficients`: Rust knows that there are twelve iterations, so it "unrolls" -the loop. All of the coefficients get stored in registers (which means -accessing the values is very fast). There are no bounds checks on the array -access. It's extremely efficient. - -Now that you know this, go use iterators and closures without fear! They make -code feel higher-level, but don't impose a runtime performance penalty for -doing so. - -## Summary - -Closures and iterators are Rust features inspired by functional programming -language ideas. They contribute to Rust's ability to clearly express high-level -ideas. The implementations of closures and iterators, as well as other zero-cost -abstractions in Rust, are such that runtime performance is not affected. - -Now that we've improved the expressiveness of our I/O project, let's look at -some more features of `cargo` that would help us get ready to share the project -with the world. diff --git a/nostarch/chapter14.md b/nostarch/chapter14.md deleted file mode 100644 index 2ce61b0..0000000 --- a/nostarch/chapter14.md +++ /dev/null @@ -1,727 +0,0 @@ - -[TOC] - -# More about Cargo and Crates.io - -We've used some features of Cargo in this book so far, but only the most basic -ones. We've used Cargo to build, run, and test our code, but it can do a lot -more. Let's go over some of its other features now. Cargo can do even more than -what we will cover in this chapter; for a full explanation, see its -documentation. - -We're going to cover: - -* Customizing your build through release profiles -* Publishing libraries on crates.io -* Organizing larger projects with workspaces -* Installing binaries from crates.io -* Extending Cargo with your own custom commands - -## Release profiles - -Cargo supports a notion of *release profiles*. These profiles control various -options for compiling your code and let you configure each profile -independently of the others. You've seen a hint of this feature in the output -of your builds: - -```text -$ cargo build - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs -$ cargo build --release - Finished release [optimized] target(s) in 0.0 secs -``` - -The "debug" and "release" notifications here indicate that the compiler is -using different profiles. Cargo supports four profiles: - -* `dev`: used for `cargo build` -* `release` used for `cargo build --release` -* `test` used for `cargo test` -* `doc` used for `cargo doc` - -We can customize our `Cargo.toml` file with `[profile.*]` sections to tweak -various compiler options for these profiles. For example, here's one of the -default options for the `dev` and `release` profiles: - -```toml -[profile.dev] -opt-level = 0 - -[profile.release] -opt-level = 3 -``` - -The `opt-level` setting controls how many optimizations Rust will apply to your -code. The setting goes from zero to three. Applying more optimizations takes -more time. When you're compiling very often in development, you'd usually want -compiling to be fast at the expense of the resulting code running slower. When -you're ready to release, it's better to spend more time compiling the one time -that you build your code to trade off for code that will run faster every time -you use that compiled code. - -We could override these defaults by changing them in `Cargo.toml`. For example, -if we wanted to use optimization level 1 in development: - -```toml -[profile.dev] -opt-level = 1 -``` - -This overrides the default setting of `0`, and now our development builds will -use more optimizations. Not as much as a release build, but a little bit more. - -For the full list of settings and the defaults for each profile, see Cargo's -documentation. at *http://doc.crates.io/* - -## Publishing a Crate to Crates.io - -We've added crates from crates.io as dependencies of our project. We can choose -to share our code for other people to use as well. Crates.io distributes the -source code of your packages, so it is primarily used to distribute code that's -open source. - -Rust and Cargo have some features that can make your published package easier -for people to find and use. We'll talk about some of those features, then cover -how to publish a package. - -### Documentation Comments - -In Chapter 3, we saw comments in Rust that start with `//`. Rust also has a -second kind of comment: the *documentation comment*. While comments can be -useful if someone is reading your code, you can generate HTML documentation -that displays the contents of documentation comments for public API items meant -for someone who's interested in knowing how to *use* your crate, as opposed to -how your crate is *implemented*. Note that documentation is only generated for -library crates, since binary crates don't have a public API that people need to -know how to use. - -Documentation comments use `///` instead of `//` and support Markdown notation -inside. They go just before the item they are documenting. Here's documentation -comments for an `add_one` function: - -
- -Filename: src/lib.rs - -````rust -/// Adds one to the number given. -/// -/// # Examples -/// -/// ``` -/// let five = 5; -/// -/// assert_eq!(6, add_one(5)); -/// # fn add_one(x: i32) -> i32 { -/// # x + 1 -/// # } -/// ``` -pub fn add_one(x: i32) -> i32 { - x + 1 -} -```` - -
- -Listing 14-1: A documentation comment for a function - -
-
- -`cargo doc` runs a tool distributed with Rust, `rustdoc`, to generate HTML -documentation from these comments. To try this out locally, you can run `cargo -doc --open`, which will build the documentation for your current crate (as well -as all of your crate's dependencies) and open it in a web browser. Navigate to -the `add_one` function and you'll see how the text in the documentation -comments gets rendered. - -Adding examples in code blocks in your documentation comments is a way to -clearly demonstrate how to use your library. There's an additional bonus reason -to do this: `cargo test` will run the code examples in your documentation as -tests! Nothing is better than documentation with examples. Nothing is worse -than examples that don't actually work because the code has changed since the -documentation has been written. Try running `cargo test` with the documentation -for the `add_one` function in Listing 14-1; you'll see a section in the test -results like this: - -```test - Doc-tests add-one - -running 1 test -test add_one_0 ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -Try changing the function or the example to see that `cargo test` will catch -that the example no longer works! - -There's another style of doc comment, `//!`, to comment containing items (e.g. -crates, modules or functions), instead of the items following it. These are -typically used inside the crate root (lib.rs) or a module's root (mod.rs) to -document the crate or the module as a whole, respectively. Here's the -documentation within the `libstd` module that contains the entire standard -library: - -``` -//! # The Rust Standard Library -//! -//! The Rust Standard Library provides the essential runtime -//! functionality for building portable Rust software. -``` - -### Exporting a Convenient Public API with `pub use` - -In Chapter 7, we covered how to organize our code into modules with the `mod` -keyword, how to make items public with the `pub` keyword, and how to bring -items into a scope with the `use` keyword. When publishing a crate for people -unfamiliar with the implementation to use, it's worth taking time to consider -if the structure of your crate that's useful for you as you're developing is -what would be useful for people depending on your crate. If the structure isn't -convenient to use from another library, you don't have to rearrange your -internal organization: you can choose to re-export items to make a different -public structure with `pub use`. - -For example, say that we made a library named `art` consisting of a `kinds` -module containing an enum named `Color` and a `utils` module containing a -function named `mix` as shown in Listing 14-2: - -
-Filename: src/lib.rs - -```rust -//! # Art -//! -//! A library for modeling artistic concepts. - -pub mod kinds { - /// The primary colors according to the RYB color model. - pub enum PrimaryColor { - Red, - Yellow, - Blue, - } - - /// The secondary colors according to the RYB color model. - pub enum SecondaryColor { - Orange, - Green, - Purple, - } -} - -pub mod utils { - use kinds::*; - - /// Combines two primary colors in equal amounts to create - /// a secondary color. - pub fn mix(c1: PrimaryColor, c2: PrimaryColor) -> SecondaryColor { - // ...snip... - } -} -``` - -
- -Listing 14-2: An `art` library with items organized into `kinds` and `utils` -modules - -
-
- -In order to use this library, another crate would have `use` statements as in -Listing 14-3: - -
-Filename: src/main.rs - -```rust,ignore -extern crate art; - -use art::kinds::PrimaryColor; -use art::utils::mix; - -fn main() { - let red = PrimaryColor::Red; - let yellow = PrimaryColor::Yellow; - mix(red, yellow); -} -``` - -
- -Listing 14-3: A program using the `art` crate's items with its internal -structure exported - -
-
- -Users of this crate shouldn't need to know that `PrimaryColor` and -`SecondaryColor` are in the `kinds` module, and `mix` is in the `utils` module; -that structure might be useful for internal organization but doesn't have much -meaning from the outside looking in. - -To change this, we can add the following `pub use` statements to the code from -Listing 14-2 to re-export the types at the top level, as shown in Listing 14-4: - -
-Filename: src/lib.rs - -```rust -//! # Art -//! -//! A library for modeling artistic concepts. - -pub use kinds::PrimaryColor; -pub use kinds::SecondaryColor; -pub use utils::mix; - -pub mod kinds { - // ...snip... -``` - -
- -Listing 14-4: Adding `pub use` statements to re-export items - -
-
- - - -Re-exports are listed and linked on the front page of the crate's API -documentation. Users of the `art` crate can still see and choose to use the -internal structure as in Listing 14-3, or they can use the more convenient -structure from Listing 14-4, as shown in Listing 14-5: - -
-Filename: src/main.rs - -```rust,ignore -extern crate art; - -use art::PrimaryColor; -use art::mix; - -fn main() { - // ...snip... -} -``` - -
- -Listing 14-5: Using the re-exported items from the `art` crate - -
-
- - - -Creating a useful public API structure is more of an art than a science. -Choosing `pub use` gives you flexibility in how you expose your crate's -internal structure to users. Take a look at some of the code of crates you've -installed to see if their internal structure differs from their public API. - -### Before Your First Publish - -Before being able to publish any crates, you'll need to create an account on -crates.io at *https://crates.io* and get an API token. To do so, visit the home page at *https://crates.io* -and log in via a GitHub account. A GitHub account is a requirement for now, but -the site might support other ways of creating an account in the future. Once -you're logged in, visit your Account Settings at *https://crates.io/me* page and run the `cargo login` -command with the API key as the page specifies, which will look something like -this: - - -```text -$ cargo login abcdefghijklmnopqrstuvwxyz012345 -``` - -This command will inform Cargo of your API token and store it locally in -*~/.cargo/config*. Note that this token is a **secret** and should not be -shared with anyone else. If it gets shared with anyone for any reason, you -should regenerate it immediately. - -### Before Publishing a New Crate - -First, your crate will need a unique name. While you're working on a crate -locally, you may name a crate whatever you'd like, but crate names on -crates.io at *https://crates.io* are allocated on a first-come-first- serve basis. Once a crate name -is taken, it cannot be used for another crate, so check on the site that the -name you'd like is available. - -If you try to publish a crate as generated by `cargo new`, you'll get a warning -and then an error: - -```text -$ cargo publish - Updating registry `https://github.com/rust-lang/crates.io-index` -warning: manifest has no description, license, license-file, documentation, -homepage or repository. -...snip... -error: api errors: missing or empty metadata fields: description, license. -Please see http://doc.crates.io/manifest.html#package-metadata for how to -upload metadata -``` - -We can include more information about our package in *Cargo.toml*. Some of -these fields are optional, but a description and a license are required in -order to publish so that people will know what your crate does and under what -terms they may use it. - -The description appears with your crate in search results and on your crate's -page. Descriptions are usually a sentence or two. The `license` field takes a -license identifier value, and the possible values have been specified by the -Linux Foundation's Software Package Data Exchange (SPDX) at *http://spdx.org/licenses/*. If you would -like to use a license that doesn't appear there, instead of the `license` key, -you can use `license-file` to specify the name of a file in your project that -contains the text of the license you want to use. - -Guidance on which license is right for your project is out of scope for this -book. Many people in the Rust community choose to license their projects in the -same way as Rust itself, with a dual license of `MIT/Apache-2.0`, which -demonstrates that you can specify multiple license identifiers separated by a -slash. So the *Cargo.toml* for a project that is ready to publish might look -like this: - - -```toml -[package] -name = "guessing_game" -version = "0.1.0" -authors = ["Your Name "] -description = "A fun game where you guess what number the computer has chosen." -license = "MIT/Apache-2.0" - -[dependencies] -``` - -Be sure to check out the documentation on crates.io at *http://doc.crates.io/manifest.html#package-metadata* that -describes other metadata you can specify to ensure your crate can be discovered -and used more easily! - - -### Publishing to Crates.io - -Now that we've created an account, saved our API token, chosen a name for our -crate, and specified the required metadata, we're ready to publish! Publishing -a crate is when a specific version is uploaded to be hosted on crates.io. - -Take care when publishing a crate, because a publish is **permanent**. The -version can never be overwritten, and the code cannot be deleted. However, -there is no limit to the number of versions which can be published. - -Let's run the `cargo publish` command, which should succeed this time since -we've now specified the required metadata: - -```text -$ cargo publish - Updating registry `https://github.com/rust-lang/crates.io-index` -Packaging guessing_game v0.1.0 (file:///projects/guessing_game) -Verifying guessing_game v0.1.0 (file:///projects/guessing_game) -Compiling guessing_game v0.1.0 -(file:///projects/guessing_game/target/package/guessing_game-0.1.0) - Finished debug [unoptimized + debuginfo] target(s) in 0.19 secs -Uploading guessing_game v0.1.0 (file:///projects/guessing_game) -``` - -Congratulations! You've now shared your code with the Rust community, and -anyone can easily add your crate as a dependency to their project. - -### Publishing a New Version of an Existing Crate - -When you've made changes to your crate and are ready to release a new version, -change the `version` value specified in your *Cargo.toml*. Use the Semantic -Versioning rules at *http://semver.org/* to decide what an appropriate next version number is -based on the kinds of changes you've made. Then run `cargo publish` to upload -the new version. - - -### Removing Versions from Crates.io with `cargo yank` - -Occasions may arise where you publish a version of a crate that actually ends -up being broken for one reason or another, such as a syntax error or forgetting -to include a file. For situations such as this, Cargo supports *yanking* a -version of a crate. - -Marking a version of a crate as yanked means that no projects will be able to -start depending on that version, but all existing projects that depend on that -version will continue to be allowed to download and depend on that version. One -of the major goals of crates.io is to act as a permanent archive of code so -that builds of all projects will continue to work, and allowing deletion of a -version would go against this goal. Essentially, a yank means that all projects -with a *Cargo.lock* will not break, while any future *Cargo.lock* files -generated will not use the yanked version. - -A yank **does not** delete any code. The yank feature is not intended for -deleting accidentally uploaded secrets, for example. If that happens, you must -reset those secrets immediately. - -To yank a version of a crate, run `cargo yank` and specify which version you -want to yank: - -```text -$ cargo yank --vers 1.0.1 -``` - -You can also undo a yank, and allow projects to start depending on a version -again, by adding `--undo` to the command: - -```text -$ cargo yank --vers 1.0.1 --undo -``` - -## Cargo Workspaces - -In Chapter 12, we built a package that included both a binary crate and a -library crate. But what if the library crate continues to get bigger and we -want to split our package up further into multiple library crates? As packages -grow, separating out major components can be quite useful. In this situation, -Cargo has a feature called *workspaces* that can help us manage multiple -related packages that are developed in tandem. - -A *workspace* is a set of packages that will all share the same *Cargo.lock* -and output directory. Let's make a project using a workspace where the code -will be trivial so that we can concentrate on the structure of a workspace. -We'll have a binary that uses two libraries: one that will provide an `add_one` -method and a second that will provide an `add_two` method. Let's start by -creating a new crate for the binary: - -```text -$ cargo new --bin adder - Created binary (application) `adder` project -$ cd adder -``` - -We need to modify the binary package's *Cargo.toml* to tell Cargo the `adder` -package is a workspace. Add this at the bottom of the file: - -```toml -[workspace] -``` - -Like many Cargo features, workspaces support convention over configuration: we -don't need to say anything more than this as long as we follow the convention. -The convention is that any crates that we depend on as sub-directories will be -part of the workspace. Let's add a path dependency to the `adder` crate by -changing the `[dependencies]` section of *Cargo.toml* to look like this: - -```toml -[dependencies] -add-one = { path = "add-one" } -``` - -If we add dependencies that don't have a `path` specified, those will be normal -dependencies that aren't in this workspace. - -Next, generate the `add-one` crate within the `adder` directory: - -```text -$ cargo new add-one - Created library `add-one` project -``` - -Your `adder` directory should now have these directories and files: - -```text -├── Cargo.toml -├── add-one -│   ├── Cargo.toml -│   └── src -│   └── lib.rs -└── src - └── main.rs -``` - -In *add-one/src/lib.rs*, let's add an implementation of an `add_one` function: - -Filename: add-one/src/lib.rs - -```rust -pub fn add_one(x: i32) -> i32 { - x + 1 -} -``` - -Open up *src/main.rs* for `adder` and add an `extern crate` line to bring the -new `add-one` library crate into scope, and change the `main` function to use -the `add_one` function: - -```rust,ignore -extern crate add_one; - -fn main() { - let num = 10; - println!("Hello, world! {} plus one is {}!", num, add_one::add_one(num)); -} -``` - -Let's build it! - -```text -$ cargo build - Compiling add-one v0.1.0 (file:///projects/adder/add-one) - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.68 secs -``` - -Note that running `cargo build` in the *adder* directory built both that crate -and the `add-one` crate in *adder/add-one*, but created only one *Cargo.lock* -and one *target* directory, both in the *adder* directory. See if you can add -an `add-two` crate in the same way. - -Let's now say that we'd like to use the `rand` crate in our `add-one` crate. -As usual, we'll add it to the `[dependencies]` section in the `Cargo.toml` for -that crate: - -Filename: add-one/Cargo.toml - -```toml -[dependencies] - -rand = "0.3.14" -``` - -And if we add `extern crate rand;` to *add-one/src/lib.rs* then run `cargo -build`, it will succeed: - -```text -$ cargo build - Updating registry `https://github.com/rust-lang/crates.io-index` - Downloading rand v0.3.14 - ...snip... - Compiling rand v0.3.14 - Compiling add-one v0.1.0 (file:///projects/adder/add-one) - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 10.18 secs -``` - -The top level *Cargo.lock* now contains information about the dependency -`add-one` has on `rand`. However, even though `rand` is used somewhere in the -workspace, we can't use it in other crates in the workspace unless we add -`rand` to their *Cargo.toml* as well. If we add `extern crate rand;` to -*src/main.rs* for the top level `adder` crate, for example, we'll get an error: - -```text -$ cargo build - Compiling adder v0.1.0 (file:///projects/adder) -error[E0463]: can't find crate for `rand` - --> src/main.rs:1:1 - | -1 | extern crate rand; - | ^^^^^^^^^^^^^^^^^^^ can't find crate -``` - -To fix this, edit *Cargo.toml* for the top level and indicate that `rand` is a -dependency for the `adder` crate. - -For another enhancement, let's add a test of the `add_one::add_one` function -within that crate: - -Filename: add-one/src/lib.rs - -```rust -pub fn add_one(x: i32) -> i32 { - x + 1 -} - -#[cfg(test)] -mod tests { - use super::*; - - #[test] - fn it_works() { - assert_eq!(3, add_one(2)); - } -} -``` - -Now run `cargo test` in the top-level *adder* directory: - -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.27 secs - Running target/debug/adder-f0253159197f7841 - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Wait a second, zero tests? We just added one! If we look at the output, we can -see that `cargo test` in a workspace only runs the tests for the top level -crate. To run tests for the other crates, we need to use the `-p` argument to -indicate we want to run tests for a particular package: - -```text -$ cargo test -p add-one - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/add_one-abcabcabc - -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests add-one - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Similarly, if you choose to publish the workspace to crates.io, each crate in -the workspace will get published separately. - -As your project grows, consider a workspace: smaller components are easier to -understand individually than one big blob of code. Keeping the crates in a -workspace can make coordination among them easier if they work together and are -often changed at the same time. - -## Installing Binaries from Crates.io with `cargo install` - -The `cargo install` command allows you to install and use binary crates -locally. This isn't intended to replace system packages; it's meant to be a -convenient way for Rust developers to install tools that others have shared on -crates.io. Only packages which have binary targets can be installed, and all -binaries are installed into the installation root's *bin* folder. If you -installed Rust using *rustup.rs* and don't have any custom configurations, this -will be `$HOME/.cargo/bin`. Add that directory to your `$PATH` to be able to -run programs you've gotten through `cargo install`. - -For example, we mentioned in Chapter 12 that there's a Rust implementation of -the `grep` tool for searching files called `ripgrep`. If we want to install -`ripgrep`, we can run: - -```text -$ cargo install ripgrep -Updating registry `https://github.com/rust-lang/crates.io-index` - Downloading ripgrep v0.3.2 - ...snip... - Compiling ripgrep v0.3.2 - Finished release [optimized + debuginfo] target(s) in 97.91 secs - Installing ~/.cargo/bin/rg -``` - -The last line of the output shows the location and the name of the installed -binary, which in the case of `ripgrep` is named `rg`. As long as the -installation directory is in our `$PATH` as mentioned above, we can then run -`rg --help` and start using a faster, rustier tool for searching files! - -## Extending Cargo with Custom Commands - -Cargo is designed to be extensible with new subcommands without having to -modify Cargo itself. If a binary in your `$PATH` is named `cargo-something`, -you can run it as if it were a Cargo subcommand by running `cargo something`. -Custom commands like this are also listed when you run `cargo --list`. It's -convenient to `cargo install` extensions to Cargo then be able to run them just -like the built-in Cargo tools! - -## Summary - -Sharing code with Cargo and crates.io is part of what makes the Rust ecosystem -useful for many different tasks. Rust's standard library is small and stable, -but crates are easy to share, use, and improve on a different timeline than the -language itself. Don't be shy about sharing code that's useful to you on -crates.io; it's likely that it will be useful to someone else as well! diff --git a/nostarch/odt/chapter02.doc b/nostarch/odt/chapter02.doc deleted file mode 100644 index 2aef420..0000000 Binary files a/nostarch/odt/chapter02.doc and /dev/null differ diff --git a/nostarch/odt/chapter03.odt b/nostarch/odt/chapter03.odt deleted file mode 100644 index 0205b90..0000000 Binary files a/nostarch/odt/chapter03.odt and /dev/null differ diff --git a/nostarch/odt/chapter04.docx b/nostarch/odt/chapter04.docx deleted file mode 100644 index 4758b87..0000000 Binary files a/nostarch/odt/chapter04.docx and /dev/null differ diff --git a/nostarch/odt/chapter05.odt b/nostarch/odt/chapter05.odt deleted file mode 100644 index e205938..0000000 Binary files a/nostarch/odt/chapter05.odt and /dev/null differ diff --git a/nostarch/odt/chapter06.docx b/nostarch/odt/chapter06.docx deleted file mode 100644 index bf34988..0000000 Binary files a/nostarch/odt/chapter06.docx and /dev/null differ diff --git a/spellcheck.sh b/spellcheck.sh deleted file mode 100755 index 0a2d168..0000000 --- a/spellcheck.sh +++ /dev/null @@ -1,92 +0,0 @@ -#!/bin/bash - -aspell --version - -# Checks project markdown files for spell errors - -# Notes: - -# This script needs dictionary file ($dict_filename) with project-specific -# valid words. If this file is missing, first invocation of a script generates -# a file of words considered typos at the moment. User should remove real typos -# from this file and leave only valid words. When script generates false -# positive after source modification, new valid word should be added -# to dictionary file. - -# Default mode of this script is interactive. Each source file is scanned for -# typos. aspell opens window, suggesting fixes for each found typo. Original -# files with errors will be backed up to files with format "filename.md.bak". - -# When running in CI, this script should be run in "list" mode (pass "list" -# as first argument). In this mode script scans all files and reports found -# errors. Exit code in this case depends on scan result: -# 1 if any errors found, -# 0 if all is clear. - -# Script skips words with length less than or equal to 3. This helps to avoid -# some false positives. - -# We can consider skipping source code in markdown files (```code```) to reduce -# rate of false positives, but then we lose ability to detect typos in code -# comments/strings etc. - -shopt -s nullglob - -dict_filename=./dictionary.txt -markdown_sources=(./src/*.md) -mode="check" - -# aspell repeatedly modifies personal dictionary for some purpose, -# so we should use a copy of our dictionary -dict_path="/tmp/$dict_filename" - -if [[ "$1" == "list" ]]; then - mode="list" -fi - -if [[ ! -f "$dict_filename" ]]; then - # Pre-check mode: generates dictionary of words aspell consider typos. - # After user validates that this file contains only valid words, we can - # look for typos using this dictionary and some default aspell dictionary. - echo "Scanning files to generate dictionary file '$dict_filename'." - echo "Please check that it doesn't contain any misspellings." - - echo "personal_ws-1.1 en 0 utf-8" > "$dict_filename" - cat "${markdown_sources[@]}" | aspell --ignore 3 list | sort -u >> "$dict_filename" -elif [[ "$mode" == "list" ]]; then - # List (default) mode: scan all files, report errors - declare -i retval=0 - - cp "$dict_filename" "$dict_path" - - if [ ! -f $dict_path ]; then - retval=1 - exit "$retval" - fi - - for fname in "${markdown_sources[@]}"; do - command=$(aspell --ignore 3 --personal="$dict_path" "$mode" < "$fname") - if [[ -n "$command" ]]; then - for error in $command; do - # TODO: Find more correct way to get line number - # (ideally from aspell). Now it can make some false positives, - # because it is just a grep - grep --with-filename --line-number --color=always "$error" "$fname" - done - retval=1 - fi - done - exit "$retval" -elif [[ "$mode" == "check" ]]; then - # Interactive mode: fix typos - cp "$dict_filename" "$dict_path" - - if [ ! -f $dict_path ]; then - retval=1 - exit "$retval" - fi - - for fname in "${markdown_sources[@]}"; do - aspell --ignore 3 --dont-backup --personal="$dict_path" "$mode" "$fname" - done -fi diff --git a/src/SUMMARY.md b/src/SUMMARY.md index 5508f87..a9b8feb 100644 --- a/src/SUMMARY.md +++ b/src/SUMMARY.md @@ -1,100 +1,135 @@ -# Rust 程序设计语言 +# The Rust Programming Language -## 开始 +[The Rust Programming Language](title-page.md) +[Foreword](foreword.md) +[Introduction](ch00-00-introduction.md) -- [简介](ch01-00-introduction.md) - - [安装](ch01-01-installation.md) +## Getting started + +- [Getting Started](ch01-00-getting-started.md) + - [Installation](ch01-01-installation.md) - [Hello, World!](ch01-02-hello-world.md) + - [Hello, Cargo!](ch01-03-hello-cargo.md) -- [猜数字游戏](ch02-00-guessing-game-tutorial.md) +- [Programming a Guessing Game](ch02-00-guessing-game-tutorial.md) -- [通用编程概念](ch03-00-common-programming-concepts.md) - - [变量和可变性](ch03-01-variables-and-mutability.md) - - [数据类型](ch03-02-data-types.md) - - [函数是如何工作的](ch03-03-how-functions-work.md) - - [注释](ch03-04-comments.md) - - [控制流](ch03-05-control-flow.md) +- [Common Programming Concepts](ch03-00-common-programming-concepts.md) + - [Variables and Mutability](ch03-01-variables-and-mutability.md) + - [Data Types](ch03-02-data-types.md) + - [Functions](ch03-03-how-functions-work.md) + - [Comments](ch03-04-comments.md) + - [Control Flow](ch03-05-control-flow.md) -- [了解所有权](ch04-00-understanding-ownership.md) - - [什么是所有权?](ch04-01-what-is-ownership.md) - - [引用和借用](ch04-02-references-and-borrowing.md) - - [切片 slice](ch04-03-slices.md) +- [Understanding Ownership](ch04-00-understanding-ownership.md) + - [What is Ownership?](ch04-01-what-is-ownership.md) + - [References and Borrowing](ch04-02-references-and-borrowing.md) + - [The Slice Type](ch04-03-slices.md) -- [结构体](ch05-00-structs.md) - - [方法语法](ch05-01-method-syntax.md) +- [Using Structs to Structure Related Data](ch05-00-structs.md) + - [Defining and Instantiating Structs](ch05-01-defining-structs.md) + - [An Example Program Using Structs](ch05-02-example-structs.md) + - [Method Syntax](ch05-03-method-syntax.md) -- [枚举和模式匹配](ch06-00-enums.md) - - [定义枚举](ch06-01-defining-an-enum.md) - - [`match` 控制流运算符](ch06-02-match.md) - - [`if let` 简单控制流](ch06-03-if-let.md) +- [Enums and Pattern Matching](ch06-00-enums.md) + - [Defining an Enum](ch06-01-defining-an-enum.md) + - [The `match` Control Flow Operator](ch06-02-match.md) + - [Concise Control Flow with `if let`](ch06-03-if-let.md) ## Basic Rust Literacy -- [Modules](ch07-00-modules.md) - - [`mod` and the Filesystem](ch07-01-mod-and-the-filesystem.md) - - [Controlling Visibility with `pub`](ch07-02-controlling-visibility-with-pub.md) - - [Importing Names with `use`](ch07-03-importing-names-with-use.md) +- [Managing Growing Projects with Packages, Crates, and Modules](ch07-00-managing-growing-projects-with-packages-crates-and-modules.md) + - [Packages and Crates](ch07-01-packages-and-crates.md) + - [Defining Modules to Control Scope and Privacy](ch07-02-defining-modules-to-control-scope-and-privacy.md) + - [Paths for Referring to an Item in the Module Tree](ch07-03-paths-for-referring-to-an-item-in-the-module-tree.md) + - [Bringing Paths Into Scope with the `use` Keyword](ch07-04-bringing-paths-into-scope-with-the-use-keyword.md) + - [Separating Modules into Different Files](ch07-05-separating-modules-into-different-files.md) -- [Fundamental Collections](ch08-00-fundamental-collections.md) - - [Vectors](ch08-01-vectors.md) - - [Strings](ch08-02-strings.md) - - [Hash Maps](ch08-03-hash-maps.md) +- [Common Collections](ch08-00-common-collections.md) + - [Storing Lists of Values with Vectors](ch08-01-vectors.md) + - [Storing UTF-8 Encoded Text with Strings](ch08-02-strings.md) + - [Storing Keys with Associated Values in Hash Maps](ch08-03-hash-maps.md) - [Error Handling](ch09-00-error-handling.md) - [Unrecoverable Errors with `panic!`](ch09-01-unrecoverable-errors-with-panic.md) - [Recoverable Errors with `Result`](ch09-02-recoverable-errors-with-result.md) - [To `panic!` or Not To `panic!`](ch09-03-to-panic-or-not-to-panic.md) -- [Generics](ch10-00-generics.md) - - [Syntax](ch10-01-syntax.md) - - [Traits](ch10-02-traits.md) - NEED DEFAULT METHOD IMPLEMENTATIONS - - [Lifetime syntax](ch10-03-lifetime-syntax.md) +- [Generic Types, Traits, and Lifetimes](ch10-00-generics.md) + - [Generic Data Types](ch10-01-syntax.md) + - [Traits: Defining Shared Behavior](ch10-02-traits.md) + - [Validating References with Lifetimes](ch10-03-lifetime-syntax.md) -- [Testing](ch11-00-testing.md) - - [Writing tests](ch11-01-writing-tests.md) - - [Running tests](ch11-02-running-tests.md) +- [Writing Automated Tests](ch11-00-testing.md) + - [How to Write Tests](ch11-01-writing-tests.md) + - [Controlling How Tests Are Run](ch11-02-running-tests.md) - [Test Organization](ch11-03-test-organization.md) -- [An I/O Project](ch12-00-an-io-project.md) +- [An I/O Project: Building a Command Line Program](ch12-00-an-io-project.md) - [Accepting Command Line Arguments](ch12-01-accepting-command-line-arguments.md) - [Reading a File](ch12-02-reading-a-file.md) - - [Improving Error Handling and Modularity](ch12-03-improving-error-handling-and-modularity.md) - - [Testing the Library's Functionality](ch12-04-testing-the-librarys-functionality.md) + - [Refactoring to Improve Modularity and Error Handling](ch12-03-improving-error-handling-and-modularity.md) + - [Developing the Library’s Functionality with Test Driven Development](ch12-04-testing-the-librarys-functionality.md) - [Working with Environment Variables](ch12-05-working-with-environment-variables.md) - - [Writing to `stderr` instead of `stdout`](ch12-06-writing-to-stderr-instead-of-stdout.md) + - [Writing Error Messages to Standard Error Instead of Standard Output](ch12-06-writing-to-stderr-instead-of-stdout.md) ## Thinking in Rust -- [Functional Language Features in Rust](ch13-00-functional-features.md) - - [Closures](ch13-01-closures.md) - - [Iterators](ch13-02-iterators.md) - - [Improving our I/O Project](ch13-03-improving-our-io-project.md) - - [Performance](ch13-04-performance.md) +- [Functional Language Features: Iterators and Closures](ch13-00-functional-features.md) + - [Closures: Anonymous Functions that Can Capture Their Environment](ch13-01-closures.md) + - [Processing a Series of Items with Iterators](ch13-02-iterators.md) + - [Improving Our I/O Project](ch13-03-improving-our-io-project.md) + - [Comparing Performance: Loops vs. Iterators](ch13-04-performance.md) - [More about Cargo and Crates.io](ch14-00-more-about-cargo.md) - - [Release Profiles](ch14-01-release-profiles.md) + - [Customizing Builds with Release Profiles](ch14-01-release-profiles.md) - [Publishing a Crate to Crates.io](ch14-02-publishing-to-crates-io.md) - [Cargo Workspaces](ch14-03-cargo-workspaces.md) - [Installing Binaries from Crates.io with `cargo install`](ch14-04-installing-binaries.md) - [Extending Cargo with Custom Commands](ch14-05-extending-cargo.md) - [Smart Pointers](ch15-00-smart-pointers.md) + - [Using `Box` to Point to Data on the Heap](ch15-01-box.md) + - [Treating Smart Pointers Like Regular References with the `Deref` Trait](ch15-02-deref.md) + - [Running Code on Cleanup with the `Drop` Trait](ch15-03-drop.md) + - [`Rc`, the Reference Counted Smart Pointer](ch15-04-rc.md) + - [`RefCell` and the Interior Mutability Pattern](ch15-05-interior-mutability.md) + - [Reference Cycles Can Leak Memory](ch15-06-reference-cycles.md) -- [Concurrency](ch16-00-concurrency.md) +- [Fearless Concurrency](ch16-00-concurrency.md) + - [Using Threads to Run Code Simultaneously](ch16-01-threads.md) + - [Using Message Passing to Transfer Data Between Threads](ch16-02-message-passing.md) + - [Shared-State Concurrency](ch16-03-shared-state.md) + - [Extensible Concurrency with the `Sync` and `Send` Traits](ch16-04-extensible-concurrency-sync-and-send.md) -- [Is Rust OOP?](ch17-00-oop.md) +- [Object Oriented Programming Features of Rust](ch17-00-oop.md) + - [Characteristics of Object-Oriented Languages](ch17-01-what-is-oo.md) + - [Using Trait Objects That Allow for Values of Different Types](ch17-02-trait-objects.md) + - [Implementing an Object-Oriented Design Pattern](ch17-03-oo-design-patterns.md) ## Advanced Topics -- [Patterns](ch18-00-patterns.md) (perhaps an appendix?) +- [Patterns and Matching](ch18-00-patterns.md) + - [All the Places Patterns Can Be Used](ch18-01-all-the-places-for-patterns.md) + - [Refutability: Whether a Pattern Might Fail to Match](ch18-02-refutability.md) + - [Pattern Syntax](ch18-03-pattern-syntax.md) -- [More Lifetimes](ch19-00-more-lifetimes.md) (perhaps merge this into advanced type system features?) +- [Advanced Features](ch19-00-advanced-features.md) + - [Unsafe Rust](ch19-01-unsafe-rust.md) + - [Advanced Traits](ch19-03-advanced-traits.md) + - [Advanced Types](ch19-04-advanced-types.md) + - [Advanced Functions and Closures](ch19-05-advanced-functions-and-closures.md) + - [Macros](ch19-06-macros.md) -- [Advanced Type System Features](ch20-00-advanced-types.md) (perhaps called "Advanced Traits"?) +- [Final Project: Building a Multithreaded Web Server](ch20-00-final-project-a-web-server.md) + - [Building a Single-Threaded Web Server](ch20-01-single-threaded.md) + - [Turning Our Single-Threaded Server into a Multithreaded Server](ch20-02-multithreaded.md) + - [Graceful Shutdown and Cleanup](ch20-03-graceful-shutdown-and-cleanup.md) - [Appendix](appendix-00.md) - - [Keywords](appendix-01-keywords.md) - - [Operators](appendix-02-operators.md) - - [Derivable Traits](appendix-03-derivable-traits.md) - - [Nightly Rust](appendix-04-nightly-rust.md) - - [Macros](appendix-05-macros.md) + - [A - Keywords](appendix-01-keywords.md) + - [B - Operators and Symbols](appendix-02-operators.md) + - [C - Derivable Traits](appendix-03-derivable-traits.md) + - [D - Useful Development Tools](appendix-04-useful-development-tools.md) + - [E - Editions](appendix-05-editions.md) + - [F - Translations of the Book](appendix-06-translation.md) + - [G - How Rust is Made and “Nightly Rust”](appendix-07-nightly-rust.md) diff --git a/src/appendix-01-keywords.md b/src/appendix-01-keywords.md index 34a7f05..c609cb4 100644 --- a/src/appendix-01-keywords.md +++ b/src/appendix-01-keywords.md @@ -1,58 +1,134 @@ -## Keywords +## Appendix A: Keywords -The following keywords are reserved by the Rust language and may not be used as -names of functions, variables, macros, modules, crates, constants, static -values, attributes, struct fields, or parameters. +The following list contains keywords that are reserved for current or future +use by the Rust language. As such, they cannot be used as identifiers (except +as raw identifiers as we’ll discuss in the “[Raw +Identifiers][raw-identifiers]” section), including names of +functions, variables, parameters, struct fields, modules, crates, constants, +macros, static values, attributes, types, traits, or lifetimes. + +[raw-identifiers]: #raw-identifiers + +### Keywords Currently in Use + +The following keywords currently have the functionality described. + +* `as` - perform primitive casting, disambiguate the specific trait containing + an item, or rename items in `use` and `extern crate` statements +* `async` - return a `Future` instead of blocking the current thread +* `await` - suspend execution until the result of a `Future` is ready +* `break` - exit a loop immediately +* `const` - define constant items or constant raw pointers +* `continue` - continue to the next loop iteration +* `crate` - link an external crate or a macro variable representing the crate in + which the macro is defined +* `dyn` - dynamic dispatch to a trait object +* `else` - fallback for `if` and `if let` control flow constructs +* `enum` - define an enumeration +* `extern` - link an external crate, function, or variable +* `false` - Boolean false literal +* `fn` - define a function or the function pointer type +* `for` - loop over items from an iterator, implement a trait, or specify a + higher-ranked lifetime +* `if` - branch based on the result of a conditional expression +* `impl` - implement inherent or trait functionality +* `in` - part of `for` loop syntax +* `let` - bind a variable +* `loop` - loop unconditionally +* `match` - match a value to patterns +* `mod` - define a module +* `move` - make a closure take ownership of all its captures +* `mut` - denote mutability in references, raw pointers, or pattern bindings +* `pub` - denote public visibility in struct fields, `impl` blocks, or modules +* `ref` - bind by reference +* `return` - return from function +* `Self` - a type alias for the type we are defining or implementing +* `self` - method subject or current module +* `static` - global variable or lifetime lasting the entire program execution +* `struct` - define a structure +* `super` - parent module of the current module +* `trait` - define a trait +* `true` - Boolean true literal +* `type` - define a type alias or associated type +* `union` - define a [union] and is only a keyword when used in a union declaration +* `unsafe` - denote unsafe code, functions, traits, or implementations +* `use` - bring symbols into scope +* `where` - denote clauses that constrain a type +* `while` - loop conditionally based on the result of an expression + +[union]: ../reference/items/unions.html + +### Keywords Reserved for Future Use + +The following keywords do not have any functionality but are reserved by Rust +for potential future use. * `abstract` -* `alignof` -* `as` * `become` * `box` -* `break` -* `const` -* `continue` -* `crate` * `do` -* `else` -* `enum` -* `extern` -* `false` * `final` -* `fn` -* `for` -* `if` -* `impl` -* `in` -* `let` -* `loop` * `macro` -* `match` -* `mod` -* `move` -* `mut` -* `offsetof` * `override` * `priv` -* `proc` -* `pub` -* `pure` -* `ref` -* `return` -* `Self` -* `self` -* `sizeof` -* `static` -* `struct` -* `super` -* `trait` -* `true` -* `type` +* `try` * `typeof` -* `unsafe` * `unsized` -* `use` * `virtual` -* `where` -* `while` * `yield` + +### Raw Identifiers + +*Raw identifiers* are the syntax that lets you use keywords where they wouldn’t +normally be allowed. You use a raw identifier by prefixing a keyword with `r#`. + +For example, `match` is a keyword. If you try to compile the following function +that uses `match` as its name: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +fn match(needle: &str, haystack: &str) -> bool { + haystack.contains(needle) +} +``` + +you’ll get this error: + +```text +error: expected identifier, found keyword `match` + --> src/main.rs:4:4 + | +4 | fn match(needle: &str, haystack: &str) -> bool { + | ^^^^^ expected identifier, found keyword +``` + +The error shows that you can’t use the keyword `match` as the function +identifier. To use `match` as a function name, you need to use the raw +identifier syntax, like this: + +Filename: src/main.rs + +```rust +fn r#match(needle: &str, haystack: &str) -> bool { + haystack.contains(needle) +} + +fn main() { + assert!(r#match("foo", "foobar")); +} +``` + +This code will compile without any errors. Note the `r#` prefix on the function +name in its definition as well as where the function is called in `main`. + +Raw identifiers allow you to use any word you choose as an identifier, even if +that word happens to be a reserved keyword. In addition, raw identifiers allow +you to use libraries written in a different Rust edition than your crate uses. +For example, `try` isn’t a keyword in the 2015 edition but is in the 2018 +edition. If you depend on a library that’s written using the 2015 edition and +has a `try` function, you’ll need to use the raw identifier syntax, `r#try` in +this case, to call that function from your 2018 edition code. See [Appendix +E][appendix-e] for more information on editions. + +[appendix-e]: appendix-05-editions.html diff --git a/src/appendix-02-operators.md b/src/appendix-02-operators.md index 958c84c..965b237 100644 --- a/src/appendix-02-operators.md +++ b/src/appendix-02-operators.md @@ -1,195 +1,205 @@ -## Operators +## Appendix B: Operators and Symbols -### Unary operator expressions +This appendix contains a glossary of Rust’s syntax, including operators and +other symbols that appear by themselves or in the context of paths, generics, +trait bounds, macros, attributes, comments, tuples, and brackets. -Rust defines the following unary operators. They are all written as prefix -operators, before the expression they apply to. +### Operators -* `-` - : Negation. Signed integer types and floating-point types support negation. It - is an error to apply negation to unsigned types; for example, the compiler - rejects `-1u32`. -* `*` - : Dereference. When applied to a pointer, it denotes the pointed-to location. - For pointers to mutable locations, the resulting value can be assigned to. - On non-pointer types, it calls the `deref` method of the `std::ops::Deref` - trait, or the `deref_mut` method of the `std::ops::DerefMut` trait (if - implemented by the type and required for an outer expression that will or - could mutate the dereference), and produces the result of dereferencing the - `&` or `&mut` borrowed pointer returned from the overload method. -* `!` - : Logical negation. On the boolean type, this flips between `true` and - `false`. On integer types, this inverts the individual bits in the - two's complement representation of the value. -* `&` and `&mut` - : Borrowing. When applied to a value, these operators produce a - reference (pointer) to that value. The value is also placed into - a borrowed state for the duration of the reference. For a shared - borrow (`&`), this implies that the value may not be mutated, but - it may be read or shared again. For a mutable borrow (`&mut`), the - value may not be accessed in any way until the borrow expires. +Table B-1 contains the operators in Rust, an example of how the operator would +appear in context, a short explanation, and whether that operator is +overloadable. If an operator is overloadable, the relevant trait to use to +overload that operator is listed. -### Binary operator expressions +Table B-1: Operators -Binary operators expressions are given in order of operator precedence. +| Operator | Example | Explanation | Overloadable? | +|----------|---------|-------------|---------------| +| `!` | `ident!(...)`, `ident!{...}`, `ident![...]` | Macro expansion | | +| `!` | `!expr` | Bitwise or logical complement | `Not` | +| `!=` | `var != expr` | Nonequality comparison | `PartialEq` | +| `%` | `expr % expr` | Arithmetic remainder | `Rem` | +| `%=` | `var %= expr` | Arithmetic remainder and assignment | `RemAssign` | +| `&` | `&expr`, `&mut expr` | Borrow | | +| `&` | `&type`, `&mut type`, `&'a type`, `&'a mut type` | Borrowed pointer type | | +| `&` | `expr & expr` | Bitwise AND | `BitAnd` | +| `&=` | `var &= expr` | Bitwise AND and assignment | `BitAndAssign` | +| `&&` | `expr && expr` | Short-circuiting logical AND | | +| `*` | `expr * expr` | Arithmetic multiplication | `Mul` | +| `*=` | `var *= expr` | Arithmetic multiplication and assignment | `MulAssign` | +| `*` | `*expr` | Dereference | | +| `*` | `*const type`, `*mut type` | Raw pointer | | +| `+` | `trait + trait`, `'a + trait` | Compound type constraint | | +| `+` | `expr + expr` | Arithmetic addition | `Add` | +| `+=` | `var += expr` | Arithmetic addition and assignment | `AddAssign` | +| `,` | `expr, expr` | Argument and element separator | | +| `-` | `- expr` | Arithmetic negation | `Neg` | +| `-` | `expr - expr` | Arithmetic subtraction | `Sub` | +| `-=` | `var -= expr` | Arithmetic subtraction and assignment | `SubAssign` | +| `->` | `fn(...) -> type`, |...| -> type | Function and closure return type | | +| `.` | `expr.ident` | Member access | | +| `..` | `..`, `expr..`, `..expr`, `expr..expr` | Right-exclusive range literal | | +| `..=` | `..=expr`, `expr..=expr` | Right-inclusive range literal | | +| `..` | `..expr` | Struct literal update syntax | | +| `..` | `variant(x, ..)`, `struct_type { x, .. }` | “And the rest” pattern binding | | +| `...` | `expr...expr` | In a pattern: inclusive range pattern | | +| `/` | `expr / expr` | Arithmetic division | `Div` | +| `/=` | `var /= expr` | Arithmetic division and assignment | `DivAssign` | +| `:` | `pat: type`, `ident: type` | Constraints | | +| `:` | `ident: expr` | Struct field initializer | | +| `:` | `'a: loop {...}` | Loop label | | +| `;` | `expr;` | Statement and item terminator | | +| `;` | `[...; len]` | Part of fixed-size array syntax | | +| `<<` | `expr << expr` | Left-shift | `Shl` | +| `<<=` | `var <<= expr` | Left-shift and assignment | `ShlAssign` | +| `<` | `expr < expr` | Less than comparison | `PartialOrd` | +| `<=` | `expr <= expr` | Less than or equal to comparison | `PartialOrd` | +| `=` | `var = expr`, `ident = type` | Assignment/equivalence | | +| `==` | `expr == expr` | Equality comparison | `PartialEq` | +| `=>` | `pat => expr` | Part of match arm syntax | | +| `>` | `expr > expr` | Greater than comparison | `PartialOrd` | +| `>=` | `expr >= expr` | Greater than or equal to comparison | `PartialOrd` | +| `>>` | `expr >> expr` | Right-shift | `Shr` | +| `>>=` | `var >>= expr` | Right-shift and assignment | `ShrAssign` | +| `@` | `ident @ pat` | Pattern binding | | +| `^` | `expr ^ expr` | Bitwise exclusive OR | `BitXor` | +| `^=` | `var ^= expr` | Bitwise exclusive OR and assignment | `BitXorAssign` | +| | | pat | pat | Pattern alternatives | | +| | | expr | expr | Bitwise OR | `BitOr` | +| |= | var |= expr | Bitwise OR and assignment | `BitOrAssign` | +| || | expr || expr | Short-circuiting logical OR | | +| `?` | `expr?` | Error propagation | | -#### Arithmetic operators +### Non-operator Symbols -Binary arithmetic expressions are syntactic sugar for calls to built-in traits, -defined in the `std::ops` module of the `std` library. This means arithmetic -operators can be overridden for user-defined types. The default meaning of the -operators on standard types is given here. +The following list contains all non-letters that don’t function as operators; +that is, they don’t behave like a function or method call. -* `+` - : Addition and array/string concatenation. - Calls the `add` method on the `std::ops::Add` trait. -* `-` - : Subtraction. - Calls the `sub` method on the `std::ops::Sub` trait. -* `*` - : Multiplication. - Calls the `mul` method on the `std::ops::Mul` trait. -* `/` - : Quotient. - Calls the `div` method on the `std::ops::Div` trait. -* `%` - : Remainder. - Calls the `rem` method on the `std::ops::Rem` trait. +Table B-2 shows symbols that appear on their own and are valid in a variety of +locations. -Note that Rust does not have a built-in operator for exponential (power) -calculation; see the `pow` method on the numeric types. +Table B-2: Stand-Alone Syntax -#### Bitwise operators +| Symbol | Explanation | +|--------|-------------| +| `'ident` | Named lifetime or loop label | +| `...u8`, `...i32`, `...f64`, `...usize`, etc. | Numeric literal of specific type | +| `"..."` | String literal | +| `r"..."`, `r#"..."#`, `r##"..."##`, etc. | Raw string literal, escape characters not processed | +| `b"..."` | Byte string literal; constructs a `[u8]` instead of a string | +| `br"..."`, `br#"..."#`, `br##"..."##`, etc. | Raw byte string literal, combination of raw and byte string literal | +| `'...'` | Character literal | +| `b'...'` | ASCII byte literal | +| |...| expr | Closure | +| `!` | Always empty bottom type for diverging functions | +| `_` | “Ignored” pattern binding; also used to make integer literals readable | -Like the arithmetic operators, bitwise operators are syntactic sugar for calls -to methods of built-in traits. This means bitwise operators can be overridden -for user-defined types. The default meaning of the operators on standard types -is given here. Bitwise `&`, `|` and `^` applied to boolean arguments are -equivalent to logical `&&`, `||` and `!=` evaluated in non-lazy fashion. +Table B-3 shows symbols that appear in the context of a path through the module +hierarchy to an item. -* `&` - : Bitwise AND. - Calls the `bitand` method of the `std::ops::BitAnd` trait. -* `|` - : Bitwise inclusive OR. - Calls the `bitor` method of the `std::ops::BitOr` trait. -* `^` - : Bitwise exclusive OR. - Calls the `bitxor` method of the `std::ops::BitXor` trait. -* `<<` - : Left shift. - Calls the `shl` method of the `std::ops::Shl` trait. -* `>>` - : Right shift (arithmetic). - Calls the `shr` method of the `std::ops::Shr` trait. +Table B-3: Path-Related Syntax -#### Lazy boolean operators +| Symbol | Explanation | +|--------|-------------| +| `ident::ident` | Namespace path | +| `::path` | Path relative to the crate root (i.e., an explicitly absolute path) | +| `self::path` | Path relative to the current module (i.e., an explicitly relative path). +| `super::path` | Path relative to the parent of the current module | +| `type::ident`, `::ident` | Associated constants, functions, and types | +| `::...` | Associated item for a type that cannot be directly named (e.g., `<&T>::...`, `<[T]>::...`, etc.) | +| `trait::method(...)` | Disambiguating a method call by naming the trait that defines it | +| `type::method(...)` | Disambiguating a method call by naming the type for which it’s defined | +| `::method(...)` | Disambiguating a method call by naming the trait and type | -The operators `||` and `&&` may be applied to operands of boolean type. The -`||` operator denotes logical 'or', and the `&&` operator denotes logical -'and'. They differ from `|` and `&` in that the right-hand operand is only -evaluated when the left-hand operand does not already determine the result of -the expression. That is, `||` only evaluates its right-hand operand when the -left-hand operand evaluates to `false`, and `&&` only when it evaluates to -`true`. +Table B-4 shows symbols that appear in the context of using generic type +parameters. -#### Comparison operators +Table B-4: Generics -Comparison operators are, like the arithmetic operators and bitwise operators, -syntactic sugar for calls to built-in traits. This means that comparison -operators can be overridden for user-defined types. The default meaning of the -operators on standard types is given here. +| Symbol | Explanation | +|--------|-------------| +| `path<...>` | Specifies parameters to generic type in a type (e.g., `Vec`) | +| `path::<...>`, `method::<...>` | Specifies parameters to generic type, function, or method in an expression; often referred to as turbofish (e.g., `"42".parse::()`) | +| `fn ident<...> ...` | Define generic function | +| `struct ident<...> ...` | Define generic structure | +| `enum ident<...> ...` | Define generic enumeration | +| `impl<...> ...` | Define generic implementation | +| `for<...> type` | Higher-ranked lifetime bounds | +| `type` | A generic type where one or more associated types have specific assignments (e.g., `Iterator`) | -* `==` - : Equal to. - Calls the `eq` method on the `std::cmp::PartialEq` trait. -* `!=` - : Unequal to. - Calls the `ne` method on the `std::cmp::PartialEq` trait. -* `<` - : Less than. - Calls the `lt` method on the `std::cmp::PartialOrd` trait. -* `>` - : Greater than. - Calls the `gt` method on the `std::cmp::PartialOrd` trait. -* `<=` - : Less than or equal. - Calls the `le` method on the `std::cmp::PartialOrd` trait. -* `>=` - : Greater than or equal. - Calls the `ge` method on the `std::cmp::PartialOrd` trait. +Table B-5 shows symbols that appear in the context of constraining generic type +parameters with trait bounds. -#### Type cast expressions +Table B-5: Trait Bound Constraints -A type cast expression is denoted with the binary operator `as`. +| Symbol | Explanation | +|--------|-------------| +| `T: U` | Generic parameter `T` constrained to types that implement `U` | +| `T: 'a` | Generic type `T` must outlive lifetime `'a` (meaning the type cannot transitively contain any references with lifetimes shorter than `'a`) | +| `T : 'static` | Generic type `T` contains no borrowed references other than `'static` ones | +| `'b: 'a` | Generic lifetime `'b` must outlive lifetime `'a` | +| `T: ?Sized` | Allow generic type parameter to be a dynamically sized type | +| `'a + trait`, `trait + trait` | Compound type constraint | -Executing an `as` expression casts the value on the left-hand side to the type -on the right-hand side. +Table B-6 shows symbols that appear in the context of calling or defining +macros and specifying attributes on an item. -An example of an `as` expression: +Table B-6: Macros and Attributes -```rust -# fn sum(values: &[f64]) -> f64 { 0.0 } -# fn len(values: &[f64]) -> i32 { 0 } +| Symbol | Explanation | +|--------|-------------| +| `#[meta]` | Outer attribute | +| `#![meta]` | Inner attribute | +| `$ident` | Macro substitution | +| `$ident:kind` | Macro capture | +| `$(…)…` | Macro repetition | +| `ident!(...)`, `ident!{...}`, `ident![...]` | Macro invocation | -fn average(values: &[f64]) -> f64 { - let sum: f64 = sum(values); - let size: f64 = len(values) as f64; - sum / size -} -``` +Table B-7 shows symbols that create comments. -Some of the conversions which can be done through the `as` operator -can also be done implicitly at various points in the program, such as -argument passing and assignment to a `let` binding with an explicit -type. Implicit conversions are limited to "harmless" conversions that -do not lose information and which have minimal or no risk of -surprising side-effects on the dynamic execution semantics. +Table B-7: Comments -#### Assignment expressions +| Symbol | Explanation | +|--------|-------------| +| `//` | Line comment | +| `//!` | Inner line doc comment | +| `///` | Outer line doc comment | +| `/*...*/` | Block comment | +| `/*!...*/` | Inner block doc comment | +| `/**...*/` | Outer block doc comment | -An *assignment expression* consists of a pattern followed by an equals -sign (`=`) and an expression. +Table B-8 shows symbols that appear in the context of using tuples. -Evaluating an assignment expression either copies or -moves its right-hand operand to its left-hand -operand. +Table B-8: Tuples -``` -# let mut x = 0; -# let y = 0; -x = y; -``` +| Symbol | Explanation | +|--------|-------------| +| `()` | Empty tuple (aka unit), both literal and type | +| `(expr)` | Parenthesized expression | +| `(expr,)` | Single-element tuple expression | +| `(type,)` | Single-element tuple type | +| `(expr, ...)` | Tuple expression | +| `(type, ...)` | Tuple type | +| `expr(expr, ...)` | Function call expression; also used to initialize tuple `struct`s and tuple `enum` variants | +| `expr.0`, `expr.1`, etc. | Tuple indexing | -#### Compound assignment expressions +Table B-9 shows the contexts in which curly braces are used. -The `+`, `-`, `*`, `/`, `%`, `&`, `|`, `^`, `<<`, and `>>` operators may be -composed with the `=` operator. The expression `lval OP= val` is equivalent to -`lval = lval OP val`. For example, `x = x + 1` may be written as `x += 1`. +Table B-9: Curly Brackets -Any such expression always has the `unit` type. +| Context | Explanation | +|---------|-------------| +| `{...}` | Block expression | +| `Type {...}` | `struct` literal | -#### Operator precedence +Table B-10 shows the contexts in which square brackets are used. -The precedence of Rust binary operators is ordered as follows, going from -strong to weak: +Table B-10: Square Brackets -```text -as : -* / % -+ - -<< >> -& -^ -| -== != < > <= >= -&& -|| -.. ... -<- -= -``` - -Operators at the same precedence level are evaluated left-to-right. Unary -operators have the same precedence level and are stronger than any of the -binary operators. +| Context | Explanation | +|---------|-------------| +| `[...]` | Array literal | +| `[expr; len]` | Array literal containing `len` copies of `expr` | +| `[type; len]` | Array type containing `len` instances of `type` | +| `expr[expr]` | Collection indexing. Overloadable (`Index`, `IndexMut`) | +| `expr[..]`, `expr[a..]`, `expr[..b]`, `expr[a..b]` | Collection indexing pretending to be collection slicing, using `Range`, `RangeFrom`, `RangeTo`, or `RangeFull` as the “index” | diff --git a/src/appendix-03-derivable-traits.md b/src/appendix-03-derivable-traits.md index 9431eb5..bc20ab1 100644 --- a/src/appendix-03-derivable-traits.md +++ b/src/appendix-03-derivable-traits.md @@ -1 +1,187 @@ -## Derivable Traits +## Appendix C: Derivable Traits + +In various places in the book, we’ve discussed the `derive` attribute, which +you can apply to a struct or enum definition. The `derive` attribute generates +code that will implement a trait with its own default implementation on the +type you’ve annotated with the `derive` syntax. + +In this appendix, we provide a reference of all the traits in the standard +library that you can use with `derive`. Each section covers: + +* What operators and methods deriving this trait will enable +* What the implementation of the trait provided by `derive` does +* What implementing the trait signifies about the type +* The conditions in which you’re allowed or not allowed to implement the trait +* Examples of operations that require the trait + +If you want different behavior from that provided by the `derive` attribute, +consult the [standard library documentation](../std/index.html) +for each trait for details of how to manually implement them. + +The rest of the traits defined in the standard library can’t be implemented on +your types using `derive`. These traits don’t have sensible default behavior, +so it’s up to you to implement them in the way that makes sense for what you’re +trying to accomplish. + +An example of a trait that can’t be derived is `Display`, which handles +formatting for end users. You should always consider the appropriate way to +display a type to an end user. What parts of the type should an end user be +allowed to see? What parts would they find relevant? What format of the data +would be most relevant to them? The Rust compiler doesn’t have this insight, so +it can’t provide appropriate default behavior for you. + +The list of derivable traits provided in this appendix is not comprehensive: +libraries can implement `derive` for their own traits, making the list of +traits you can use `derive` with truly open-ended. Implementing `derive` +involves using a procedural macro, which is covered in the +[“Macros”][macros] section of Chapter 19. + +### `Debug` for Programmer Output + +The `Debug` trait enables debug formatting in format strings, which you +indicate by adding `:?` within `{}` placeholders. + +The `Debug` trait allows you to print instances of a type for debugging +purposes, so you and other programmers using your type can inspect an instance +at a particular point in a program’s execution. + +The `Debug` trait is required, for example, in use of the `assert_eq!` macro. +This macro prints the values of instances given as arguments if the equality +assertion fails so programmers can see why the two instances weren’t equal. + +### `PartialEq` and `Eq` for Equality Comparisons + +The `PartialEq` trait allows you to compare instances of a type to check for +equality and enables use of the `==` and `!=` operators. + +Deriving `PartialEq` implements the `eq` method. When `PartialEq` is derived on +structs, two instances are equal only if *all* fields are equal, and the +instances are not equal if any fields are not equal. When derived on enums, +each variant is equal to itself and not equal to the other variants. + +The `PartialEq` trait is required, for example, with the use of the +`assert_eq!` macro, which needs to be able to compare two instances of a type +for equality. + +The `Eq` trait has no methods. Its purpose is to signal that for every value of +the annotated type, the value is equal to itself. The `Eq` trait can only be +applied to types that also implement `PartialEq`, although not all types that +implement `PartialEq` can implement `Eq`. One example of this is floating point +number types: the implementation of floating point numbers states that two +instances of the not-a-number (`NaN`) value are not equal to each other. + +An example of when `Eq` is required is for keys in a `HashMap` so the +`HashMap` can tell whether two keys are the same. + +### `PartialOrd` and `Ord` for Ordering Comparisons + +The `PartialOrd` trait allows you to compare instances of a type for sorting +purposes. A type that implements `PartialOrd` can be used with the `<`, `>`, +`<=`, and `>=` operators. You can only apply the `PartialOrd` trait to types +that also implement `PartialEq`. + +Deriving `PartialOrd` implements the `partial_cmp` method, which returns an +`Option` that will be `None` when the values given don’t produce an +ordering. An example of a value that doesn’t produce an ordering, even though +most values of that type can be compared, is the not-a-number (`NaN`) floating +point value. Calling `partial_cmp` with any floating point number and the `NaN` +floating point value will return `None`. + +When derived on structs, `PartialOrd` compares two instances by comparing the +value in each field in the order in which the fields appear in the struct +definition. When derived on enums, variants of the enum declared earlier in the +enum definition are considered less than the variants listed later. + +The `PartialOrd` trait is required, for example, for the `gen_range` method +from the `rand` crate that generates a random value in the range specified by a +range expression. + +The `Ord` trait allows you to know that for any two values of the annotated +type, a valid ordering will exist. The `Ord` trait implements the `cmp` method, +which returns an `Ordering` rather than an `Option` because a valid +ordering will always be possible. You can only apply the `Ord` trait to types +that also implement `PartialOrd` and `Eq` (and `Eq` requires `PartialEq`). When +derived on structs and enums, `cmp` behaves the same way as the derived +implementation for `partial_cmp` does with `PartialOrd`. + +An example of when `Ord` is required is when storing values in a `BTreeSet`, +a data structure that stores data based on the sort order of the values. + +### `Clone` and `Copy` for Duplicating Values + +The `Clone` trait allows you to explicitly create a deep copy of a value, and +the duplication process might involve running arbitrary code and copying heap +data. See the [“Ways Variables and Data Interact: +Clone”][ways-variables-and-data-interact-clone] section in +Chapter 4 for more information on `Clone`. + +Deriving `Clone` implements the `clone` method, which when implemented for the +whole type, calls `clone` on each of the parts of the type. This means all the +fields or values in the type must also implement `Clone` to derive `Clone`. + +An example of when `Clone` is required is when calling the `to_vec` method on a +slice. The slice doesn’t own the type instances it contains, but the vector +returned from `to_vec` will need to own its instances, so `to_vec` calls +`clone` on each item. Thus, the type stored in the slice must implement `Clone`. + +The `Copy` trait allows you to duplicate a value by only copying bits stored on +the stack; no arbitrary code is necessary. See the [“Stack-Only Data: +Copy”][stack-only-data-copy] section in Chapter 4 for more +information on `Copy`. + +The `Copy` trait doesn’t define any methods to prevent programmers from +overloading those methods and violating the assumption that no arbitrary code +is being run. That way, all programmers can assume that copying a value will be +very fast. + +You can derive `Copy` on any type whose parts all implement `Copy`. A type that +implements `Copy` must also implement `Clone`, because a type that implements +`Copy` has a trivial implementation of `Clone` that performs the same task as +`Copy`. + +The `Copy` trait is rarely required; types that implement `Copy` have +optimizations available, meaning you don’t have to call `clone`, which makes +the code more concise. + +Everything possible with `Copy` you can also accomplish with `Clone`, but the +code might be slower or have to use `clone` in places. + +### `Hash` for Mapping a Value to a Value of Fixed Size + +The `Hash` trait allows you to take an instance of a type of arbitrary size and +map that instance to a value of fixed size using a hash function. Deriving +`Hash` implements the `hash` method. The derived implementation of the `hash` +method combines the result of calling `hash` on each of the parts of the type, +meaning all fields or values must also implement `Hash` to derive `Hash`. + +An example of when `Hash` is required is in storing keys in a `HashMap` +to store data efficiently. + +### `Default` for Default Values + +The `Default` trait allows you to create a default value for a type. Deriving +`Default` implements the `default` function. The derived implementation of the +`default` function calls the `default` function on each part of the type, +meaning all fields or values in the type must also implement `Default` to +derive `Default`. + +The `Default::default` function is commonly used in combination with the struct +update syntax discussed in the [“Creating Instances From Other Instances With +Struct Update +Syntax”][creating-instances-from-other-instances-with-struct-update-syntax] +section in Chapter 5. You can customize a few fields of a struct and then +set and use a default value for the rest of the fields by using +`..Default::default()`. + +The `Default` trait is required when you use the method `unwrap_or_default` on +`Option` instances, for example. If the `Option` is `None`, the method +`unwrap_or_default` will return the result of `Default::default` for the type +`T` stored in the `Option`. + +[creating-instances-from-other-instances-with-struct-update-syntax]: +ch05-01-defining-structs.html#creating-instances-from-other-instances-with-struct-update-syntax +[stack-only-data-copy]: +ch04-01-what-is-ownership.html#stack-only-data-copy +[ways-variables-and-data-interact-clone]: +ch04-01-what-is-ownership.html#ways-variables-and-data-interact-clone +[macros]: ch19-06-macros.html#macros diff --git a/src/appendix-04-nightly-rust.md b/src/appendix-04-nightly-rust.md deleted file mode 100644 index f99a3f3..0000000 --- a/src/appendix-04-nightly-rust.md +++ /dev/null @@ -1 +0,0 @@ -# Nightly Rust diff --git a/src/appendix-04-useful-development-tools.md b/src/appendix-04-useful-development-tools.md new file mode 100644 index 0000000..2909559 --- /dev/null +++ b/src/appendix-04-useful-development-tools.md @@ -0,0 +1,183 @@ +## Appendix D - Useful Development Tools + +In this appendix, we talk about some useful development tools that the Rust +project provides. We’ll look at automatic formatting, quick ways to apply +warning fixes, a linter, and integrating with IDEs. + +### Automatic Formatting with `rustfmt` + +The `rustfmt` tool reformats your code according to the community code style. +Many collaborative projects use `rustfmt` to prevent arguments about which +style to use when writing Rust: everyone formats their code using the tool. + +To install `rustfmt`, enter the following: + +```console +$ rustup component add rustfmt +``` + +This command gives you `rustfmt` and `cargo-fmt`, similar to how Rust gives you +both `rustc` and `cargo`. To format any Cargo project, enter the following: + +```console +$ cargo fmt +``` + +Running this command reformats all the Rust code in the current crate. This +should only change the code style, not the code semantics. For more information +on `rustfmt`, see [its documentation][rustfmt]. + +[rustfmt]: https://github.com/rust-lang/rustfmt + +### Fix Your Code with `rustfix` + +The rustfix tool is included with Rust installations and can automatically fix +some compiler warnings. If you’ve written code in Rust, you’ve probably seen +compiler warnings. For example, consider this code: + +Filename: src/main.rs + +```rust +fn do_something() {} + +fn main() { + for i in 0..100 { + do_something(); + } +} +``` + +Here, we’re calling the `do_something` function 100 times, but we never use the +variable `i` in the body of the `for` loop. Rust warns us about that: + +```console +$ cargo build + Compiling myprogram v0.1.0 (file:///projects/myprogram) +warning: unused variable: `i` + --> src/main.rs:4:9 + | +4 | for i in 1..100 { + | ^ help: consider using `_i` instead + | + = note: #[warn(unused_variables)] on by default + + Finished dev [unoptimized + debuginfo] target(s) in 0.50s +``` + +The warning suggests that we use `_i` as a name instead: the underscore +indicates that we intend for this variable to be unused. We can automatically +apply that suggestion using the `rustfix` tool by running the command `cargo +fix`: + +```console +$ cargo fix + Checking myprogram v0.1.0 (file:///projects/myprogram) + Fixing src/main.rs (1 fix) + Finished dev [unoptimized + debuginfo] target(s) in 0.59s +``` + +When we look at *src/main.rs* again, we’ll see that `cargo fix` has changed the +code: + +Filename: src/main.rs + +```rust +fn do_something() {} + +fn main() { + for _i in 0..100 { + do_something(); + } +} +``` + +The `for` loop variable is now named `_i`, and the warning no longer appears. + +You can also use the `cargo fix` command to transition your code between +different Rust editions. Editions are covered in Appendix E. + +### More Lints with Clippy + +The Clippy tool is a collection of lints to analyze your code so you can catch +common mistakes and improve your Rust code. + +To install Clippy, enter the following: + +```console +$ rustup component add clippy +``` + +To run Clippy’s lints on any Cargo project, enter the following: + +```console +$ cargo clippy +``` + +For example, say you write a program that uses an approximation of a +mathematical constant, such as pi, as this program does: + +Filename: src/main.rs + +```rust +fn main() { + let x = 3.1415; + let r = 8.0; + println!("the area of the circle is {}", x * r * r); +} +``` + +Running `cargo clippy` on this project results in this error: + +```text +error: approximate value of `f{32, 64}::consts::PI` found. Consider using it directly + --> src/main.rs:2:13 + | +2 | let x = 3.1415; + | ^^^^^^ + | + = note: #[deny(clippy::approx_constant)] on by default + = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/master/index.html#approx_constant +``` + +This error lets you know that Rust has this constant defined more precisely and +that your program would be more correct if you used the constant instead. You +would then change your code to use the `PI` constant. The following code +doesn’t result in any errors or warnings from Clippy: + +Filename: src/main.rs + +```rust +fn main() { + let x = std::f64::consts::PI; + let r = 8.0; + println!("the area of the circle is {}", x * r * r); +} +``` + +For more information on Clippy, see [its documentation][clippy]. + +[clippy]: https://github.com/rust-lang/rust-clippy + +### IDE Integration Using the Rust Language Server + +To help IDE integration, the Rust project distributes the *Rust Language +Server* (`rls`). This tool speaks the [Language Server +Protocol][lsp], which is a specification for IDEs and programming +languages to communicate with each other. Different clients can use the `rls`, +such as [the Rust plug-in for Visual Studio Code][vscode]. + +[lsp]: http://langserver.org/ +[vscode]: https://marketplace.visualstudio.com/items?itemName=rust-lang.rust + +To install the `rls`, enter the following: + +```console +$ rustup component add rls +``` + +Then install the language server support in your particular IDE; you’ll gain +abilities such as autocompletion, jump to definition, and inline errors. + +For more information on the `rls`, see [its documentation][rls]. + +[rls]: https://github.com/rust-lang/rls diff --git a/src/appendix-05-editions.md b/src/appendix-05-editions.md new file mode 100644 index 0000000..db98ecc --- /dev/null +++ b/src/appendix-05-editions.md @@ -0,0 +1,57 @@ +## Appendix E - Editions + +In Chapter 1, you saw that `cargo new` adds a bit of metadata to your +*Cargo.toml* file about an edition. This appendix talks about what that means! + +The Rust language and compiler have a six-week release cycle, meaning users get +a constant stream of new features. Other programming languages release larger +changes less often; Rust releases smaller updates more frequently. After a +while, all of these tiny changes add up. But from release to release, it can be +difficult to look back and say, “Wow, between Rust 1.10 and Rust 1.31, Rust has +changed a lot!” + +Every two or three years, the Rust team produces a new Rust *edition*. Each +edition brings together the features that have landed into a clear package with +fully updated documentation and tooling. New editions ship as part of the usual +six-week release process. + +Editions serve different purposes for different people: + +* For active Rust users, a new edition brings together incremental changes into + an easy-to-understand package. +* For non-users, a new edition signals that some major advancements have + landed, which might make Rust worth another look. +* For those developing Rust, a new edition provides a rallying point for the + project as a whole. + +At the time of this writing, two Rust editions are available: Rust 2015 and +Rust 2018. This book is written using Rust 2018 edition idioms. + +The `edition` key in *Cargo.toml* indicates which edition the compiler should +use for your code. If the key doesn’t exist, Rust uses `2015` as the edition +value for backward compatibility reasons. + +Each project can opt in to an edition other than the default 2015 edition. +Editions can contain incompatible changes, such as including a new keyword that +conflicts with identifiers in code. However, unless you opt in to those +changes, your code will continue to compile even as you upgrade the Rust +compiler version you use. + +All Rust compiler versions support any edition that existed prior to that +compiler’s release, and they can link crates of any supported editions +together. Edition changes only affect the way the compiler initially parses +code. Therefore, if you’re using Rust 2015 and one of your dependencies uses +Rust 2018, your project will compile and be able to use that dependency. The +opposite situation, where your project uses Rust 2018 and a dependency uses +Rust 2015, works as well. + +To be clear: most features will be available on all editions. Developers using +any Rust edition will continue to see improvements as new stable releases are +made. However, in some cases, mainly when new keywords are added, some new +features might only be available in later editions. You will need to switch +editions if you want to take advantage of such features. + +For more details, the [*Edition +Guide*](https://doc.rust-lang.org/stable/edition-guide/) is a complete book +about editions that enumerates the differences between editions and explains +how to automatically upgrade your code to a new edition via `cargo fix`. diff --git a/src/appendix-05-macros.md b/src/appendix-05-macros.md deleted file mode 100644 index cef030b..0000000 --- a/src/appendix-05-macros.md +++ /dev/null @@ -1,5 +0,0 @@ -# Macros - -## Basics of writing your own macros - -## Macros are changing, go see X for more info diff --git a/src/appendix-06-translation.md b/src/appendix-06-translation.md new file mode 100644 index 0000000..cbd3974 --- /dev/null +++ b/src/appendix-06-translation.md @@ -0,0 +1,27 @@ +## Appendix F: Translations of the Book + +For resources in languages other than English. Most are still in progress; see +[the Translations label][label] to help or let us know about a new translation! + +[label]: https://github.com/rust-lang/book/issues?q=is%3Aopen+is%3Aissue+label%3ATranslations + +- [Português](https://github.com/rust-br/rust-book-pt-br) (BR) +- [Português](https://github.com/nunojesus/rust-book-pt-pt) (PT) +- [简体中文](https://github.com/KaiserY/trpl-zh-cn) +- [Українська](https://github.com/pavloslav/rust-book-uk-ua) +- [Español](https://github.com/thecodix/book), [alternate](https://github.com/ManRR/rust-book-es) +- [Italiano](https://github.com/AgeOfWar/rust-book-it) +- [Русский](https://github.com/rust-lang-ru/book) +- [한국어](https://github.com/rinthel/rust-lang-book-ko) +- [日本語](https://github.com/rust-lang-ja/book-ja) +- [Français](https://github.com/Jimskapt/rust-book-fr) +- [Polski](https://github.com/paytchoo/book-pl) +- [עברית](https://github.com/idanmel/rust-book-heb) +- [Cebuano](https://github.com/agentzero1/book) +- [Tagalog](https://github.com/josephace135/book) +- [Esperanto](https://github.com/psychoslave/Rust-libro) +- [ελληνική](https://github.com/TChatzigiannakis/rust-book-greek) +- [Svenska](https://github.com/sebras/book) +- [Farsi](https://github.com/pomokhtari/rust-book-fa) +- [Deutsch](https://github.com/rust-lang-de/rustbook-de) +- [Turkish](https://github.com/RustDili/dokuman/tree/master/ceviriler), [online](https://rustdili.github.io/) diff --git a/src/appendix-07-nightly-rust.md b/src/appendix-07-nightly-rust.md new file mode 100644 index 0000000..46e619c --- /dev/null +++ b/src/appendix-07-nightly-rust.md @@ -0,0 +1,201 @@ +## Appendix G - How Rust is Made and “Nightly Rust” + +This appendix is about how Rust is made and how that affects you as a Rust +developer. + +### Stability Without Stagnation + +As a language, Rust cares a *lot* about the stability of your code. We want +Rust to be a rock-solid foundation you can build on, and if things were +constantly changing, that would be impossible. At the same time, if we can’t +experiment with new features, we may not find out important flaws until after +their release, when we can no longer change things. + +Our solution to this problem is what we call “stability without stagnation”, +and our guiding principle is this: you should never have to fear upgrading to a +new version of stable Rust. Each upgrade should be painless, but should also +bring you new features, fewer bugs, and faster compile times. + +### Choo, Choo! Release Channels and Riding the Trains + +Rust development operates on a *train schedule*. That is, all development is +done on the `master` branch of the Rust repository. Releases follow a software +release train model, which has been used by Cisco IOS and other software +projects. There are three *release channels* for Rust: + +* Nightly +* Beta +* Stable + +Most Rust developers primarily use the stable channel, but those who want to +try out experimental new features may use nightly or beta. + +Here’s an example of how the development and release process works: let’s +assume that the Rust team is working on the release of Rust 1.5. That release +happened in December of 2015, but it will provide us with realistic version +numbers. A new feature is added to Rust: a new commit lands on the `master` +branch. Each night, a new nightly version of Rust is produced. Every day is a +release day, and these releases are created by our release infrastructure +automatically. So as time passes, our releases look like this, once a night: + +```text +nightly: * - - * - - * +``` + +Every six weeks, it’s time to prepare a new release! The `beta` branch of the +Rust repository branches off from the `master` branch used by nightly. Now, +there are two releases: + +```text +nightly: * - - * - - * + | +beta: * +``` + +Most Rust users do not use beta releases actively, but test against beta in +their CI system to help Rust discover possible regressions. In the meantime, +there’s still a nightly release every night: + +```text +nightly: * - - * - - * - - * - - * + | +beta: * +``` + +Let’s say a regression is found. Good thing we had some time to test the beta +release before the regression snuck into a stable release! The fix is applied +to `master`, so that nightly is fixed, and then the fix is backported to the +`beta` branch, and a new release of beta is produced: + +```text +nightly: * - - * - - * - - * - - * - - * + | +beta: * - - - - - - - - * +``` + +Six weeks after the first beta was created, it’s time for a stable release! The +`stable` branch is produced from the `beta` branch: + +```text +nightly: * - - * - - * - - * - - * - - * - * - * + | +beta: * - - - - - - - - * + | +stable: * +``` + +Hooray! Rust 1.5 is done! However, we’ve forgotten one thing: because the six +weeks have gone by, we also need a new beta of the *next* version of Rust, 1.6. +So after `stable` branches off of `beta`, the next version of `beta` branches +off of `nightly` again: + +```text +nightly: * - - * - - * - - * - - * - - * - * - * + | | +beta: * - - - - - - - - * * + | +stable: * +``` + +This is called the “train model” because every six weeks, a release “leaves the +station”, but still has to take a journey through the beta channel before it +arrives as a stable release. + +Rust releases every six weeks, like clockwork. If you know the date of one Rust +release, you can know the date of the next one: it’s six weeks later. A nice +aspect of having releases scheduled every six weeks is that the next train is +coming soon. If a feature happens to miss a particular release, there’s no need +to worry: another one is happening in a short time! This helps reduce pressure +to sneak possibly unpolished features in close to the release deadline. + +Thanks to this process, you can always check out the next build of Rust and +verify for yourself that it’s easy to upgrade to: if a beta release doesn’t +work as expected, you can report it to the team and get it fixed before the +next stable release happens! Breakage in a beta release is relatively rare, but +`rustc` is still a piece of software, and bugs do exist. + +### Unstable Features + +There’s one more catch with this release model: unstable features. Rust uses a +technique called “feature flags” to determine what features are enabled in a +given release. If a new feature is under active development, it lands on +`master`, and therefore, in nightly, but behind a *feature flag*. If you, as a +user, wish to try out the work-in-progress feature, you can, but you must be +using a nightly release of Rust and annotate your source code with the +appropriate flag to opt in. + +If you’re using a beta or stable release of Rust, you can’t use any feature +flags. This is the key that allows us to get practical use with new features +before we declare them stable forever. Those who wish to opt into the bleeding +edge can do so, and those who want a rock-solid experience can stick with +stable and know that their code won’t break. Stability without stagnation. + +This book only contains information about stable features, as in-progress +features are still changing, and surely they’ll be different between when this +book was written and when they get enabled in stable builds. You can find +documentation for nightly-only features online. + +### Rustup and the Role of Rust Nightly + +Rustup makes it easy to change between different release channels of Rust, on a +global or per-project basis. By default, you’ll have stable Rust installed. To +install nightly, for example: + +```console +$ rustup toolchain install nightly +``` + +You can see all of the *toolchains* (releases of Rust and associated +components) you have installed with `rustup` as well. Here’s an example on one +of your authors’ Windows computer: + +```powershell +> rustup toolchain list +stable-x86_64-pc-windows-msvc (default) +beta-x86_64-pc-windows-msvc +nightly-x86_64-pc-windows-msvc +``` + +As you can see, the stable toolchain is the default. Most Rust users use stable +most of the time. You might want to use stable most of the time, but use +nightly on a specific project, because you care about a cutting-edge feature. +To do so, you can use `rustup override` in that project’s directory to set the +nightly toolchain as the one `rustup` should use when you’re in that directory: + +```console +$ cd ~/projects/needs-nightly +$ rustup override set nightly +``` + +Now, every time you call `rustc` or `cargo` inside of +*~/projects/needs-nightly*, `rustup` will make sure that you are using nightly +Rust, rather than your default of stable Rust. This comes in handy when you +have a lot of Rust projects! + +### The RFC Process and Teams + +So how do you learn about these new features? Rust’s development model follows +a *Request For Comments (RFC) process*. If you’d like an improvement in Rust, +you can write up a proposal, called an RFC. + +Anyone can write RFCs to improve Rust, and the proposals are reviewed and +discussed by the Rust team, which is comprised of many topic subteams. There’s +a full list of the teams [on Rust’s +website](https://www.rust-lang.org/governance), which includes teams for +each area of the project: language design, compiler implementation, +infrastructure, documentation, and more. The appropriate team reads the +proposal and the comments, writes some comments of their own, and eventually, +there’s consensus to accept or reject the feature. + +If the feature is accepted, an issue is opened on the Rust repository, and +someone can implement it. The person who implements it very well may not be the +person who proposed the feature in the first place! When the implementation is +ready, it lands on the `master` branch behind a feature gate, as we discussed +in the [“Unstable Features”](#unstable-features) section. + +After some time, once Rust developers who use nightly releases have been able +to try out the new feature, team members will discuss the feature, how it’s +worked out on nightly, and decide if it should make it into stable Rust or not. +If the decision is to move forward, the feature gate is removed, and the +feature is now considered stable! It rides the trains into a new stable release +of Rust. diff --git a/src/ch01-00-introduction.md b/src/ch00-00-introduction.md similarity index 100% rename from src/ch01-00-introduction.md rename to src/ch00-00-introduction.md diff --git a/src/ch01-00-getting-started.md b/src/ch01-00-getting-started.md new file mode 100644 index 0000000..ff5e324 --- /dev/null +++ b/src/ch01-00-getting-started.md @@ -0,0 +1,8 @@ +# Getting Started + +Let’s start your Rust journey! There’s a lot to learn, but every journey starts +somewhere. In this chapter, we’ll discuss: + +* Installing Rust on Linux, macOS, and Windows +* Writing a program that prints `Hello, world!` +* Using `cargo`, Rust’s package manager and build system diff --git a/src/ch01-03-hello-cargo.md b/src/ch01-03-hello-cargo.md new file mode 100644 index 0000000..0f11be8 --- /dev/null +++ b/src/ch01-03-hello-cargo.md @@ -0,0 +1,251 @@ +## Hello, Cargo! + +Cargo is Rust’s build system and package manager. Most Rustaceans use this tool +to manage their Rust projects because Cargo handles a lot of tasks for you, +such as building your code, downloading the libraries your code depends on, and +building those libraries. (We call libraries your code needs *dependencies*.) + +The simplest Rust programs, like the one we’ve written so far, don’t have any +dependencies. So if we had built the “Hello, world!” project with Cargo, it +would only use the part of Cargo that handles building your code. As you write +more complex Rust programs, you’ll add dependencies, and if you start a project +using Cargo, adding dependencies will be much easier to do. + +Because the vast majority of Rust projects use Cargo, the rest of this book +assumes that you’re using Cargo too. Cargo comes installed with Rust if you +used the official installers discussed in the +[“Installation”][installation] section. If you installed Rust +through some other means, check whether Cargo is installed by entering the +following into your terminal: + +```console +$ cargo --version +``` + +If you see a version number, you have it! If you see an error, such as `command +not found`, look at the documentation for your method of installation to +determine how to install Cargo separately. + +### Creating a Project with Cargo + +Let’s create a new project using Cargo and look at how it differs from our +original “Hello, world!” project. Navigate back to your *projects* directory (or +wherever you decided to store your code). Then, on any operating system, run +the following: + +```console +$ cargo new hello_cargo +$ cd hello_cargo +``` + +The first command creates a new directory called *hello_cargo*. We’ve named +our project *hello_cargo*, and Cargo creates its files in a directory of the +same name. + +Go into the *hello_cargo* directory and list the files. You’ll see that Cargo +has generated two files and one directory for us: a *Cargo.toml* file and a +*src* directory with a *main.rs* file inside. + +It has also initialized a new Git repository along with a *.gitignore* file. +Git files won’t be generated if you run `cargo new` within an existing Git +repository; you can override this behavior by using `cargo new --vcs=git`. + +> Note: Git is a common version control system. You can change `cargo new` to +> use a different version control system or no version control system by using +> the `--vcs` flag. Run `cargo new --help` to see the available options. + +Open *Cargo.toml* in your text editor of choice. It should look similar to the +code in Listing 1-2. + +Filename: Cargo.toml + +```toml +[package] +name = "hello_cargo" +version = "0.1.0" +authors = ["Your Name "] +edition = "2018" + +[dependencies] +``` + +Listing 1-2: Contents of *Cargo.toml* generated by `cargo +new` + +This file is in the [*TOML*](https://toml.io) (*Tom’s Obvious, +Minimal Language*) format, which is Cargo’s configuration format. + +The first line, `[package]`, is a section heading that indicates that the +following statements are configuring a package. As we add more information to +this file, we’ll add other sections. + +The next four lines set the configuration information Cargo needs to compile +your program: the name, the version, who wrote it, and the edition of Rust to +use. Cargo gets your name and email information from your environment, so if +that information is not correct, fix the information now and then save the +file. We’ll talk about the `edition` key in Appendix E. + +The last line, `[dependencies]`, is the start of a section for you to list any +of your project’s dependencies. In Rust, packages of code are referred to as +*crates*. We won’t need any other crates for this project, but we will in the +first project in Chapter 2, so we’ll use this dependencies section then. + +Now open *src/main.rs* and take a look: + +Filename: src/main.rs + +```rust +fn main() { + println!("Hello, world!"); +} +``` + +Cargo has generated a “Hello, world!” program for you, just like the one we +wrote in Listing 1-1! So far, the differences between our previous project and +the project Cargo generates are that Cargo placed the code in the *src* +directory, and we have a *Cargo.toml* configuration file in the top directory. + +Cargo expects your source files to live inside the *src* directory. The +top-level project directory is just for README files, license information, +configuration files, and anything else not related to your code. Using Cargo +helps you organize your projects. There’s a place for everything, and +everything is in its place. + +If you started a project that doesn’t use Cargo, as we did with the “Hello, +world!” project, you can convert it to a project that does use Cargo. Move the +project code into the *src* directory and create an appropriate *Cargo.toml* +file. + +### Building and Running a Cargo Project + +Now let’s look at what’s different when we build and run the “Hello, world!” +program with Cargo! From your *hello_cargo* directory, build your project by +entering the following command: + +```console +$ cargo build + Compiling hello_cargo v0.1.0 (file:///projects/hello_cargo) + Finished dev [unoptimized + debuginfo] target(s) in 2.85 secs +``` + +This command creates an executable file in *target/debug/hello_cargo* (or +*target\debug\hello_cargo.exe* on Windows) rather than in your current +directory. You can run the executable with this command: + +```console +$ ./target/debug/hello_cargo # or .\target\debug\hello_cargo.exe on Windows +Hello, world! +``` + +If all goes well, `Hello, world!` should print to the terminal. Running `cargo +build` for the first time also causes Cargo to create a new file at the top +level: *Cargo.lock*. This file keeps track of the exact versions of +dependencies in your project. This project doesn’t have dependencies, so the +file is a bit sparse. You won’t ever need to change this file manually; Cargo +manages its contents for you. + +We just built a project with `cargo build` and ran it with +`./target/debug/hello_cargo`, but we can also use `cargo run` to compile the +code and then run the resulting executable all in one command: + +```console +$ cargo run + Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs + Running `target/debug/hello_cargo` +Hello, world! +``` + +Notice that this time we didn’t see output indicating that Cargo was compiling +`hello_cargo`. Cargo figured out that the files hadn’t changed, so it just ran +the binary. If you had modified your source code, Cargo would have rebuilt the +project before running it, and you would have seen this output: + +```console +$ cargo run + Compiling hello_cargo v0.1.0 (file:///projects/hello_cargo) + Finished dev [unoptimized + debuginfo] target(s) in 0.33 secs + Running `target/debug/hello_cargo` +Hello, world! +``` + +Cargo also provides a command called `cargo check`. This command quickly checks +your code to make sure it compiles but doesn’t produce an executable: + +```console +$ cargo check + Checking hello_cargo v0.1.0 (file:///projects/hello_cargo) + Finished dev [unoptimized + debuginfo] target(s) in 0.32 secs +``` + +Why would you not want an executable? Often, `cargo check` is much faster than +`cargo build`, because it skips the step of producing an executable. If you’re +continually checking your work while writing the code, using `cargo check` will +speed up the process! As such, many Rustaceans run `cargo check` periodically +as they write their program to make sure it compiles. Then they run `cargo +build` when they’re ready to use the executable. + +Let’s recap what we’ve learned so far about Cargo: + +* We can build a project using `cargo build`. +* We can build and run a project in one step using `cargo run`. +* We can build a project without producing a binary to check for errors using + `cargo check`. +* Instead of saving the result of the build in the same directory as our code, + Cargo stores it in the *target/debug* directory. + +An additional advantage of using Cargo is that the commands are the same no +matter which operating system you’re working on. So, at this point, we’ll no +longer provide specific instructions for Linux and macOS versus Windows. + +### Building for Release + +When your project is finally ready for release, you can use `cargo build +--release` to compile it with optimizations. This command will create an +executable in *target/release* instead of *target/debug*. The optimizations +make your Rust code run faster, but turning them on lengthens the time it takes +for your program to compile. This is why there are two different profiles: one +for development, when you want to rebuild quickly and often, and another for +building the final program you’ll give to a user that won’t be rebuilt +repeatedly and that will run as fast as possible. If you’re benchmarking your +code’s running time, be sure to run `cargo build --release` and benchmark with +the executable in *target/release*. + +### Cargo as Convention + +With simple projects, Cargo doesn’t provide a lot of value over just using +`rustc`, but it will prove its worth as your programs become more intricate. +With complex projects composed of multiple crates, it’s much easier to let +Cargo coordinate the build. + +Even though the `hello_cargo` project is simple, it now uses much of the real +tooling you’ll use in the rest of your Rust career. In fact, to work on any +existing projects, you can use the following commands to check out the code +using Git, change to that project’s directory, and build: + +```console +$ git clone example.org/someproject +$ cd someproject +$ cargo build +``` + +For more information about Cargo, check out [its documentation]. + +[its documentation]: https://doc.rust-lang.org/cargo/ + +## Summary + +You’re already off to a great start on your Rust journey! In this chapter, +you’ve learned how to: + +* Install the latest stable version of Rust using `rustup` +* Update to a newer Rust version +* Open locally installed documentation +* Write and run a “Hello, world!” program using `rustc` directly +* Create and run a new project using the conventions of Cargo + +This is a great time to build a more substantial program to get used to reading +and writing Rust code. So, in Chapter 2, we’ll build a guessing game program. +If you would rather start by learning how common programming concepts work in +Rust, see Chapter 3 and then return to Chapter 2. + +[installation]: ch01-01-installation.html#installation diff --git a/src/ch02-00-guessing-game-tutorial.md b/src/ch02-00-guessing-game-tutorial.md index 8ce70a6..ba494eb 100644 --- a/src/ch02-00-guessing-game-tutorial.md +++ b/src/ch02-00-guessing-game-tutorial.md @@ -1,4 +1,4 @@ -# Guessing Game +# Programming a Guessing Game Let’s jump into Rust by working through a hands-on project together! This chapter introduces you to a few common Rust concepts by showing you how to use @@ -8,36 +8,30 @@ these ideas in more detail. In this chapter, you’ll practice the fundamentals. We’ll implement a classic beginner programming problem: a guessing game. Here’s how it works: the program will generate a random integer between 1 and 100. It -will then prompt the player to enter a guess. After entering a guess, it will -indicate whether the guess is too low or too high. If the guess is correct, the -game will print congratulations and exit. +will then prompt the player to enter a guess. After a guess is entered, the +program will indicate whether the guess is too low or too high. If the guess is +correct, the game will print a congratulatory message and exit. ## Setting Up a New Project To set up a new project, go to the *projects* directory that you created in -Chapter 1, and make a new project using Cargo, like so: +Chapter 1 and make a new project using Cargo, like so: -```text -$ cargo new guessing_game --bin +```console +$ cargo new guessing_game $ cd guessing_game ``` The first command, `cargo new`, takes the name of the project (`guessing_game`) -as the first argument. The `--bin` flag tells Cargo to make a binary project, -similar to the one in Chapter 1. The second command changes to the new -project’s directory. +as the first argument. The second command changes to the new project’s +directory. Look at the generated *Cargo.toml* file: Filename: Cargo.toml ```toml -[package] -name = "guessing_game" -version = "0.1.0" -authors = ["Your Name "] - -[dependencies] +{{#include ../listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/Cargo.toml}} ``` If the author information that Cargo obtained from your environment is not @@ -49,132 +43,113 @@ you. Check out the *src/main.rs* file: Filename: src/main.rs ```rust -fn main() { - println!("Hello, world!"); -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/src/main.rs}} ``` Now let’s compile this “Hello, world!” program and run it in the same step using the `cargo run` command: -```text -$ cargo run - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/debug/guessing_game` -Hello, world! +```console +{{#include ../listings/ch02-guessing-game-tutorial/no-listing-01-cargo-new/output.txt}} ``` The `run` command comes in handy when you need to rapidly iterate on a project, -and this game is such a project: we want to quickly test each iteration -before moving on to the next one. +as we’ll do in this game, quickly testing each iteration before moving on to +the next one. Reopen the *src/main.rs* file. You’ll be writing all the code in this file. ## Processing a Guess -The first part of the program will ask for user input, process that input, and -check that the input is in the expected form. To start, we’ll allow the player -to input a guess. Enter the code in Listing 2-1 into *src/main.rs*. +The first part of the guessing game program will ask for user input, process +that input, and check that the input is in the expected form. To start, we’ll +allow the player to input a guess. Enter the code in Listing 2-1 into +*src/main.rs*. -
Filename: src/main.rs ```rust,ignore -use std::io; - -fn main() { - println!("Guess the number!"); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - println!("You guessed: {}", guess); -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:all}} ``` -
+Listing 2-1: Code that gets a guess from the user and +prints it -Listing 2-1: Code to get a guess from the user and print it out - -
-
- -This code contains a lot of information, so let’s go over it bit by bit. To -obtain user input and then print the result as output, we need to import the -`io` (input/output) library from the standard library (which is known as `std`): +This code contains a lot of information, so let’s go over it line by line. To +obtain user input and then print the result as output, we need to bring the +`io` (input/output) library into scope. The `io` library comes from the +standard library (which is known as `std`): ```rust,ignore -use std::io; +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:io}} ``` -By default, Rust imports only a few types into every program in [the -*prelude*][prelude]. If a type you want to use isn’t in the -prelude, you have to import that type into your program explicitly with a `use` +By default, Rust brings only a few types into the scope of every program in +[the *prelude*][prelude]. If a type you want to use isn’t in the +prelude, you have to bring that type into scope explicitly with a `use` statement. Using the `std::io` library provides you with a number of useful -`io`-related features, including the functionality to accept user input. +features, including the ability to accept user input. -[prelude]: https://doc.rust-lang.org/std/prelude/ +[prelude]: ../std/prelude/index.html As you saw in Chapter 1, the `main` function is the entry point into the program: ```rust,ignore -fn main() { +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:main}} ``` -The `fn` syntax declares a new function, the `()` indicate there are no -parameters, and `{` starts the body of the function. +The `fn` syntax declares a new function, the parentheses, `()`, indicate there +are no parameters, and the curly bracket, `{`, starts the body of the function. As you also learned in Chapter 1, `println!` is a macro that prints a string to the screen: ```rust,ignore -println!("Guess the number!"); - -println!("Please input your guess."); +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:print}} ``` -This code is just printing a prompt stating what the game is and requesting -input from the user. +This code is printing a prompt stating what the game is and requesting input +from the user. ### Storing Values with Variables Next, we’ll create a place to store the user input, like this: ```rust,ignore -let mut guess = String::new(); +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:string}} ``` Now the program is getting interesting! There’s a lot going on in this little -line. Notice that this is a `let` statement, which is used to create -*variables*. Here’s another example: +line. Notice that this is a `let` statement, which is used to create a +*variable*. Here’s another example: ```rust,ignore let foo = bar; ``` -This line will create a new variable named `foo` and bind it to the value -`bar`. In Rust, variables are immutable by default. The following example shows -how to use `mut` before the variable name to make a variable mutable: +This line creates a new variable named `foo` and binds it to the value of the +`bar` variable. In Rust, variables are immutable by default. We’ll be +discussing this concept in detail in the [“Variables and +Mutability”][variables-and-mutability] section in Chapter 3. +The following example shows how to use `mut` before the variable name to make +a variable mutable: -```rust +```rust,ignore let foo = 5; // immutable let mut bar = 5; // mutable ``` > Note: The `//` syntax starts a comment that continues until the end of the -> line. Rust ignores everything in comments. +> line. Rust ignores everything in comments, which are discussed in more detail +> in Chapter 3. -Now you know that `let mut guess` will introduce a mutable variable named -`guess`. On the other side of the equal sign (`=`) is the value that `guess` is -bound to, which is the result of calling `String::new`, a function that returns -a new instance of a `String`. [`String`][string] is a string -type provided by the standard library that is a growable, UTF-8 encoded bit of -text. +Let’s return to the guessing game program. You now know that `let mut guess` +will introduce a mutable variable named `guess`. On the other side of the equal +sign (`=`) is the value that `guess` is bound to, which is the result of +calling `String::new`, a function that returns a new instance of a `String`. +[`String`][string] is a string type provided by the standard +library that is a growable, UTF-8 encoded bit of text. [string]: ../std/string/struct.String.html @@ -183,7 +158,7 @@ function* of the `String` type. An associated function is implemented on a type, in this case `String`, rather than on a particular instance of a `String`. Some languages call this a *static method*. -This `new` function creates a new, empty `String`. You’ll find a `new` function +This `new` function creates a new, empty string. You’ll find a `new` function on many types, because it’s a common name for a function that makes a new value of some kind. @@ -191,15 +166,14 @@ To summarize, the `let mut guess = String::new();` line has created a mutable variable that is currently bound to a new, empty instance of a `String`. Whew! Recall that we included the input/output functionality from the standard -library with `use std::io;` on the first line of the program. Now we’ll call an -associated function, `stdin`, on `io`: +library with `use std::io;` on the first line of the program. Now we’ll call +the `stdin` function from the `io` module: ```rust,ignore -io::stdin().read_line(&mut guess) - .expect("Failed to read line"); +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:read}} ``` -If we didn’t have the `use std::io` line at the beginning of the program, we +If we hadn’t put the `use std::io` line at the beginning of the program, we could have written this function call as `std::io::stdin`. The `stdin` function returns an instance of [`std::io::Stdin`][iostdin], which is a type that represents a handle to the standard input for your terminal. @@ -214,25 +188,28 @@ guess`. [read_line]: ../std/io/struct.Stdin.html#method.read_line The job of `read_line` is to take whatever the user types into standard input -and place that into a string, so it takes that string as an argument. The -string argument needs to be mutable so the method can change the string’s -content by adding the user input. +and append that into a string (without overwriting its contents), so it takes +that string as an argument. The string argument needs to be mutable so the +method can change the string’s content by adding the user input. The `&` indicates that this argument is a *reference*, which gives you a way to let multiple parts of your code access one piece of data without needing to copy that data into memory multiple times. References are a complex feature, and one of Rust’s major advantages is how safe and easy it is to use references. You don’t need to know a lot of those details to finish this -program: Chapter 4 will explain references more thoroughly. For now, all you -need to know is that like variables, references are immutable by default. -Hence, we need to write `&mut guess` rather than `&guess` to make it mutable. +program. For now, all you need to know is that like variables, references are +immutable by default. Hence, you need to write `&mut guess` rather than +`&guess` to make it mutable. (Chapter 4 will explain references more +thoroughly.) -We’re not quite done with this line of code. Although it’s a single line of -text, it’s only the first part of the single logical line of code. The second -part is this method: +### Handling Potential Failure with the `Result` Type + +We’re still working on this line of code. Although we’re now discussing a third +line of text, it’s still part of a single logical line of code. The next part +is this method: ```rust,ignore -.expect("Failed to read line"); +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:expect}} ``` When you call a method with the `.foo()` syntax, it’s often wise to introduce a @@ -243,16 +220,14 @@ written this code as: io::stdin().read_line(&mut guess).expect("Failed to read line"); ``` -However, one long line is difficult to read, so it’s best to divide it, two -lines for two method calls. Now let’s discuss what this line does. +However, one long line is difficult to read, so it’s best to divide it. Now +let’s discuss what this line does. -### Handling Potential Failure with the `Result` Type - -As mentioned earlier, `read_line` puts what the user types into the string we’re -passing it, but it also returns a value—in this case, an +As mentioned earlier, `read_line` puts what the user types into the string +we’re passing it, but it also returns a value—in this case, an [`io::Result`][ioresult]. Rust has a number of types named -`Result` in its standard library: a generic [`Result`][result] as -well as specific versions for submodules, such as `io::Result`. +`Result` in its standard library: a generic [`Result`][result] +as well as specific versions for submodules, such as `io::Result`. [ioresult]: ../std/io/type.Result.html [result]: ../std/result/enum.Result.html @@ -264,55 +239,52 @@ in more detail. [enums]: ch06-00-enums.html -For `Result`, the variants are `Ok` or `Err`. `Ok` indicates the operation was -successful, and inside the `Ok` variant is the successfully generated value. -`Err` means the operation failed, and `Err` contains information about how or -why the operation failed. +For `Result`, the variants are `Ok` or `Err`. The `Ok` variant indicates the +operation was successful, and inside `Ok` is the successfully generated value. +The `Err` variant means the operation failed, and `Err` contains information +about how or why the operation failed. -The purpose of these `Result` types is to encode error handling information. -Values of the `Result` type, like any type, have methods defined on them. An -instance of `io::Result` has an [`expect` method][expect] that -you can call. If this instance of `io::Result` is an `Err` value, `expect` will -cause the program to crash and display the message that you passed as an -argument to `expect`. If the `read_line` method returns an `Err`, it would -likely be the result of an error coming from the underlying operating system. -If this instance of `io::Result` is an `Ok` value, `expect` will take the -return value that `Ok` is holding and return just that value to you so you -could use it. In this case, that value is the number of characters the user +The purpose of these `Result` types is to encode error-handling information. +Values of the `Result` type, like values of any type, have methods defined on +them. An instance of `io::Result` has an [`expect` method][expect] that you can call. If this instance of `io::Result` is an `Err` value, +`expect` will cause the program to crash and display the message that you +passed as an argument to `expect`. If the `read_line` method returns an `Err`, +it would likely be the result of an error coming from the underlying operating +system. If this instance of `io::Result` is an `Ok` value, `expect` will take +the return value that `Ok` is holding and return just that value to you so you +can use it. In this case, that value is the number of bytes in what the user entered into standard input. [expect]: ../std/result/enum.Result.html#method.expect -If we don’t call `expect`, the program will compile, but we’ll get a warning: +If you don’t call `expect`, the program will compile, but you’ll get a warning: -```text -$ cargo build - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) -src/main.rs:10:5: 10:39 warning: unused result which must be used, -#[warn(unused_must_use)] on by default -src/main.rs:10 io::stdin().read_line(&mut guess); - ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +```console +{{#include ../listings/ch02-guessing-game-tutorial/no-listing-02-without-expect/output.txt}} ``` -Rust warns that we haven’t used the `Result` value returned from `read_line`, -indicating that the program hasn’t handled a possible error. The right way to -suppress the warning is to actually write error handling, but since we just -want to crash this program when a problem occurs, we can use `expect`. You’ll -learn about recovering from errors in Chapter 9. +Rust warns that you haven’t used the `Result` value returned from `read_line`, +indicating that the program hasn’t handled a possible error. + +The right way to suppress the warning is to actually write error handling, but +because you just want to crash this program when a problem occurs, you can use +`expect`. You’ll learn about recovering from errors in Chapter 9. ### Printing Values with `println!` Placeholders -Aside from the closing curly brace, there’s only one more line to discuss in +Aside from the closing curly bracket, there’s only one more line to discuss in the code added so far, which is the following: ```rust,ignore -println!("You guessed: {}", guess); +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-01/src/main.rs:print_guess}} ``` -This line prints out the string we saved the user’s input in. The set of `{}` -is a placeholder that holds a value in place. You can print more than one value -using `{}`: the first set of `{}` holds the first value listed after the format -string, the second set holds the second value, and so on. Printing out multiple +This line prints the string we saved the user’s input in. The set of curly +brackets, `{}`, is a placeholder: think of `{}` as little crab pincers that +hold a value in place. You can print more than one value using curly brackets: +the first set of curly brackets holds the first value listed after the format +string, the second set holds the second value, and so on. Printing multiple values in one call to `println!` would look like this: ```rust @@ -322,15 +294,22 @@ let y = 10; println!("x = {} and y = {}", x, y); ``` -This code would print out `x = 5 and y = 10`. +This code would print `x = 5 and y = 10`. ### Testing the First Part -Let’s test the first part of the guessing game. You can run it using `cargo run`: +Let’s test the first part of the guessing game. Run it using `cargo run`: -```text + + +```console $ cargo run Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished dev [unoptimized + debuginfo] target(s) in 6.44s Running `target/debug/guessing_game` Guess the number! Please input your guess. @@ -353,99 +332,127 @@ library. However, the Rust team does provide a [`rand` crate][randcrate]. ### Using a Crate to Get More Functionality -Remember that a *crate* is a package of Rust code. The project we’ve been -building is a *binary crate*, which is an executable. The `rand` crate is a -*library crate*, which contains code intended to be used in other programs. +Remember that a crate is a collection of Rust source code files. +The project we’ve been building is a *binary crate*, which is an executable. +The `rand` crate is a *library crate*, which contains code intended to be +used in other programs. Cargo’s use of external crates is where it really shines. Before we can write code that uses `rand`, we need to modify the *Cargo.toml* file to include the `rand` crate as a dependency. Open that file now and add the following line to the bottom beneath the `[dependencies]` section header that Cargo created for -you: +you. Be sure to specify `rand` exactly as we have here, or the code examples in +this tutorial may not work. + + Filename: Cargo.toml ```toml -[dependencies] - -rand = "0.3.14" +{{#include ../listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.toml:9:}} ``` In the *Cargo.toml* file, everything that follows a header is part of a section that continues until another section starts. The `[dependencies]` section is where you tell Cargo which external crates your project depends on and which versions of those crates you require. In this case, we’ll specify the `rand` -crate with the semantic version specifier `0.3.14`. Cargo understands [Semantic +crate with the semantic version specifier `0.8.3`. Cargo understands [Semantic Versioning][semver] (sometimes called *SemVer*), which is a -standard for writing version numbers. The number `0.3.14` is actually shorthand -for `^0.3.14`, which means “any version that has a public API compatible with -version 0.3.14.” +standard for writing version numbers. The number `0.8.3` is actually shorthand +for `^0.8.3`, which means any version that is at least `0.8.3` but below +`0.9.0`. Cargo considers these versions to have public APIs compatible with +version `0.8.3`, and this specification ensures you'll get the latest patch +release that will still compile with the code in this chapter. Any version +`0.9.0` or greater is not guaranteed to have the same API as what the following +examples use. [semver]: http://semver.org Now, without changing any of the code, let’s build the project, as shown in -Listing 2-2: +Listing 2-2. -
+ -```text +```console $ cargo build - Updating registry `https://github.com/rust-lang/crates.io-index` - Downloading rand v0.3.14 - Downloading libc v0.2.14 - Compiling libc v0.2.14 - Compiling rand v0.3.14 + Updating crates.io index + Downloaded rand v0.8.3 + Downloaded libc v0.2.86 + Downloaded getrandom v0.2.2 + Downloaded cfg-if v1.0.0 + Downloaded ppv-lite86 v0.2.10 + Downloaded rand_chacha v0.3.0 + Downloaded rand_core v0.6.2 + Compiling rand_core v0.6.2 + Compiling libc v0.2.86 + Compiling getrandom v0.2.2 + Compiling cfg-if v1.0.0 + Compiling ppv-lite86 v0.2.10 + Compiling rand_chacha v0.3.0 + Compiling rand v0.8.3 Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished dev [unoptimized + debuginfo] target(s) in 2.53s ``` -
- -Listing 2-2: The output from running `cargo build` after adding the rand crate -as a dependency - -
-
+Listing 2-2: The output from running `cargo build` after +adding the rand crate as a dependency You may see different version numbers (but they will all be compatible with -the code, thanks to SemVer!), and the lines may be in a different order. +the code, thanks to SemVer!), different lines (depending on the operating +system), and the lines may be in a different order. Now that we have an external dependency, Cargo fetches the latest versions of everything from the *registry*, which is a copy of data from [Crates.io][cratesio]. Crates.io is where people in the Rust ecosystem post their open source Rust projects for others to use. -[cratesio]: https://crates.io +[cratesio]: https://crates.io/ After updating the registry, Cargo checks the `[dependencies]` section and -downloads any you don’t have yet. In this case, although we only listed `rand` -as a dependency, Cargo also grabbed a copy of `libc`, because `rand` depends on -`libc` to work. After downloading them, Rust compiles them and then compiles -the project with the dependencies available. +downloads any crates you don’t have yet. In this case, although we only listed +`rand` as a dependency, Cargo also grabbed other crates that `rand` depends on +to work. After downloading the crates, Rust compiles them and then compiles the +project with the dependencies available. -If you immediately run `cargo build` again without making any changes, you won’t -get any output. Cargo knows it has already downloaded and compiled the -dependencies, and you haven't changed anything about them in your *Cargo.toml* -file. Cargo also knows that you haven't changed anything about your code, so it -doesn't recompile that either. With nothing to do, it simply exits. If you open -up the *src/main.rs* file, make a trivial change, then save it and build again, -you’ll only see one line of output: +If you immediately run `cargo build` again without making any changes, you +won’t get any output aside from the `Finished` line. Cargo knows it has already +downloaded and compiled the dependencies, and you haven’t changed anything +about them in your *Cargo.toml* file. Cargo also knows that you haven’t changed +anything about your code, so it doesn’t recompile that either. With nothing to +do, it simply exits. -```text +If you open up the *src/main.rs* file, make a trivial change, and then save it +and build again, you’ll only see two lines of output: + + + +```console $ cargo build Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished dev [unoptimized + debuginfo] target(s) in 2.53 secs ``` -This line shows Cargo only updates the build with your tiny change to the -*src/main.rs* file. Your dependencies haven't changed, so Cargo knows it can +These lines show Cargo only updates the build with your tiny change to the +*src/main.rs* file. Your dependencies haven’t changed, so Cargo knows it can reuse what it has already downloaded and compiled for those. It just rebuilds your part of the code. -#### The *Cargo.lock* File Ensures Reproducible Builds +#### Ensuring Reproducible Builds with the *Cargo.lock* File Cargo has a mechanism that ensures you can rebuild the same artifact every time you or anyone else builds your code: Cargo will use only the versions of the dependencies you specified until you indicate otherwise. For example, what -happens if next week version `v0.3.15` of the `rand` crate comes out and +happens if next week version 0.8.4 of the `rand` crate comes out and contains an important bug fix but also contains a regression that will break your code? @@ -457,136 +464,122 @@ the *Cargo.lock* file. When you build your project in the future, Cargo will see that the *Cargo.lock* file exists and use the versions specified there rather than doing all the work of figuring out versions again. This lets you have a reproducible build automatically. In other words, your project will -remain at `0.3.14` until you explicitly upgrade, thanks to the *Cargo.lock* +remain at `0.8.3` until you explicitly upgrade, thanks to the *Cargo.lock* file. #### Updating a Crate to Get a New Version When you *do* want to update a crate, Cargo provides another command, `update`, -which will: +which will ignore the *Cargo.lock* file and figure out all the latest versions +that fit your specifications in *Cargo.toml*. If that works, Cargo will write +those versions to the *Cargo.lock* file. -1. Ignore the *Cargo.lock* file and figure out all the latest versions that fit -your specifications in *Cargo.toml*. -1. If that works, Cargo will write those versions to the *Cargo.lock* file. +But by default, Cargo will only look for versions greater than `0.8.3` and less +than `0.9.0`. If the `rand` crate has released two new versions, `0.8.4` and +`0.9.0`, you would see the following if you ran `cargo update`: -But by default, Cargo will only look for versions larger than `0.3.0` and -smaller than `0.4.0`. If the `rand` crate has released two new versions, -`0.3.15` and `0.4.0`, you would see the following if you ran `cargo update`: + -```text +```console $ cargo update - Updating registry `https://github.com/rust-lang/crates.io-index` - Updating rand v0.3.14 -> v0.3.15 + Updating crates.io index + Updating rand v0.8.3 -> v0.8.4 ``` At this point, you would also notice a change in your *Cargo.lock* file noting -that the version of the `rand` crate you are now using is `0.3.15`. +that the version of the `rand` crate you are now using is `0.8.4`. -If you wanted to use `rand` version `0.4.0` or any version in the `0.4.x` +If you wanted to use `rand` version `0.9.0` or any version in the `0.9.x` series, you’d have to update the *Cargo.toml* file to look like this instead: ```toml [dependencies] - -rand = "0.4.0" +rand = "0.9.0" ``` The next time you run `cargo build`, Cargo will update the registry of crates available and reevaluate your `rand` requirements according to the new version -you specified. +you have specified. There’s a lot more to say about [Cargo][doccargo] and [its -ecosystem][doccratesio] that Chapter 14 will discuss, but for -now, that’s all you need to know. Cargo makes it very easy to reuse libraries, -so Rustaceans are able to write smaller projects that are assembled from a -number of packages. +ecosystem][doccratesio] which we’ll discuss in Chapter 14, but +for now, that’s all you need to know. Cargo makes it very easy to reuse +libraries, so Rustaceans are able to write smaller projects that are assembled +from a number of packages. [doccargo]: http://doc.crates.io [doccratesio]: http://doc.crates.io/crates-io.html ### Generating a Random Number -Let’s start *using* `rand`. The next step is to update *src/main.rs*, as shown -in Listing 2-3: +Now that you’ve added the `rand` crate to *Cargo.toml*, let’s start using +`rand`. The next step is to update *src/main.rs*, as shown in Listing 2-3. -
Filename: src/main.rs ```rust,ignore -extern crate rand; - -use std::io; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - println!("You guessed: {}", guess); -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-03/src/main.rs:all}} ``` -
+Listing 2-3: Adding code to generate a random +number -Listing 2-3: Code changes needed in order to generate a random number +First, we add a `use` line: `use rand::Rng`. The `Rng` trait defines +methods that random number generators implement, and this trait must be in +scope for us to use those methods. Chapter 10 will cover traits in detail. -
-
- -We’re adding a `extern crate rand;` line to the top that lets Rust know we’ll be -using that external dependency. This also does the equivalent of calling `use -rand`, so now we can call anything in the `rand` crate by prefixing it with -`rand::`. - -Next, we’re adding another `use` line: `use rand::Rng`. `Rng` is a trait that -defines methods that random number generators implement, and this trait must be -in scope for us to use those methods. Chapter 10 will cover traits in detail. - -Also, we’re adding two more lines in the middle. The `rand::thread_rng` function +Next, we’re adding two lines in the middle. The `rand::thread_rng` function will give us the particular random number generator that we’re going to use: one that is local to the current thread of execution and seeded by the -operating system. Next, we call the `gen_range` method on the random number -generator. This method is defined by the `Rng` trait that we brought into -scope with the `use rand::Rng` statement. The `gen_range` method takes two -numbers as arguments and generates a random number between them. It’s inclusive -on the lower bound but exclusive on the upper bound, so we need to specify `1` -and `101` to request a number between 1 and 100. +operating system. Then we call the `gen_range` method on the random number +generator. This method is defined by the `Rng` trait that we brought into scope +with the `use rand::Rng` statement. The `gen_range` method takes a range +expression as an argument and generates a random number in the range. The kind +of range expression we’re using here takes the form `start..end`. It’s +inclusive on the lower bound but exclusive on the upper bound, so we need to +specify `1..101` to request a number between 1 and 100. Alternatively, we could +pass the range `1..=100`, which is equivalent. -Knowing which traits to import and which functions and methods to use from a -crate isn’t something that you’ll just *know*. Instructions for using a crate -are in each crate’s documentation. Another neat feature of Cargo is that you -can run the `cargo doc --open` command that will build documentation provided -by all of your dependencies locally and open it in your browser. If you’re -interested in other functionality in the `rand` crate, for example, run `cargo -doc --open` and click `rand` in the sidebar on the left. +> Note: You won’t just know which traits to use and which methods and functions +> to call from a crate. Instructions for using a crate are in each crate’s +> documentation. Another neat feature of Cargo is that you can run the `cargo +> doc --open` command, which will build documentation provided by all of your +> dependencies locally and open it in your browser. If you’re interested in +> other functionality in the `rand` crate, for example, run `cargo doc --open` +> and click `rand` in the sidebar on the left. -The second line that we added to the code prints the secret number. This is -useful while we’re developing the program to be able to test it, but we’ll -delete it from the final version. It’s not much of a game if the program prints -the answer as soon as it starts! +The second line that we added to the middle of the code prints the secret +number. This is useful while we’re developing the program to be able to test +it, but we’ll delete it from the final version. It’s not much of a game if the +program prints the answer as soon as it starts! Try running the program a few times: -```text + + +```console $ cargo run Compiling guessing_game v0.1.0 (file:///projects/guessing_game) + Finished dev [unoptimized + debuginfo] target(s) in 2.53s Running `target/debug/guessing_game` Guess the number! The secret number is: 7 Please input your guess. 4 You guessed: 4 + $ cargo run + Finished dev [unoptimized + debuginfo] target(s) in 0.02s Running `target/debug/guessing_game` Guess the number! The secret number is: 83 @@ -600,70 +593,30 @@ You should get different random numbers, and they should all be numbers between ## Comparing the Guess to the Secret Number -Now that we have user input and a random number, we can compare them. That -step is shown in Listing 2-4: +Now that we have user input and a random number, we can compare them. That step +is shown in Listing 2-4. Note that this code won’t compile quite yet, as we +will explain. -
Filename: src/main.rs -```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), - } -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-04/src/main.rs:here}} ``` -
+Listing 2-4: Handling the possible return values of +comparing two numbers -Listing 2-4: Handling the possible return values of comparing two numbers - -
-
- -The first new bit here is another `use`, bringing a type called -`std::cmp::Ordering` into scope from the standard library. `Ordering` is -another enum, like `Result`, but the variants for `Ordering` are `Less`, +The first new bit here is another `use` statement, bringing a type called +`std::cmp::Ordering` into scope from the standard library. Like `Result`, +`Ordering` is another enum, but the variants for `Ordering` are `Less`, `Greater`, and `Equal`. These are the three outcomes that are possible when you compare two values. -Then we add five new lines at the bottom that use the `Ordering` type: - -```rust,ignore -match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), -} -``` - -The `cmp` method compares two values and can be called on anything that can be +Then we add five new lines at the bottom that use the `Ordering` type. The +`cmp` method compares two values and can be called on anything that can be compared. It takes a reference to whatever you want to compare with: here it’s -comparing the `guess` to the `secret_number`. `cmp` returns a variant of the -`Ordering` enum we imported with the `use` statement. We use a +comparing the `guess` to the `secret_number`. Then it returns a variant of the +`Ordering` enum we brought into scope with the `use` statement. We use a [`match`][match] expression to decide what to do next based on which variant of `Ordering` was returned from the call to `cmp` with the values in `guess` and `secret_number`. @@ -675,114 +628,74 @@ the code that should be run if the value given to the beginning of the `match` expression fits that arm’s pattern. Rust takes the value given to `match` and looks through each arm’s pattern in turn. The `match` construct and patterns are powerful features in Rust that let you express a variety of situations your -code might encounter and helps ensure that you handle them all. These features -will be covered in detail in Chapter 6 and Chapter 19, respectively. +code might encounter and make sure that you handle them all. These features +will be covered in detail in Chapter 6 and Chapter 18, respectively. Let’s walk through an example of what would happen with the `match` expression -used here. Say that the user has guessed 50, and the randomly generated secret +used here. Say that the user has guessed 50 and the randomly generated secret number this time is 38. When the code compares 50 to 38, the `cmp` method will -return `Ordering::Greater`, because 50 is greater than 38. `Ordering::Greater` -is the value that the `match` expression gets. It looks at the first arm’s -pattern, `Ordering::Less`, but the value `Ordering::Greater` does not match -`Ordering::Less`. So it ignores the code in that arm and moves to the next arm. -The next arm’s pattern, `Ordering::Greater`, *does* match -`Ordering::Greater`! The associated code in that arm will execute and print -`Too big!` to the screen. The `match` expression ends because it has no need to -look at the last arm in this particular scenario. +return `Ordering::Greater`, because 50 is greater than 38. The `match` +expression gets the `Ordering::Greater` value and starts checking each arm’s +pattern. It looks at the first arm’s pattern, `Ordering::Less`, and sees that +the value `Ordering::Greater` does not match `Ordering::Less`, so it ignores +the code in that arm and moves to the next arm. The next arm’s pattern, +`Ordering::Greater`, *does* match `Ordering::Greater`! The associated code in +that arm will execute and print `Too big!` to the screen. The `match` +expression ends because it has no need to look at the last arm in this scenario. However, the code in Listing 2-4 won’t compile yet. Let’s try it: -```text -$ cargo build - Compiling guessing_game v0.1.0 (file:///projects/guessing_game) -error[E0308]: mismatched types - --> src/main.rs:23:21 - | -23 | match guess.cmp(&secret_number) { - | ^^^^^^^^^^^^^^ expected struct `std::string::String`, found integral variable - | - = note: expected type `&std::string::String` - = note: found type `&{integer}` - -error: aborting due to previous error -Could not compile `guessing_game`. +```console +{{#include ../listings/ch02-guessing-game-tutorial/listing-02-04/output.txt}} ``` The core of the error states that there are *mismatched types*. Rust has a strong, static type system. However, it also has type inference. When we wrote -`let guess = String::new()`, Rust was able to infer that `guess` should be a -`String` and didn’t make us write the type. The `secret_number`, on the other +`let mut guess = String::new()`, Rust was able to infer that `guess` should be +a `String` and didn’t make us write the type. The `secret_number`, on the other hand, is a number type. A few number types can have a value between 1 and 100: `i32`, a 32-bit number; `u32`, an unsigned 32-bit number; `i64`, a 64-bit number; as well as others. Rust defaults to an `i32`, which is the type of -`secret_number` unless we add type information elsewhere that would cause Rust -to infer a different numerical type. The reason for the error is that Rust will -not compare a string and a number type. +`secret_number` unless you add type information elsewhere that would cause Rust +to infer a different numerical type. The reason for the error is that Rust +cannot compare a string and a number type. Ultimately, we want to convert the `String` the program reads as input into a -real number type so we can compare it to the guess numerically. We can do -that by adding the following two lines to the `main` function body: +real number type so we can compare it numerically to the secret number. We can +do that by adding another line to the `main` function body: Filename: src/main.rs ```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), - } -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/no-listing-03-convert-string-to-number/src/main.rs:here}} ``` -The two new lines are: +The line is: ```rust,ignore -let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); +let guess: u32 = guess.trim().parse().expect("Please type a number!"); ``` -We create a variable named `guess`. But wait, doesn’t the program -already have a variable named `guess`? It does, but Rust allows us to -*shadow* the previous value of `guess` with a new one. This feature is often -used in similar situations in which you want to convert a value from one type -to another type. Shadowing lets us reuse the `guess` variable name rather than -forcing us to create two unique variables, like `guess_str` and `guess` for -example. (Chapter 3 covers shadowing in more detail.) +We create a variable named `guess`. But wait, doesn’t the program already have +a variable named `guess`? It does, but Rust allows us to *shadow* the previous +value of `guess` with a new one. This feature is often used in situations in +which you want to convert a value from one type to another type. Shadowing lets +us reuse the `guess` variable name rather than forcing us to create two unique +variables, such as `guess_str` and `guess` for example. (Chapter 3 covers +shadowing in more detail.) We bind `guess` to the expression `guess.trim().parse()`. The `guess` in the expression refers to the original `guess` that was a `String` with the input in it. The `trim` method on a `String` instance will eliminate any whitespace at -the beginning and end. `u32` can only contain numerical characters, but the -user must press the Return key to satisfy `read_line`. When the user presses -Return, a newline character is added to the string. For example, if the user -types 5 and presses return, `guess` looks like this: `5\n`. The `\n` represents -“newline,” the return key. The `trim` method eliminates `\n`, resulting in just -`5`. +the beginning and end. Although `u32` can contain only numerical characters, +the user must press enter to satisfy +`read_line`. When the user presses enter, a +newline character is added to the string. For example, if the user types 5 and presses enter, +`guess` looks like this: `5\n`. The `\n` represents “newline,” the result of +pressing enter (On Windows, pressing enter results in a carriage return and a newline, +`\r\n`). The `trim` method eliminates `\n` or `\r\n`, resulting in just `5`. The [`parse` method on strings][parse] parses a string into some kind of number. Because this method can parse a variety of number types, we @@ -799,21 +712,29 @@ comparison will be between two values of the same type! The call to `parse` could easily cause an error. If, for example, the string contained `A👍%`, there would be no way to convert that to a number. Because it -might fail, the `parse` method returns a `Result` type, much like the -`read_line` method does as discussed earlier in “Handling Potential Failure -with the Result Type” on page XX. We’ll treat this `Result` the same way by -using the `expect` method again. If `parse` returns an `Err` `Result` variant -because it couldn’t create a number from the string, the `expect` call will -crash the game and print the message we give it. If `parse` can successfully -convert the string to a number, it will return the `Ok` variant of `Result`, -and `expect` will return the number that we want from the `Ok` value. +might fail, the `parse` method returns a `Result` type, much as the `read_line` +method does (discussed earlier in [“Handling Potential Failure with the +`Result` Type”](#handling-potential-failure-with-the-result-type)). We’ll treat this `Result` the same way by using the `expect` method +again. If `parse` returns an `Err` `Result` variant because it couldn’t create +a number from the string, the `expect` call will crash the game and print the +message we give it. If `parse` can successfully convert the string to a number, +it will return the `Ok` variant of `Result`, and `expect` will return the +number that we want from the `Ok` value. Let’s run the program now! -```text + + +```console $ cargo run Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/guessing_game` + Finished dev [unoptimized + debuginfo] target(s) in 0.43s + Running `target/debug/guessing_game` Guess the number! The secret number is: 58 Please input your guess. @@ -832,63 +753,42 @@ Let’s change that by adding a loop! ## Allowing Multiple Guesses with Looping -The `loop` keyword gives us an infinite loop. Add that now to give users more -chances at guessing the number: +The `loop` keyword creates an infinite loop. We’ll add that now to give users +more chances at guessing the number: Filename: src/main.rs ```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - loop { - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => println!("You win!"), - } - } -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/no-listing-04-looping/src/main.rs:here}} ``` As you can see, we’ve moved everything into a loop from the guess input prompt -onward. Be sure to indent those lines another four spaces each, and run the -program again. Notice that there is a new problem because the program is doing -exactly what we told it to do: ask for another guess forever! It doesn’t seem -like the user can quit! +onward. Be sure to indent the lines inside the loop another four spaces each +and run the program again. Notice that there is a new problem because the +program is doing exactly what we told it to do: ask for another guess forever! +It doesn’t seem like the user can quit! -The user could always halt the program by using the keyboard shortcut `Ctrl-C`. -But there’s another way to escape this insatiable monster that we mentioned in -the `parse` discussion in “Comparing the Guesses” on page XX: if the user -enters a non-number answer, the program will crash. The user can take advantage -of that in order to quit, as shown here: +The user could always interrupt the program by using the keyboard shortcut ctrl-c. But there’s another way to escape this +insatiable monster, as mentioned in the `parse` discussion in [“Comparing the +Guess to the Secret Number”](#comparing-the-guess-to-the-secret-number): if the user enters a non-number answer, the program will crash. The +user can take advantage of that in order to quit, as shown here: -```text + + +```console $ cargo run Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/guessing_game` + Finished dev [unoptimized + debuginfo] target(s) in 1.50s + Running `target/debug/guessing_game` Guess the number! The secret number is: 59 Please input your guess. @@ -905,9 +805,8 @@ You guessed: 59 You win! Please input your guess. quit -thread 'main' panicked at 'Please type a number!: ParseIntError { kind: InvalidDigit }', src/libcore/result.rs:785 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/guess` (exit code: 101) +thread 'main' panicked at 'Please type a number!: ParseIntError { kind: InvalidDigit }', src/main.rs:28:47 +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace ``` Typing `quit` actually quits the game, but so will any other non-number input. @@ -916,96 +815,72 @@ stop when the correct number is guessed. ### Quitting After a Correct Guess -Let’s program the game to quit when the user wins by adding a `break`: +Let’s program the game to quit when the user wins by adding a `break` statement: Filename: src/main.rs ```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - println!("The secret number is: {}", secret_number); - - loop { - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = guess.trim().parse() - .expect("Please type a number!"); - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => { - println!("You win!"); - break; - } - } - } -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/no-listing-05-quitting/src/main.rs:here}} ``` -By adding the `break` line after `You win!`, the program will exit the loop -when the user guesses the secret number correctly. Exiting the loop also means +Adding the `break` line after `You win!` makes the program exit the loop when +the user guesses the secret number correctly. Exiting the loop also means exiting the program, because the loop is the last part of `main`. ### Handling Invalid Input To further refine the game’s behavior, rather than crashing the program when the user inputs a non-number, let’s make the game ignore a non-number so the -user can continue guessing. We can do that by altering the line where `guess` is -converted from a `String` to a `u32`: +user can continue guessing. We can do that by altering the line where `guess` +is converted from a `String` to a `u32`, as shown in Listing 2-5. + +Filename: src/main.rs ```rust,ignore -let guess: u32 = match guess.trim().parse() { - Ok(num) => num, - Err(_) => continue, -}; +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-05/src/main.rs:here}} ``` +Listing 2-5: Ignoring a non-number guess and asking for +another guess instead of crashing the program + Switching from an `expect` call to a `match` expression is how you generally -move from crash on error to actually handling the error. Remember that `parse` -returns a `Result` type, and `Result` is an enum that has the variants `Ok` or -`Err`. We’re using a `match` expression here, like we did with the `Ordering` +move from crashing on an error to handling the error. Remember that `parse` +returns a `Result` type and `Result` is an enum that has the variants `Ok` or +`Err`. We’re using a `match` expression here, as we did with the `Ordering` result of the `cmp` method. -If `parse` is able to successfully turn the string into a number, it will return -an `Ok` value that contains the resulting number. That `Ok` value will match the -first arm’s pattern, and the `match` expression will just return the `num` value -that `parse` produced and put inside the `Ok` value. That number will end up -right where we want it in the new `guess` variable we’re creating. +If `parse` is able to successfully turn the string into a number, it will +return an `Ok` value that contains the resulting number. That `Ok` value will +match the first arm’s pattern, and the `match` expression will just return the +`num` value that `parse` produced and put inside the `Ok` value. That number +will end up right where we want it in the new `guess` variable we’re creating. If `parse` is *not* able to turn the string into a number, it will return an `Err` value that contains more information about the error. The `Err` value -does not match the `Ok(num)` pattern in the first `match` arm, but it does match -the `Err(_)` pattern in the second arm. The `_` is a catchall value; in this -example, we’re saying we want to match all `Err` values, no matter what -information they have inside them. So the program will execute the second arm’s -code, `continue`, which means to go to the next iteration of the `loop` and ask -for another guess. So effectively, the program ignores all errors that `parse` -might encounter! +does not match the `Ok(num)` pattern in the first `match` arm, but it does +match the `Err(_)` pattern in the second arm. The underscore, `_`, is a +catchall value; in this example, we’re saying we want to match all `Err` +values, no matter what information they have inside them. So the program will +execute the second arm’s code, `continue`, which tells the program to go to the +next iteration of the `loop` and ask for another guess. So, effectively, the +program ignores all errors that `parse` might encounter! -Now everything in the program should work as expected. Let’s try it by running -`cargo run`: +Now everything in the program should work as expected. Let’s try it: -```text + + +```console $ cargo run Compiling guessing_game v0.1.0 (file:///projects/guessing_game) - Running `target/guessing_game` + Finished dev [unoptimized + debuginfo] target(s) in 4.45s + Running `target/debug/guessing_game` Guess the number! The secret number is: 61 Please input your guess. @@ -1024,69 +899,31 @@ You guessed: 61 You win! ``` -Awesome! With one tiny final tweak, we will finish the guessing game: recall -that the program is still printing out the secret number. That worked well for +Awesome! With one tiny final tweak, we will finish the guessing game. Recall +that the program is still printing the secret number. That worked well for testing, but it ruins the game. Let’s delete the `println!` that outputs the -secret number. Listing 2-5 shows the final code: +secret number. Listing 2-6 shows the final code. -
Filename: src/main.rs ```rust,ignore -extern crate rand; - -use std::io; -use std::cmp::Ordering; -use rand::Rng; - -fn main() { - println!("Guess the number!"); - - let secret_number = rand::thread_rng().gen_range(1, 101); - - loop { - println!("Please input your guess."); - - let mut guess = String::new(); - - io::stdin().read_line(&mut guess) - .expect("Failed to read line"); - - let guess: u32 = match guess.trim().parse() { - Ok(num) => num, - Err(_) => continue, - }; - - println!("You guessed: {}", guess); - - match guess.cmp(&secret_number) { - Ordering::Less => println!("Too small!"), - Ordering::Greater => println!("Too big!"), - Ordering::Equal => { - println!("You win!"); - break; - } - } - } -} +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-06/src/main.rs}} ``` -
- -Listing 2-5: Complete code of the guessing game - -
-
+Listing 2-6: Complete guessing game code ## Summary -At this point, you’ve successfully built the guessing game! Congratulations! +At this point, you’ve successfully built the guessing game. Congratulations! This project was a hands-on way to introduce you to many new Rust concepts: -`let`, `match`, methods, associated functions, using external crates, and more. -In the next few chapters, you’ll learn about these concepts in more detail. -Chapter 3 covers concepts that most programming languages have, such as +`let`, `match`, methods, associated functions, the use of external crates, and +more. In the next few chapters, you’ll learn about these concepts in more +detail. Chapter 3 covers concepts that most programming languages have, such as variables, data types, and functions, and shows how to use them in Rust. -Chapter 4 explores ownership, which is a Rust feature that is most different -from other languages. Chapter 5 discusses structs and method syntax, and -Chapter 6 endeavors to explain enums. +Chapter 4 explores ownership, a feature that makes Rust different from other +languages. Chapter 5 discusses structs and method syntax, and Chapter 6 +explains how enums work. + +[variables-and-mutability]: +ch03-01-variables-and-mutability.html#variables-and-mutability diff --git a/src/ch03-00-common-programming-concepts.md b/src/ch03-00-common-programming-concepts.md index f218bee..1b8b14c 100644 --- a/src/ch03-00-common-programming-concepts.md +++ b/src/ch03-00-common-programming-concepts.md @@ -10,4 +10,4 @@ > > Rust 语言有一组**关键字**(*keywords*),和其他语言一样,这些关键字被保留下来只提供给语言作特殊使用。请记住,这些关键字不能用作变量或函数的名称。大多数关键字都有特殊的含义,在 Rust 程序中可使用它们执行多种任务;有少数关键字暂时没有相关联的功能,但这些功能将来可能会加入到 Rust 中。在附录 A 中可找到关键字列表。 - + \ No newline at end of file diff --git a/src/ch03-03-how-functions-work.md b/src/ch03-03-how-functions-work.md index 6baf2b1..7319b49 100644 --- a/src/ch03-03-how-functions-work.md +++ b/src/ch03-03-how-functions-work.md @@ -1,48 +1,52 @@ -## 函数是如何工作的 +## Functions -函数在 Rust 代码中无处不在。您在此语言中已经看到其中一个最重要的函数:主函数(`main` 函数),这是许多程序的入口。您也看过 `fn` 关键字,它允许你声明新的函数。 +Functions are pervasive in Rust code. You’ve already seen one of the most +important functions in the language: the `main` function, which is the entry +point of many programs. You’ve also seen the `fn` keyword, which allows you to +declare new functions. -Rust 代码使用“蛇形命名”(*snake case*)作为函数和变量名的常规风格。蛇形命名所有字母都是小写字母,并以下划线分隔单词。下面给出一个包含函数定义例子的程序: +Rust code uses *snake case* as the conventional style for function and variable +names. In snake case, all letters are lowercase and underscores separate words. +Here’s a program that contains an example function definition: -文件名:src/main.rs +Filename: src/main.rs ```rust -fn main() { - println!("Hello, world!"); - - another_function(); -} - -fn another_function() { - println!("Another function."); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-16-functions/src/main.rs}} ``` -Rust 中的函数定义以 `fn` 开头,并在函数名后面有一对圆括号。大括号告诉编译器函数体开始和结束的位置。 +Function definitions in Rust start with `fn` and have a set of parentheses +after the function name. The curly brackets tell the compiler where the +function body begins and ends. -我们可以通过输入函数名称并连着一组圆括号来调用我们定义的任何函数。因为在程序中定义了 `another_function`,所以可以从 `main` 函数中调用它。注意我们在源代码中定义的 `another_function` 在 `main` 函数之后;当然我们也可以在 `main` 函数前面定义它。Rust 不在乎您定义函数的位置,只在乎函数已经在某个地方被定义过。 +We can call any function we’ve defined by entering its name followed by a set +of parentheses. Because `another_function` is defined in the program, it can be +called from inside the `main` function. Note that we defined `another_function` +*after* the `main` function in the source code; we could have defined it before +as well. Rust doesn’t care where you define your functions, only that they’re +defined somewhere. -我们新建一个名为 `functions` 的二进制项目来进一步探索函数。将 `another_function` 示例放在 `src / main.rs` 中并运行它。您将看到以下输出: +Let’s start a new binary project named *functions* to explore functions +further. Place the `another_function` example in *src/main.rs* and run it. You +should see the following output: -```text -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -Hello, world! -Another function. +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-16-functions/output.txt}} ``` -在 `main` 函数中,代码行按出现的先后顺序执行。首先,打印“Hello,world!”消息,然后调用 `another_function`,并打印其消息。 +The lines execute in the order in which they appear in the `main` function. +First, the “Hello, world!” message prints, and then `another_function` is +called and its message is printed. ### Function Parameters Functions can also be defined to have *parameters*, which are special variables -that are part of a function's signature. When a function has parameters, we can -provide it with concrete values for those parameters. Technically, the concrete -values are called *arguments*, but in casual conversation people tend to use -the words "parameter" and "argument" interchangeably for either the variables in -a function's definition or the concrete values passed in when you call a -function. +that are part of a function’s signature. When a function has parameters, you +can provide it with concrete values for those parameters. Technically, the +concrete values are called *arguments*, but in casual conversation, people tend +to use the words *parameter* and *argument* interchangeably for either the +variables in a function’s definition or the concrete values passed in when you +call a function. The following rewritten version of `another_function` shows what parameters look like in Rust: @@ -50,27 +54,18 @@ look like in Rust: Filename: src/main.rs ```rust -fn main() { - another_function(5); -} - -fn another_function(x: i32) { - println!("The value of x is: {}", x); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/src/main.rs}} ``` Try running this program; you should get the following output: -```text -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -The value of x is: 5 +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-17-functions-with-parameters/output.txt}} ``` The declaration of `another_function` has one parameter named `x`. The type of `x` is specified as `i32`. When `5` is passed to `another_function`, the -`println!` macro puts `5` where the pair of curly braces were in the format +`println!` macro puts `5` where the pair of curly brackets were in the format string. In function signatures, you *must* declare the type of each parameter. This is @@ -84,109 +79,78 @@ declarations with commas, like this: Filename: src/main.rs ```rust -fn main() { - another_function(5, 6); -} - -fn another_function(x: i32, y: i32) { - println!("The value of x is: {}", x); - println!("The value of y is: {}", y); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/src/main.rs}} ``` This example creates a function with two parameters, both of which are `i32` -types. The function then prints out the values in both of its parameters. Note -that function parameters don't all need to be the same type - they just happen -to be in this example. +types. The function then prints the values in both of its parameters. Note that +function parameters don’t all need to be the same type, they just happen to be +in this example. -Let’s try running this code. Replace the program currently in your *function* -project’s *src/main.rs* file with the preceding example, and run it using -`cargo run`: +Let’s try running this code. Replace the program currently in your *functions* +project’s *src/main.rs* file with the preceding example and run it using `cargo +run`: -```text -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -The value of x is: 5 -The value of y is: 6 +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-18-functions-with-multiple-parameters/output.txt}} ``` -Because we called the function with `5` as the value for `x` and `6` as the -value for `y`, the two strings are printed using those values. +Because we called the function with `5` as the value for `x` and `6` is passed +as the value for `y`, the two strings are printed with these values. -### Function Bodies +### Function Bodies Contain Statements and Expressions Function bodies are made up of a series of statements optionally ending in an expression. So far, we’ve only covered functions without an ending expression, -but we have seen expressions as parts of statements. Because Rust is an +but you have seen an expression as part of a statement. Because Rust is an expression-based language, this is an important distinction to understand. Other languages don’t have the same distinctions, so let’s look at what statements and expressions are and how their differences affect the bodies of functions. -### Statements and Expressions - We’ve actually already used statements and expressions. *Statements* are instructions that perform some action and do not return a value. *Expressions* evaluate to a resulting value. Let’s look at some examples. Creating a variable and assigning a value to it with the `let` keyword is a -statement. In Listing 3-3, `let y = 6;` is a statement: +statement. In Listing 3-1, `let y = 6;` is a statement. -
Filename: src/main.rs ```rust -fn main() { - let y = 6; -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/listing-03-01/src/main.rs}} ``` -
- -Listing 3-3: A `main` function declaration containing one statement. - -
-
+Listing 3-1: A `main` function declaration containing one statement Function definitions are also statements; the entire preceding example is a statement in itself. Statements do not return values. Therefore, you can’t assign a `let` statement -to another variable, as the following code tries to do: +to another variable, as the following code tries to do; you’ll get an error: Filename: src/main.rs -```rust,ignore -fn main() { - let x = (let y = 6); -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/src/main.rs}} ``` -When you run this program, you’ll get an error like this: +When you run this program, the error you’ll get looks like this: -```text -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) -error: expected expression, found statement (`let`) - --> src/main.rs:2:14 - | -2 | let x = (let y = 6); - | ^^^ - | - = note: variable declaration using `let` is a statement +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/output.txt}} ``` The `let y = 6` statement does not return a value, so there isn’t anything for -`x` to bind to. This is different than in other languages, such as C and Ruby, -where the assignment returns the value of the assignment. In those languages, -you can write `x = y = 6` and have both `x` and `y` have the value `6`; that is -not the case in Rust. +`x` to bind to. This is different from what happens in other languages, such as +C and Ruby, where the assignment returns the value of the assignment. In those +languages, you can write `x = y = 6` and have both `x` and `y` have the value +`6`; that is not the case in Rust. Expressions evaluate to something and make up most of the rest of the code that you’ll write in Rust. Consider a simple math operation, such as `5 + 6`, which is an expression that evaluates to the value `11`. Expressions can be part of -statements: in Listing 3-3 that had the statement `let y = 6;`, `6` is an +statements: in Listing 3-1, the `6` in the statement `let y = 6;` is an expression that evaluates to the value `6`. Calling a function is an expression. Calling a macro is an expression. The block that we use to create new scopes, `{}`, is an expression, for example: @@ -194,16 +158,7 @@ new scopes, `{}`, is an expression, for example: Filename: src/main.rs ```rust -fn main() { - let x = 5; - - let y = { - let x = 3; - x + 1 - }; - - println!("The value of y is: {}", y); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-20-blocks-are-expressions/src/main.rs}} ``` This expression: @@ -216,44 +171,35 @@ This expression: ``` is a block that, in this case, evaluates to `4`. That value gets bound to `y` -as part of the `let` statement. Note the line without a semicolon at the end, -unlike most of the lines you’ve seen so far. Expressions do not include ending -semicolons. If you add a semicolon to the end of an expression, you turn it -into a statement, which will then not return a value. Keep this in mind as you -explore function return values and expressions next. +as part of the `let` statement. Note the `x + 1` line without a semicolon at +the end, which is unlike most of the lines you’ve seen so far. Expressions do +not include ending semicolons. If you add a semicolon to the end of an +expression, you turn it into a statement, which will then not return a value. +Keep this in mind as you explore function return values and expressions next. ### Functions with Return Values Functions can return values to the code that calls them. We don’t name return values, but we do declare their type after an arrow (`->`). In Rust, the return value of the function is synonymous with the value of the final expression in -the block of the body of a function. Here’s an example of a function that -returns a value: +the block of the body of a function. You can return early from a function by +using the `return` keyword and specifying a value, but most functions return +the last expression implicitly. Here’s an example of a function that returns a +value: Filename: src/main.rs ```rust -fn five() -> i32 { - 5 -} - -fn main() { - let x = five(); - - println!("The value of x is: {}", x); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-21-function-return-values/src/main.rs}} ``` There are no function calls, macros, or even `let` statements in the `five` function—just the number `5` by itself. That’s a perfectly valid function in -Rust. Note that the function’s return type is specified, too, as `-> i32`. Try +Rust. Note that the function’s return type is specified too, as `-> i32`. Try running this code; the output should look like this: -```text -$ cargo run - Compiling functions v0.1.0 (file:///projects/functions) - Running `target/debug/functions` -The value of x is: 5 +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-21-function-return-values/output.txt}} ``` The `5` in `five` is the function’s return value, which is why the return type @@ -268,60 +214,36 @@ let x = 5; Second, the `five` function has no parameters and defines the type of the return value, but the body of the function is a lonely `5` with no semicolon -because it’s an expression whose value we want to return. Let’s look at another -example: +because it’s an expression whose value we want to return. + +Let’s look at another example: Filename: src/main.rs ```rust -fn main() { - let x = plus_one(5); - - println!("The value of x is: {}", x); -} - -fn plus_one(x: i32) -> i32 { - x + 1 -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-22-function-parameter-and-return/src/main.rs}} ``` -Running this code will print `The value of x is: 6`. What happens if we place a +Running this code will print `The value of x is: 6`. But if we place a semicolon at the end of the line containing `x + 1`, changing it from an -expression to a statement? +expression to a statement, we’ll get an error. Filename: src/main.rs -```rust,ignore -fn main() { - let x = plus_one(5); - - println!("The value of x is: {}", x); -} - -fn plus_one(x: i32) -> i32 { - x + 1; -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/src/main.rs}} ``` -Running this code produces an error, as follows: +Compiling this code produces an error, as follows: -```text -error[E0269]: not all control paths return a value - --> src/main.rs:7:1 - | -7 | fn plus_one(x: i32) -> i32 { - | ^ - | -help: consider removing this semicolon: - --> src/main.rs:8:10 - | -8 | x + 1; - | ^ +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-23-statements-dont-return-values/output.txt}} ``` -The main error message, “not all control paths return a value,” reveals the -core issue with this code. The definition of the function `plus_one` says that -it will return an `i32`, but statements don’t evaluate to a value. Therefore, -nothing is returned, which contradicts the function definition and results in -an error. In this output, Rust provides a message to possibly help rectify this -issue: it suggests removing the semicolon, which would fix the error. +The main error message, “mismatched types,” reveals the core issue with this +code. The definition of the function `plus_one` says that it will return an +`i32`, but statements don’t evaluate to a value, which is expressed by `()`, +an empty tuple. Therefore, nothing is returned, which contradicts the function +definition and results in an error. In this output, Rust provides a message to +possibly help rectify this issue: it suggests removing the semicolon, which +would fix the error. diff --git a/src/ch03-05-control-flow.md b/src/ch03-05-control-flow.md index c9ec026..0c2134a 100644 --- a/src/ch03-05-control-flow.md +++ b/src/ch03-05-control-flow.md @@ -1,14 +1,14 @@ ## Control Flow -Deciding whether or not to run some code depending on if a condition is true or -deciding to run some code repeatedly while a condition is true are basic +Deciding whether or not to run some code depending on if a condition is true +and deciding to run some code repeatedly while a condition is true are basic building blocks in most programming languages. The most common constructs that let you control the flow of execution of Rust code are `if` expressions and loops. ### `if` Expressions -An `if` expression allows us to branch our code depending on conditions. We +An `if` expression allows you to branch your code depending on conditions. You provide a condition and then state, “If this condition is met, run this block of code. If the condition is not met, do not run this block of code.” @@ -18,25 +18,20 @@ the `if` expression. In the *src/main.rs* file, input the following: Filename: src/main.rs ```rust -fn main() { - let number = 3; - - if number < 5 { - println!("condition was true"); - } else { - println!("condition was false"); - } -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-26-if-true/src/main.rs}} ``` All `if` expressions start with the keyword `if`, which is followed by a condition. In this case, the condition checks whether or not the variable `number` has a value less than 5. The block of code we want to execute if the condition is true is placed immediately after the condition inside curly -braces. Blocks of code associated with the conditions in `if` expressions are +brackets. Blocks of code associated with the conditions in `if` expressions are sometimes called *arms*, just like the arms in `match` expressions that we -discussed in the “Comparing the Guess to the Secret Number” section of -Chapter 2. Optionally, we can also include an `else` expression, which we chose +discussed in the [“Comparing the Guess to the Secret +Number”][comparing-the-guess-to-the-secret-number] section of +Chapter 2. + +Optionally, we can also include an `else` expression, which we chose to do here, to give the program an alternative block of code to execute should the condition evaluate to false. If you don’t provide an `else` expression and the condition is false, the program will just skip the `if` block and move on @@ -44,204 +39,125 @@ to the next bit of code. Try running this code; you should see the following output: -```text -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -condition was true +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-26-if-true/output.txt}} ``` Let’s try changing the value of `number` to a value that makes the condition `false` to see what happens: ```rust,ignore -let number = 7; +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-27-if-false/src/main.rs:here}} ``` Run the program again, and look at the output: -```text -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -condition was false +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-27-if-false/output.txt}} ``` -It’s also worth noting that the condition in this code *must* be a `bool`. To -see what happens if the condition isn’t a `bool`, try running the following -code: +It’s also worth noting that the condition in this code *must* be a `bool`. If +the condition isn’t a `bool`, we’ll get an error. For example, try running the +following code: Filename: src/main.rs -```rust,ignore -fn main() { - let number = 3; - - if number { - println!("number was three"); - } -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/src/main.rs}} ``` The `if` condition evaluates to a value of `3` this time, and Rust throws an error: -```text - Compiling branches v0.1.0 (file:///projects/branches) -error[E0308]: mismatched types - --> src/main.rs:4:8 - | -4 | if number { - | ^^^^^^ expected bool, found integral variable - | - = note: expected type `bool` - = note: found type `{integer}` - -error: aborting due to previous error -Could not compile `branches`. +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-28-if-condition-must-be-bool/output.txt}} ``` -The error indicates that Rust expected a `bool` but got an integer. Rust will -not automatically try to convert non-boolean types to a boolean, unlike -languages such as Ruby and JavaScript. You must be explicit and always provide -`if` with a `boolean` as its condition. If we want the `if` code block to run +The error indicates that Rust expected a `bool` but got an integer. Unlike +languages such as Ruby and JavaScript, Rust will not automatically try to +convert non-Boolean types to a Boolean. You must be explicit and always provide +`if` with a Boolean as its condition. If we want the `if` code block to run only when a number is not equal to `0`, for example, we can change the `if` expression to the following: Filename: src/main.rs ```rust -fn main() { - let number = 3; - - if number != 0 { - println!("number was something other than zero"); - } -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-29-if-not-equal-0/src/main.rs}} ``` Running this code will print `number was something other than zero`. -#### Multiple Conditions with `else if` +#### Handling Multiple Conditions with `else if` -We can have multiple conditions by combining `if` and `else` in an `else if` +You can have multiple conditions by combining `if` and `else` in an `else if` expression. For example: Filename: src/main.rs ```rust -fn main() { - let number = 6; - - if number % 4 == 0 { - println!("number is divisible by 4"); - } else if number % 3 == 0 { - println!("number is divisible by 3"); - } else if number % 2 == 0 { - println!("number is divisible by 2"); - } else { - println!("number is not divisible by 4, 3, or 2"); - } -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-30-else-if/src/main.rs}} ``` This program has four possible paths it can take. After running it, you should see the following output: -```text -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -number is divisible by 3 +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-30-else-if/output.txt}} ``` When this program executes, it checks each `if` expression in turn and executes the first body for which the condition holds true. Note that even though 6 is divisible by 2, we don’t see the output `number is divisible by 2`, nor do we -see the `number is not divisible by 4, 3, or 2` text from the `else` block. The -reason is that Rust will only execute the block for the first true condition, -and once it finds one, it won’t even check the rest. +see the `number is not divisible by 4, 3, or 2` text from the `else` block. +That’s because Rust only executes the block for the first true condition, and +once it finds one, it doesn’t even check the rest. Using too many `else if` expressions can clutter your code, so if you have more than one, you might want to refactor your code. Chapter 6 describes a powerful Rust branching construct called `match` for these cases. -#### Using `if` in a `let` statement +#### Using `if` in a `let` Statement Because `if` is an expression, we can use it on the right side of a `let` -statement, for instance in Listing 3-4: +statement, as in Listing 3-2. -
Filename: src/main.rs ```rust -fn main() { - let condition = true; - let number = if condition { - 5 - } else { - 6 - }; - - println!("The value of number is: {}", number); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/listing-03-02/src/main.rs}} ``` -
- -Listing 3-4: Assigning the result of an `if` expression to a variable - -
-
+Listing 3-2: Assigning the result of an `if` expression +to a variable The `number` variable will be bound to a value based on the outcome of the `if` expression. Run this code to see what happens: -```text -$ cargo run - Compiling branches v0.1.0 (file:///projects/branches) - Running `target/debug/branches` -The value of number is: 5 +```console +{{#include ../listings/ch03-common-programming-concepts/listing-03-02/output.txt}} ``` Remember that blocks of code evaluate to the last expression in them, and numbers by themselves are also expressions. In this case, the value of the whole `if` expression depends on which block of code executes. This means the values that have the potential to be results from each arm of the `if` must be -the same type; in Listing 3-4, the results of both the `if` arm and the `else` -arm were `i32` integers. But what happens if the types are mismatched, as in -the following example? +the same type; in Listing 3-2, the results of both the `if` arm and the `else` +arm were `i32` integers. If the types are mismatched, as in the following +example, we’ll get an error: Filename: src/main.rs -```rust,ignore -fn main() { - let condition = true; - - let number = if condition { - 5 - } else { - "six" - }; - - println!("The value of number is: {}", number); -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/src/main.rs}} ``` -When we run this code, we’ll get an error. The `if` and `else` arms have value -types that are incompatible, and Rust indicates exactly where to find the -problem in the program: +When we try to compile this code, we’ll get an error. The `if` and `else` arms +have value types that are incompatible, and Rust indicates exactly where to +find the problem in the program: -```text - Compiling branches v0.1.0 (file:///projects/branches) -error[E0308]: if and else have incompatible types - --> src/main.rs:4:18 - | -4 | let number = if condition { - | ^ expected integral variable, found reference - | - = note: expected type `{integer}` - = note: found type `&’static str` +```console +{{#include ../listings/ch03-common-programming-concepts/no-listing-31-arms-must-return-same-type/output.txt}} ``` The expression in the `if` block evaluates to an integer, and the expression in @@ -273,20 +189,24 @@ like this: Filename: src/main.rs ```rust,ignore -fn main() { - loop { - println!("again!"); - } -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-32-loop/src/main.rs}} ``` When we run this program, we’ll see `again!` printed over and over continuously until we stop the program manually. Most terminals support a keyboard shortcut, - ctrl-C, to halt a program that is stuck in a continual loop. Give it a try: +ctrl-c, to interrupt a program that is stuck in +a continual loop. Give it a try: -```text + + +```console $ cargo run Compiling loops v0.1.0 (file:///projects/loops) + Finished dev [unoptimized + debuginfo] target(s) in 0.29s Running `target/debug/loops` again! again! @@ -295,45 +215,61 @@ again! ^Cagain! ``` -The symbol `^C` represents where you pressed ctrl-C. You may or may not see the -word `again!` printed after the `^C`, depending on where the code was in the -loop when it received the halt signal. +The symbol `^C` represents where you pressed ctrl-c +. You may or may not see the word `again!` printed after the `^C`, +depending on where the code was in the loop when it received the interrupt +signal. Fortunately, Rust provides another, more reliable way to break out of a loop. You can place the `break` keyword within the loop to tell the program when to stop executing the loop. Recall that we did this in the guessing game in the -“Quitting After a Correct Guess” section of Chapter 2 to exit the -program when the user won the game by guessing the correct number. +[“Quitting After a Correct Guess”][quitting-after-a-correct-guess] section of Chapter 2 to exit the program when the user won the game by +guessing the correct number. + +#### Returning Values from Loops + +One of the uses of a `loop` is to retry an operation you know might fail, such +as checking whether a thread has completed its job. However, you might need to +pass the result of that operation to the rest of your code. To do this, you can +add the value you want returned after the `break` expression you use to stop +the loop; that value will be returned out of the loop so you can use it, as +shown here: + +```rust +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-33-return-value-from-loop/src/main.rs}} +``` + +Before the loop, we declare a variable named `counter` and initialize it to +`0`. Then we declare a variable named `result` to hold the value returned from +the loop. On every iteration of the loop, we add `1` to the `counter` variable, +and then check whether the counter is equal to `10`. When it is, we use the +`break` keyword with the value `counter * 2`. After the loop, we use a +semicolon to end the statement that assigns the value to `result`. Finally, we +print the value in `result`, which in this case is 20. #### Conditional Loops with `while` It’s often useful for a program to evaluate a condition within a loop. While -the condition is true, the loop runs. When the condition ceases to be true, you -call `break`, stopping the loop. This loop type could be implemented using a -combination of `loop`, `if`, `else`, and `break`; you could try that now in a -program, if you’d like. +the condition is true, the loop runs. When the condition ceases to be true, the +program calls `break`, stopping the loop. This loop type could be implemented +using a combination of `loop`, `if`, `else`, and `break`; you could try that +now in a program, if you’d like. However, this pattern is so common that Rust has a built-in language construct -for it, and it’s called a `while` loop. The following example uses `while`: the -program loops three times, counting down each time. Then, after the loop, it -prints another message and exits: +for it, called a `while` loop. Listing 3-3 uses `while`: the program loops +three times, counting down each time, and then, after the loop, it prints +another message and exits. Filename: src/main.rs ```rust -fn main() { - let mut number = 3; - - while number != 0 { - println!("{}!", number); - - number = number - 1; - } - - println!("LIFTOFF!!!"); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/listing-03-03/src/main.rs}} ``` +Listing 3-3: Using a `while` loop to run code while a +condition holds true + This construct eliminates a lot of nesting that would be necessary if you used `loop`, `if`, `else`, and `break`, and it’s clearer. While a condition holds true, the code runs; otherwise, it exits the loop. @@ -341,45 +277,24 @@ true, the code runs; otherwise, it exits the loop. #### Looping Through a Collection with `for` You could use the `while` construct to loop over the elements of a collection, -such as an array. For example: +such as an array. For example, let’s look at Listing 3-4. -
Filename: src/main.rs ```rust -fn main() { - let a = [10, 20, 30, 40, 50]; - let mut index = 0; - - while index < 5 { - println!("the value is: {}", a[index]); - - index = index + 1; - } -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/listing-03-04/src/main.rs}} ``` -
- -Listing 3-5: Looping through each element of a collection using a `while` loop - -
-
+Listing 3-4: Looping through each element of a collection +using a `while` loop Here, the code counts up through the elements in the array. It starts at index `0`, and then loops until it reaches the final index in the array (that is, -when `index < 5` is no longer true). Running this code will print out every -element in the array: +when `index < 5` is no longer true). Running this code will print every element +in the array: -```text -$ cargo run - Compiling loops v0.1.0 (file:///projects/loops) - Running `target/debug/loops` -the value is: 10 -the value is: 20 -the value is: 30 -the value is: 40 -the value is: 50 +```console +{{#include ../listings/ch03-common-programming-concepts/listing-03-04/output.txt}} ``` All five array values appear in the terminal, as expected. Even though `index` @@ -387,47 +302,37 @@ will reach a value of `5` at some point, the loop stops executing before trying to fetch a sixth value from the array. But this approach is error prone; we could cause the program to panic if the -index length is incorrect. It’s also slow, because the compiler adds -runtime code to perform the conditional check on every element on every -iteration through the loop. +index length is incorrect. It’s also slow, because the compiler adds runtime +code to perform the conditional check on every element on every iteration +through the loop. -As a more efficient alternative, you can use a `for` loop and execute some code -for each item in a collection. A `for` loop looks like this: +As a more concise alternative, you can use a `for` loop and execute some code +for each item in a collection. A `for` loop looks like the code in Listing 3-5. -
Filename: src/main.rs ```rust -fn main() { - let a = [10, 20, 30, 40, 50]; - - for element in a.iter() { - println!("the value is: {}", element); - } -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/listing-03-05/src/main.rs}} ``` -
+Listing 3-5: Looping through each element of a collection +using a `for` loop -Listing 3-6: Looping through each element of a collection using a `for` loop - -
-
- -When we run this code, we’ll see the same output as in Listing 3-5. More +When we run this code, we’ll see the same output as in Listing 3-4. More importantly, we’ve now increased the safety of the code and eliminated the chance of bugs that might result from going beyond the end of the array or not going far enough and missing some items. -For example, in the code in Listing 3-5, if you removed an item from the `a` -array but forgot to update the condition to `while index < 4`, the code would -panic. Using the `for` loop, you don’t need to remember to change any other -code if you changed the number of values in the array. +For example, in the code in Listing 3-4, if you changed the definition of the +`a` array to have four elements but forgot to update the condition to `while +index < 4`, the code would panic. Using the `for` loop, you wouldn’t need to +remember to change any other code if you changed the number of values in the +array. The safety and conciseness of `for` loops make them the most commonly used loop construct in Rust. Even in situations in which you want to run some code a certain number of times, as in the countdown example that used a `while` loop -in Listing 3-5, most Rustaceans would use a `for` loop. The way to do that +in Listing 3-3, most Rustaceans would use a `for` loop. The way to do that would be to use a `Range`, which is a type provided by the standard library that generates all numbers in sequence starting from one number and ending before another number. @@ -438,12 +343,7 @@ we’ve not yet talked about, `rev`, to reverse the range: Filename: src/main.rs ```rust -fn main() { - for number in (1..4).rev() { - println!("{}!", number); - } - println!("LIFTOFF!!!"); -} +{{#rustdoc_include ../listings/ch03-common-programming-concepts/no-listing-34-for-range/src/main.rs}} ``` This code is a bit nicer, isn’t it? @@ -451,13 +351,19 @@ This code is a bit nicer, isn’t it? ## Summary You made it! That was a sizable chapter: you learned about variables, scalar -and`if` expressions, and loops! If you want to practice with the concepts -discussed in this chapter, try building programs to do the following: +and compound data types, functions, comments, `if` expressions, and loops! If +you want to practice with the concepts discussed in this chapter, try building +programs to do the following: * Convert temperatures between Fahrenheit and Celsius. * Generate the nth Fibonacci number. * Print the lyrics to the Christmas carol “The Twelve Days of Christmas,” -taking advantage of the repetition in the song. + taking advantage of the repetition in the song. When you’re ready to move on, we’ll talk about a concept in Rust that *doesn’t* commonly exist in other programming languages: ownership. + +[comparing-the-guess-to-the-secret-number]: +ch02-00-guessing-game-tutorial.html#comparing-the-guess-to-the-secret-number +[quitting-after-a-correct-guess]: +ch02-00-guessing-game-tutorial.html#quitting-after-a-correct-guess diff --git a/src/ch04-00-understanding-ownership.md b/src/ch04-00-understanding-ownership.md index 0b132e5..a58d673 100644 --- a/src/ch04-00-understanding-ownership.md +++ b/src/ch04-00-understanding-ownership.md @@ -2,6 +2,6 @@ Ownership is Rust’s most unique feature, and it enables Rust to make memory safety guarantees without needing a garbage collector. Therefore, it’s -important to understand how ownership works in Rust. In this chapter we’ll talk -about ownership as well as several related features: borrowing, slices, and how -Rust lays data out in memory. +important to understand how ownership works in Rust. In this chapter, we’ll +talk about ownership as well as several related features: borrowing, slices, +and how Rust lays data out in memory. diff --git a/src/ch04-01-what-is-ownership.md b/src/ch04-01-what-is-ownership.md index 85c6105..fad2f7e 100644 --- a/src/ch04-01-what-is-ownership.md +++ b/src/ch04-01-what-is-ownership.md @@ -8,7 +8,8 @@ Some languages have garbage collection that constantly looks for no longer used memory as the program runs; in other languages, the programmer must explicitly allocate and free the memory. Rust uses a third approach: memory is managed through a system of ownership with a set of rules that the compiler checks at -compile time. No run-time costs are incurred for any of the ownership features. +compile time. None of the ownership features slow down your program while it’s +running. Because ownership is a new concept for many programmers, it does take some time to get used to. The good news is that the more experienced you become with Rust @@ -20,79 +21,78 @@ the features that make Rust unique. In this chapter, you’ll learn ownership by working through some examples that focus on a very common data structure: strings. - - > ### The Stack and the Heap > -> In many programming languages, we don’t have to think about the stack and the -> heap very often. But in a systems programming language like Rust, whether a -> value is on the stack or the heap has more of an effect on how the language -> behaves and why we have to make certain decisions. We’ll describe parts of -> ownership in relation to the stack and the heap later in this chapter, so here -> is a brief explanation in preparation. +> In many programming languages, you don’t have to think about the stack and +> the heap very often. But in a systems programming language like Rust, whether +> a value is on the stack or the heap has more of an effect on how the language +> behaves and why you have to make certain decisions. Parts of ownership will +> be described in relation to the stack and the heap later in this chapter, so +> here is a brief explanation in preparation. > -> Both the stack and the heap are parts of memory that is available to your code -> to use at runtime, but they are structured in different ways. The stack stores -> values in the order it gets them and removes the values in the opposite order. -> This is referred to as *last in, first out*. Think of a stack of plates: when -> you add more plates, you put them on top of the pile, and when you need a -> plate, you take one off the top. Adding or removing plates from the middle or -> bottom wouldn’t work as well! Adding data is called *pushing onto the stack*, -> and removing data is called *popping off the stack*. +> Both the stack and the heap are parts of memory that are available to your +> code to use at runtime, but they are structured in different ways. The stack +> stores values in the order it gets them and removes the values in the +> opposite order. This is referred to as *last in, first out*. Think of a stack +> of plates: when you add more plates, you put them on top of the pile, and +> when you need a plate, you take one off the top. Adding or removing plates +> from the middle or bottom wouldn’t work as well! Adding data is called +> *pushing onto the stack*, and removing data is called *popping off the stack*. > -> The stack is fast because of the way it accesses the data: it never has to -> search for a place to put new data or a place to get data from because that -> place is always the top. Another property that makes the stack fast is that all -> data on the stack must take up a known, fixed size. -> -> For data with a size unknown to us at compile time or a size that might change, -> we can store data on the heap instead. The heap is less organized: when we put -> data on the heap, we ask for some amount of space. The operating system finds -> an empty spot somewhere in the heap that is big enough, marks it as being in -> use, and returns to us a pointer to that location. This process is called -> *allocating on the heap*, and sometimes we abbreviate the phrase as just -> “allocating.” Pushing values onto the stack is not considered allocating. -> Because the pointer is a known, fixed size, we can store the pointer on the -> stack, but when we want the actual data, we have to follow the pointer. +> All data stored on the stack must have a known, fixed size. Data with an +> unknown size at compile time or a size that might change must be stored on +> the heap instead. The heap is less organized: when you put data on the heap, +> you request a certain amount of space. The memory allocator finds an empty +> spot in the heap that is big enough, marks it as being in use, and returns a +> *pointer*, which is the address of that location. This process is called +> *allocating on the heap* and is sometimes abbreviated as just *allocating*. +> Pushing values onto the stack is not considered allocating. Because the +> pointer is a known, fixed size, you can store the pointer on the stack, but +> when you want the actual data, you must follow the pointer. > > Think of being seated at a restaurant. When you enter, you state the number of -> people in your group, and the staff finds an empty table that fits everyone and -> leads you there. If someone in your group comes late, they can ask where you’ve -> been seated to find you. +> people in your group, and the staff finds an empty table that fits everyone +> and leads you there. If someone in your group comes late, they can ask where +> you’ve been seated to find you. +> +> Pushing to the stack is faster than allocating on the heap because the +> allocator never has to search for a place to store new data; that +> location is always at the top of the stack. Comparatively, allocating space +> on the heap requires more work, because the allocator must first find +> a big enough space to hold the data and then perform bookkeeping to prepare +> for the next allocation. > > Accessing data in the heap is slower than accessing data on the stack because -> we have to follow a pointer to get there. Contemporary processors are faster if -> they jump around less in memory. Continuing the analogy, consider a server at a -> restaurant taking orders from many tables. It’s most efficient to get all the -> orders at one table before moving on to the next table. Taking an order from -> table A, then an order from table B, then one from A again, and then one from B -> again would be a much slower process. By the same token, a processor can do its -> job better if it works on data that’s close to other data (as it is on the -> stack) rather than farther away (as it can be on the heap). Allocating a large -> amount of space on the heap can also take time. +> you have to follow a pointer to get there. Contemporary processors are faster +> if they jump around less in memory. Continuing the analogy, consider a server +> at a restaurant taking orders from many tables. It’s most efficient to get +> all the orders at one table before moving on to the next table. Taking an +> order from table A, then an order from table B, then one from A again, and +> then one from B again would be a much slower process. By the same token, a +> processor can do its job better if it works on data that’s close to other +> data (as it is on the stack) rather than farther away (as it can be on the +> heap). Allocating a large amount of space on the heap can also take time. > -> When our code calls a function, the values passed into the function (including, -> potentially, pointers to data on the heap) and the function’s local variables -> get pushed onto the stack. When the function is over, those values get popped -> off the stack. +> When your code calls a function, the values passed into the function +> (including, potentially, pointers to data on the heap) and the function’s +> local variables get pushed onto the stack. When the function is over, those +> values get popped off the stack. > -> Keeping track of what parts of code are using what data on the heap, minimizing -> the amount of duplicate data on the heap, and cleaning up unused data on the -> heap so we don’t run out of space are all problems that ownership addresses. -> Once you understand ownership, you won’t need to think about the stack and the -> heap very often, but knowing that managing heap data is why ownership exists -> can help explain why it works the way it does. -> - +> Keeping track of what parts of code are using what data on the heap, +> minimizing the amount of duplicate data on the heap, and cleaning up unused +> data on the heap so you don’t run out of space are all problems that ownership +> addresses. Once you understand ownership, you won’t need to think about the +> stack and the heap very often, but knowing that managing heap data is why +> ownership exists can help explain why it works the way it does. ### Ownership Rules First, let’s take a look at the ownership rules. Keep these rules in mind as we -work through the examples that illustrate the rules: +work through the examples that illustrate them: -> 1. Each value in Rust has a variable that’s called its *owner*. -> 2. There can only be one owner at a time. -> 3. When the owner goes out of scope, the value will be dropped. +* Each value in Rust has a variable that’s called its *owner*. +* There can only be one owner at a time. +* When the owner goes out of scope, the value will be dropped. ### Variable Scope @@ -114,50 +114,41 @@ let s = "hello"; The variable `s` refers to a string literal, where the value of the string is hardcoded into the text of our program. The variable is valid from the point at which it’s declared until the end of the current *scope*. Listing 4-1 has -comments annotating where the variable `s` is valid: - -
+comments annotating where the variable `s` is valid. ```rust -{ // s is not valid here, it’s not yet declared - let s = "hello"; // s is valid from this point forward - - // do stuff with s -} // this scope is now over, and s is no longer valid +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-01/src/main.rs:here}} ``` -
- -Listing 4-1: A variable and the scope in which it is valid - -
-
+Listing 4-1: A variable and the scope in which it is +valid In other words, there are two important points in time here: -1. When `s` comes *into scope*, it is valid. -1. It remains so until it goes *out of scope*. +* When `s` comes *into scope*, it is valid. +* It remains valid until it goes *out of scope*. At this point, the relationship between scopes and when variables are valid is -similar to other programming languages. Now we’ll build on top of this +similar to that in other programming languages. Now we’ll build on top of this understanding by introducing the `String` type. ### The `String` Type To illustrate the rules of ownership, we need a data type that is more complex -than the ones we covered in Chapter 3. All the data types we’ve looked at -previously are stored on the stack and popped off the stack when their scope is -over, but we want to look at data that is stored on the heap and explore how -Rust knows when to clean up that data. +than the ones we covered in the [“Data Types”][data-types] +section of Chapter 3. The types covered previously are all stored on the stack +and popped off the stack when their scope is over, but we want to look at data +that is stored on the heap and explore how Rust knows when to clean up that +data. We’ll use `String` as the example here and concentrate on the parts of `String` -that relate to ownership. These aspects also apply to other complex data types -provided by the standard library and that you create. We’ll discuss `String` in -more depth in Chapter 8. +that relate to ownership. These aspects also apply to other complex data types, +whether they are provided by the standard library or created by you. We’ll +discuss `String` in more depth in Chapter 8. We’ve already seen string literals, where a string value is hardcoded into our -program. String literals are convenient, but they aren’t always suitable for -every situation in which you want to use text. One reason is that they’re +program. String literals are convenient, but they aren’t suitable for every +situation in which we may want to use text. One reason is that they’re immutable. Another is that not every string value can be known when we write our code: for example, what if we want to take user input and store it? For these situations, Rust has a second string type, `String`. This type is @@ -171,18 +162,15 @@ let s = String::from("hello"); The double colon (`::`) is an operator that allows us to namespace this particular `from` function under the `String` type rather than using some sort -of name like `string_from`. We’ll discuss this syntax more in the “Method -Syntax” section of Chapter 5 and when we talk about namespacing with modules in -Chapter 7. +of name like `string_from`. We’ll discuss this syntax more in the [“Method +Syntax”][method-syntax] section of Chapter 5 and when we talk +about namespacing with modules in [“Paths for Referring to an Item in the +Module Tree”][paths-module-tree] in Chapter 7. This kind of string *can* be mutated: ```rust -let mut s = String::from("hello"); - -s.push_str(", world!"); // push_str() appends a literal to a String - -println!("{}", s); // This will print `hello, world!` +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-01-can-mutate-string/src/main.rs:here}} ``` So, what’s the difference here? Why can `String` be mutated but literals @@ -190,20 +178,20 @@ cannot? The difference is how these two types deal with memory. ### Memory and Allocation -In the case of a string literal, we know the contents at compile time so the -text is hardcoded directly into the final executable, making string literals -fast and efficient. But these properties only come from its immutability. -Unfortunately, we can’t put a blob of memory into the binary for each piece of -text whose size is unknown at compile time and whose size might change while -running the program. +In the case of a string literal, we know the contents at compile time, so the +text is hardcoded directly into the final executable. This is why string +literals are fast and efficient. But these properties only come from the string +literal’s immutability. Unfortunately, we can’t put a blob of memory into the +binary for each piece of text whose size is unknown at compile time and whose +size might change while running the program. With the `String` type, in order to support a mutable, growable piece of text, we need to allocate an amount of memory on the heap, unknown at compile time, to hold the contents. This means: -1. The memory must be requested from the operating system at runtime. -2. We need a way of returning this memory to the operating system when we’re -done with our `String`. +* The memory must be requested from the memory allocator at runtime. +* We need a way of returning this memory to the allocator when we’re + done with our `String`. That first part is done by us: when we call `String::from`, its implementation requests the memory it needs. This is pretty much universal in programming @@ -211,34 +199,28 @@ languages. However, the second part is different. In languages with a *garbage collector (GC)*, the GC keeps track and cleans up memory that isn’t being used anymore, -and we, as the programmer, don’t need to think about it. Without a GC, it’s the -programmer’s responsibility to identify when memory is no longer being used and -call code to explicitly return it, just as we did to request it. Doing this -correctly has historically been a difficult programming problem. If we forget, -we’ll waste memory. If we do it too early, we’ll have an invalid variable. If -we do it twice, that’s a bug too. We need to pair exactly one `allocate` with -exactly one `free`. +and we don’t need to think about it. Without a GC, it’s our responsibility to +identify when memory is no longer being used and call code to explicitly return +it, just as we did to request it. Doing this correctly has historically been a +difficult programming problem. If we forget, we’ll waste memory. If we do it +too early, we’ll have an invalid variable. If we do it twice, that’s a bug too. +We need to pair exactly one `allocate` with exactly one `free`. Rust takes a different path: the memory is automatically returned once the variable that owns it goes out of scope. Here’s a version of our scope example from Listing 4-1 using a `String` instead of a string literal: ```rust -{ - let s = String::from("hello"); // s is valid from this point forward - - // do stuff with s -} // this scope is now over, and s is no - // longer valid +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-02-string-scope/src/main.rs:here}} ``` There is a natural point at which we can return the memory our `String` needs -to the operating system: when `s` goes out of scope. When a variable goes out -of scope, Rust calls a special function for us. This function is called `drop`, +to the allocator: when `s` goes out of scope. When a variable goes out of +scope, Rust calls a special function for us. This function is called [`drop`], and it’s where the author of `String` can put the code to return the memory. -Rust calls `drop` automatically at the closing `}`. +Rust calls `drop` automatically at the closing curly bracket. -> Note: In C++, this pattern of deallocating resources at the end of an item's +> Note: In C++, this pattern of deallocating resources at the end of an item’s > lifetime is sometimes called *Resource Acquisition Is Initialization (RAII)*. > The `drop` function in Rust will be familiar to you if you’ve used RAII > patterns. @@ -251,97 +233,71 @@ we’ve allocated on the heap. Let’s explore some of those situations now. #### Ways Variables and Data Interact: Move Multiple variables can interact with the same data in different ways in Rust. -Let’s look at an example using an integer in Listing 4-2: - -
+Let’s look at an example using an integer in Listing 4-2. ```rust -let x = 5; -let y = x; +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-02/src/main.rs:here}} ``` -
+Listing 4-2: Assigning the integer value of variable `x` +to `y` -Listing 4-2: Assigning the integer value of variable `x` to `y` - -
-
- -We can probably guess what this is doing based on our experience with other -languages: “Bind the value `5` to `x`; then make a copy of the value in `x` and -bind it to `y`.” We now have two variables, `x` and `y`, and both equal `5`. -This is indeed what is happening because integers are simple values with a -known, fixed size, and these two `5` values are pushed onto the stack. +We can probably guess what this is doing: “bind the value `5` to `x`; then make +a copy of the value in `x` and bind it to `y`.” We now have two variables, `x` +and `y`, and both equal `5`. This is indeed what is happening, because integers +are simple values with a known, fixed size, and these two `5` values are pushed +onto the stack. Now let’s look at the `String` version: ```rust -let s1 = String::from("hello"); -let s2 = s1; +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-03-string-move/src/main.rs:here}} ``` This looks very similar to the previous code, so we might assume that the way it works would be the same: that is, the second line would make a copy of the value in `s1` and bind it to `s2`. But this isn’t quite what happens. -To explain this more thoroughly, let’s look at what `String` looks like under -the covers in Figure 4-3. A `String` is made up of three parts, shown on the -left: a pointer to the memory that holds the contents of the string, a length, -and a capacity. This group of data is stored on the stack. On the right is the -memory on the heap that holds the contents. +Take a look at Figure 4-1 to see what is happening to `String` under the +covers. A `String` is made up of three parts, shown on the left: a pointer to +the memory that holds the contents of the string, a length, and a capacity. +This group of data is stored on the stack. On the right is the memory on the +heap that holds the contents. -
String in memory -
- -Figure 4-3: Representation in memory of a `String` holding the value `"hello"` -bound to `s1` - -
-
+Figure 4-1: Representation in memory of a `String` +holding the value `"hello"` bound to `s1` The length is how much memory, in bytes, the contents of the `String` is currently using. The capacity is the total amount of memory, in bytes, that the -`String` has received from the operating system. The difference between length +`String` has received from the allocator. The difference between length and capacity matters, but not in this context, so for now, it’s fine to ignore the capacity. When we assign `s1` to `s2`, the `String` data is copied, meaning we copy the pointer, the length, and the capacity that are on the stack. We do not copy the data on the heap that the pointer refers to. In other words, the data -representation in memory looks like Figure 4-4. +representation in memory looks like Figure 4-2. -
s1 and s2 pointing to the same value -
+Figure 4-2: Representation in memory of the variable `s2` +that has a copy of the pointer, length, and capacity of `s1` -Figure 4-4: Representation in memory of the variable `s2` that has a copy of -the pointer, length, and capacity of `s1` - -
-
- -The representation does *not* look like Figure 4-5, which is what memory would +The representation does *not* look like Figure 4-3, which is what memory would look like if Rust instead copied the heap data as well. If Rust did this, the -operation `s2 = s1` could potentially be very expensive in terms of runtime -performance if the data on the heap was large. +operation `s2 = s1` could be very expensive in terms of runtime performance if +the data on the heap were large. -
s1 and s2 to two places -
- -Figure 4-5: Another possibility of what `s2 = s1` might do if Rust copied the -heap data as well - -
-
+Figure 4-3: Another possibility for what `s2 = s1` might +do if Rust copied the heap data as well Earlier, we said that when a variable goes out of scope, Rust automatically calls the `drop` function and cleans up the heap memory for that variable. But -Figure 4-4 shows both data pointers pointing to the same location. This is a +Figure 4-2 shows both data pointers pointing to the same location. This is a problem: when `s2` and `s1` go out of scope, they will both try to free the same memory. This is known as a *double free* error and is one of the memory safety bugs we mentioned previously. Freeing memory twice can lead to memory @@ -349,49 +305,32 @@ corruption, which can potentially lead to security vulnerabilities. To ensure memory safety, there’s one more detail to what happens in this situation in Rust. Instead of trying to copy the allocated memory, Rust -considers `s1` to no longer be valid and therefore, Rust doesn’t need to free +considers `s1` to no longer be valid and, therefore, Rust doesn’t need to free anything when `s1` goes out of scope. Check out what happens when you try to -use `s1` after `s2` is created: +use `s1` after `s2` is created; it won’t work: -```rust,ignore -let s1 = String::from("hello"); -let s2 = s1; - -println!("{}", s1); +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/src/main.rs:here}} ``` You’ll get an error like this because Rust prevents you from using the invalidated reference: -```text -error[E0382]: use of moved value: `s1` - --> src/main.rs:4:27 - | -3 | let s2 = s1; - | -- value moved here -4 | println!("{}, world!",s1); - | ^^ value used here after move - | - = note: move occurs because `s1` has type `std::string::String`, -which does not implement the `Copy` trait +```console +{{#include ../listings/ch04-understanding-ownership/no-listing-04-cant-use-after-move/output.txt}} ``` -If you’ve heard the terms “shallow copy” and “deep copy” while working with +If you’ve heard the terms *shallow copy* and *deep copy* while working with other languages, the concept of copying the pointer, length, and capacity -without copying the data probably sounds like a shallow copy. But because Rust -also invalidates the first variable, instead of calling this a shallow copy, -it’s known as a *move*. Here we would read this by saying that `s1` was *moved* -into `s2`. So what actually happens is shown in Figure 4-6. +without copying the data probably sounds like making a shallow copy. But +because Rust also invalidates the first variable, instead of being called a +shallow copy, it’s known as a *move*. In this example, we would say that +`s1` was *moved* into `s2`. So what actually happens is shown in Figure 4-4. -
s1 moved to s2 -
- -Figure 4-6: Representation in memory after `s1` has been invalidated - -
-
+Figure 4-4: Representation in memory after `s1` has been +invalidated That solves our problem! With only `s2` valid, when it goes out of scope, it alone will free the memory, and we’re done. @@ -410,14 +349,11 @@ programming languages, you’ve probably seen them before. Here’s an example of the `clone` method in action: ```rust -let s1 = String::from("hello"); -let s2 = s1.clone(); - -println!("s1 = {}, s2 = {}", s1, s2); +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-05-clone/src/main.rs:here}} ``` -This works just fine and is how you can explicitly produce the behavior shown -in Figure 4-5, where the heap data *does* get copied. +This works just fine and explicitly produces the behavior shown in Figure 4-3, +where the heap data *does* get copied. When you see a call to `clone`, you know that some arbitrary code is being executed and that code may be expensive. It’s a visual indicator that something @@ -425,135 +361,86 @@ different is going on. #### Stack-Only Data: Copy -There’s another wrinkle we haven’t talked about yet. This code using integers, -part of which was shown earlier in Listing 4-2, works and is valid: +There’s another wrinkle we haven’t talked about yet. This code using integers – +part of which was shown in Listing 4-2 – works and is valid: ```rust -let x = 5; -let y = x; - -println!("x = {}, y = {}", x, y); +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-06-copy/src/main.rs:here}} ``` But this code seems to contradict what we just learned: we don’t have a call to `clone`, but `x` is still valid and wasn’t moved into `y`. -The reason is that types like integers that have a known size at compile time -are stored entirely on the stack, so copies of the actual values are quick to -make. That means there’s no reason we would want to prevent `x` from being +The reason is that types such as integers that have a known size at compile +time are stored entirely on the stack, so copies of the actual values are quick +to make. That means there’s no reason we would want to prevent `x` from being valid after we create the variable `y`. In other words, there’s no difference between deep and shallow copying here, so calling `clone` wouldn’t do anything -differently from the usual shallow copying and we can leave it out. +different from the usual shallow copying and we can leave it out. Rust has a special annotation called the `Copy` trait that we can place on types like integers that are stored on the stack (we’ll talk more about traits -in Chapter 10). If a type has the `Copy` trait, an older variable is still -usable after assignment. Rust won’t let us annotate a type with the `Copy` -trait if the type, or any of its parts, has implemented the `Drop` trait. If -the type needs something special to happen when the value goes out of scope and -we add the `Copy` annotation to that type, we’ll get a compile time error. +in Chapter 10). If a type implements the `Copy` trait, an older variable is +still usable after assignment. Rust won’t let us annotate a type with the +`Copy` trait if the type, or any of its parts, has implemented the `Drop` +trait. If the type needs something special to happen when the value goes out of +scope and we add the `Copy` annotation to that type, we’ll get a compile-time +error. To learn about how to add the `Copy` annotation to your type to +implement the trait, see [“Derivable Traits”][derivable-traits] +in Appendix C. -So what types are `Copy`? You can check the documentation for the given type to -be sure, but as a general rule, any group of simple scalar values can be -`Copy`, and nothing that requires allocation or is some form of resource is -`Copy`. Here are some of the types that are `Copy`: +So what types implement the `Copy` trait? You can check the documentation for +the given type to be sure, but as a general rule, any group of simple scalar +values can implement `Copy`, and nothing that requires allocation or is some +form of resource can implement `Copy`. Here are some of the types that +implement `Copy`: -* All the integer types, like `u32`. -* The boolean type, `bool`, with values `true` and `false`. -* All the floating point types, like `f64`. -* Tuples, but only if they contain types that are also `Copy`. `(i32, i32)` is -`Copy`, but `(i32, String)` is not. +* All the integer types, such as `u32`. +* The Boolean type, `bool`, with values `true` and `false`. +* All the floating point types, such as `f64`. +* The character type, `char`. +* Tuples, if they only contain types that also implement `Copy`. For example, + `(i32, i32)` implements `Copy`, but `(i32, String)` does not. ### Ownership and Functions -The semantics for passing a value to a function are similar to assigning a -value to a variable. Passing a variable to a function will move or copy, just -like assignment. Listing 4-7 has an example with some annotations showing where -variables go into and out of scope: +The semantics for passing a value to a function are similar to those for +assigning a value to a variable. Passing a variable to a function will move or +copy, just as assignment does. Listing 4-3 has an example with some annotations +showing where variables go into and out of scope. -
Filename: src/main.rs ```rust -fn main() { - let s = String::from("hello"); // s comes into scope. - - takes_ownership(s); // s's value moves into the function... - // ... and so is no longer valid here. - let x = 5; // x comes into scope. - - makes_copy(x); // x would move into the function, - // but i32 is Copy, so it’s okay to still - // use x afterward. - -} // Here, x goes out of scope, then s. But since s's value was moved, nothing - // special happens. - -fn takes_ownership(some_string: String) { // some_string comes into scope. - println!("{}", some_string); -} // Here, some_string goes out of scope and `drop` is called. The backing - // memory is freed. - -fn makes_copy(some_integer: i32) { // some_integer comes into scope. - println!("{}", some_integer); -} // Here, some_integer goes out of scope. Nothing special happens. +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-03/src/main.rs}} ``` -
- -Listing 4-7: Functions with ownership and scope annotated - -
-
+Listing 4-3: Functions with ownership and scope +annotated If we tried to use `s` after the call to `takes_ownership`, Rust would throw a -compile time error. These static checks protect us from mistakes. Try adding +compile-time error. These static checks protect us from mistakes. Try adding code to `main` that uses `s` and `x` to see where you can use them and where the ownership rules prevent you from doing so. ### Return Values and Scope -Returning values can also transfer ownership. Here’s an example with similar -annotations to those in Listing 4-7: +Returning values can also transfer ownership. Listing 4-4 is an example with +similar annotations to those in Listing 4-3. Filename: src/main.rs ```rust -fn main() { - let s1 = gives_ownership(); // gives_ownership moves its return - // value into s1. - - let s2 = String::from("hello"); // s2 comes into scope. - - let s3 = takes_and_gives_back(s2); // s2 is moved into - // takes_and_gives_back, which also - // moves its return value into s3. -} // Here, s3 goes out of scope and is dropped. s2 goes out of scope but was - // moved, so nothing happens. s1 goes out of scope and is dropped. - -fn gives_ownership() -> String { // gives_ownership will move its - // return value into the function - // that calls it. - - let some_string = String::from("hello"); // some_string comes into scope. - - some_string // some_string is returned and - // moves out to the calling - // function. -} - -// takes_and_gives_back will take a String and return one. -fn takes_and_gives_back(a_string: String) -> String { // a_string comes into - // scope. - - a_string // a_string is returned and moves out to the calling function. -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-04/src/main.rs}} ``` -The ownership of variables follows the same pattern every time: assigning a -value to another variable moves it, and when heap data values’ variables go out -of scope, if the data hasn’t been moved to be owned by another variable, the -value will be cleaned up by `drop`. +Listing 4-4: Transferring ownership of return +values + +The ownership of a variable follows the same pattern every time: assigning a +value to another variable moves it. When a variable that includes data on the +heap goes out of scope, the value will be cleaned up by `drop` unless the data +has been moved to be owned by another variable. Taking ownership and then returning ownership with every function is a bit tedious. What if we want to let a function use a value but not take ownership? @@ -561,26 +448,22 @@ It’s quite annoying that anything we pass in also needs to be passed back if w want to use it again, in addition to any data resulting from the body of the function that we might want to return as well. -It’s possible to return multiple values using a tuple, like this: +It’s possible to return multiple values using a tuple, as shown in Listing 4-5. Filename: src/main.rs ```rust -fn main() { - let s1 = String::from("hello"); - - let (s2, len) = calculate_length(s1); - - println!("The length of '{}' is {}.", s2, len); -} - -fn calculate_length(s: String) -> (String, usize) { - let length = s.len(); // len() returns the length of a String. - - (s, length) -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-05/src/main.rs}} ``` +Listing 4-5: Returning ownership of parameters + But this is too much ceremony and a lot of work for a concept that should be -common. Luckily for us, Rust has a feature for this concept, and it’s called +common. Luckily for us, Rust has a feature for this concept, called *references*. + +[data-types]: ch03-02-data-types.html#data-types +[derivable-traits]: appendix-03-derivable-traits.html +[method-syntax]: ch05-03-method-syntax.html#method-syntax +[paths-module-tree]: ch07-03-paths-for-referring-to-an-item-in-the-module-tree.html +[`drop`]: ../std/ops/trait.Drop.html#tymethod.drop diff --git a/src/ch04-02-references-and-borrowing.md b/src/ch04-02-references-and-borrowing.md index c6bf43f..6697d75 100644 --- a/src/ch04-02-references-and-borrowing.md +++ b/src/ch04-02-references-and-borrowing.md @@ -1,57 +1,42 @@ ## References and Borrowing -The issue with the tuple code at the end of the preceding section is that we -have to return the `String` to the calling function so we can still use the -`String` after the call to `calculate_length`, because the `String` was moved -into `calculate_length`. +The issue with the tuple code in Listing 4-5 is that we have to return the +`String` to the calling function so we can still use the `String` after the +call to `calculate_length`, because the `String` was moved into +`calculate_length`. Here is how you would define and use a `calculate_length` function that has a -*reference* to an object as a parameter instead of taking ownership of the +reference to an object as a parameter instead of taking ownership of the value: Filename: src/main.rs ```rust -fn main() { - let s1 = String::from("hello"); - - let len = calculate_length(&s1); - - println!("The length of '{}' is {}.", s1, len); -} - -fn calculate_length(s: &String) -> usize { - s.len() -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-07-reference/src/main.rs:all}} ``` First, notice that all the tuple code in the variable declaration and the function return value is gone. Second, note that we pass `&s1` into -`calculate_length`, and in its definition, we take `&String` rather than +`calculate_length` and, in its definition, we take `&String` rather than `String`. These ampersands are *references*, and they allow you to refer to some value -without taking ownership of it. Figure 4-8 shows a diagram. +without taking ownership of it. Figure 4-5 shows a diagram. -
&String s pointing at String s1 -
+Figure 4-5: A diagram of `&String s` pointing at `String +s1` -Figure 4-8: `&String s` pointing at `String s1` - -
-
+> Note: The opposite of referencing by using `&` is *dereferencing*, which is +> accomplished with the dereference operator, `*`. We’ll see some uses of the +> dereference operator in Chapter 8 and discuss details of dereferencing in +> Chapter 15. Let’s take a closer look at the function call here: ```rust -# fn calculate_length(s: &String) -> usize { -# s.len() -# } -let s1 = String::from("hello"); - -let len = calculate_length(&s1); +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-07-reference/src/main.rs:here}} ``` The `&s1` syntax lets us create a reference that *refers* to the value of `s1` @@ -62,55 +47,34 @@ Likewise, the signature of the function uses `&` to indicate that the type of the parameter `s` is a reference. Let’s add some explanatory annotations: ```rust -fn calculate_length(s: &String) -> usize { // s is a reference to a String - s.len() -} // Here, s goes out of scope. But because it does not have ownership of what - // it refers to, nothing happens. +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/src/main.rs:here}} ``` The scope in which the variable `s` is valid is the same as any function -parameter's scope, but we don’t drop what the reference points to when it goes -out of scope because we don’t have ownership. Functions that have references as -parameters instead of the actual values mean we won’t need to return the values -in order to give back ownership, since we never had ownership. +parameter’s scope, but we don’t drop what the reference points to when it goes +out of scope because we don’t have ownership. When functions have references as +parameters instead of the actual values, we won’t need to return the values in +order to give back ownership, because we never had ownership. We call having references as function parameters *borrowing*. As in real life, if a person owns something, you can borrow it from them. When you’re done, you have to give it back. So what happens if we try to modify something we’re borrowing? Try the code in -Listing 4-9. Spoiler alert: it doesn’t work! +Listing 4-6. Spoiler alert: it doesn’t work! -
Filename: src/main.rs -```rust,ignore -fn main() { - let s = String::from("hello"); - - change(&s); -} - -fn change(some_string: &String) { - some_string.push_str(", world"); -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-06/src/main.rs}} ``` -
- -Listing 4-9: Attempting to modify a borrowed value - -
-
+Listing 4-6: Attempting to modify a borrowed value Here’s the error: -```text -error: cannot borrow immutable borrowed content `*some_string` as mutable - --> error.rs:8:5 - | -8 | some_string.push_str(", world"); - | ^^^^^^^^^^^ +```console +{{#include ../listings/ch04-understanding-ownership/listing-04-06/output.txt}} ``` Just as variables are immutable by default, so are references. We’re not @@ -118,64 +82,45 @@ allowed to modify something we have a reference to. ### Mutable References -We can fix the error in the code from Listing 4-9 with just a small tweak: +We can fix the error in the code from Listing 4-6 with just a small tweak: Filename: src/main.rs ```rust -fn main() { - let mut s = String::from("hello"); - - change(&mut s); -} - -fn change(some_string: &mut String) { - some_string.push_str(", world"); -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-09-fixes-listing-04-06/src/main.rs}} ``` First, we had to change `s` to be `mut`. Then we had to create a mutable reference with `&mut s` and accept a mutable reference with `some_string: &mut String`. -But mutable references have one big restriction: you can only have one mutable +But mutable references have one big restriction: you can have only one mutable reference to a particular piece of data in a particular scope. This code will fail: Filename: src/main.rs -```rust,ignore -let mut s = String::from("hello"); - -let r1 = &mut s; -let r2 = &mut s; +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/src/main.rs:here}} ``` Here’s the error: -```text -error[E0499]: cannot borrow `s` as mutable more than once at a time - --> borrow_twice.rs:5:19 - | -4 | let r1 = &mut s; - | - first mutable borrow occurs here -5 | let r2 = &mut s; - | ^ second mutable borrow occurs here -6 | } - | - first borrow ends here +```console +{{#include ../listings/ch04-understanding-ownership/no-listing-10-multiple-mut-not-allowed/output.txt}} ``` This restriction allows for mutation but in a very controlled fashion. It’s something that new Rustaceans struggle with, because most languages let you -mutate whenever you’d like. The benefit of having this restriction is that Rust -can prevent data races at compile time. +mutate whenever you’d like. -A *data race* is a particular type of race condition in which these three -behaviors occur: +The benefit of having this restriction is that Rust can prevent data races at +compile time. A *data race* is similar to a race condition and happens when +these three behaviors occur: -1. Two or more pointers access the same data at the same time. -1. At least one of the pointers is being used to write to the data. -1. There’s no mechanism being used to synchronize access to the data. +* Two or more pointers access the same data at the same time. +* At least one of the pointers is being used to write to the data. +* There’s no mechanism being used to synchronize access to the data. Data races cause undefined behavior and can be difficult to diagnose and fix when you’re trying to track them down at runtime; Rust prevents this problem @@ -185,41 +130,20 @@ As always, we can use curly brackets to create a new scope, allowing for multiple mutable references, just not *simultaneous* ones: ```rust -let mut s = String::from("hello"); - -{ - let r1 = &mut s; - -} // r1 goes out of scope here, so we can make a new reference with no problems. - -let r2 = &mut s; +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-11-muts-in-separate-scopes/src/main.rs:here}} ``` A similar rule exists for combining mutable and immutable references. This code results in an error: -```rust,ignore -let mut s = String::from("hello"); - -let r1 = &s; // no problem -let r2 = &s; // no problem -let r3 = &mut s; // BIG PROBLEM +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/src/main.rs:here}} ``` Here’s the error: -```text -error[E0502]: cannot borrow `s` as mutable because it is also borrowed as -immutable - --> borrow_thrice.rs:6:19 - | -4 | let r1 = &s; // no problem - | - immutable borrow occurs here -5 | let r2 = &s; // no problem -6 | let r3 = &mut s; // BIG PROBLEM - | ^ mutable borrow occurs here -7 | } - | - immutable borrow ends here +```console +{{#include ../listings/ch04-understanding-ownership/no-listing-12-immutable-and-mutable-not-allowed/output.txt}} ``` Whew! We *also* cannot have a mutable reference while we have an immutable one. @@ -228,10 +152,23 @@ from under them! However, multiple immutable references are okay because no one who is just reading the data has the ability to affect anyone else’s reading of the data. -Even though these errors may be frustrating at times, remember that it’s the -Rust compiler pointing out a potential bug early (at compile time rather than -at runtime) and showing you exactly where the problem is instead of you having -to track down why sometimes your data isn’t what you thought it should be. +Note that a reference’s scope starts from where it is introduced and continues +through the last time that reference is used. For instance, this code will +compile because the last usage of the immutable references occurs before the +mutable reference is introduced: + +```rust,edition2018 +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/src/main.rs:here}} +``` + +The scopes of the immutable references `r1` and `r2` end after the `println!` +where they are last used, which is before the mutable reference `r3` is +created. These scopes don’t overlap, so this code is allowed. + +Even though borrowing errors may be frustrating at times, remember that it’s +the Rust compiler pointing out a potential bug early (at compile time rather +than at runtime) and showing you exactly where the problem is. Then you don’t +have to track down why your data isn’t what you thought it was. ### Dangling References @@ -239,46 +176,28 @@ In languages with pointers, it’s easy to erroneously create a *dangling pointer*, a pointer that references a location in memory that may have been given to someone else, by freeing some memory while preserving a pointer to that memory. In Rust, by contrast, the compiler guarantees that references will -never be dangling references: if we have a reference to some data, the compiler -will ensure that the data will not go out of scope before the reference to the -data does. +never be dangling references: if you have a reference to some data, the +compiler will ensure that the data will not go out of scope before the +reference to the data does. -Let’s try to create a dangling reference: +Let’s try to create a dangling reference, which Rust will prevent with a +compile-time error: Filename: src/main.rs -```rust,ignore -fn main() { - let reference_to_nothing = dangle(); -} - -fn dangle() -> &String { - let s = String::from("hello"); - - &s -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-14-dangling-reference/src/main.rs}} ``` Here’s the error: -```text -error[E0106]: missing lifetime specifier - --> dangle.rs:5:16 - | -5 | fn dangle() -> &String { - | ^^^^^^^ - | - = help: this function's return type contains a borrowed value, but there is no - value for it to be borrowed from - = help: consider giving it a 'static lifetime - -error: aborting due to previous error +```console +{{#include ../listings/ch04-understanding-ownership/no-listing-14-dangling-reference/output.txt}} ``` -This error message refers to a feature we haven’t covered yet: *lifetimes*. -We’ll discuss lifetimes in detail in Chapter 10. But, if you disregard the -parts about lifetimes, the message does contain the key to why this code is a -problem: +This error message refers to a feature we haven’t covered yet: lifetimes. We’ll +discuss lifetimes in detail in Chapter 10. But, if you disregard the parts +about lifetimes, the message does contain the key to why this code is a problem: ```text this function's return type contains a borrowed value, but there is no value @@ -288,29 +207,21 @@ for it to be borrowed from. Let’s take a closer look at exactly what’s happening at each stage of our `dangle` code: -```rust,ignore -fn dangle() -> &String { // dangle returns a reference to a String +Filename: src/main.rs - let s = String::from("hello"); // s is a new String - - &s // we return a reference to the String, s -} // Here, s goes out of scope, and is dropped. Its memory goes away. - // Danger! +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/src/main.rs:here}} ``` Because `s` is created inside `dangle`, when the code of `dangle` is finished, `s` will be deallocated. But we tried to return a reference to it. That means -this reference would be pointing to an invalid `String`! That’s no good. Rust +this reference would be pointing to an invalid `String`. That’s no good! Rust won’t let us do this. -The correct code here is to return the `String` directly: +The solution here is to return the `String` directly: ```rust -fn no_dangle() -> String { - let s = String::from("hello"); - - s -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-16-no-dangle/src/main.rs:here}} ``` This works without any problems. Ownership is moved out, and nothing is @@ -320,9 +231,8 @@ deallocated. Let’s recap what we’ve discussed about references: -1. At any given time, you can have *either* but not both of: - * One mutable reference. - * Any number of immutable references. -2. References must always be valid. +* At any given time, you can have *either* one mutable reference *or* any + number of immutable references. +* References must always be valid. Next, we’ll look at a different kind of reference: slices. diff --git a/src/ch04-03-slices.md b/src/ch04-03-slices.md index ef334d5..a6008f4 100644 --- a/src/ch04-03-slices.md +++ b/src/ch04-03-slices.md @@ -1,4 +1,4 @@ -## Slices +## The Slice Type Another data type that does not have ownership is the *slice*. Slices let you reference a contiguous sequence of elements in a collection rather than the @@ -6,8 +6,8 @@ whole collection. Here’s a small programming problem: write a function that takes a string and returns the first word it finds in that string. If the function doesn’t find a -space in the string, it means the whole string is one word, so the entire -string should be returned. +space in the string, the whole string must be one word, so the entire string +should be returned. Let’s think about the signature of this function: @@ -18,53 +18,37 @@ fn first_word(s: &String) -> ? This function, `first_word`, has a `&String` as a parameter. We don’t want ownership, so this is fine. But what should we return? We don’t really have a way to talk about *part* of a string. However, we could return the index of the -end of the word. Let’s try that as shown in Listing 4-10: +end of the word. Let’s try that, as shown in Listing 4-7. -
Filename: src/main.rs ```rust -fn first_word(s: &String) -> usize { - let bytes = s.as_bytes(); - - for (i, &item) in bytes.iter().enumerate() { - if item == b' ' { - return i; - } - } - - s.len() -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-07/src/main.rs:here}} ``` -
+Listing 4-7: The `first_word` function that returns a +byte index value into the `String` parameter -Listing 4-10: The `first_word` function that returns a byte index value into -the `String` parameter - -
-
- -Let’s break down this code a bit. Because we need to go through the `String` -element by element and check whether a value is a space, we’ll convert our -`String` to an array of bytes using the `as_bytes` method: +Because we need to go through the `String` element by element and check whether +a value is a space, we’ll convert our `String` to an array of bytes using the +`as_bytes` method: ```rust,ignore -let bytes = s.as_bytes(); +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-07/src/main.rs:as_bytes}} ``` -Next, we create an iterator over the array of bytes using the `iter` method : +Next, we create an iterator over the array of bytes using the `iter` method: ```rust,ignore -for (i, &item) in bytes.iter().enumerate() { +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-07/src/main.rs:iter}} ``` -We’ll discuss iterators in more detail in Chapter 16. For now, know that `iter` -is a method that returns each element in a collection, and `enumerate` wraps -the result of `iter` and returns each element as part of a tuple instead. The -first element of the returned tuple is the index, and the second element is a -reference to the element. This is a bit more convenient than calculating the -index ourselves. +We’ll discuss iterators in more detail in Chapter 13. For now, know that `iter` +is a method that returns each element in a collection and that `enumerate` +wraps the result of `iter` and returns each element as part of a tuple instead. +The first element of the tuple returned from `enumerate` is the index, and the +second element is a reference to the element. This is a bit more convenient +than calculating the index ourselves. Because the `enumerate` method returns a tuple, we can use patterns to destructure that tuple, just like everywhere else in Rust. So in the `for` @@ -72,65 +56,34 @@ loop, we specify a pattern that has `i` for the index in the tuple and `&item` for the single byte in the tuple. Because we get a reference to the element from `.iter().enumerate()`, we use `&` in the pattern. -We search for the byte that represents the space by using the byte literal -syntax. If we find a space, we return the position. Otherwise, we return the -length of the string by using `s.len()`: +Inside the `for` loop, we search for the byte that represents the space by +using the byte literal syntax. If we find a space, we return the position. +Otherwise, we return the length of the string by using `s.len()`: ```rust,ignore - if item == b' ' { - return i; - } -} -s.len() +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-07/src/main.rs:inside_for}} ``` We now have a way to find out the index of the end of the first word in the string, but there’s a problem. We’re returning a `usize` on its own, but it’s only a meaningful number in the context of the `&String`. In other words, because it’s a separate value from the `String`, there’s no guarantee that it -will still be valid in the future. Consider the program in Listing 4-11 that -uses the `first_word` function from Listing 4-10: +will still be valid in the future. Consider the program in Listing 4-8 that +uses the `first_word` function from Listing 4-7. -
Filename: src/main.rs ```rust -# fn first_word(s: &String) -> usize { -# let bytes = s.as_bytes(); -# -# for (i, &item) in bytes.iter().enumerate() { -# if item == b' ' { -# return i; -# } -# } -# -# s.len() -# } -# -fn main() { - let mut s = String::from("hello world"); - - let word = first_word(&s); // word will get the value 5. - - s.clear(); // This empties the String, making it equal to "". - - // word still has the value 5 here, but there's no more string that - // we could meaningfully use the value 5 with. word is now totally invalid! -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-08/src/main.rs:here}} ``` -
+Listing 4-8: Storing the result from calling the +`first_word` function and then changing the `String` contents -Listing 4-11: Storing the result from calling the `first_word` function then -changing the `String` contents - -
-
- -This program compiles without any errors and also would if we used `word` after -calling `s.clear()`. `word` isn’t connected to the state of `s` at all, so -`word` still contains the value `5`. We could use that value `5` with the -variable `s` to try to extract the first word out, but this would be a bug +This program compiles without any errors and would also do so if we used `word` +after calling `s.clear()`. Because `word` isn’t connected to the state of `s` +at all, `word` still contains the value `5`. We could use that value `5` with +the variable `s` to try to extract the first word out, but this would be a bug because the contents of `s` have changed since we saved `5` in `word`. Having to worry about the index in `word` getting out of sync with the data in @@ -141,45 +94,39 @@ we write a `second_word` function. Its signature would have to look like this: fn second_word(s: &String) -> (usize, usize) { ``` -Now we’re tracking a start *and* an ending index, and we have even more values -that were calculated from data in a particular state but aren’t tied to that -state at all. We now have three unrelated variables floating around that need -to be kept in sync. +Now we’re tracking a starting *and* an ending index, and we have even more +values that were calculated from data in a particular state but aren’t tied to +that state at all. We now have three unrelated variables floating around that +need to be kept in sync. Luckily, Rust has a solution to this problem: string slices. ### String Slices -A *string slice* is a reference to part of a `String`, and looks like this: +A *string slice* is a reference to part of a `String`, and it looks like this: ```rust -let s = String::from("hello world"); - -let hello = &s[0..5]; -let world = &s[6..11]; +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-17-slice/src/main.rs:here}} ``` This is similar to taking a reference to the whole `String` but with the extra `[0..5]` bit. Rather than a reference to the entire `String`, it’s a reference -to an internal position in the `String` and the number of elements that it -refers to. +to a portion of the `String`. -We create slices with a range of `[starting_index..ending_index]`, but the -slice data structure actually stores the starting position and the length of -the slice. So in the case of `let world = &s[6..11];`, `world` would be a slice -that contains a pointer to the 6th byte of `s` and a length value of 5. +We can create slices using a range within brackets by specifying +`[starting_index..ending_index]`, where `starting_index` is the first position +in the slice and `ending_index` is one more than the last position in the +slice. Internally, the slice data structure stores the starting position and +the length of the slice, which corresponds to `ending_index` minus +`starting_index`. So in the case of `let world = &s[6..11];`, `world` would be +a slice that contains a pointer to the 7th byte (counting from 1) of `s` with a length value of 5. -Figure 4-12 shows this in a diagram. +Figure 4-6 shows this in a diagram. -
world containing a pointer to the 6th byte of String s and a length 5 -
- -Figure 4-12: String slice referring to part of a `String` - -
-
+Figure 4-6: String slice referring to part of a +`String` With Rust’s `..` range syntax, if you want to start at the first index (zero), you can drop the value before the two periods. In other words, these are equal: @@ -215,27 +162,24 @@ let slice = &s[0..len]; let slice = &s[..]; ``` +> Note: String slice range indices must occur at valid UTF-8 character +> boundaries. If you attempt to create a string slice in the middle of a +> multibyte character, your program will exit with an error. For the purposes +> of introducing string slices, we are assuming ASCII only in this section; a +> more thorough discussion of UTF-8 handling is in the [“Storing UTF-8 Encoded +> Text with Strings”][strings] section of Chapter 8. + With all this information in mind, let’s rewrite `first_word` to return a slice. The type that signifies “string slice” is written as `&str`: Filename: src/main.rs ```rust -fn first_word(s: &String) -> &str { - let bytes = s.as_bytes(); - - for (i, &item) in bytes.iter().enumerate() { - if item == b' ' { - return &s[0..i]; - } - } - - &s[..] -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-18-first-word-slice/src/main.rs:here}} ``` We get the index for the end of the word in the same way as we did in Listing -4-10, by looking for the first occurrence of a space. When we find a space, we +4-7, by looking for the first occurrence of a space. When we find a space, we return a string slice using the start of the string and the index of the space as the starting and ending indices. @@ -249,51 +193,33 @@ Returning a slice would also work for a `second_word` function: fn second_word(s: &String) -> &str { ``` -We now have a straightforward API that’s much harder to mess up, since the +We now have a straightforward API that’s much harder to mess up, because the compiler will ensure the references into the `String` remain valid. Remember -the bug in the program in Listing 4-11, when we got the index to the end of the +the bug in the program in Listing 4-8, when we got the index to the end of the first word but then cleared the string so our index was invalid? That code was logically incorrect but didn’t show any immediate errors. The problems would show up later if we kept trying to use the first word index with an emptied string. Slices make this bug impossible and let us know we have a problem with our code much sooner. Using the slice version of `first_word` will throw a -compile time error: +compile-time error: Filename: src/main.rs -```rust,ignore -fn main() { - let mut s = String::from("hello world"); - - let word = first_word(&s); - - s.clear(); // Error! -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-19-slice-error/src/main.rs:here}} ``` Here’s the compiler error: -```text -17:6 error: cannot borrow `s` as mutable because it is also borrowed as - immutable [E0502] - s.clear(); // Error! - ^ -15:29 note: previous borrow of `s` occurs here; the immutable borrow prevents - subsequent moves or mutable borrows of `s` until the borrow ends - let word = first_word(&s); - ^ -18:2 note: previous borrow ends here -fn main() { - -} -^ +```console +{{#include ../listings/ch04-understanding-ownership/no-listing-19-slice-error/output.txt}} ``` Recall from the borrowing rules that if we have an immutable reference to something, we cannot also take a mutable reference. Because `clear` needs to -truncate the `String`, it tries to take a mutable reference, which fails. Not -only has Rust made our API easier to use, but it has also eliminated an entire -class of errors at compile time! +truncate the `String`, it needs to get a mutable reference. Rust disallows +this, and compilation fails. Not only has Rust made our API easier to use, but +it has also eliminated an entire class of errors at compile time! #### String Literals Are Slices @@ -310,54 +236,33 @@ immutable reference. #### String Slices as Parameters -Knowing that you can take slices of literals and `String`s leads us to one more -improvement on `first_word`, and that’s its signature: +Knowing that you can take slices of literals and `String` values leads us to +one more improvement on `first_word`, and that’s its signature: ```rust,ignore fn first_word(s: &String) -> &str { ``` -A more experienced Rustacean would write the following line instead because it -allows us to use the same function on both `String`s and `&str`s: +A more experienced Rustacean would write the signature shown in Listing 4-9 +instead because it allows us to use the same function on both `&String` values +and `&str` values. ```rust,ignore -fn first_word(s: &str) -> &str { +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-09/src/main.rs:here}} ``` +Listing 4-9: Improving the `first_word` function by using +a string slice for the type of the `s` parameter + If we have a string slice, we can pass that directly. If we have a `String`, we can pass a slice of the entire `String`. Defining a function to take a string -slice instead of a reference to a String makes our API more general and useful +slice instead of a reference to a `String` makes our API more general and useful without losing any functionality: Filename: src/main.rs ```rust -# fn first_word(s: &str) -> &str { -# let bytes = s.as_bytes(); -# -# for (i, &item) in bytes.iter().enumerate() { -# if item == b' ' { -# return &s[0..i]; -# } -# } -# -# &s[..] -# } -fn main() { - let my_string = String::from("hello world"); - - // first_word works on slices of `String`s - let word = first_word(&my_string[..]); - - let my_string_literal = "hello world"; - - // first_word works on slices of string literals - let word = first_word(&my_string_literal[..]); - - // since string literals *are* string slices already, - // this works too, without the slice syntax! - let word = first_word(my_string_literal); -} +{{#rustdoc_include ../listings/ch04-understanding-ownership/listing-04-09/src/main.rs:usage}} ``` ### Other Slices @@ -369,13 +274,15 @@ more general slice type, too. Consider this array: let a = [1, 2, 3, 4, 5]; ``` -Just like we might want to refer to a part of a string, we might want to refer -to part of an array and would do so like this: +Just as we might want to refer to a part of a string, we might want to refer +to part of an array. We’d do so like this: ```rust let a = [1, 2, 3, 4, 5]; let slice = &a[1..3]; + +assert_eq!(slice, &[2, 3]); ``` This slice has the type `&[i32]`. It works the same way as string slices do, by @@ -385,12 +292,14 @@ detail when we talk about vectors in Chapter 8. ## Summary -The concepts of ownership, borrowing, and slices are what ensure memory safety -in Rust programs at compile time. The Rust language gives you control over your -memory usage like other systems programming languages, but having the owner of -data automatically clean up that data when the owner goes out of scope means -you don’t have to write and debug extra code to get this control. +The concepts of ownership, borrowing, and slices ensure memory safety in Rust +programs at compile time. The Rust language gives you control over your memory +usage in the same way as other systems programming languages, but having the +owner of data automatically clean up that data when the owner goes out of scope +means you don’t have to write and debug extra code to get this control. Ownership affects how lots of other parts of Rust work, so we’ll talk about -these concepts further throughout the rest of the book. Let’s move on to the -next chapter and look at grouping pieces of data together in a `struct`. +these concepts further throughout the rest of the book. Let’s move on to +Chapter 5 and look at grouping pieces of data together in a `struct`. + +[strings]: ch08-02-strings.html#storing-utf-8-encoded-text-with-strings diff --git a/src/ch05-00-structs.md b/src/ch05-00-structs.md index 997ea1e..aa9cb77 100644 --- a/src/ch05-00-structs.md +++ b/src/ch05-00-structs.md @@ -1,429 +1,11 @@ -# Structs +# Using Structs to Structure Related Data -A `struct`, short for *structure*, is a custom data type that lets us name and +A *struct*, or *structure*, is a custom data type that lets you name and package together multiple related values that make up a meaningful group. If -you come from an object-oriented language, a `struct` is like an object’s data -attributes. In the next section of this chapter, we’ll talk about how to define -methods on our structs; methods are how you specify the *behavior* that goes -along with a struct’s data. The `struct` and `enum` (that we will talk about in -Chapter 6) concepts are the building blocks for creating new types in your -program’s domain in order to take full advantage of Rust’s compile-time type -checking. - -One way of thinking about structs is that they are similar to tuples, which we -talked about in Chapter 3. Like tuples, the pieces of a struct can be different -types. Unlike tuples, we name each piece of data so that it’s clearer what the -values mean. Structs are more flexible as a result of these names: we don’t -have to rely on the order of the data to specify or access the values of an -instance. - -To define a struct, we enter the keyword `struct` and give the whole struct a -name. A struct’s name should describe what the significance is of these pieces -of data being grouped together. Then, inside curly braces, we define the names -of the pieces of data, which we call *fields*, and specify each field’s type. -For example, Listing 5-1 shows a struct to store information about a user -account: - -
- -```rust -struct User { - username: String, - email: String, - sign_in_count: u64, - active: bool, -} -``` - -
- -Listing 5-1: A `User` struct definition - -
-
- -To use a struct once we've defined it, we create an *instance* of that struct -by specifying concrete values for each of the fields. Creating an instance is -done by stating the name of the struct, then curly braces with `key: value` -pairs inside it where the keys are the names of the fields and the values are -the data we want to store in those fields. The fields don’t have to be -specified in the same order in which the struct declared them. In other words, -the struct definition is like a general template for the type, and instances -fill in that template with particular data to create values of the type. For -example, we can declare a particular user like this: - -```rust -# struct User { -# username: String, -# email: String, -# sign_in_count: u64, -# active: bool, -# } -# -let user1 = User { - email: String::from("someone@example.com"), - username: String::from("someusername123"), - active: true, - sign_in_count: 1, -}; -``` - -To get a particular value out of a struct, we can use dot notation. If we -wanted just this user’s email address, we can say `user1.email`. - -## Ownership of Struct Data - -In the `User` struct definition in Listing 5-1, we used the owned `String` type -rather than the `&str` string slice type. This is a deliberate choice because -we want instances of this struct to own all of its data, and for that data to -be valid for as long as the entire struct is valid. - -It is possible for structs to store references to data owned by something else, -but to do so requires the use of *lifetimes*, a feature of Rust that we'll -discuss in Chapter 10. Lifetimes ensure that the data a struct references is -valid for as long as the struct is. If you try to store a reference in a struct -without specifying lifetimes, like this: - -Filename: src/main.rs - -```rust,ignore -struct User { - username: &str, - email: &str, - sign_in_count: u64, - active: bool, -} - -fn main() { - let user1 = User { - email: "someone@example.com", - username: "someusername123", - active: true, - sign_in_count: 1, - }; -} -``` - -The compiler will complain that it needs lifetime specifiers: - -```text -error[E0106]: missing lifetime specifier - --> - | -2 | username: &str, - | ^ expected lifetime parameter - -error[E0106]: missing lifetime specifier - --> - | -3 | email: &str, - | ^ expected lifetime parameter -``` - -We will talk about how to fix these errors in order to store references in -structs in Chapter 10, but for now, fix errors like these by switching to owned -types like `String` instead of references like `&str`. - -## An Example Program - -To understand when we might want to use structs, let’s write a program that -calculates the area of a rectangle. We’ll start off with single variables, then -refactor our program until we’re using structs instead. - -Let’s make a new binary project with Cargo called *rectangles* that will take -the length and width of a rectangle specified in pixels and will calculate the -area of the rectangle. Listing 5-2 has a short program with one way of doing -just that in our project’s *src/main.rs*: - -
-Filename: src/main.rs - -```rust -fn main() { - let length1 = 50; - let width1 = 30; - - println!( - "The area of the rectangle is {} square pixels.", - area(length1, width1) - ); -} - -fn area(length: u32, width: u32) -> u32 { - length * width -} -``` - -
- -Listing 5-2: Calculating the area of a rectangle specified by its length and -width in separate variables - -
-
- -Let’s try running this program with `cargo run`: - -```text -The area of the rectangle is 1500 square pixels. -``` - -### Refactoring with Tuples - -Our little program works okay; it figures out the area of the rectangle by -calling the `area` function with each dimension. But we can do better. The -length and the width are related to each other since together they describe one -rectangle. - -The issue with this method is evident in the signature of `area`: - -```rust,ignore -fn area(length: u32, width: u32) -> u32 { -``` - -The `area` function is supposed to calculate the area of one rectangle, but our -function has two parameters. The parameters are related, but that’s not -expressed anywhere in our program itself. It would be more readable and more -manageable to group length and width together. - -We’ve already discussed one way we might do that in Chapter 3: tuples. Listing -5-3 has a version of our program which uses tuples: - -
-Filename: src/main.rs - -```rust -fn main() { - let rect1 = (50, 30); - - println!( - "The area of the rectangle is {} square pixels.", - area(rect1) - ); -} - -fn area(dimensions: (u32, u32)) -> u32 { - dimensions.0 * dimensions.1 -} -``` - -
- -Listing 5-3: Specifying the length and width of the rectangle with a tuple - -
-
- - - -In one way, this is a little better. Tuples let us add a bit of structure, and -we’re now passing just one argument when we call `area`. But in another way -this method is less clear: tuples don’t give names to their elements, so our -calculation has gotten more confusing because we have to index into the parts -of the tuple: - - - -```rust,ignore -dimensions.0 * dimensions.1 -``` - -It doesn’t matter if we mix up length and width for the area calculation, but -if we were to draw the rectangle on the screen it would matter! We would have -to remember that `length` was the tuple index `0` and `width` was the tuple -index `1`. If someone else was to work on this code, they would have to figure -this out and remember it as well. It would be easy to forget or mix these -values up and cause errors, since we haven’t conveyed the meaning of our data -in our code. - -### Refactoring with Structs: Adding More Meaning - -Here is where we bring in structs. We can transform our tuple into a data type -with a name for the whole as well as names for the parts, as shown in Listing -5-4: - -
-Filename: src/main.rs - -```rust -struct Rectangle { - length: u32, - width: u32, -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!( - "The area of the rectangle is {} square pixels.", - area(&rect1) - ); -} - -fn area(rectangle: &Rectangle) -> u32 { - rectangle.length * rectangle.width -} -``` - -
- -Listing 5-4: Defining a `Rectangle` struct - -
-
- - - -Here we’ve defined a struct and given it the name `Rectangle`. Inside the `{}` -we defined the fields to be `length` and `width`, both of which have type -`u32`. Then in `main`, we create a particular instance of a `Rectangle` that -has a length of 50 and a width of 30. - -Our `area` function is now defined with one parameter that we’ve named -`rectangle` whose type is an immutable borrow of a struct `Rectangle` instance. -As we covered in Chapter 4, we want to borrow the struct rather than take -ownership of it so that `main` keeps its ownership and can continue using -`rect1`, so that’s why we have the `&` in the function signature and at the -call site. - -The `area` function accesses the `length` and `width` fields of the -`Rectangle`. Our function signature for `area` now says exactly what we mean: -calculate the area of a `Rectangle`, using its `length` and `width` fields. -This conveys that the length and width are related to each other, and gives -descriptive names to the values rather than using the tuple index values of `0` -and `1`. This is a win for clarity. - -### Adding Useful Functionality with Derived Traits - -It’d be nice to be able to print out an instance of our `Rectangle` while we’re -debugging our program and see the values for all its fields. Listing 5-5 tries -using the `println!` macro as we have been: - -
-Filename: src/main.rs - -```rust,ignore -struct Rectangle { - length: u32, - width: u32, -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!("rect1 is {}", rect1); -} -``` - -
- -Listing 5-5: Attempting to print a `Rectangle` instance - -
-
- -If we run this, we get an error with this core message: - -```text -error[E0277]: the trait bound `Rectangle: std::fmt::Display` is not satisfied -``` - -The `println!` macro can do many kinds of formatting, and by default, `{}` -tells `println!` to use formatting known as `Display`: output intended for -direct end-user consumption. The primitive types we’ve seen so far implement -`Display` by default, as there’s only one way you’d want to show a `1` or any -other primitive type to a user. But with structs, the way `println!` should -format the output is less clear as there are more display possibilities: Do you -want commas or not? Do you want to print the struct `{}`s? Should all the -fields be shown? Because of this ambiguity, Rust doesn’t try to guess what we -want and structs do not have a provided implementation of `Display`. - -If we keep reading the errors, though, we’ll find this helpful note: - -```text -note: `Rectangle` cannot be formatted with the default formatter; try using -`:?` instead if you are using a format string -``` - -Let’s try it! The `println!` will now look like -`println!("rect1 is {:?}", rect1);`. Putting the specifier `:?` inside -the `{}` tells `println!` we want to use an output format called `Debug`. -`Debug` is a trait that enables us to print out our struct in a way that is -useful for developers so that we can see its value while we are debugging our -code. - -Let’s try running with this change and… drat. We still get an error: - -```text -error: the trait bound `Rectangle: std::fmt::Debug` is not satisfied -``` - -Again, though, the compiler has given us a helpful note! - -```text -note: `Rectangle` cannot be formatted using `:?`; if it is defined in your -crate, add `#[derive(Debug)]` or manually implement it -``` - -Rust *does* include functionality to print out debugging information, but we -have to explicitly opt-in to having that functionality be available for our -struct. To do that, we add the annotation `#[derive(Debug)]` just before our -struct definition, as shown in Listing 5-6: - -
- -```rust -#[derive(Debug)] -struct Rectangle { - length: u32, - width: u32, -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!("rect1 is {:?}", rect1); -} -``` - -
- -Listing 5-6: Adding the annotation to derive the `Debug` trait and printing the -`Rectangle` instance using debug formatting - -
-
- -At this point, if we run this program, we won’t get any errors and we’ll see -the following output: - -```text -rect1 is Rectangle { length: 50, width: 30 } -``` - -Nice! It’s not the prettiest output, but it shows the values of all the fields -for this instance, which would definitely help during debugging. If we want -output that is a bit prettier and easier to read, which can be helpful with -larger structs, we can use `{:#?}` in place of `{:?}` in the `println!` string. -If we use the pretty debug style in this example, the output will look like: - -```text -rect1 is Rectangle { - length: 50, - width: 30 -} -``` - -There are a number of traits Rust has provided for us to use with the `derive` -annotation that can add useful behavior to our custom types. Those traits and -their behaviors are listed in Appendix C. We’ll be covering how to implement -these traits with custom behavior, as well as creating your own traits, in -Chapter 10. - -Our `area` function is pretty specific—it only computes the area of rectangles. -It would be nice to tie this behavior together more closely with our -`Rectangle` struct, since it’s behavior that our `Rectangle` type has -specifically. Let’s now look at how we can continue to refactor this code by -turning the `area` function into an `area` *method* defined on our `Rectangle` -type. +you’re familiar with an object-oriented language, a *struct* is like an +object’s data attributes. In this chapter, we’ll compare and contrast tuples +with structs, demonstrate how to use structs, and discuss how to define methods +and associated functions to specify behavior associated with a struct’s data. +Structs and enums (discussed in Chapter 6) are the building blocks for creating +new types in your program’s domain to take full advantage of Rust’s compile +time type checking. diff --git a/src/ch05-01-defining-structs.md b/src/ch05-01-defining-structs.md new file mode 100644 index 0000000..91cd017 --- /dev/null +++ b/src/ch05-01-defining-structs.md @@ -0,0 +1,241 @@ +## Defining and Instantiating Structs + +Structs are similar to tuples, which were discussed in Chapter 3. Like tuples, +the pieces of a struct can be different types. Unlike with tuples, you’ll name +each piece of data so it’s clear what the values mean. As a result of these +names, structs are more flexible than tuples: you don’t have to rely on the +order of the data to specify or access the values of an instance. + +To define a struct, we enter the keyword `struct` and name the entire struct. A +struct’s name should describe the significance of the pieces of data being +grouped together. Then, inside curly brackets, we define the names and types of +the pieces of data, which we call *fields*. For example, Listing 5-1 shows a +struct that stores information about a user account. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-01/src/main.rs:here}} +``` + +Listing 5-1: A `User` struct definition + +To use a struct after we’ve defined it, we create an *instance* of that struct +by specifying concrete values for each of the fields. We create an instance by +stating the name of the struct and then add curly brackets containing `key: +value` pairs, where the keys are the names of the fields and the values are the +data we want to store in those fields. We don’t have to specify the fields in +the same order in which we declared them in the struct. In other words, the +struct definition is like a general template for the type, and instances fill +in that template with particular data to create values of the type. For +example, we can declare a particular user as shown in Listing 5-2. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-02/src/main.rs:here}} +``` + +Listing 5-2: Creating an instance of the `User` +struct + +To get a specific value from a struct, we can use dot notation. If we wanted +just this user’s email address, we could use `user1.email` wherever we wanted +to use this value. If the instance is mutable, we can change a value by using +the dot notation and assigning into a particular field. Listing 5-3 shows how +to change the value in the `email` field of a mutable `User` instance. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-03/src/main.rs:here}} +``` + +Listing 5-3: Changing the value in the `email` field of a +`User` instance + +Note that the entire instance must be mutable; Rust doesn’t allow us to mark +only certain fields as mutable. As with any expression, we can construct a new +instance of the struct as the last expression in the function body to +implicitly return that new instance. + +Listing 5-4 shows a `build_user` function that returns a `User` instance with +the given email and username. The `active` field gets the value of `true`, and +the `sign_in_count` gets a value of `1`. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-04/src/main.rs:here}} +``` + +Listing 5-4: A `build_user` function that takes an email +and username and returns a `User` instance + +It makes sense to name the function parameters with the same name as the struct +fields, but having to repeat the `email` and `username` field names and +variables is a bit tedious. If the struct had more fields, repeating each name +would get even more annoying. Luckily, there’s a convenient shorthand! + +### Using the Field Init Shorthand when Variables and Fields Have the Same Name + +Because the parameter names and the struct field names are exactly the same in +Listing 5-4, we can use the *field init shorthand* syntax to rewrite +`build_user` so that it behaves exactly the same but doesn’t have the +repetition of `email` and `username`, as shown in Listing 5-5. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-05/src/main.rs:here}} +``` + +Listing 5-5: A `build_user` function that uses field init +shorthand because the `email` and `username` parameters have the same name as +struct fields + +Here, we’re creating a new instance of the `User` struct, which has a field +named `email`. We want to set the `email` field’s value to the value in the +`email` parameter of the `build_user` function. Because the `email` field and +the `email` parameter have the same name, we only need to write `email` rather +than `email: email`. + +### Creating Instances From Other Instances With Struct Update Syntax + +It’s often useful to create a new instance of a struct that uses most of an old +instance’s values but changes some. You’ll do this using *struct update syntax*. + +First, Listing 5-6 shows how we create a new `User` instance in `user2` without +the update syntax. We set new values for `email` and `username` but otherwise +use the same values from `user1` that we created in Listing 5-2. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-06/src/main.rs:here}} +``` + +Listing 5-6: Creating a new `User` instance using some of +the values from `user1` + +Using struct update syntax, we can achieve the same effect with less code, as +shown in Listing 5-7. The syntax `..` specifies that the remaining fields not +explicitly set should have the same value as the fields in the given instance. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-07/src/main.rs:here}} +``` + +Listing 5-7: Using struct update syntax to set new +`email` and `username` values for a `User` instance but use the rest of the +values from the fields of the instance in the `user1` variable + +The code in Listing 5-7 also creates an instance in `user2` that has a +different value for `email` and `username` but has the same values for the +`active` and `sign_in_count` fields from `user1`. + +### Using Tuple Structs without Named Fields to Create Different Types + +You can also define structs that look similar to tuples, called *tuple +structs*. Tuple structs have the added meaning the struct name provides but +don’t have names associated with their fields; rather, they just have the types +of the fields. Tuple structs are useful when you want to give the whole tuple a +name and make the tuple be a different type from other tuples, and naming each +field as in a regular struct would be verbose or redundant. + +To define a tuple struct, start with the `struct` keyword and the struct name +followed by the types in the tuple. For example, here are definitions and +usages of two tuple structs named `Color` and `Point`: + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/no-listing-01-tuple-structs/src/main.rs:here}} +``` + +Note that the `black` and `origin` values are different types, because they’re +instances of different tuple structs. Each struct you define is its own type, +even though the fields within the struct have the same types. For example, a +function that takes a parameter of type `Color` cannot take a `Point` as an +argument, even though both types are made up of three `i32` values. Otherwise, +tuple struct instances behave like tuples: you can destructure them into their +individual pieces, you can use a `.` followed by the index to access an +individual value, and so on. + +### Unit-Like Structs Without Any Fields + +You can also define structs that don’t have any fields! These are called +*unit-like structs* because they behave similarly to `()`, the unit type. +Unit-like structs can be useful in situations in which you need to implement a +trait on some type but don’t have any data that you want to store in the type +itself. We’ll discuss traits in Chapter 10. + +> ### Ownership of Struct Data +> +> In the `User` struct definition in Listing 5-1, we used the owned `String` +> type rather than the `&str` string slice type. This is a deliberate choice +> because we want instances of this struct to own all of its data and for that +> data to be valid for as long as the entire struct is valid. +> +> It’s possible for structs to store references to data owned by something else, +> but to do so requires the use of *lifetimes*, a Rust feature that we’ll +> discuss in Chapter 10. Lifetimes ensure that the data referenced by a struct +> is valid for as long as the struct is. Let’s say you try to store a reference +> in a struct without specifying lifetimes, like this, which won’t work: +> +> Filename: src/main.rs +> +> +> +> ```rust,ignore,does_not_compile +> struct User { +> username: &str, +> email: &str, +> sign_in_count: u64, +> active: bool, +> } +> +> fn main() { +> let user1 = User { +> email: "someone@example.com", +> username: "someusername123", +> active: true, +> sign_in_count: 1, +> }; +> } +> ``` +> +> The compiler will complain that it needs lifetime specifiers: +> +> ```console +> $ cargo run +> Compiling structs v0.1.0 (file:///projects/structs) +> error[E0106]: missing lifetime specifier +> --> src/main.rs:2:15 +> | +> 2 | username: &str, +> | ^ expected named lifetime parameter +> | +> help: consider introducing a named lifetime parameter +> | +> 1 | struct User<'a> { +> 2 | username: &'a str, +> | +> +> error[E0106]: missing lifetime specifier +> --> src/main.rs:3:12 +> | +> 3 | email: &str, +> | ^ expected named lifetime parameter +> | +> help: consider introducing a named lifetime parameter +> | +> 1 | struct User<'a> { +> 2 | username: &str, +> 3 | email: &'a str, +> | +> +> error: aborting due to 2 previous errors +> +> For more information about this error, try `rustc --explain E0106`. +> error: could not compile `structs` +> +> To learn more, run the command again with --verbose. +> ``` +> +> In Chapter 10, we’ll discuss how to fix these errors so you can store +> references in structs, but for now, we’ll fix errors like these using owned +> types like `String` instead of references like `&str`. + + diff --git a/src/ch05-01-method-syntax.md b/src/ch05-01-method-syntax.md deleted file mode 100644 index e769001..0000000 --- a/src/ch05-01-method-syntax.md +++ /dev/null @@ -1,254 +0,0 @@ -## Method Syntax - -*Methods* are similar to functions: they’re declared with the `fn` keyword and -their name, they can have parameters and return values, and they contain some -code that gets run when they’re called from somewhere else. Methods are -different from functions, however, because they’re defined within the context -of a struct (or an enum or a trait object, which we will cover in Chapters 6 -and 13, respectively), and their first parameter is always `self`, which -represents the instance of the struct that the method is being called on. - -### Defining Methods - -Let’s change our `area` function that has a `Rectangle` instance as a parameter -and instead make an `area` method defined on the `Rectangle` struct, as shown -in Listing 5-7: - -
-Filename: src/main.rs - -```rust -#[derive(Debug)] -struct Rectangle { - length: u32, - width: u32, -} - -impl Rectangle { - fn area(&self) -> u32 { - self.length * self.width - } -} - -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - - println!( - "The area of the rectangle is {} square pixels.", - rect1.area() - ); -} -``` - -
- -Listing 5-7: Defining an `area` method on the `Rectangle` struct - -
-
- - - -In order to make the function be defined within the context of `Rectangle`, we -start an `impl` block (`impl` is short for *implementation*). Then we move the -function within the `impl` curly braces, and change the first (and in this -case, only) parameter to be `self` in the signature and everywhere within the -body. Then in `main` where we called the `area` function and passed `rect1` as -an argument, we can instead use *method syntax* to call the `area` method on -our `Rectangle` instance. Method syntax is taking an instance and adding a dot -followed by the method name, parentheses, and any arguments. - -In the signature for `area`, we get to use `&self` instead of `rectangle: -&Rectangle` because Rust knows the type of `self` is `Rectangle` due to this -method being inside the `impl Rectangle` context. Note we still need to have -the `&` before `self`, just like we had `&Rectangle`. Methods can choose to -take ownership of `self`, borrow `self` immutably as we’ve done here, or borrow -`self` mutably, just like any other parameter. - -We’ve chosen `&self` here for the same reason we used `&Rectangle` in the -function version: we don’t want to take ownership, and we just want to be able -to read the data in the struct, not write to it. If we wanted to be able to -change the instance that we’ve called the method on as part of what the method -does, we’d put `&mut self` as the first parameter instead. Having a method that -takes ownership of the instance by having just `self` as the first parameter is -rarer; this is usually used when the method transforms `self` into something -else and we want to prevent the caller from using the original instance after -the transformation. - -The main benefit of using methods over functions, in addition to getting to use -method syntax and not having to repeat the type of `self` in every method’s -signature, is for organization. We’ve put all the things we can do with an -instance of a type together in one `impl` block, rather than make future users -of our code search for capabilities of `Rectangle` all over the place. - - - -> ### Where’s the `->` operator? -> -> In languages like C++, there are two different operators for calling methods: -> `.` if you’re calling a method on the object directly, and `->` if you’re -> calling the method on a pointer to the object and thus need to dereference the -> pointer first. In other words, if `object` is a pointer, `object->something()` -> is like `(*object).something()`. -> -> Rust doesn’t have an equivalent to the `->` operator; instead, Rust has a -> feature called *automatic referencing and dereferencing*. Calling methods is -> one of the few places in Rust that has behavior like this. -> -> Here’s how it works: when you call a method with `object.something()`, Rust -> will automatically add in `&`, `&mut`, or `*` so that `object` matches the -> signature of the method. In other words, these are the same: -> -> ```rust -> # #[derive(Debug,Copy,Clone)] -> # struct Point { -> # x: f64, -> # y: f64, -> # } -> # -> # impl Point { -> # fn distance(&self, other: &Point) -> f64 { -> # let x_squared = f64::powi(other.x - self.x, 2); -> # let y_squared = f64::powi(other.y - self.y, 2); -> # -> # f64::sqrt(x_squared + y_squared) -> # } -> # } -> # let p1 = Point { x: 0.0, y: 0.0 }; -> # let p2 = Point { x: 5.0, y: 6.5 }; -> p1.distance(&p2); -> (&p1).distance(&p2); -> ``` -> -> The first one looks much, much cleaner. This automatic referencing behavior -> works because methods have a clear receiver — the type of `self`. Given the -> receiver and name of a method, Rust can figure out definitively whether the -> method is just reading (so needs `&self`), mutating (so `&mut self`), or -> consuming (so `self`). The fact that Rust makes borrowing implicit for method -> receivers is a big part of making ownership ergonomic in practice. - - - -### Methods with More Parameters - -Let’s practice some more with methods by implementing a second method on our -`Rectangle` struct. This time, we’d like for an instance of `Rectangle` to take -another instance of `Rectangle` and return `true` if the second rectangle could -fit completely within `self` and `false` if it would not. That is, if we run -the code in Listing 5-8, once we've defined the `can_hold` method: - -
-Filename: src/main.rs - -```rust,ignore -fn main() { - let rect1 = Rectangle { length: 50, width: 30 }; - let rect2 = Rectangle { length: 40, width: 10 }; - let rect3 = Rectangle { length: 45, width: 60 }; - - println!("Can rect1 hold rect2? {}", rect1.can_hold(&rect2)); - println!("Can rect1 hold rect3? {}", rect1.can_hold(&rect3)); -} -``` - -
- -Listing 5-8: Demonstration of using the as-yet-unwritten `can_hold` method - -
-
- -We want to see this output, since both of `rect2`’s dimensions are smaller than -`rect1`’s, but `rect3` is wider than `rect1`: - -```text -Can rect1 hold rect2? true -Can rect1 hold rect3? false -``` - -We know we want to define a method, so it will be within the `impl Rectangle` -block. The method name will be `can_hold`, and it will take an immutable borrow -of another `Rectangle` as a parameter. We can tell what the type of the -parameter will be by looking at a call site: `rect1.can_hold(&rect2)` passes in -`&rect2`, which is an immutable borrow to `rect2`, an instance of `Rectangle`. -This makes sense, since we only need to read `rect2` (rather than write, which -would mean we’d need a mutable borrow) and we want `main` to keep ownership of -`rect2` so that we could use it again after calling this method. The return -value of `can_hold` will be a boolean, and the implementation will check to see -if `self`’s length and width are both greater than the length and width of the -other `Rectangle`, respectively. Let’s add this new method to the `impl` block -from Listing 5-7: - -Filename: src/main.rs - -```rust -# #[derive(Debug)] -# struct Rectangle { -# length: u32, -# width: u32, -# } -# -impl Rectangle { - fn area(&self) -> u32 { - self.length * self.width - } - - fn can_hold(&self, other: &Rectangle) -> bool { - self.length > other.length && self.width > other.width - } -} -``` - - - -If we run this with the `main` from Listing 5-8, we will get our desired output! -Methods can have multiple parameters that we add to the signature after the -`self` parameter, and those parameters work just like parameters in functions -do. - -### Associated Functions - -One more useful feature of `impl` blocks: we’re allowed to define functions -within `impl` blocks that *don’t* take `self` as a parameter. These are called -*associated functions*, since they’re associated with the struct. They’re still -functions though, not methods, since they don’t have an instance of the struct -to work with. You’ve already used an associated function: `String::from`. - -Associated functions are often used for constructors that will return a new -instance of the struct. For example, we could provide an associated function -that would have one dimension parameter and use that as both length and width, -thus making it easier to create a square `Rectangle` rather than having to -specify the same value twice: - -Filename: src/main.rs - -```rust -# #[derive(Debug)] -# struct Rectangle { -# length: u32, -# width: u32, -# } -# -impl Rectangle { - fn square(size: u32) -> Rectangle { - Rectangle { length: size, width: size } - } -} -``` - -To call this associated function, we use the `::` syntax with the struct name: -`let sq = Rectangle::square(3);`, for example. This function is namespaced by -the struct: the `::` syntax is used for both associated functions and -namespaces created by modules, which we’ll learn about in Chapter 7. - -## Summary - -Structs let us create custom types that are meaningful for our domain. By using -structs, we can keep associated pieces of data connected to each other and name -each piece to make our code clear. Methods let us specify the behavior that -instances of our structs have, and associated functions let us namespace -functionality that is particular to our struct without having an instance -available. - -Structs aren’t the only way we can create custom types, though; let’s turn to -the `enum` feature of Rust and add another tool to our toolbox. diff --git a/src/ch05-02-example-structs.md b/src/ch05-02-example-structs.md new file mode 100644 index 0000000..c6cb8a1 --- /dev/null +++ b/src/ch05-02-example-structs.md @@ -0,0 +1,205 @@ +## An Example Program Using Structs + +To understand when we might want to use structs, let’s write a program that +calculates the area of a rectangle. We’ll start with single variables, and then +refactor the program until we’re using structs instead. + +Let’s make a new binary project with Cargo called *rectangles* that will take +the width and height of a rectangle specified in pixels and calculate the area +of the rectangle. Listing 5-8 shows a short program with one way of doing +exactly that in our project’s *src/main.rs*. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-08/src/main.rs:all}} +``` + +Listing 5-8: Calculating the area of a rectangle +specified by separate width and height variables + +Now, run this program using `cargo run`: + +```console +{{#include ../listings/ch05-using-structs-to-structure-related-data/listing-05-08/output.txt}} +``` + +Even though Listing 5-8 works and figures out the area of the rectangle by +calling the `area` function with each dimension, we can do better. The width +and the height are related to each other because together they describe one +rectangle. + +The issue with this code is evident in the signature of `area`: + +```rust,ignore +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-08/src/main.rs:here}} +``` + +The `area` function is supposed to calculate the area of one rectangle, but the +function we wrote has two parameters. The parameters are related, but that’s +not expressed anywhere in our program. It would be more readable and more +manageable to group width and height together. We’ve already discussed one way +we might do that in [“The Tuple Type”][the-tuple-type] section +of Chapter 3: by using tuples. + +### Refactoring with Tuples + +Listing 5-9 shows another version of our program that uses tuples. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-09/src/main.rs}} +``` + +Listing 5-9: Specifying the width and height of the +rectangle with a tuple + +In one way, this program is better. Tuples let us add a bit of structure, and +we’re now passing just one argument. But in another way, this version is less +clear: tuples don’t name their elements, so our calculation has become more +confusing because we have to index into the parts of the tuple. + +It doesn’t matter if we mix up width and height for the area calculation, but +if we want to draw the rectangle on the screen, it would matter! We would have +to keep in mind that `width` is the tuple index `0` and `height` is the tuple +index `1`. If someone else worked on this code, they would have to figure this +out and keep it in mind as well. It would be easy to forget or mix up these +values and cause errors, because we haven’t conveyed the meaning of our data in +our code. + +### Refactoring with Structs: Adding More Meaning + +We use structs to add meaning by labeling the data. We can transform the tuple +we’re using into a data type with a name for the whole as well as names for the +parts, as shown in Listing 5-10. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-10/src/main.rs}} +``` + +Listing 5-10: Defining a `Rectangle` struct + +Here we’ve defined a struct and named it `Rectangle`. Inside the curly +brackets, we defined the fields as `width` and `height`, both of which have +type `u32`. Then in `main`, we created a particular instance of `Rectangle` +that has a width of 30 and a height of 50. + +Our `area` function is now defined with one parameter, which we’ve named +`rectangle`, whose type is an immutable borrow of a struct `Rectangle` +instance. As mentioned in Chapter 4, we want to borrow the struct rather than +take ownership of it. This way, `main` retains its ownership and can continue +using `rect1`, which is the reason we use the `&` in the function signature and +where we call the function. + +The `area` function accesses the `width` and `height` fields of the `Rectangle` +instance. Our function signature for `area` now says exactly what we mean: +calculate the area of `Rectangle`, using its `width` and `height` fields. This +conveys that the width and height are related to each other, and it gives +descriptive names to the values rather than using the tuple index values of `0` +and `1`. This is a win for clarity. + +### Adding Useful Functionality with Derived Traits + +It’d be nice to be able to print an instance of `Rectangle` while we’re +debugging our program and see the values for all its fields. Listing 5-11 tries +using the `println!` macro as we have used in previous chapters. This won’t +work, however. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-11/src/main.rs}} +``` + +Listing 5-11: Attempting to print a `Rectangle` +instance + +When we compile this code, we get an error with this core message: + +```text +{{#include ../listings/ch05-using-structs-to-structure-related-data/listing-05-11/output.txt:3}} +``` + +The `println!` macro can do many kinds of formatting, and by default, the curly +brackets tell `println!` to use formatting known as `Display`: output intended +for direct end user consumption. The primitive types we’ve seen so far +implement `Display` by default, because there’s only one way you’d want to show +a `1` or any other primitive type to a user. But with structs, the way +`println!` should format the output is less clear because there are more +display possibilities: Do you want commas or not? Do you want to print the +curly brackets? Should all the fields be shown? Due to this ambiguity, Rust +doesn’t try to guess what we want, and structs don’t have a provided +implementation of `Display`. + +If we continue reading the errors, we’ll find this helpful note: + +```text +{{#include ../listings/ch05-using-structs-to-structure-related-data/listing-05-11/output.txt:9:10}} +``` + +Let’s try it! The `println!` macro call will now look like `println!("rect1 is +{:?}", rect1);`. Putting the specifier `:?` inside the curly brackets tells +`println!` we want to use an output format called `Debug`. The `Debug` trait +enables us to print our struct in a way that is useful for developers so we can +see its value while we’re debugging our code. + +Compile the code with this change. Drat! We still get an error: + +```text +{{#include ../listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/output.txt:3}} +``` + +But again, the compiler gives us a helpful note: + +```text +{{#include ../listings/ch05-using-structs-to-structure-related-data/output-only-01-debug/output.txt:9:10}} +``` + +Rust *does* include functionality to print out debugging information, but we +have to explicitly opt in to make that functionality available for our struct. +To do that, we add the annotation `#[derive(Debug)]` just before the struct +definition, as shown in Listing 5-12. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-12/src/main.rs}} +``` + +Listing 5-12: Adding the annotation to derive the `Debug` +trait and printing the `Rectangle` instance using debug formatting + +Now when we run the program, we won’t get any errors, and we’ll see the +following output: + +```console +{{#include ../listings/ch05-using-structs-to-structure-related-data/listing-05-12/output.txt}} +``` + +Nice! It’s not the prettiest output, but it shows the values of all the fields +for this instance, which would definitely help during debugging. When we have +larger structs, it’s useful to have output that’s a bit easier to read; in +those cases, we can use `{:#?}` instead of `{:?}` in the `println!` string. +When we use the `{:#?}` style in the example, the output will look like this: + +```console +{{#include ../listings/ch05-using-structs-to-structure-related-data/output-only-02-pretty-debug/output.txt}} +``` + +Rust has provided a number of traits for us to use with the `derive` annotation +that can add useful behavior to our custom types. Those traits and their +behaviors are listed in [Appendix C][app-c]. We’ll cover how to +implement these traits with custom behavior as well as how to create your own +traits in Chapter 10. + +Our `area` function is very specific: it only computes the area of rectangles. +It would be helpful to tie this behavior more closely to our `Rectangle` +struct, because it won’t work with any other type. Let’s look at how we can +continue to refactor this code by turning the `area` function into an `area` +*method* defined on our `Rectangle` type. + +[the-tuple-type]: ch03-02-data-types.html#the-tuple-type +[app-c]: appendix-03-derivable-traits.md diff --git a/src/ch05-03-method-syntax.md b/src/ch05-03-method-syntax.md new file mode 100644 index 0000000..7fced77 --- /dev/null +++ b/src/ch05-03-method-syntax.md @@ -0,0 +1,211 @@ +## Method Syntax + +*Methods* are similar to functions: they’re declared with the `fn` keyword and +their name, they can have parameters and a return value, and they contain some +code that is run when they’re called from somewhere else. However, methods are +different from functions in that they’re defined within the context of a struct +(or an enum or a trait object, which we cover in Chapters 6 and 17, +respectively), and their first parameter is always `self`, which represents the +instance of the struct the method is being called on. + +### Defining Methods + +Let’s change the `area` function that has a `Rectangle` instance as a parameter +and instead make an `area` method defined on the `Rectangle` struct, as shown +in Listing 5-13. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-13/src/main.rs}} +``` + +Listing 5-13: Defining an `area` method on the +`Rectangle` struct + +To define the function within the context of `Rectangle`, we start an `impl` +(implementation) block. Then we move the `area` function within the `impl` +curly brackets and change the first (and in this case, only) parameter to be +`self` in the signature and everywhere within the body. In `main`, where we +called the `area` function and passed `rect1` as an argument, we can instead +use *method syntax* to call the `area` method on our `Rectangle` instance. +The method syntax goes after an instance: we add a dot followed by the method +name, parentheses, and any arguments. + +In the signature for `area`, we use `&self` instead of `rectangle: &Rectangle` +because Rust knows the type of `self` is `Rectangle` due to this method’s being +inside the `impl Rectangle` context. Note that we still need to use the `&` +before `self`, just as we did in `&Rectangle`. Methods can take ownership of +`self`, borrow `self` immutably as we’ve done here, or borrow `self` mutably, +just as they can any other parameter. + +We’ve chosen `&self` here for the same reason we used `&Rectangle` in the +function version: we don’t want to take ownership, and we just want to read the +data in the struct, not write to it. If we wanted to change the instance that +we’ve called the method on as part of what the method does, we’d use `&mut +self` as the first parameter. Having a method that takes ownership of the +instance by using just `self` as the first parameter is rare; this technique is +usually used when the method transforms `self` into something else and you want +to prevent the caller from using the original instance after the transformation. + +The main benefit of using methods instead of functions, in addition to using +method syntax and not having to repeat the type of `self` in every method’s +signature, is for organization. We’ve put all the things we can do with an +instance of a type in one `impl` block rather than making future users of our +code search for capabilities of `Rectangle` in various places in the library we +provide. + +> ### Where’s the `->` Operator? +> +> In C and C++, two different operators are used for calling methods: you use +> `.` if you’re calling a method on the object directly and `->` if you’re +> calling the method on a pointer to the object and need to dereference the +> pointer first. In other words, if `object` is a pointer, +> `object->something()` is similar to `(*object).something()`. +> +> Rust doesn’t have an equivalent to the `->` operator; instead, Rust has a +> feature called *automatic referencing and dereferencing*. Calling methods is +> one of the few places in Rust that has this behavior. +> +> Here’s how it works: when you call a method with `object.something()`, Rust +> automatically adds in `&`, `&mut`, or `*` so `object` matches the signature of +> the method. In other words, the following are the same: +> +> +> ```rust +> # #[derive(Debug,Copy,Clone)] +> # struct Point { +> # x: f64, +> # y: f64, +> # } +> # +> # impl Point { +> # fn distance(&self, other: &Point) -> f64 { +> # let x_squared = f64::powi(other.x - self.x, 2); +> # let y_squared = f64::powi(other.y - self.y, 2); +> # +> # f64::sqrt(x_squared + y_squared) +> # } +> # } +> # let p1 = Point { x: 0.0, y: 0.0 }; +> # let p2 = Point { x: 5.0, y: 6.5 }; +> p1.distance(&p2); +> (&p1).distance(&p2); +> ``` +> +> The first one looks much cleaner. This automatic referencing behavior works +> because methods have a clear receiver—the type of `self`. Given the receiver +> and name of a method, Rust can figure out definitively whether the method is +> reading (`&self`), mutating (`&mut self`), or consuming (`self`). The fact +> that Rust makes borrowing implicit for method receivers is a big part of +> making ownership ergonomic in practice. + +### Methods with More Parameters + +Let’s practice using methods by implementing a second method on the `Rectangle` +struct. This time, we want an instance of `Rectangle` to take another instance +of `Rectangle` and return `true` if the second `Rectangle` can fit completely +within `self`; otherwise it should return `false`. That is, we want to be able +to write the program shown in Listing 5-14, once we’ve defined the `can_hold` +method. + +Filename: src/main.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-14/src/main.rs}} +``` + +Listing 5-14: Using the as-yet-unwritten `can_hold` +method + +And the expected output would look like the following, because both dimensions +of `rect2` are smaller than the dimensions of `rect1` but `rect3` is wider than +`rect1`: + +```text +Can rect1 hold rect2? true +Can rect1 hold rect3? false +``` + +We know we want to define a method, so it will be within the `impl Rectangle` +block. The method name will be `can_hold`, and it will take an immutable borrow +of another `Rectangle` as a parameter. We can tell what the type of the +parameter will be by looking at the code that calls the method: +`rect1.can_hold(&rect2)` passes in `&rect2`, which is an immutable borrow to +`rect2`, an instance of `Rectangle`. This makes sense because we only need to +read `rect2` (rather than write, which would mean we’d need a mutable borrow), +and we want `main` to retain ownership of `rect2` so we can use it again after +calling the `can_hold` method. The return value of `can_hold` will be a +Boolean, and the implementation will check whether the width and height of +`self` are both greater than the width and height of the other `Rectangle`, +respectively. Let’s add the new `can_hold` method to the `impl` block from +Listing 5-13, shown in Listing 5-15. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-15/src/main.rs:here}} +``` + +Listing 5-15: Implementing the `can_hold` method on +`Rectangle` that takes another `Rectangle` instance as a parameter + +When we run this code with the `main` function in Listing 5-14, we’ll get our +desired output. Methods can take multiple parameters that we add to the +signature after the `self` parameter, and those parameters work just like +parameters in functions. + +### Associated Functions + +Another useful feature of `impl` blocks is that we’re allowed to define +functions within `impl` blocks that *don’t* take `self` as a parameter. These +are called *associated functions* because they’re associated with the struct. +They’re still functions, not methods, because they don’t have an instance of +the struct to work with. You’ve already used the `String::from` associated +function. + +Associated functions are often used for constructors that will return a new +instance of the struct. For example, we could provide an associated function +that would have one dimension parameter and use that as both width and height, +thus making it easier to create a square `Rectangle` rather than having to +specify the same value twice: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/no-listing-03-associated-functions/src/main.rs:here}} +``` + +To call this associated function, we use the `::` syntax with the struct name; +`let sq = Rectangle::square(3);` is an example. This function is namespaced by +the struct: the `::` syntax is used for both associated functions and +namespaces created by modules. We’ll discuss modules in Chapter 7. + +### Multiple `impl` Blocks + +Each struct is allowed to have multiple `impl` blocks. For example, Listing +5-15 is equivalent to the code shown in Listing 5-16, which has each method +in its own `impl` block. + +```rust +{{#rustdoc_include ../listings/ch05-using-structs-to-structure-related-data/listing-05-16/src/main.rs:here}} +``` + +Listing 5-16: Rewriting Listing 5-15 using multiple `impl` +blocks + +There’s no reason to separate these methods into multiple `impl` blocks here, +but this is valid syntax. We’ll see a case in which multiple `impl` blocks are +useful in Chapter 10, where we discuss generic types and traits. + +## Summary + +Structs let you create custom types that are meaningful for your domain. By +using structs, you can keep associated pieces of data connected to each other +and name each piece to make your code clear. Methods let you specify the +behavior that instances of your structs have, and associated functions let you +namespace functionality that is particular to your struct without having an +instance available. + +But structs aren’t the only way you can create custom types: let’s turn to +Rust’s enum feature to add another tool to your toolbox. diff --git a/src/ch06-00-enums.md b/src/ch06-00-enums.md index f88f4ed..cf7ea67 100644 --- a/src/ch06-00-enums.md +++ b/src/ch06-00-enums.md @@ -1,7 +1,7 @@ # Enums and Pattern Matching In this chapter we’ll look at *enumerations*, also referred to as *enums*. -Enums allow you to define a type by enumerating its possible values. First, +Enums allow you to define a type by enumerating its possible *variants*. First, we’ll define and use an enum to show how an enum can encode meaning along with data. Next, we’ll explore a particularly useful enum, called `Option`, which expresses that a value can be either something or nothing. Then we’ll look at @@ -12,4 +12,4 @@ enums in your code. Enums are a feature in many languages, but their capabilities differ in each language. Rust’s enums are most similar to *algebraic data types* in functional -languages like F#, OCaml, and Haskell. +languages, such as F#, OCaml, and Haskell. diff --git a/src/ch06-01-defining-an-enum.md b/src/ch06-01-defining-an-enum.md index 6409fd6..be794ce 100644 --- a/src/ch06-01-defining-an-enum.md +++ b/src/ch06-01-defining-an-enum.md @@ -5,24 +5,21 @@ are useful and more appropriate than structs in this case. Say we need to work with IP addresses. Currently, two major standards are used for IP addresses: version four and version six. These are the only possibilities for an IP address that our program will come across: we can *enumerate* all possible -values, which is where enumeration gets its name. +variants, which is where enumeration gets its name. -Any IP address can be either a version four or a version six address but not +Any IP address can be either a version four or a version six address, but not both at the same time. That property of IP addresses makes the enum data -structure appropriate for this case, because enum values can only be one of the -variants. Both version four and version six addresses are still fundamentally -IP addresses, so they should be treated as the same type when the code is -handling situations that apply to any kind of IP address. +structure appropriate, because enum values can only be one of its variants. +Both version four and version six addresses are still fundamentally IP +addresses, so they should be treated as the same type when the code is handling +situations that apply to any kind of IP address. We can express this concept in code by defining an `IpAddrKind` enumeration and -listing the possible kinds an IP address can be, `V4` and `V6`. These are known -as the *variants* of the enum: +listing the possible kinds an IP address can be, `V4` and `V6`. These are the +variants of the enum: ```rust -enum IpAddrKind { - V4, - V6, -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs:def}} ``` `IpAddrKind` is now a custom data type that we can use elsewhere in our code. @@ -32,13 +29,7 @@ enum IpAddrKind { We can create instances of each of the two variants of `IpAddrKind` like this: ```rust -# enum IpAddrKind { -# V4, -# V6, -# } -# -let four = IpAddrKind::V4; -let six = IpAddrKind::V6; +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs:instance}} ``` Note that the variants of the enum are namespaced under its identifier, and we @@ -48,64 +39,26 @@ both values `IpAddrKind::V4` and `IpAddrKind::V6` are of the same type: `IpAddrKind`: ```rust -# enum IpAddrKind { -# V4, -# V6, -# } -# -fn route(ip_type: IpAddrKind) { } +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs:fn}} ``` And we can call this function with either variant: ```rust -# enum IpAddrKind { -# V4, -# V6, -# } -# -# fn route(ip_type: IpAddrKind) { } -# -route(IpAddrKind::V4); -route(IpAddrKind::V6); +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-01-defining-enums/src/main.rs:fn_call}} ``` Using enums has even more advantages. Thinking more about our IP address type, at the moment we don’t have a way to store the actual IP address *data*; we only know what *kind* it is. Given that you just learned about structs in -Chapter 5, you might tackle this problem as shown in Listing 6-1: - -
+Chapter 5, you might tackle this problem as shown in Listing 6-1. ```rust -enum IpAddrKind { - V4, - V6, -} - -struct IpAddr { - kind: IpAddrKind, - address: String, -} - -let home = IpAddr { - kind: IpAddrKind::V4, - address: String::from("127.0.0.1"), -}; - -let loopback = IpAddr { - kind: IpAddrKind::V6, - address: String::from("::1"), -}; +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-01/src/main.rs:here}} ``` -
- -Listing 6-1: Storing the data and `IpAddrKind` variant of an IP address using a -`struct` - -
-
+Listing 6-1: Storing the data and `IpAddrKind` variant of +an IP address using a `struct` Here, we’ve defined a struct `IpAddr` that has two fields: a `kind` field that is of type `IpAddrKind` (the enum we defined previously) and an `address` field @@ -116,20 +69,13 @@ the value `IpAddrKind::V4` as its `kind` with associated address data of it. We’ve used a struct to bundle the `kind` and `address` values together, so now the variant is associated with the value. -We can represent the same concept in a more concise way using just an enum -rather than an enum as part of a struct by putting data directly into each enum +We can represent the same concept in a more concise way using just an enum, +rather than an enum inside a struct, by putting data directly into each enum variant. This new definition of the `IpAddr` enum says that both `V4` and `V6` variants will have associated `String` values: ```rust -enum IpAddr { - V4(String), - V6(String), -} - -let home = IpAddr::V4(String::from("127.0.0.1")); - -let loopback = IpAddr::V6(String::from("::1")); +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-02-enum-with-data/src/main.rs:here}} ``` We attach data to each variant of the enum directly, so there is no need for an @@ -143,34 +89,27 @@ still express `V6` addresses as one `String` value, we wouldn’t be able to wit a struct. Enums handle this case with ease: ```rust -enum IpAddr { - V4(u8, u8, u8, u8), - V6(String), -} - -let home = IpAddr::V4(127, 0, 0, 1); - -let loopback = IpAddr::V6(String::from("::1")); +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-03-variants-with-different-data/src/main.rs:here}} ``` -We’ve shown several different possibilities that we could define in our code -for storing IP addresses of the two different varieties using an enum. However, -as it turns out, wanting to store IP addresses and encode which kind they are -is so common that [the standard library has a definition we can -use!][IpAddr] Let’s look at how the standard library defines -`IpAddr`: it has the exact enum and variants that we’ve defined and used, but -it embeds the address data inside the variants in the form of two different -structs, which are defined differently for each variant: +We’ve shown several different ways to define data structures to store version +four and version six IP addresses. However, as it turns out, wanting to store +IP addresses and encode which kind they are is so common that [the standard +library has a definition we can use!][IpAddr] Let’s look at how +the standard library defines `IpAddr`: it has the exact enum and variants that +we’ve defined and used, but it embeds the address data inside the variants in +the form of two different structs, which are defined differently for each +variant: [IpAddr]: ../std/net/enum.IpAddr.html ```rust struct Ipv4Addr { - // details elided + // --snip-- } struct Ipv6Addr { - // details elided + // --snip-- } enum IpAddr { @@ -187,84 +126,51 @@ what you might come up with. Note that even though the standard library contains a definition for `IpAddr`, we can still create and use our own definition without conflict because we haven’t brought the standard library’s definition into our scope. We’ll talk -more about importing types in Chapter 7. +more about bringing types into scope in Chapter 7. Let’s look at another example of an enum in Listing 6-2: this one has a wide -variety of types embedded in its variants: - -
+variety of types embedded in its variants. ```rust -enum Message { - Quit, - Move { x: i32, y: i32 }, - Write(String), - ChangeColor(i32, i32, i32), -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-02/src/main.rs:here}} ``` -
- -Listing 6-2: A `Message` enum whose variants each store different amounts and -types of values - -
-
+Listing 6-2: A `Message` enum whose variants each store +different amounts and types of values This enum has four variants with different types: * `Quit` has no data associated with it at all. * `Move` includes an anonymous struct inside it. * `Write` includes a single `String`. -* `ChangeColor` includes three `i32`s. +* `ChangeColor` includes three `i32` values. -Defining an enum with variants like the ones in Listing 6-2 is similar to -defining different kinds of struct definitions except the enum doesn’t use the +Defining an enum with variants such as the ones in Listing 6-2 is similar to +defining different kinds of struct definitions, except the enum doesn’t use the `struct` keyword and all the variants are grouped together under the `Message` type. The following structs could hold the same data that the preceding enum variants hold: ```rust -struct QuitMessage; // unit struct -struct MoveMessage { - x: i32, - y: i32, -} -struct WriteMessage(String); // tuple struct -struct ChangeColorMessage(i32, i32, i32); // tuple struct +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-04-structs-similar-to-message-enum/src/main.rs:here}} ``` But if we used the different structs, which each have their own type, we -wouldn’t be able to as easily define a function that could take any of these -kinds of messages as we could with the `Message` enum defined in Listing 6-2, -which is a single type. +couldn’t as easily define a function to take any of these kinds of messages as +we could with the `Message` enum defined in Listing 6-2, which is a single type. There is one more similarity between enums and structs: just as we’re able to define methods on structs using `impl`, we’re also able to define methods on enums. Here’s a method named `call` that we could define on our `Message` enum: ```rust -# enum Message { -# Quit, -# Move { x: i32, y: i32 }, -# Write(String), -# ChangeColor(i32, i32, i32), -# } -# -impl Message { - fn call(&self) { - // method body would be defined here - } -} - -let m = Message::Write(String::from("hello")); -m.call(); +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-05-methods-on-enums/src/main.rs:here}} ``` The body of the method would use `self` to get the value that we called the method on. In this example, we’ve created a variable `m` that has the value -`Message::Write("hello")`, and that is what `self` will be in the body of the -`call` method when `m.call()` runs. +`Message::Write(String::from("hello"))`, and that is what `self` will be in the +body of the `call` method when `m.call()` runs. Let’s look at another enum in the standard library that is very common and useful: `Option`. @@ -277,8 +183,9 @@ This section explores a case study of `Option`, which is another enum defined by the standard library. The `Option` type is used in many places because it encodes the very common scenario in which a value could be something or it could be nothing. Expressing this concept in terms of the type system means the -compiler can check that you’ve handled all the cases you should be handling, -which can prevent bugs that are extremely common in other programming languages. +compiler can check whether you’ve handled all the cases you should be handling; +this functionality can prevent bugs that are extremely common in other +programming languages. Programming language design is often thought of in terms of which features you include, but the features you exclude are important too. Rust doesn’t have the @@ -286,27 +193,26 @@ null feature that many other languages have. *Null* is a value that means there is no value there. In languages with null, variables can always be in one of two states: null or not-null. -In “Null References: The Billion Dollar Mistake,” Tony Hoare, the inventor of -null, has this to say: +In his 2009 presentation “Null References: The Billion Dollar Mistake,” Tony +Hoare, the inventor of null, has this to say: > I call it my billion-dollar mistake. At that time, I was designing the first > comprehensive type system for references in an object-oriented language. My > goal was to ensure that all use of references should be absolutely safe, with -> checking performed automatically by the compiler. But I couldn't resist the +> checking performed automatically by the compiler. But I couldn’t resist the > temptation to put in a null reference, simply because it was so easy to > implement. This has led to innumerable errors, vulnerabilities, and system > crashes, which have probably caused a billion dollars of pain and damage in > the last forty years. -The problem with null values is that if you try to actually use a value that’s -null as if it is a not-null value, you’ll get an error of some kind. Because -this null or not-null property is pervasive, it’s extremely easy to make this -kind of error. +The problem with null values is that if you try to use a null value as a +not-null value, you’ll get an error of some kind. Because this null or not-null +property is pervasive, it’s extremely easy to make this kind of error. However, the concept that null is trying to express is still a useful one: a null is a value that is currently invalid or absent for some reason. -The problem isn’t with the actual concept but with the particular +The problem isn’t really with the concept but with the particular implementation. As such, Rust does not have nulls, but it does have an enum that can encode the concept of a value being present or absent. This enum is `Option`, and it is [defined by the standard library][option] @@ -322,10 +228,10 @@ enum Option { ``` The `Option` enum is so useful that it’s even included in the prelude; you -don’t need to import it explicitly. In addition, so are its variants: you can -use `Some` and `None` directly without prefixing them with `Option::`. -`Option` is still just a regular enum, and `Some(T)` and `None` are still -variants of type `Option`. +don’t need to bring it into scope explicitly. In addition, so are its variants: +you can use `Some` and `None` directly without the `Option::` prefix. The +`Option` enum is still just a regular enum, and `Some(T)` and `None` are +still variants of type `Option`. The `` syntax is a feature of Rust we haven’t talked about yet. It’s a generic type parameter, and we’ll cover generics in more detail in Chapter 10. @@ -334,47 +240,35 @@ For now, all you need to know is that `` means the `Some` variant of the using `Option` values to hold number types and string types: ```rust -let some_number = Some(5); -let some_string = Some("a string"); - -let absent_number: Option = None; +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/src/main.rs:here}} ``` If we use `None` rather than `Some`, we need to tell Rust what type of -`Option` we have, because the compiler can't infer the type that the `Some` +`Option` we have, because the compiler can’t infer the type that the `Some` variant will hold by looking only at a `None` value. -When we have a `Some` value, we know that a value is present, and the value is +When we have a `Some` value, we know that a value is present and the value is held within the `Some`. When we have a `None` value, in some sense, it means the same thing as null: we don’t have a valid value. So why is having `Option` any better than having null? In short, because `Option` and `T` (where `T` can be any type) are different -types, the compiler won’t let us use an `Option` value as if it was +types, the compiler won’t let us use an `Option` value as if it were definitely a valid value. For example, this code won’t compile because it’s -trying to compare an `Option` to an `i8`: +trying to add an `i8` to an `Option`: -```rust,ignore -let x: i8 = 5; -let y: Option = Some(5); - -let sum = x + y; +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/src/main.rs:here}} ``` If we run this code, we get an error message like this: -```text -error[E0277]: the trait bound `i8: std::ops::Add>` is -not satisfied - --> - | -7 | let sum = x + y; - | ^^^^^ - | +```console +{{#include ../listings/ch06-enums-and-pattern-matching/no-listing-07-cant-use-option-directly/output.txt}} ``` Intense! In effect, this error message means that Rust doesn’t understand how -to add an `Option` and an `i8`, because they’re different types. When we +to add an `i8` and an `Option`, because they’re different types. When we have a value of a type like `i8` in Rust, the compiler will ensure that we always have a valid value. We can proceed confidently without having to check for null before using that value. Only when we have an `Option` (or @@ -387,14 +281,14 @@ perform `T` operations with it. Generally, this helps catch one of the most common issues with null: assuming that something isn’t null when it actually is. -Not having to worry about missing an assumption of having a not-null value -helps you to be more confident in your code. In order to have a value that can -possibly be null, you must explicitly opt in by making the type of that value -`Option`. Then, when you use that value, you are required to explicitly -handle the case when the value is null. Everywhere that a value has a type that -isn’t an `Option`, you *can* safely assume that the value isn’t null. This -was a deliberate design decision for Rust to limit null’s pervasiveness and -increase the safety of Rust code. +Not having to worry about incorrectly assuming a not-null value helps you to be +more confident in your code. In order to have a value that can possibly be +null, you must explicitly opt in by making the type of that value `Option`. +Then, when you use that value, you are required to explicitly handle the case +when the value is null. Everywhere that a value has a type that isn’t an +`Option`, you *can* safely assume that the value isn’t null. This was a +deliberate design decision for Rust to limit null’s pervasiveness and increase +the safety of Rust code. So, how do you get the `T` value out of a `Some` variant when you have a value of type `Option` so you can use that value? The `Option` enum has a large @@ -404,10 +298,10 @@ the methods on `Option` will be extremely useful in your journey with Rust. [docs]: ../std/option/enum.Option.html -In general, in order to use an `Option` value, we want to have code that -will handle each variant. We want some code that will run only when we have a -`Some(T)` value, and this code is allowed to use the inner `T`. We want some -other code to run if we have a `None` value, and that code doesn’t have a `T` +In general, in order to use an `Option` value, you want to have code that +will handle each variant. You want some code that will run only when you have a +`Some(T)` value, and this code is allowed to use the inner `T`. You want some +other code to run if you have a `None` value, and that code doesn’t have a `T` value available. The `match` expression is a control flow construct that does just this when used with enums: it will run different code depending on which variant of the enum it has, and that code can use the data inside the matching diff --git a/src/ch06-02-match.md b/src/ch06-02-match.md index 4adf4c1..5110c0d 100644 --- a/src/ch06-02-match.md +++ b/src/ch06-02-match.md @@ -1,58 +1,37 @@ ## The `match` Control Flow Operator -Rust has an extremely powerful control-flow operator called `match` that allows -us to compare a value against a series of patterns and then execute code based +Rust has an extremely powerful control flow operator called `match` that allows +you to compare a value against a series of patterns and then execute code based on which pattern matches. Patterns can be made up of literal values, variable -names, wildcards, and many other things; Chapter 18 will be about all the -different kinds of patterns and what they do. The power of `match` comes from -the expressiveness of the patterns and the compiler checks that make sure all +names, wildcards, and many other things; Chapter 18 covers all the different +kinds of patterns and what they do. The power of `match` comes from the +expressiveness of the patterns and the fact that the compiler confirms that all possible cases are handled. -Think of a `match` expression kind of like a coin sorting machine: coins slide +Think of a `match` expression as being like a coin-sorting machine: coins slide down a track with variously sized holes along it, and each coin falls through the first hole it encounters that it fits into. In the same way, values go through each pattern in a `match`, and at the first pattern the value “fits,” -the value will fall into the associated code block to be used during execution. +the value falls into the associated code block to be used during execution. Because we just mentioned coins, let’s use them as an example using `match`! We can write a function that can take an unknown United States coin and, in a similar way as the counting machine, determine which coin it is and return its -value in cents, as shown here in Listing 6-3: - -
+value in cents, as shown here in Listing 6-3. ```rust -enum Coin { - Penny, - Nickel, - Dime, - Quarter, -} - -fn value_in_cents(coin: Coin) -> i32 { - match coin { - Coin::Penny => 1, - Coin::Nickel => 5, - Coin::Dime => 10, - Coin::Quarter => 25, - } -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-03/src/main.rs:here}} ``` -
- -Listing 6-3: An enum and a `match` expression that has the variants of the enum -as its patterns. - -
-
+Listing 6-3: An enum and a `match` expression that has +the variants of the enum as its patterns Let’s break down the `match` in the `value_in_cents` function. First, we list the `match` keyword followed by an expression, which in this case is the value `coin`. This seems very similar to an expression used with `if`, but there’s a -big difference: with `if`, the expression needs to return a boolean value. -Here, it can be any type. The type of `coin` in this example is the `Coin` enum -that we defined in Listing 6-3. +big difference: with `if`, the expression needs to return a Boolean value, but +here, it can be any type. The type of `coin` in this example is the `Coin` enum +that we defined on line 1. Next are the `match` arms. An arm has two parts: a pattern and some code. The first arm here has a pattern that is the value `Coin::Penny` and then the `=>` @@ -62,78 +41,42 @@ is just the value `1`. Each arm is separated from the next with a comma. When the `match` expression executes, it compares the resulting value against the pattern of each arm, in order. If a pattern matches the value, the code associated with that pattern is executed. If that pattern doesn’t match the -value, execution continues to the next arm, much like a coin sorting machine. +value, execution continues to the next arm, much as in a coin-sorting machine. We can have as many arms as we need: in Listing 6-3, our `match` has four arms. The code associated with each arm is an expression, and the resulting value of the expression in the matching arm is the value that gets returned for the entire `match` expression. -Curly braces typically aren’t used if the match arm code is short, as it is in -Listing 6-3 where each arm just returns a value. If you want to run multiple -lines of code in a match arm, you can use curly braces. For example, the -following code would print out “Lucky penny!” every time the method was called -with a `Coin::Penny` but would still return the last value of the block, `1`: +Curly brackets typically aren’t used if the match arm code is short, as it is +in Listing 6-3 where each arm just returns a value. If you want to run multiple +lines of code in a match arm, you can use curly brackets. For example, the +following code would print “Lucky penny!” every time the method was called with +a `Coin::Penny` but would still return the last value of the block, `1`: ```rust -# enum Coin { -# Penny, -# Nickel, -# Dime, -# Quarter, -# } -# -fn value_in_cents(coin: Coin) -> i32 { - match coin { - Coin::Penny => { - println!("Lucky penny!"); - 1 - }, - Coin::Nickel => 5, - Coin::Dime => 10, - Coin::Quarter => 25, - } -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-08-match-arm-multiple-lines/src/main.rs:here}} ``` ### Patterns that Bind to Values -Another useful feature of match arms is that they can bind to parts of the +Another useful feature of match arms is that they can bind to the parts of the values that match the pattern. This is how we can extract values out of enum variants. As an example, let’s change one of our enum variants to hold data inside it. -From 1999 through 2008, the United States printed quarters with different +From 1999 through 2008, the United States minted quarters with different designs for each of the 50 states on one side. No other coins got state designs, so only quarters have this extra value. We can add this information to -our `enum` by changing the `Quarter` variant to include a `State` value stored -inside it, which we've done here in Listing 6-4: - -
+our `enum` by changing the `Quarter` variant to include a `UsState` value stored +inside it, which we’ve done here in Listing 6-4. ```rust -#[derive(Debug)] // So we can inspect the state in a minute -enum UsState { - Alabama, - Alaska, - // ... etc -} - -enum Coin { - Penny, - Nickel, - Dime, - Quarter(UsState), -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-04/src/main.rs:here}} ``` -
- -Listing 6-4: A `Coin` enum where the `Quarter` variant also holds a `UsState` -value - -
-
+Listing 6-4: A `Coin` enum in which the `Quarter` variant +also holds a `UsState` value Let’s imagine that a friend of ours is trying to collect all 50 state quarters. While we sort our loose change by coin type, we’ll also call out the name of @@ -146,30 +89,7 @@ pattern that matches values of the variant `Coin::Quarter`. When a quarter’s state. Then we can use `state` in the code for that arm, like so: ```rust -# #[derive(Debug)] -# enum UsState { -# Alabama, -# Alaska, -# } -# -# enum Coin { -# Penny, -# Nickel, -# Dime, -# Quarter(UsState), -# } -# -fn value_in_cents(coin: Coin) -> i32 { - match coin { - Coin::Penny => 1, - Coin::Nickel => 5, - Coin::Dime => 10, - Coin::Quarter(state) => { - println!("State quarter from {:?}!", state); - 25 - }, - } -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-09-variable-in-pattern/src/main.rs:here}} ``` If we were to call `value_in_cents(Coin::Quarter(UsState::Alaska))`, `coin` @@ -181,71 +101,52 @@ state value out of the `Coin` enum variant for `Quarter`. ### Matching with `Option` -In the previous section we wanted to get the inner `T` value out of the `Some` +In the previous section, we wanted to get the inner `T` value out of the `Some` case when using `Option`; we can also handle `Option` using `match` as we did with the `Coin` enum! Instead of comparing coins, we’ll compare the variants of `Option`, but the way that the `match` expression works remains the same. -Let’s say we want to write a function that takes an `Option`, and if -there’s a value inside, adds one to that value. If there isn’t a value inside, +Let’s say we want to write a function that takes an `Option` and, if +there’s a value inside, adds 1 to that value. If there isn’t a value inside, the function should return the `None` value and not attempt to perform any operations. This function is very easy to write, thanks to `match`, and will look like -Listing 6-5: - -
+Listing 6-5. ```rust -fn plus_one(x: Option) -> Option { - match x { - None => None, - Some(i) => Some(i + 1), - } -} - -let five = Some(5); -let six = plus_one(five); -let none = plus_one(None); +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs:here}} ``` -
- -Listing 6-5: A function that uses a `match` expression on an `Option` - -
-
- -#### Matching `Some(T)` +Listing 6-5: A function that uses a `match` expression on +an `Option` Let’s examine the first execution of `plus_one` in more detail. When we call `plus_one(five)`, the variable `x` in the body of `plus_one` will have the value `Some(5)`. We then compare that against each match arm. ```rust,ignore -None => None, +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs:first_arm}} ``` The `Some(5)` value doesn’t match the pattern `None`, so we continue to the next arm. ```rust,ignore -Some(i) => Some(i + 1), +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs:second_arm}} ``` -Does `Some(5)` match `Some(i)`? Why yes it does! We have the same variant. -The `i` binds to the value contained in `Some`, so `i` takes the value `5`. The -code in the match arm is then executed, so we add one to the value of `i` and +Does `Some(5)` match `Some(i)`? Why yes it does! We have the same variant. The +`i` binds to the value contained in `Some`, so `i` takes the value `5`. The +code in the match arm is then executed, so we add 1 to the value of `i` and create a new `Some` value with our total `6` inside. -#### Matching `None` - -Now let’s consider the second call of `plus_one` in Listing 6-5 where `x` is +Now let’s consider the second call of `plus_one` in Listing 6-5, where `x` is `None`. We enter the `match` and compare to the first arm. ```rust,ignore -None => None, +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs:first_arm}} ``` It matches! There’s no value to add to, so the program stops and returns the @@ -261,26 +162,18 @@ consistently a user favorite. ### Matches Are Exhaustive There’s one other aspect of `match` we need to discuss. Consider this version -of our `plus_one` function: +of our `plus_one` function that has a bug and won’t compile: -```rust,ignore -fn plus_one(x: Option) -> Option { - match x { - Some(i) => Some(i + 1), - } -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/src/main.rs:here}} ``` We didn’t handle the `None` case, so this code will cause a bug. Luckily, it’s a bug Rust knows how to catch. If we try to compile this code, we’ll get this error: -```text -error[E0004]: non-exhaustive patterns: `None` not covered - --> - | -6 | match x { - | ^ pattern `None` not covered +```console +{{#include ../listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/output.txt}} ``` Rust knows that we didn’t cover every possible case and even knows which @@ -288,25 +181,18 @@ pattern we forgot! Matches in Rust are *exhaustive*: we must exhaust every last possibility in order for the code to be valid. Especially in the case of `Option`, when Rust prevents us from forgetting to explicitly handle the `None` case, it protects us from assuming that we have a value when we might -have null, thus making the billion dollar mistake discussed earlier. +have null, thus making the billion-dollar mistake discussed earlier impossible. ### The `_` Placeholder -Rust also has a pattern we can use in situations when we don’t want to list all -possible values. For example, a `u8` can have valid values of 0 through 255. If -we only care about the values 1, 3, 5, and 7, we don’t want to have to list out -0, 2, 4, 6, 8, 9 all the way up to 255. Fortunately, we don’t have to: we can -use the special pattern `_` instead: +Rust also has a pattern we can use when we don’t want to list all possible +values. For example, a `u8` can have valid values of 0 through 255. If we only +care about the values 1, 3, 5, and 7, we don’t want to have to list out 0, 2, +4, 6, 8, 9 all the way up to 255. Fortunately, we don’t have to: we can use the +special pattern `_` instead: ```rust -let some_u8_value = 0u8; -match some_u8_value { - 1 => println!("one"), - 3 => println!("three"), - 5 => println!("five"), - 7 => println!("seven"), - _ => (), -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-11-underscore-placeholder/src/main.rs:here}} ``` The `_` pattern will match any value. By putting it after our other arms, the @@ -316,4 +202,9 @@ can say that we want to do nothing for all the possible values that we don’t list before the `_` placeholder. However, the `match` expression can be a bit wordy in a situation in which we -only care about *one* of the cases. For this situation, Rust provides `if let`. +care about only *one* of the cases. For this situation, Rust provides `if let`. + +More about patterns and matching can be found in [chapter 18][ch18-00-patterns]. + +[ch18-00-patterns]: +ch18-00-patterns.html diff --git a/src/ch06-03-if-let.md b/src/ch06-03-if-let.md index 7c62616..3eb0cc3 100644 --- a/src/ch06-03-if-let.md +++ b/src/ch06-03-if-let.md @@ -1,27 +1,16 @@ ## Concise Control Flow with `if let` The `if let` syntax lets you combine `if` and `let` into a less verbose way to -handle values that match one pattern and ignore the rest. Consider the program -in Listing 6-6 that matches on an `Option` value but only wants to execute -code if the value is three: - -
+handle values that match one pattern while ignoring the rest. Consider the +program in Listing 6-6 that matches on an `Option` value but only wants to +execute code if the value is 3. ```rust -let some_u8_value = Some(0u8); -match some_u8_value { - Some(3) => println!("three"), - _ => (), -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-06/src/main.rs:here}} ``` -
- -Listing 6-6: A `match` that only cares about executing code when the value is -`Some(3)` - -
-
+Listing 6-6: A `match` that only cares about executing +code when the value is `Some(3)` We want to do something with the `Some(3)` match but do nothing with any other `Some` value or the `None` value. To satisfy the `match` expression, we @@ -32,21 +21,18 @@ Instead, we could write this in a shorter way using `if let`. The following code behaves the same as the `match` in Listing 6-6: ```rust -# let some_u8_value = Some(0u8); -if let Some(3) = some_u8_value { - println!("three"); -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/src/main.rs:here}} ``` -`if let` takes a pattern and an expression separated by an `=`. It works the -same way as a `match`, where the expression is given to the `match` and the -pattern is its first arm. +The syntax `if let` takes a pattern and an expression separated by an equal +sign. It works the same way as a `match`, where the expression is given to the +`match` and the pattern is its first arm. -Using `if let` means you have less to type, less indentation, and less -boilerplate code. However, we’ve lost the exhaustive checking that `match` -enforces. Choosing between `match` and `if let` depends on what you’re doing in -your particular situation and if gaining conciseness is an appropriate -trade-off for losing exhaustive checking. +Using `if let` means less typing, less indentation, and less boilerplate code. +However, you lose the exhaustive checking that `match` enforces. Choosing +between `match` and `if let` depends on what you’re doing in your particular +situation and whether gaining conciseness is an appropriate trade-off for +losing exhaustive checking. In other words, you can think of `if let` as syntax sugar for a `match` that runs code when the value matches one pattern and then ignores all other values. @@ -60,48 +46,13 @@ announcing the state of the quarters, we could do that with a `match` expression like this: ```rust -# #[derive(Debug)] -# enum UsState { -# Alabama, -# Alaska, -# } -# -# enum Coin { -# Penny, -# Nickel, -# Dime, -# Quarter(UsState), -# } -# let coin = Coin::Penny; -let mut count = 0; -match coin { - Coin::Quarter(state) => println!("State quarter from {:?}!", state), - _ => count += 1, -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-13-count-and-announce-match/src/main.rs:here}} ``` Or we could use an `if let` and `else` expression like this: ```rust -# #[derive(Debug)] -# enum UsState { -# Alabama, -# Alaska, -# } -# -# enum Coin { -# Penny, -# Nickel, -# Dime, -# Quarter(UsState), -# } -# let coin = Coin::Penny; -let mut count = 0; -if let Coin::Quarter(state) = coin { - println!("State quarter from {:?}!", state); -} else { - count += 1; -} +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/no-listing-14-count-and-announce-if-let-else/src/main.rs:here}} ``` If you have a situation in which your program has logic that is too verbose to @@ -117,7 +68,7 @@ values, depending on how many cases you need to handle. Your Rust programs can now express concepts in your domain using structs and enums. Creating custom types to use in your API ensures type safety: the -compiler will make certain your functions only get values of the type each +compiler will make certain your functions get only values of the type each function expects. In order to provide a well-organized API to your users that is straightforward diff --git a/src/ch07-00-managing-growing-projects-with-packages-crates-and-modules.md b/src/ch07-00-managing-growing-projects-with-packages-crates-and-modules.md new file mode 100644 index 0000000..b61cae4 --- /dev/null +++ b/src/ch07-00-managing-growing-projects-with-packages-crates-and-modules.md @@ -0,0 +1,49 @@ +# Managing Growing Projects with Packages, Crates, and Modules + +As you write large programs, organizing your code will be important because +keeping track of your entire program in your head will become impossible. By +grouping related functionality and separating code with distinct features, +you’ll clarify where to find code that implements a particular feature and +where to go to change how a feature works. + +The programs we’ve written so far have been in one module in one file. As a +project grows, you can organize code by splitting it into multiple modules and +then multiple files. A package can contain multiple binary crates and +optionally one library crate. As a package grows, you can extract parts into +separate crates that become external dependencies. This chapter covers all +these techniques. For very large projects of a set of interrelated packages +that evolve together, Cargo provides workspaces, which we’ll cover in the +[“Cargo Workspaces”][workspaces] section in Chapter 14. + +In addition to grouping functionality, encapsulating implementation details +lets you reuse code at a higher level: once you’ve implemented an operation, +other code can call that code via the code’s public interface without knowing +how the implementation works. The way you write code defines which parts are +public for other code to use and which parts are private implementation details +that you reserve the right to change. This is another way to limit the amount +of detail you have to keep in your head. + +A related concept is scope: the nested context in which code is written has a +set of names that are defined as “in scope.” When reading, writing, and +compiling code, programmers and compilers need to know whether a particular +name at a particular spot refers to a variable, function, struct, enum, module, +constant, or other item and what that item means. You can create scopes and +change which names are in or out of scope. You can’t have two items with the +same name in the same scope; tools are available to resolve name conflicts. + +Rust has a number of features that allow you to manage your code’s +organization, including which details are exposed, which details are private, +and what names are in each scope in your programs. These features, sometimes +collectively referred to as the *module system*, include: + +* **Packages:** A Cargo feature that lets you build, test, and share crates +* **Crates:** A tree of modules that produces a library or executable +* **Modules** and **use:** Let you control the organization, scope, and + privacy of paths +* **Paths:** A way of naming an item, such as a struct, function, or module + +In this chapter, we’ll cover all these features, discuss how they interact, and +explain how to use them to manage scope. By the end, you should have a solid +understanding of the module system and be able to work with scopes like a pro! + +[workspaces]: ch14-03-cargo-workspaces.html diff --git a/src/ch07-00-modules.md b/src/ch07-00-modules.md deleted file mode 100644 index 19ff0f9..0000000 --- a/src/ch07-00-modules.md +++ /dev/null @@ -1,23 +0,0 @@ -# Modules - -When you start writing programs in Rust, your code might live solely in the -`main` function. As your code grows, you’ll eventually move functionality out -into other functions, both for re-use and for better organization. By splitting -your code up into smaller chunks, each chunk is easier to understand on its -own. But what happens if you find yourself with too many functions? Rust has a -module system that handles the problem of wanting to re-use code while -keeping your code organized. - -In the same way that you extract lines of code into a function, you can extract -functions (and other code like structs and enums too) into different modules. A -*module* is a namespace that contains definitions of functions or types, and -you can choose whether those definitions are visible outside their module -(public) or not (private). Here’s an overview of how modules work: - -* You declare a new module with the keyword `mod` -* By default, everything is set as private, but you can use the `pub` keyword - to make the module public, and therefore visible outside of the namespace. -* The `use` keyword allows you to bring modules, or the definitions inside - modules, into scope so that it’s easier to refer to them. - -We’ll take a look at each of these parts and see how they fit into the whole. diff --git a/src/ch07-01-mod-and-the-filesystem.md b/src/ch07-01-mod-and-the-filesystem.md deleted file mode 100644 index 193877f..0000000 --- a/src/ch07-01-mod-and-the-filesystem.md +++ /dev/null @@ -1,484 +0,0 @@ -## `mod` and the Filesystem - -We’ll start our module example by making a new project with Cargo, but instead -of creating a binary crate, we’re going to make a library crate: a project that -other people can pull into their projects as a dependency. We saw this with the -`rand` crate in Chapter 2. - -We’ll create a skeleton of a library that provides some general networking -functionality; we’re going to concentrate on the organization of the modules -and functions, but not worry about what code goes in the function bodies. We’ll -call our library `communicator`. By default, cargo will create a library unless -another type of project is specified, so if we leave off the `--bin` option -that we’ve been using so far our project will be a library: - -```text -$ cargo new communicator -$ cd communicator -``` - -Notice that Cargo generated *src/lib.rs* instead of *src/main.rs*. Inside -*src/lib.rs* we’ll find this: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} -``` - -Cargo creates an empty test to help us get our library started, rather -than the “Hello, world!” binary that we get with the `--bin` option. We’ll look -at the `#[]` and `mod tests` syntax a little later, but for now just make sure -to leave it in your *src/lib.rs*. - -Since we don’t have a *src/main.rs*, there’s nothing for Cargo to execute with -the `cargo run` command. Therefore, we will be using the `cargo build` command -to only compile our library crate’s code. - -We’re going to look at different options for organizing your library’s code -which will be suitable in a variety of situations, depending on the intentions -you have for your code. - -### Module Definitions - -For our `communicator` networking library, we’re first going to define a module -named `network` that contains the definition of a function called `connect`. -Every module definition in Rust starts with the `mod` keyword. Add this code to -the beginning of the *lib.rs* file, above the test code: - -Filename: src/lib.rs - -```rust -mod network { - fn connect() { - } -} -``` - -After the `mod` keyword, we put the name of the module, `network`, then a block -of code in curly braces. Everything inside this block is inside the namespace -`network`. In this case, we have a single function, `connect`. If we wanted to -call this function from a script outside the `network` module, we would need to -specify the module and use the namespace syntax `::`, like so: -`network::connect()`, rather than just `connect()`. - -We can also have multiple modules, side-by-side, in the same *src/lib.rs* file. -For example, to have a `client` module too, that also has a function named -`connect`, we can add: - -
-Filename: src/lib.rs - -```rust -mod network { - fn connect() { - } -} - -mod client { - fn connect() { - } -} -``` - -
- -Listing 7-1: The `network` module and the `client` module defined side-by-side -in *src/lib.rs* - -
-
- -Now we have a `network::connect` function and a `client::connect` function. -These can have completely different functionality, and the function names do -not conflict with each other since they’re in different modules. - -While in this case, we’re building a library, there's nothing special about -*lib.rs*. We could also make use of submodules in a *main.rs* as well. In fact, -we can also put modules inside of modules. This can be useful as your modules -grow to keep related functionality organized together and separate -functionality apart. The choice of how you organize your code depends on how -you think about the relationship between the parts of your code. For instance, -the `client` code and its `connect` function might make more sense to users of -our library if it was inside the `network` namespace instead, like so: - -
-Filename: src/lib.rs - -```rust -mod network { - fn connect() { - } - - mod client { - fn connect() { - } - } -} -``` - -
- -Listing 7-2: Moving the `client` module inside of the `network` module - -
-
- -In your *src/lib.rs* file, replace the existing `mod network` and `mod client` -definitions with this one that has the `client` module as an inner module of -`network`. Now we have the functions `network::connect` and -`network::client::connect`: again, the two functions named `connect` don’t -conflict with each other since they’re in different namespaces. - -In this way, modules form a hierarchy. The contents of *src/lib.rs* are at the -topmost level, and the submodules are at lower levels. Here’s what the -organization of our example from Listing 7-1 looks like when thought of this -way: - -```text -communicator - ├── network - └── client -``` - -And here’s the example from Listing 7-2: - -```text -communicator - └── network - └── client -``` - -You can see that in Listing 7-2, `client` is a child of the `network` module, -rather than a sibling. More complicated projects can have a lot of modules, and -they’ll need to be organized logically in order to keep track of them. What -“logically” means in your project is up to you and depends on how you and users -of your library think about your project’s domain. Use the techniques we’ve -shown here to create side-by-side modules and nested modules in whatever -structure you would like. - -### Moving Modules to Other Files - -Modules form a hierarchical structure, much like another structure in computing -that you’re used to: file systems! We can use Rust’s module system along with -multiple files to split Rust projects up so that not everything lives in -*src/lib.rs*. For this example, we will start with this code in *src/lib.rs*: - -
-File: src/lib.rs - -```rust -mod client { - fn connect() { - } -} - -mod network { - fn connect() { - } - - mod server { - fn connect() { - } - } -} -``` - -
- -Listing 7-3: Three modules, `client`, `network`, and `network::server` all -defined in *src/lib.rs* - -
-
- -which has this module hierarchy: - -```text -communicator - ├── client - └── network - └── server -``` - -If these modules had many functions, and each function was getting long, we -would have to scroll through this file to find the code we wanted to work with. -This would be a good reason to pull each of the `client`, `network`, and -`server` modules out of *src/lib.rs* and into their own files. Let’s start by -extracting the `client` module into another file. First, replace the `client` -module code in *src/lib.rs* with the following: - -File: src/lib.rs - -```rust,ignore -mod client; - -mod network { - fn connect() { - } - - mod server { - fn connect() { - } - } -} -``` - - - -We’re still *defining* the `client` module here, but by removing the curly -braces and definitions inside the `client` module and replacing them with a -semicolon, we’re letting Rust know to look in another location for the code -defined inside that module. - -So now we need to create the external file with that module name. Create a -*client.rs* file in your *src/* directory, then open it up and enter the -following, which is the `connect` function in the `client` module that we -removed in the previous step: - -File: src/client.rs - -```rust -fn connect() { -} -``` - -Note that we don’t need a `mod` declaration in this file; that’s because we -already declared the `client` module with `mod` in *src/lib.rs*. This file just -provides the *contents* of the `client` module. If we put a `mod client` here, -we’d be giving the `client` module its own submodule named `client`! - -Rust only knows to look in *src/lib.rs* by default. If we want to add more -files to our project, we need to tell Rust in *src/lib.rs* to look in other -files; this is why `mod client` needs to be defined in *src/lib.rs* and can’t -be defined in *src/client.rs*. - -Now, everything should compile successfully, though you’ll get a few warnings. -Remember to use `cargo build` instead of `cargo run` since we have a library -crate rather than a binary crate: - -```text -$ cargo build - Compiling communicator v0.1.0 (file:///projects/communicator) - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/client.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/lib.rs:4:5 - | -4 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/lib.rs:8:9 - | -8 | fn connect() { - | ^ -``` - -These warnings tell us that we have functions that are never used. Don’t worry -about those warnings for now; we’ll address them later in the chapter. The good -news is that they’re just warnings; our project was built successfully! - -Let’s extract the `network` module into its own file next, using the same -pattern. In *src/lib.rs*, delete the body of the `network` module and add a -semicolon to the declaration, like so: - -Filename: src/lib.rs - -```rust,ignore -mod client; - -mod network; -``` - -Then create a new *src/network.rs* file and enter the following: - -Filename: src/network.rs - -```rust -fn connect() { -} - -mod server { - fn connect() { - } -} -``` - -Notice that we still have a `mod` declaration within this module file; -this is because we still want `server` to be a sub-module of `network`. - -Now run `cargo build` again. Success! We have one more module to extract: -`server`. Because it’s a sub-module—that is, a module within a module—our -current tactic of extracting a module into a file named after that module won’t -work. We’re going to try anyway so that we can see the error. First change -*src/network.rs* to have `mod server;` instead of the `server` module’s -contents: - -Filename: src/network.rs - -```rust,ignore -fn connect() { -} - -mod server; -``` - -Then create a *src/server.rs* file and enter the contents of the `server` -module that we extracted: - -Filename: src/server.rs - -```rust -fn connect() { -} -``` - -When we try to `cargo build`, we’ll get this error: - -
- -```text -$ cargo build - Compiling communicator v0.1.0 (file:///projects/communicator) -error: cannot declare a new module at this location - --> src/network.rs:4:5 - | -4 | mod server; - | ^^^^^^ - | -note: maybe move this module `network` to its own directory via `network/mod.rs` - --> src/network.rs:4:5 - | -4 | mod server; - | ^^^^^^ -note: ... or maybe `use` the module `server` instead of possibly redeclaring it - --> src/network.rs:4:5 - | -4 | mod server; - | ^^^^^^ -``` - -
- -Listing 7-4: Error when trying to extract the `server` submodule into -*src/server.rs* - -
-
- -The error says we `cannot declare a new module at this location` and is -pointing to the `mod server;` line in *src/network.rs*. So *src/network.rs* is -different than *src/lib.rs* somehow; let’s keep reading to understand why. - -The note in the middle of Listing 7-4 is actually pretty helpful, as it points -out something we haven’t yet talked about doing: - -> note: maybe move this module `network` to its own directory via -`network/mod.rs` - -Instead of continuing to follow the same file naming pattern we used -previously, we can do what the note suggests: - -1. Make a new *directory* named *network*, the parent module’s name -2. Move the *src/network.rs* file into the new *network* directory and rename - it so that it is now *src/network/mod.rs* -3. Move the submodule file *src/server.rs* into the *network* directory - -Here are commands to carry out these steps: - -```text -$ mkdir src/network -$ mv src/network.rs src/network/mod.rs -$ mv src/server.rs src/network -``` - -Now if we try to `cargo build`, compilation will work (we’ll still have -warnings though). Our module layout still looks like this, which is exactly the -same as it did when we had all the code in *src/lib.rs* in Listing 7-3: - -```text -communicator - ├── client - └── network - └── server -``` - -The corresponding file layout now looks like this: - -```text -├── src -│   ├── client.rs -│   ├── lib.rs -│   └── network -│   ├── mod.rs -│   └── server.rs -``` - -So when we wanted to extract the `network::server` module, why did we have to -also change the *src/network.rs* file into the *src/network/mod.rs* file, and -also put the code for `network::server` in the `network` directory in -*src/network/server.rs*, instead of just being able to extract the -`network::server` into *src/server.rs*? The reason is that Rust wouldn’t be -able to tell that `server` was supposed to be a submodule of `network` if the -*server.rs* file was in the *src* directory. To make it clearer why Rust can’t -tell, let’s consider a different example where we have this module hierarchy -with all the definitions in *src/lib.rs*: - -```text -communicator - ├── client - └── network - └── client -``` - -In this example, we have three modules again, `client`, `network`, and -`network::client`. If we follow the same steps we originally did above for -extracting modules into files, for the `client` module we would create -*src/client.rs*. For the `network` module, we would create *src/network.rs*. -Then we wouldn’t be able to extract the `network::client` module into a -*src/client.rs* file, because that already exists for the top-level `client` -module! If we put the code in both the `client` and `network::client` modules -in the *src/client.rs* file, Rust would not have any way to know whether the -code was for `client` or for `network::client`. - -Therefore, once we wanted to extract a file for the `network::client` submodule -of the `network` module, we needed to create a directory for the `network` -module instead of a *src/network.rs* file. The code that is in the `network` -module then goes into the *src/network/mod.rs* file, and the submodule -`network::client` can have its own *src/network/client.rs* file. Now the -top-level *src/client.rs* is unambiguously the code that belongs to the -`client` module. - -### Rules of Module File Systems - -In summary, these are the rules of modules with regards to files: - -* If a module named `foo` has no submodules, you should put the declarations - for `foo` in a file named *foo.rs*. -* If a module named `foo` does have submodules, you should put the declarations - for `foo` in a file named *foo/mod.rs*. -* The first two rules apply recursively, so that if a module named `foo` has a - submodule named `bar` and `bar` does not have submodules, you should have the - following files in your *src* directory: - - ```text - ├── foo - │   ├── bar.rs (contains the declarations in `foo::bar`) - │   └── mod.rs (contains the declarations in `foo`, including `mod bar`) - ``` - -* The modules themselves should be declared in their parent module’s file using - the `mod` keyword. - -Next, we’ll talk about the `pub` keyword, and get rid of those warnings! diff --git a/src/ch07-01-packages-and-crates.md b/src/ch07-01-packages-and-crates.md new file mode 100644 index 0000000..a24b608 --- /dev/null +++ b/src/ch07-01-packages-and-crates.md @@ -0,0 +1,64 @@ +## Packages and Crates + +The first parts of the module system we’ll cover are packages and crates. A +crate is a binary or library. The *crate root* is a source file that the Rust +compiler starts from and makes up the root module of your crate (we’ll explain +modules in depth in the [“Defining Modules to Control Scope and +Privacy”][modules] section). A *package* is one or more crates +that provide a set of functionality. A package contains a *Cargo.toml* file +that describes how to build those crates. + +Several rules determine what a package can contain. A package *must* contain +zero or one library crates, and no more. It can contain as many binary crates +as you’d like, but it must contain at least one crate (either library or +binary). + +Let’s walk through what happens when we create a package. First, we enter the +command `cargo new`: + +```console +$ cargo new my-project + Created binary (application) `my-project` package +$ ls my-project +Cargo.toml +src +$ ls my-project/src +main.rs +``` + +When we entered the command, Cargo created a *Cargo.toml* file, giving us a +package. Looking at the contents of *Cargo.toml*, there’s no mention of +*src/main.rs* because Cargo follows a convention that *src/main.rs* is the +crate root of a binary crate with the same name as the package. Likewise, Cargo +knows that if the package directory contains *src/lib.rs*, the package contains +a library crate with the same name as the package, and *src/lib.rs* is its +crate root. Cargo passes the crate root files to `rustc` to build the library +or binary. + +Here, we have a package that only contains *src/main.rs*, meaning it only +contains a binary crate named `my-project`. If a package contains *src/main.rs* +and *src/lib.rs*, it has two crates: a library and a binary, both with the same +name as the package. A package can have multiple binary crates by placing files +in the *src/bin* directory: each file will be a separate binary crate. + +A crate will group related functionality together in a scope so the +functionality is easy to share between multiple projects. For example, the +`rand` crate we used in [Chapter 2][rand] provides functionality +that generates random numbers. We can use that functionality in our own +projects by bringing the `rand` crate into our project’s scope. All the +functionality provided by the `rand` crate is accessible through the crate’s +name, `rand`. + +Keeping a crate’s functionality in its own scope clarifies whether particular +functionality is defined in our crate or the `rand` crate and prevents +potential conflicts. For example, the `rand` crate provides a trait named +`Rng`. We can also define a `struct` named `Rng` in our own crate. Because a +crate’s functionality is namespaced in its own scope, when we add `rand` as a +dependency, the compiler isn’t confused about what the name `Rng` refers to. In +our crate, it refers to the `struct Rng` that we defined. We would access the +`Rng` trait from the `rand` crate as `rand::Rng`. + +Let’s move on and talk about the module system! + +[modules]: ch07-02-defining-modules-to-control-scope-and-privacy.html +[rand]: ch02-00-guessing-game-tutorial.html#generating-a-random-number diff --git a/src/ch07-02-controlling-visibility-with-pub.md b/src/ch07-02-controlling-visibility-with-pub.md deleted file mode 100644 index ce43462..0000000 --- a/src/ch07-02-controlling-visibility-with-pub.md +++ /dev/null @@ -1,295 +0,0 @@ -## Controlling Visibility with `pub` - -We resolved the error messages shown in Listing 7-4 by moving the `network` and -`network::server` code into the *src/network/mod.rs* and -*src/network/server.rs* files, respectively. At that point, `cargo build` was -able to build our project, but we still get some warning messages about the -`client::connect`, `network::connect`, and `network::server::connect` functions -not being used: - -```text -warning: function is never used: `connect`, #[warn(dead_code)] on by default -src/client.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/mod.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -So why are we receiving these warnings? After all, we’re building a library -with functions that are intended to be used by our *users*, and not necessarily -by us within our own project, so it shouldn’t matter that these `connect` -functions go unused. The point of creating them is that they will be used by -another project and not our own. - -To understand why this program invokes these warnings, let’s try using the -`connect` library as if we were another project, calling it externally. We can -do that by creating a binary crate in the same directory as our library crate, -by making a *src/main.rs* file containing this code: - -Filename: src/main.rs - -```rust,ignore -extern crate communicator; - -fn main() { - communicator::client::connect(); -} -``` - -We use the `extern crate` command to bring the `communicator` library crate -into scope, because our package actually now contains *two* crates. Cargo -treats *src/main.rs* as the root file of a binary crate, which is separate from -the existing library crate whose root file is *src/lib.rs*. This pattern is -quite common for executable projects: most functionality is in a library crate, -and the binary crate uses that library crate. This way, other programs can also -use the library crate, and it’s a nice separation of concerns. - -Our binary crate right now just calls our library’s `connect` function from the -`client` module. However, invoking `cargo build` will now give us an error -after the warnings: - -```text -error: module `client` is private - --> src/main.rs:4:5 - | -4 | communicator::client::connect(); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -``` - -Ah ha! This tells us that the `client` module is private, and this is the crux -of the warnings. It’s also the first time we’ve run into the concepts of -*public* and *private* in the context of Rust. The default state of all code in -Rust is private: no one else is allowed to use the code. If you don’t use a -private function within your own program, since your own program is the only -code allowed to use that function, Rust will warn you that the function has -gone unused. - -Once we specify that a function like `client::connect` is public, not only will -our call to that function from our binary crate be allowed, the warning that -the function is unused will go away. Marking something public lets Rust know -that we intend for the function to be used by code outside of our program. Rust -considers the theoretical external usage that’s now possible as the function -“being used.” Thus, when something is marked as public, Rust will not require -that it’s used in our own program and will stop warning that the item is -unused. - -### Making a Function Public - -To tell Rust to make something public, we add the `pub` keyword to the start of -the declaration of the item we want to make public. We’ll focus on fixing the -warning that tells us that `client::connect` has gone unused for now, as well -as the “module `client` is private” error from our binary crate. Modify -*src/lib.rs* to make the `client` module public, like so: - -Filename: src/lib.rs - -```rust,ignore -pub mod client; - -mod network; -``` - -The `pub` goes right before `mod`. Let’s try building again: - -```text - -error: function `connect` is private - --> src/main.rs:4:5 - | -4 | communicator::client::connect(); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -``` - -Hooray! We have a different error! Yes, different error messages are a cause -for celebration. The new error says “function `connect` is private”, so let’s -edit `src/client.rs` to make `client::connect` public too: - -Filename: src/client.rs - -```rust -pub fn connect() { -} -``` - -And run `cargo build` again: - -```text -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/mod.rs:1:1 - | -1 | fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -It compiled, and the warning about `client::connect` not being used is gone! - -Unused code warnings don’t always indicate that something needs to be made -public: if you *didn’t* want these functions to be part of your public API, -unused code warnings could be alerting you to code you no longer needed and can -safely delete. They could also be alerting you to a bug, if you had just -accidentally removed all places within your library where this function is -called. - -In our case though, we *do* want the other two functions to be part of our -crate’s public API, so let’s mark them as `pub` as well to try to get rid of -the remaining warnings. Modify *src/network/mod.rs* to be: - -Filename: src/network/mod.rs - -```rust,ignore -pub fn connect() { -} - -mod server; -``` - -And compile: - -```text -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/mod.rs:1:1 - | -1 | pub fn connect() { - | ^ - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -Hmmm, we’re still getting an unused function warning even though -`network::connect` is set to `pub`. This is because the function is public -within the module, but the `network` module that the function resides in is not -public. We’re working from the interior of the library out this time, where -with `client::connect` we worked from the outside in. We need to change -`src/lib.rs` to make `network` public too: - -Filename: src/lib.rs - -```rust,ignore -pub mod client; - -pub mod network; -``` - -Now if we compile, that warning is gone: - -```text -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -Only one warning left! Try to fix this one on your own! - -### Privacy Rules - -Overall, these are the rules for item visibility: - -1. If an item is public, it can be accessed through any of its - parent modules. -2. If an item is private, it may be accessed only by the current module and its - child modules. - -### Privacy Examples - -Let’s look at a few more examples to get some practice. Create a new library -project and enter the code in Listing 7-5 into your new project’s *src/lib.rs*: - -
-Filename: src/lib.rs - -```rust,ignore -mod outermost { - pub fn middle_function() {} - - fn middle_secret_function() {} - - mod inside { - pub fn inner_function() {} - - fn secret_function() {} - } -} - -fn try_me() { - outermost::middle_function(); - outermost::middle_secret_function(); - outermost::inside::inner_function(); - outermost::inside::secret_function(); -} -``` - -
- -Listing 7-5: Examples of private and public functions, some of which are -incorrect - -
-
- -Before you try to compile this code, make a guess about which lines in `try_me` -function will have errors. Then try compiling to see if you were right, and read -on for discussion of the errors! - -#### Looking at the Errors - -The `try_me` function is in the root module of our project. The module named -`outermost` is private, but the second privacy rule says the `try_me` function -is allowed to access the `outermost` module since `outermost` is in the current -(root) module, as is `try_me`. - -The call to `outermost::middle_function` will work. This is because -`middle_function` is public, and `try_me` is accessing `middle_function` -through its parent module, `outermost`. We determined in the previous paragraph -that this module is accessible. - -The call to `outermost::middle_secret_function` will cause a compilation error. -`middle_secret_function` is private, so the second rule applies. The root -module is neither the current module of `middle_secret_function` (`outermost` -is), nor is it a child module of the current module of `middle_secret_function`. - -The module named `inside` is private and has no child modules, so it can only -be accessed by its current module, `outermost`. That means the `try_me` -function is not allowed to call `outermost::inside::inner_function` or -`outermost::inside::secret_function` either. - -#### Fixing the Errors - -Here are some suggestions for changing the code in an attempt to fix the -errors. Before you try each one, make a guess as to whether it will fix the -errors, then compile to see if you’re right and use the privacy rules to -understand why. - -* What if the `inside` module was public? -* What if `outermost` was public and `inside` was private? -* What if, in the body of `inner_function`, you called - `::outermost::middle_secret_function()`? (The two colons at the beginning - mean that we want to refer to the namespaces starting from the root - namespace.) - -Feel free to design more experiments and try them out! - -Next, let’s talk about bringing items into a scope with the `use` keyword. diff --git a/src/ch07-02-defining-modules-to-control-scope-and-privacy.md b/src/ch07-02-defining-modules-to-control-scope-and-privacy.md new file mode 100644 index 0000000..a215870 --- /dev/null +++ b/src/ch07-02-defining-modules-to-control-scope-and-privacy.md @@ -0,0 +1,87 @@ +## Defining Modules to Control Scope and Privacy + +In this section, we’ll talk about modules and other parts of the module system, +namely *paths* that allow you to name items; the `use` keyword that brings a +path into scope; and the `pub` keyword to make items public. We’ll also discuss +the `as` keyword, external packages, and the glob operator. For now, let’s +focus on modules! + +*Modules* let us organize code within a crate into groups for readability and +easy reuse. Modules also control the *privacy* of items, which is whether an +item can be used by outside code (*public*) or is an internal implementation +detail and not available for outside use (*private*). + +As an example, let’s write a library crate that provides the functionality of a +restaurant. We’ll define the signatures of functions but leave their bodies +empty to concentrate on the organization of the code, rather than actually +implement a restaurant in code. + +In the restaurant industry, some parts of a restaurant are referred to as +*front of house* and others as *back of house*. Front of house is where +customers are; this is where hosts seat customers, servers take orders and +payment, and bartenders make drinks. Back of house is where the chefs and cooks +work in the kitchen, dishwashers clean up, and managers do administrative work. + +To structure our crate in the same way that a real restaurant works, we can +organize the functions into nested modules. Create a new library named +`restaurant` by running `cargo new --lib restaurant`; then put the code in +Listing 7-1 into *src/lib.rs* to define some modules and function signatures. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-01/src/lib.rs}} +``` + +Listing 7-1: A `front_of_house` module containing other +modules that then contain functions + +We define a module by starting with the `mod` keyword and then specify the +name of the module (in this case, `front_of_house`) and place curly brackets +around the body of the module. Inside modules, we can have other modules, as in +this case with the modules `hosting` and `serving`. Modules can also hold +definitions for other items, such as structs, enums, constants, traits, or—as +in Listing 7-1—functions. + +By using modules, we can group related definitions together and name why +they’re related. Programmers using this code would have an easier time finding +the definitions they wanted to use because they could navigate the code based +on the groups rather than having to read through all the definitions. +Programmers adding new functionality to this code would know where to place the +code to keep the program organized. + +Earlier, we mentioned that *src/main.rs* and *src/lib.rs* are called crate +roots. The reason for their name is that the contents of either of these two +files form a module named `crate` at the root of the crate’s module structure, +known as the *module tree*. + +Listing 7-2 shows the module tree for the structure in Listing 7-1. + +```text +crate + └── front_of_house + ├── hosting + │ ├── add_to_waitlist + │ └── seat_at_table + └── serving + ├── take_order + ├── serve_order + └── take_payment +``` + +Listing 7-2: The module tree for the code in Listing +7-1 + +This tree shows how some of the modules nest inside one another (for example, +`hosting` nests inside `front_of_house`). The tree also shows that some modules +are *siblings* to each other, meaning they’re defined in the same module +(`hosting` and `serving` are defined within `front_of_house`). To continue the +family metaphor, if module A is contained inside module B, we say that module A +is the *child* of module B and that module B is the *parent* of module A. +Notice that the entire module tree is rooted under the implicit module named +`crate`. + +The module tree might remind you of the filesystem’s directory tree on your +computer; this is a very apt comparison! Just like directories in a filesystem, +you use modules to organize your code. And just like files in a directory, we +need a way to find our modules. diff --git a/src/ch07-03-importing-names-with-use.md b/src/ch07-03-importing-names-with-use.md deleted file mode 100644 index 42be7ec..0000000 --- a/src/ch07-03-importing-names-with-use.md +++ /dev/null @@ -1,278 +0,0 @@ -## Importing Names - -We’ve covered how to call functions defined within a module using the module -name as part of the call, as in the call to the `namespaces` function shown -here in Listing 7-6. - -
-Filename: src/main.rs - -```rust -pub mod a { - pub mod series { - pub mod of { - pub fn namespaces() {} - } - } -} - -fn main() { - a::series::of::namespaces(); -} -``` - -
- -Listing 7-6: Calling a function by fully specifying its enclosing module’s -namespaces - -
-
- -As you can see, referring to the fully qualified name can get quite lengthy. -Luckily, Rust has a keyword to make these calls more concise. - -### Concise Imports with `use` - -Rust’s `use` keyword works to shorten lengthy function calls by bringing the -modules of the function you want to call into a scope. Here’s an example of -bringing the `a::series::of` namespace into a binary crate’s root scope: - -Filename: src/main.rs - -```rust -pub mod a { - pub mod series { - pub mod of { - pub fn namespaces() {} - } - } -} - -use a::series::of; - -fn main() { - of::namespaces(); -} -``` - -The line `use a::series::of;` has made it so that anywhere in this scope that -we would want to refer to the `of` namespace, instead of having to say -`a::series::of`, we can replace that with `of`. - -The `use` keyword brings only what we have specified into scope; it does not -bring children of modules into scope. That’s why we still have to say -`of::namespaces` when we want to call the `namespaces` function. - -We could have chosen to bring the function itself into scope, by instead -specifying the function in the `use` as follows: - -```rust -pub mod a { - pub mod series { - pub mod of { - pub fn namespaces() {} - } - } -} - -use a::series::of::namespaces; - -fn main() { - namespaces(); -} -``` - -This allows us to exclude any of the modules and just reference the function at -the callsite. - -Since enums also form this kind of namespace, we can import an enum’s variants -with `use` as well. For any kind of `use` statement, if you’re importing -multiple items from one namespace, you can list them using curly braces and -commas in the last position, like so: - -```rust -enum TrafficLight { - Red, - Yellow, - Green, -} - -use TrafficLight::{Red, Yellow}; - -fn main() { - let red = Red; - let yellow = Yellow; - let green = TrafficLight::Green; // because we didn’t `use` TrafficLight::Green -} -``` - -### Glob Imports with `*` - -To import all the items in a namespace at once, we can use the `*` syntax. For -example: - -```rust -enum TrafficLight { - Red, - Yellow, - Green, -} - -use TrafficLight::*; - -fn main() { - let red = Red; - let yellow = Yellow; - let green = Green; -} -``` - -The `*` is called a *glob*, and it will import everything that’s visible inside -of the namespace. Globs should be used sparingly: they are convenient, but you -might also pull in more things than you expected and cause naming conflicts. - -### Using `super` to Access a Parent Module - -As you now know, when you create a library crate, Cargo makes a `tests` module -for you. Let’s go into more detail about that now. In your `communicator` -project, open *src/lib.rs*. - -Filename: src/lib.rs - -```rust,ignore -pub mod client; - -pub mod network; - -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} -``` - -We’ll explain more about testing in Chapter 12, but parts of this should make -sense now: we have a module named `tests` that lives next to our other modules -and contains one function named `it_works`. Even though there are special -annotations, the `tests` module is just another module! So our module hierarchy -looks like this: - -```text -communicator - ├── client - ├── network - | └── client - └── tests -``` - -Tests are for exercising the code within our library, so let’s try to call -our `client::connect` function from this `it_works` function, even though -we’re not going to be checking any functionality right now: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - client::connect(); - } -} -``` - -Run the tests by invoking the `cargo test` command: - -```text -$ cargo test - Compiling communicator v0.1.0 (file:///projects/communicator) -error[E0433]: failed to resolve. Use of undeclared type or module `client` - --> src/lib.rs:9:9 - | -9 | client::connect(); - | ^^^^^^^^^^^^^^^ Use of undeclared type or module `client` - -warning: function is never used: `connect`, #[warn(dead_code)] on by default - --> src/network/server.rs:1:1 - | -1 | fn connect() { - | ^ -``` - -The compilation failed, but why? We don’t need to place `communicator::` in -front of the function like we did in `src/main.rs` because we are definitely -within the `communicator` library crate here. The reason is that paths are -always relative to the current module, which here is `tests`. The only -exception is in a `use` statement, where paths are relative to the crate root -by default. Our `tests` module needs the `client` module in its scope! - -So how do we get back up one module in the module hierarchy to be able to call -the `client::connect` function in the `tests` module? In the `tests` module, we -can either use leading colons to let Rust know that we want to start from the -root and list the whole path: - -```rust,ignore -::client::connect(); -``` - -Or we can use `super` to move up one module in the hierarchy from our current -module: - -```rust,ignore -super::client::connect(); -``` - -These two options don’t look all that different in this example, but if you’re -deeper in a module hierarchy, starting from the root every time would get long. -In those cases, using `super` to get from the current module to sibling modules -is a good shortcut. Plus, if you’ve specified the path from the root in many -places in your code and then you rearrange your modules by moving a subtree to -another place, you’d end up needing to update the path in a lot of places, -which would be tedious. - -It would also be annoying to have to type `super::` all the time in each test, -but you’ve already seen the tool for that solution: `use`! The `super::` -functionality changes the path you give to `use` so that it is relative to the -parent module instead of to the root module. - -For these reasons, in the `tests` module especially, `use super::something` is -usually the way to go. So now our test looks like this: - -Filename: src/lib.rs - -```rust -#[cfg(test)] -mod tests { - use super::client; - - #[test] - fn it_works() { - client::connect(); - } -} -``` - -If we run `cargo test` again, the test will pass and the first part of the test -result output will be: - -```text -$ cargo test - Compiling communicator v0.1.0 (file:///projects/communicator) - Running target/debug/communicator-92007ddb5330fa5a - -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -## Summary - -Now you know techniques for organizing your code! Use these to group related -functionality together, keep files from getting too long, and present a tidy -public API to users of your library. - -Next, let’s look at some collection data structures in the standard library -that you can make use of in your nice, neat code! diff --git a/src/ch07-03-paths-for-referring-to-an-item-in-the-module-tree.md b/src/ch07-03-paths-for-referring-to-an-item-in-the-module-tree.md new file mode 100644 index 0000000..fc3980e --- /dev/null +++ b/src/ch07-03-paths-for-referring-to-an-item-in-the-module-tree.md @@ -0,0 +1,261 @@ +## Paths for Referring to an Item in the Module Tree + +To show Rust where to find an item in a module tree, we use a path in the same +way we use a path when navigating a filesystem. If we want to call a function, +we need to know its path. + +A path can take two forms: + +* An *absolute path* starts from a crate root by using a crate name or a + literal `crate`. +* A *relative path* starts from the current module and uses `self`, `super`, or + an identifier in the current module. + +Both absolute and relative paths are followed by one or more identifiers +separated by double colons (`::`). + +Let’s return to the example in Listing 7-1. How do we call the +`add_to_waitlist` function? This is the same as asking, what’s the path of the +`add_to_waitlist` function? In Listing 7-3, we simplified our code a bit by +removing some of the modules and functions. We’ll show two ways to call the +`add_to_waitlist` function from a new function `eat_at_restaurant` defined in +the crate root. The `eat_at_restaurant` function is part of our library crate’s +public API, so we mark it with the `pub` keyword. In the [”Exposing Paths with +the `pub` Keyword”][pub] section, we’ll go into more detail +about `pub`. Note that this example won’t compile just yet; we’ll explain why +in a bit. + +Filename: src/lib.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-03/src/lib.rs}} +``` + +Listing 7-3: Calling the `add_to_waitlist` function using +absolute and relative paths + +The first time we call the `add_to_waitlist` function in `eat_at_restaurant`, +we use an absolute path. The `add_to_waitlist` function is defined in the same +crate as `eat_at_restaurant`, which means we can use the `crate` keyword to +start an absolute path. + +After `crate`, we include each of the successive modules until we make our way +to `add_to_waitlist`. You can imagine a filesystem with the same structure, and +we’d specify the path `/front_of_house/hosting/add_to_waitlist` to run the +`add_to_waitlist` program; using the `crate` name to start from the crate root +is like using `/` to start from the filesystem root in your shell. + +The second time we call `add_to_waitlist` in `eat_at_restaurant`, we use a +relative path. The path starts with `front_of_house`, the name of the module +defined at the same level of the module tree as `eat_at_restaurant`. Here the +filesystem equivalent would be using the path +`front_of_house/hosting/add_to_waitlist`. Starting with a name means that the +path is relative. + +Choosing whether to use a relative or absolute path is a decision you’ll make +based on your project. The decision should depend on whether you’re more likely +to move item definition code separately from or together with the code that +uses the item. For example, if we move the `front_of_house` module and the +`eat_at_restaurant` function into a module named `customer_experience`, we’d +need to update the absolute path to `add_to_waitlist`, but the relative path +would still be valid. However, if we moved the `eat_at_restaurant` function +separately into a module named `dining`, the absolute path to the +`add_to_waitlist` call would stay the same, but the relative path would need to +be updated. Our preference is to specify absolute paths because it’s more +likely to move code definitions and item calls independently of each other. + +Let’s try to compile Listing 7-3 and find out why it won’t compile yet! The +error we get is shown in Listing 7-4. + +```console +{{#include ../listings/ch07-managing-growing-projects/listing-07-03/output.txt}} +``` + +Listing 7-4: Compiler errors from building the code in +Listing 7-3 + +The error messages say that module `hosting` is private. In other words, we +have the correct paths for the `hosting` module and the `add_to_waitlist` +function, but Rust won’t let us use them because it doesn’t have access to the +private sections. + +Modules aren’t useful only for organizing your code. They also define Rust’s +*privacy boundary*: the line that encapsulates the implementation details +external code isn’t allowed to know about, call, or rely on. So, if you want to +make an item like a function or struct private, you put it in a module. + +The way privacy works in Rust is that all items (functions, methods, structs, +enums, modules, and constants) are private by default. Items in a parent module +can’t use the private items inside child modules, but items in child modules +can use the items in their ancestor modules. The reason is that child modules +wrap and hide their implementation details, but the child modules can see the +context in which they’re defined. To continue with the restaurant metaphor, +think of the privacy rules as being like the back office of a restaurant: what +goes on in there is private to restaurant customers, but office managers can +see and do everything in the restaurant in which they operate. + +Rust chose to have the module system function this way so that hiding inner +implementation details is the default. That way, you know which parts of the +inner code you can change without breaking outer code. But you can expose inner +parts of child modules' code to outer ancestor modules by using the `pub` +keyword to make an item public. + +### Exposing Paths with the `pub` Keyword + +Let’s return to the error in Listing 7-4 that told us the `hosting` module is +private. We want the `eat_at_restaurant` function in the parent module to have +access to the `add_to_waitlist` function in the child module, so we mark the +`hosting` module with the `pub` keyword, as shown in Listing 7-5. + +Filename: src/lib.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-05/src/lib.rs}} +``` + +Listing 7-5: Declaring the `hosting` module as `pub` to +use it from `eat_at_restaurant` + +Unfortunately, the code in Listing 7-5 still results in an error, as shown in +Listing 7-6. + +```console +{{#include ../listings/ch07-managing-growing-projects/listing-07-05/output.txt}} +``` + +Listing 7-6: Compiler errors from building the code in +Listing 7-5 + +What happened? Adding the `pub` keyword in front of `mod hosting` makes the +module public. With this change, if we can access `front_of_house`, we can +access `hosting`. But the *contents* of `hosting` are still private; making the +module public doesn’t make its contents public. The `pub` keyword on a module +only lets code in its ancestor modules refer to it. + +The errors in Listing 7-6 say that the `add_to_waitlist` function is private. +The privacy rules apply to structs, enums, functions, and methods as well as +modules. + +Let’s also make the `add_to_waitlist` function public by adding the `pub` +keyword before its definition, as in Listing 7-7. + +Filename: src/lib.rs + +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-07/src/lib.rs}} +``` + +Listing 7-7: Adding the `pub` keyword to `mod hosting` +and `fn add_to_waitlist` lets us call the function from +`eat_at_restaurant` + +Now the code will compile! Let’s look at the absolute and the relative path and +double-check why adding the `pub` keyword lets us use these paths in +`add_to_waitlist` with respect to the privacy rules. + +In the absolute path, we start with `crate`, the root of our crate’s module +tree. Then the `front_of_house` module is defined in the crate root. The +`front_of_house` module isn’t public, but because the `eat_at_restaurant` +function is defined in the same module as `front_of_house` (that is, +`eat_at_restaurant` and `front_of_house` are siblings), we can refer to +`front_of_house` from `eat_at_restaurant`. Next is the `hosting` module marked +with `pub`. We can access the parent module of `hosting`, so we can access +`hosting`. Finally, the `add_to_waitlist` function is marked with `pub` and we +can access its parent module, so this function call works! + +In the relative path, the logic is the same as the absolute path except for the +first step: rather than starting from the crate root, the path starts from +`front_of_house`. The `front_of_house` module is defined within the same module +as `eat_at_restaurant`, so the relative path starting from the module in which +`eat_at_restaurant` is defined works. Then, because `hosting` and +`add_to_waitlist` are marked with `pub`, the rest of the path works, and this +function call is valid! + +### Starting Relative Paths with `super` + +We can also construct relative paths that begin in the parent module by using +`super` at the start of the path. This is like starting a filesystem path with +the `..` syntax. Why would we want to do this? + +Consider the code in Listing 7-8 that models the situation in which a chef +fixes an incorrect order and personally brings it out to the customer. The +function `fix_incorrect_order` calls the function `serve_order` by specifying +the path to `serve_order` starting with `super`: + +Filename: src/lib.rs + +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-08/src/lib.rs}} +``` + +Listing 7-8: Calling a function using a relative path +starting with `super` + +The `fix_incorrect_order` function is in the `back_of_house` module, so we can +use `super` to go to the parent module of `back_of_house`, which in this case +is `crate`, the root. From there, we look for `serve_order` and find it. +Success! We think the `back_of_house` module and the `serve_order` function are +likely to stay in the same relationship to each other and get moved together +should we decide to reorganize the crate’s module tree. Therefore, we used +`super` so we’ll have fewer places to update code in the future if this code +gets moved to a different module. + +### Making Structs and Enums Public + +We can also use `pub` to designate structs and enums as public, but there are a +few extra details. If we use `pub` before a struct definition, we make the +struct public, but the struct’s fields will still be private. We can make each +field public or not on a case-by-case basis. In Listing 7-9, we’ve defined a +public `back_of_house::Breakfast` struct with a public `toast` field but a +private `seasonal_fruit` field. This models the case in a restaurant where the +customer can pick the type of bread that comes with a meal, but the chef +decides which fruit accompanies the meal based on what’s in season and in +stock. The available fruit changes quickly, so customers can’t choose the fruit +or even see which fruit they’ll get. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-09/src/lib.rs}} +``` + +Listing 7-9: A struct with some public fields and some +private fields + +Because the `toast` field in the `back_of_house::Breakfast` struct is public, +in `eat_at_restaurant` we can write and read to the `toast` field using dot +notation. Notice that we can’t use the `seasonal_fruit` field in +`eat_at_restaurant` because `seasonal_fruit` is private. Try uncommenting the +line modifying the `seasonal_fruit` field value to see what error you get! + +Also, note that because `back_of_house::Breakfast` has a private field, the +struct needs to provide a public associated function that constructs an +instance of `Breakfast` (we’ve named it `summer` here). If `Breakfast` didn’t +have such a function, we couldn’t create an instance of `Breakfast` in +`eat_at_restaurant` because we couldn’t set the value of the private +`seasonal_fruit` field in `eat_at_restaurant`. + +In contrast, if we make an enum public, all of its variants are then public. We +only need the `pub` before the `enum` keyword, as shown in Listing 7-10. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-10/src/lib.rs}} +``` + +Listing 7-10: Designating an enum as public makes all its +variants public + +Because we made the `Appetizer` enum public, we can use the `Soup` and `Salad` +variants in `eat_at_restaurant`. Enums aren’t very useful unless their variants +are public; it would be annoying to have to annotate all enum variants with +`pub` in every case, so the default for enum variants is to be public. Structs +are often useful without their fields being public, so struct fields follow the +general rule of everything being private by default unless annotated with `pub`. + +There’s one more situation involving `pub` that we haven’t covered, and that is +our last module system feature: the `use` keyword. We’ll cover `use` by itself +first, and then we’ll show how to combine `pub` and `use`. + +[pub]: ch07-03-paths-for-referring-to-an-item-in-the-module-tree.html#exposing-paths-with-the-pub-keyword diff --git a/src/ch07-04-bringing-paths-into-scope-with-the-use-keyword.md b/src/ch07-04-bringing-paths-into-scope-with-the-use-keyword.md new file mode 100644 index 0000000..3e4f1aa --- /dev/null +++ b/src/ch07-04-bringing-paths-into-scope-with-the-use-keyword.md @@ -0,0 +1,291 @@ +## Bringing Paths into Scope with the `use` Keyword + +It might seem like the paths we’ve written to call functions so far are +inconveniently long and repetitive. For example, in Listing 7-7, whether we +chose the absolute or relative path to the `add_to_waitlist` function, every +time we wanted to call `add_to_waitlist` we had to specify `front_of_house` and +`hosting` too. Fortunately, there’s a way to simplify this process. We can +bring a path into a scope once and then call the items in that path as if +they’re local items with the `use` keyword. + +In Listing 7-11, we bring the `crate::front_of_house::hosting` module into the +scope of the `eat_at_restaurant` function so we only have to specify +`hosting::add_to_waitlist` to call the `add_to_waitlist` function in +`eat_at_restaurant`. + +Filename: src/lib.rs + +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-11/src/lib.rs}} +``` + +Listing 7-11: Bringing a module into scope with +`use` + +Adding `use` and a path in a scope is similar to creating a symbolic link in +the filesystem. By adding `use crate::front_of_house::hosting` in the crate +root, `hosting` is now a valid name in that scope, just as though the `hosting` +module had been defined in the crate root. Paths brought into scope with `use` +also check privacy, like any other paths. + +You can also bring an item into scope with `use` and a relative path. Listing +7-12 shows how to specify a relative path to get the same behavior as in +Listing 7-11. + +Filename: src/lib.rs + +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-12/src/lib.rs}} +``` + +Listing 7-12: Bringing a module into scope with `use` and +a relative path + +### Creating Idiomatic `use` Paths + +In Listing 7-11, you might have wondered why we specified `use +crate::front_of_house::hosting` and then called `hosting::add_to_waitlist` in +`eat_at_restaurant` rather than specifying the `use` path all the way out to +the `add_to_waitlist` function to achieve the same result, as in Listing 7-13. + +Filename: src/lib.rs + +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-13/src/lib.rs}} +``` + +Listing 7-13: Bringing the `add_to_waitlist` function +into scope with `use`, which is unidiomatic + +Although both Listing 7-11 and 7-13 accomplish the same task, Listing 7-11 is +the idiomatic way to bring a function into scope with `use`. Bringing the +function’s parent module into scope with `use` so we have to specify the parent +module when calling the function makes it clear that the function isn’t locally +defined while still minimizing repetition of the full path. The code in Listing +7-13 is unclear as to where `add_to_waitlist` is defined. + +On the other hand, when bringing in structs, enums, and other items with `use`, +it’s idiomatic to specify the full path. Listing 7-14 shows the idiomatic way +to bring the standard library’s `HashMap` struct into the scope of a binary +crate. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-14/src/main.rs}} +``` + +Listing 7-14: Bringing `HashMap` into scope in an +idiomatic way + +There’s no strong reason behind this idiom: it’s just the convention that has +emerged, and folks have gotten used to reading and writing Rust code this way. + +The exception to this idiom is if we’re bringing two items with the same name +into scope with `use` statements, because Rust doesn’t allow that. Listing 7-15 +shows how to bring two `Result` types into scope that have the same name but +different parent modules and how to refer to them. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-15/src/lib.rs:here}} +``` + +Listing 7-15: Bringing two types with the same name into +the same scope requires using their parent modules. + +As you can see, using the parent modules distinguishes the two `Result` types. +If instead we specified `use std::fmt::Result` and `use std::io::Result`, we’d +have two `Result` types in the same scope and Rust wouldn’t know which one we +meant when we used `Result`. + +### Providing New Names with the `as` Keyword + +There’s another solution to the problem of bringing two types of the same name +into the same scope with `use`: after the path, we can specify `as` and a new +local name, or alias, for the type. Listing 7-16 shows another way to write the +code in Listing 7-15 by renaming one of the two `Result` types using `as`. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-16/src/lib.rs:here}} +``` + +Listing 7-16: Renaming a type when it’s brought into +scope with the `as` keyword + +In the second `use` statement, we chose the new name `IoResult` for the +`std::io::Result` type, which won’t conflict with the `Result` from `std::fmt` +that we’ve also brought into scope. Listing 7-15 and Listing 7-16 are +considered idiomatic, so the choice is up to you! + +### Re-exporting Names with `pub use` + +When we bring a name into scope with the `use` keyword, the name available in +the new scope is private. To enable the code that calls our code to refer to +that name as if it had been defined in that code’s scope, we can combine `pub` +and `use`. This technique is called *re-exporting* because we’re bringing +an item into scope but also making that item available for others to bring into +their scope. + +Listing 7-17 shows the code in Listing 7-11 with `use` in the root module +changed to `pub use`. + +Filename: src/lib.rs + +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-17/src/lib.rs}} +``` + +Listing 7-17: Making a name available for any code to use +from a new scope with `pub use` + +By using `pub use`, external code can now call the `add_to_waitlist` function +using `hosting::add_to_waitlist`. If we hadn’t specified `pub use`, the +`eat_at_restaurant` function could call `hosting::add_to_waitlist` in its +scope, but external code couldn’t take advantage of this new path. + +Re-exporting is useful when the internal structure of your code is different +from how programmers calling your code would think about the domain. For +example, in this restaurant metaphor, the people running the restaurant think +about “front of house” and “back of house.” But customers visiting a restaurant +probably won’t think about the parts of the restaurant in those terms. With +`pub use`, we can write our code with one structure but expose a different +structure. Doing so makes our library well organized for programmers working on +the library and programmers calling the library. + +### Using External Packages + +In Chapter 2, we programmed a guessing game project that used an external +package called `rand` to get random numbers. To use `rand` in our project, we +added this line to *Cargo.toml*: + + + +Filename: Cargo.toml + +```toml +{{#include ../listings/ch02-guessing-game-tutorial/listing-02-02/Cargo.toml:9:}} +``` + +Adding `rand` as a dependency in *Cargo.toml* tells Cargo to download the +`rand` package and any dependencies from [crates.io](https://crates.io/) and +make `rand` available to our project. + +Then, to bring `rand` definitions into the scope of our package, we added a +`use` line starting with the name of the crate, `rand`, and listed the items +we wanted to bring into scope. Recall that in the [“Generating a Random +Number”][rand] section in Chapter 2, we brought the `Rng` trait +into scope and called the `rand::thread_rng` function: + +```rust,ignore +{{#rustdoc_include ../listings/ch02-guessing-game-tutorial/listing-02-03/src/main.rs:ch07-04}} +``` + +Members of the Rust community have made many packages available at +[crates.io](https://crates.io/), and pulling any of them into your package +involves these same steps: listing them in your package’s *Cargo.toml* file and +using `use` to bring items from their crates into scope. + +Note that the standard library (`std`) is also a crate that’s external to our +package. Because the standard library is shipped with the Rust language, we +don’t need to change *Cargo.toml* to include `std`. But we do need to refer to +it with `use` to bring items from there into our package’s scope. For example, +with `HashMap` we would use this line: + +```rust +use std::collections::HashMap; +``` + +This is an absolute path starting with `std`, the name of the standard library +crate. + +### Using Nested Paths to Clean Up Large `use` Lists + +If we’re using multiple items defined in the same crate or same module, +listing each item on its own line can take up a lot of vertical space in our +files. For example, these two `use` statements we had in the Guessing Game in +Listing 2-4 bring items from `std` into scope: + +Filename: src/main.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch07-managing-growing-projects/no-listing-01-use-std-unnested/src/main.rs:here}} +``` + +Instead, we can use nested paths to bring the same items into scope in one +line. We do this by specifying the common part of the path, followed by two +colons, and then curly brackets around a list of the parts of the paths that +differ, as shown in Listing 7-18. + +Filename: src/main.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-18/src/main.rs:here}} +``` + +Listing 7-18: Specifying a nested path to bring multiple +items with the same prefix into scope + +In bigger programs, bringing many items into scope from the same crate or +module using nested paths can reduce the number of separate `use` statements +needed by a lot! + +We can use a nested path at any level in a path, which is useful when combining +two `use` statements that share a subpath. For example, Listing 7-19 shows two +`use` statements: one that brings `std::io` into scope and one that brings +`std::io::Write` into scope. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-19/src/lib.rs}} +``` + +Listing 7-19: Two `use` statements where one is a subpath +of the other + +The common part of these two paths is `std::io`, and that’s the complete first +path. To merge these two paths into one `use` statement, we can use `self` in +the nested path, as shown in Listing 7-20. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-20/src/lib.rs}} +``` + +Listing 7-20: Combining the paths in Listing 7-19 into +one `use` statement + +This line brings `std::io` and `std::io::Write` into scope. + +### The Glob Operator + +If we want to bring *all* public items defined in a path into scope, we can +specify that path followed by `*`, the glob operator: + +```rust +use std::collections::*; +``` + +This `use` statement brings all public items defined in `std::collections` into +the current scope. Be careful when using the glob operator! Glob can make it +harder to tell what names are in scope and where a name used in your program +was defined. + +The glob operator is often used when testing to bring everything under test +into the `tests` module; we’ll talk about that in the [“How to Write +Tests”][writing-tests] section in Chapter 11. The glob operator +is also sometimes used as part of the prelude pattern: see [the standard +library documentation](../std/prelude/index.html#other-preludes) +for more information on that pattern. + +[rand]: ch02-00-guessing-game-tutorial.html#generating-a-random-number +[writing-tests]: ch11-01-writing-tests.html#how-to-write-tests diff --git a/src/ch07-05-separating-modules-into-different-files.md b/src/ch07-05-separating-modules-into-different-files.md new file mode 100644 index 0000000..639bbd9 --- /dev/null +++ b/src/ch07-05-separating-modules-into-different-files.md @@ -0,0 +1,77 @@ +## Separating Modules into Different Files + +So far, all the examples in this chapter defined multiple modules in one file. +When modules get large, you might want to move their definitions to a separate +file to make the code easier to navigate. + +For example, let’s start from the code in Listing 7-17 and move the +`front_of_house` module to its own file *src/front_of_house.rs* by changing the +crate root file so it contains the code shown in Listing 7-21. In this case, +the crate root file is *src/lib.rs*, but this procedure also works with binary +crates whose crate root file is *src/main.rs*. + +Filename: src/lib.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-21-and-22/src/lib.rs}} +``` + +Listing 7-21: Declaring the `front_of_house` module whose +body will be in *src/front_of_house.rs* + +And *src/front_of_house.rs* gets the definitions from the body of the +`front_of_house` module, as shown in Listing 7-22. + +Filename: src/front_of_house.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch07-managing-growing-projects/listing-07-21-and-22/src/front_of_house.rs}} +``` + +Listing 7-22: Definitions inside the `front_of_house` +module in *src/front_of_house.rs* + +Using a semicolon after `mod front_of_house` rather than using a block tells +Rust to load the contents of the module from another file with the same name as +the module. To continue with our example and extract the `hosting` module to +its own file as well, we change *src/front_of_house.rs* to contain only the +declaration of the `hosting` module: + +Filename: src/front_of_house.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house.rs}} +``` + +Then we create a *src/front_of_house* directory and a file +*src/front_of_house/hosting.rs* to contain the definitions made in the +`hosting` module: + +Filename: src/front_of_house/hosting.rs + +```rust +{{#rustdoc_include ../listings/ch07-managing-growing-projects/no-listing-02-extracting-hosting/src/front_of_house/hosting.rs}} +``` + +The module tree remains the same, and the function calls in `eat_at_restaurant` +will work without any modification, even though the definitions live in +different files. This technique lets you move modules to new files as they grow +in size. + +Note that the `pub use crate::front_of_house::hosting` statement in +*src/lib.rs* also hasn’t changed, nor does `use` have any impact on what files +are compiled as part of the crate. The `mod` keyword declares modules, and Rust +looks in a file with the same name as the module for the code that goes into +that module. + +## Summary + +Rust lets you split a package into multiple crates and a crate into modules +so you can refer to items defined in one module from another module. You can do +this by specifying absolute or relative paths. These paths can be brought into +scope with a `use` statement so you can use a shorter path for multiple uses of +the item in that scope. Module code is private by default, but you can make +definitions public by adding the `pub` keyword. + +In the next chapter, we’ll look at some collection data structures in the +standard library that you can use in your neatly organized code. diff --git a/src/ch08-00-common-collections.md b/src/ch08-00-common-collections.md new file mode 100644 index 0000000..edba30a --- /dev/null +++ b/src/ch08-00-common-collections.md @@ -0,0 +1,25 @@ +# Common Collections + +Rust’s standard library includes a number of very useful data structures called +*collections*. Most other data types represent one specific value, but +collections can contain multiple values. Unlike the built-in array and tuple +types, the data these collections point to is stored on the heap, which means +the amount of data does not need to be known at compile time and can grow or +shrink as the program runs. Each kind of collection has different capabilities +and costs, and choosing an appropriate one for your current situation is a +skill you’ll develop over time. In this chapter, we’ll discuss three +collections that are used very often in Rust programs: + +* A *vector* allows you to store a variable number of values next to each other. +* A *string* is a collection of characters. We’ve mentioned the `String` type + previously, but in this chapter we’ll talk about it in depth. +* A *hash map* allows you to associate a value with a particular key. It’s a + particular implementation of the more general data structure called a *map*. + +To learn about the other kinds of collections provided by the standard library, +see [the documentation][collections]. + +[collections]: ../std/collections/index.html + +We’ll discuss how to create and update vectors, strings, and hash maps, as well +as what makes each special. diff --git a/src/ch08-00-fundamental-collections.md b/src/ch08-00-fundamental-collections.md deleted file mode 100644 index 37f2ddd..0000000 --- a/src/ch08-00-fundamental-collections.md +++ /dev/null @@ -1,21 +0,0 @@ -# Fundamental Collections - -Rust's standard library includes a number of really useful data structures -called *collections*. Most other data types represent one specific value, but -collections can contain multiple values. Unlike the built-in array and tuple -types, the data these collections point to is stored on the heap, which means -the amount of data does not need to be known at compile time and can grow or -shrink as the program runs. Each kind of collection has different capabilities -and costs, and choosing an appropriate one for the situation you're in is a -skill you'll develop over time. In this chapter, we'll go over three -collections which are used very often in Rust programs: - -* A *vector* allows us to store a variable number of values next to each other. -* A *string* is a collection of characters. We've seen the `String` type - before, but we'll talk about it in depth now. -* A *hash map* allows us to associate a value with a particular key. - -There are more specialized variants of each of these data structures for -particular situations, but these are the most fundamental and common. We're -going to discuss how to create and update each of the collections, as well as -what makes each special. diff --git a/src/ch08-01-vectors.md b/src/ch08-01-vectors.md index 02a4ade..934eff4 100644 --- a/src/ch08-01-vectors.md +++ b/src/ch08-01-vectors.md @@ -1,240 +1,243 @@ -## Vectors +## Storing Lists of Values with Vectors -The first type we'll look at is `Vec`, also known as a *vector*. Vectors -allow us to store more than one value in a single data structure that puts all -the values next to each other in memory. Vectors can only store values of the -same type. They are useful in situations where you have a list of items, such -as the lines of text in a file or the prices of items in a shopping cart. +The first collection type we’ll look at is `Vec`, also known as a *vector*. +Vectors allow you to store more than one value in a single data structure that +puts all the values next to each other in memory. Vectors can only store values +of the same type. They are useful when you have a list of items, such as the +lines of text in a file or the prices of items in a shopping cart. ### Creating a New Vector -To create a new, empty vector, we can call the `Vec::new` function: +To create a new, empty vector, we can call the `Vec::new` function, as shown in +Listing 8-1. ```rust -let v: Vec = Vec::new(); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-01/src/main.rs:here}} ``` -Note that we added a type annotation here. Since we aren't inserting any values -into this vector, Rust doesn't know what kind of elements we intend to store. -This is an important point. Vectors are homogeneous: they may store many values, -but those values must all be the same type. Vectors are implemented using -generics, which Chapter 10 will cover how to use in your own types. For now, -all you need to know is that the `Vec` type provided by the standard library -can hold any type, and when a specific `Vec` holds a specific type, the type -goes within angle brackets. We've told Rust that the `Vec` in `v` will hold -elements of the `i32` type. +Listing 8-1: Creating a new, empty vector to hold values +of type `i32` -In real code, Rust can infer the type of value we want to store once we insert -values, so you rarely need to do this type annotation. It's more common to -create a `Vec` that has initial values, and Rust provides the `vec!` macro for -convenience. The macro will create a new `Vec` that holds the values we give -it. This will create a new `Vec` that holds the values `1`, `2`, and `3`: +Note that we added a type annotation here. Because we aren’t inserting any +values into this vector, Rust doesn’t know what kind of elements we intend to +store. This is an important point. Vectors are implemented using generics; +we’ll cover how to use generics with your own types in Chapter 10. For now, +know that the `Vec` type provided by the standard library can hold any type, +and when a specific vector holds a specific type, the type is specified within +angle brackets. In Listing 8-1, we’ve told Rust that the `Vec` in `v` will +hold elements of the `i32` type. + +In more realistic code, Rust can often infer the type of value you want to +store once you insert values, so you rarely need to do this type annotation. +It’s more common to create a `Vec` that has initial values, and Rust +provides the `vec!` macro for convenience. The macro will create a new vector +that holds the values you give it. Listing 8-2 creates a new `Vec` that +holds the values `1`, `2`, and `3`. The integer type is `i32` because that’s +the default integer type, as we discussed in the [“Data Types”][data-types] section of Chapter 3. ```rust -let v = vec![1, 2, 3]; +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-02/src/main.rs:here}} ``` -Because we've given initial `i32` values, Rust can infer that the type of `v` -is `Vec`, and the type annotation isn't necessary. Let's look at how to -modify a vector next. +Listing 8-2: Creating a new vector containing +values + +Because we’ve given initial `i32` values, Rust can infer that the type of `v` +is `Vec`, and the type annotation isn’t necessary. Next, we’ll look at how +to modify a vector. ### Updating a Vector -To create a vector then add elements to it, we can use the `push` method: +To create a vector and then add elements to it, we can use the `push` method, +as shown in Listing 8-3. ```rust -let mut v = Vec::new(); - -v.push(5); -v.push(6); -v.push(7); -v.push(8); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-03/src/main.rs:here}} ``` -As with any variable as we discussed in Chapter 3, if we want to be able to -change its value, we need to make it mutable with the `mut` keyword. The -numbers we place inside are all `i32`s, and Rust infers this from the data, so -we don't need the `Vec` annotation. +Listing 8-3: Using the `push` method to add values to a +vector -### Dropping a Vector Drops its Elements +As with any variable, if we want to be able to change its value, we need to +make it mutable using the `mut` keyword, as discussed in Chapter 3. The numbers +we place inside are all of type `i32`, and Rust infers this from the data, so +we don’t need the `Vec` annotation. -Like any other `struct`, a vector will be freed when it goes out of scope: +### Dropping a Vector Drops Its Elements + +Like any other `struct`, a vector is freed when it goes out of scope, as +annotated in Listing 8-4. ```rust -{ - let v = vec![1, 2, 3, 4]; - - // do stuff with v - -} // <- v goes out of scope and is freed here +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-04/src/main.rs:here}} ``` -When the vector gets dropped, all of its contents will also be dropped, meaning +Listing 8-4: Showing where the vector and its elements +are dropped + +When the vector gets dropped, all of its contents are also dropped, meaning those integers it holds will be cleaned up. This may seem like a -straightforward point, but can get a little more complicated once we start to -introduce references to the elements of the vector. Let's tackle that next! +straightforward point but can get a bit more complicated when you start to +introduce references to the elements of the vector. Let’s tackle that next! ### Reading Elements of Vectors Now that you know how to create, update, and destroy vectors, knowing how to read their contents is a good next step. There are two ways to reference a -value stored in a vector. In the examples, we've annotated the types of the +value stored in a vector. In the examples, we’ve annotated the types of the values that are returned from these functions for extra clarity. -This example shows both methods of accessing a value in a vector either with -indexing syntax or the `get` method: +Listing 8-5 shows both methods of accessing a value in a vector, either with +indexing syntax or the `get` method. ```rust -let v = vec![1, 2, 3, 4, 5]; - -let third: &i32 = &v[2]; -let third: Option<&i32> = v.get(2); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-05/src/main.rs:here}} ``` -There are a few things to note here. First, that we use the index value of `2` -to get the third element: vectors are indexed by number, starting at zero. -Second, the two different ways to get the third element are: using `&` and -`[]`s, which gives us a reference, or using the `get` method with the index -passed as an argument, which gives us an `Option<&T>`. +Listing 8-5: Using indexing syntax or the `get` method to +access an item in a vector -The reason Rust has two ways to reference an element is so that you can choose -how the program behaves when you try to use an index value that the vector -doesn't have an element for. As an example, what should a program do if it has -a vector that holds five elements then tries to access an element at index 100 -like this: +Note two details here. First, we use the index value of `2` to get the third +element: vectors are indexed by number, starting at zero. Second, the two ways +to get the third element are by using `&` and `[]`, which gives us a reference, +or by using the `get` method with the index passed as an argument, which gives +us an `Option<&T>`. -```rust,should_panic -let v = vec![1, 2, 3, 4, 5]; +Rust has two ways to reference an element so you can choose how the program +behaves when you try to use an index value that the vector doesn’t have an +element for. As an example, let’s see what a program will do if it has a vector +that holds five elements and then tries to access an element at index 100, as +shown in Listing 8-6. -let does_not_exist = &v[100]; -let does_not_exist = v.get(100); +```rust,should_panic,panics +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-06/src/main.rs:here}} ``` -When you run this, you will find that with the first `[]` method, Rust will -cause a `panic!` when a non-existent element is referenced. This method would -be preferable if you want your program to consider an attempt to access an -element past the end of the vector to be a fatal error that should crash the -program. +Listing 8-6: Attempting to access the element at index +100 in a vector containing five elements -When the `get` method is passed an index that is outside the array, it will -return `None` without `panic!`ing. You would use this if accessing an element -beyond the range of the vector will happen occasionally under normal -circumstances. Your code can then have logic to handle having either -`Some(&element)` or `None`, as we discussed in Chapter 6. For example, the -index could be coming from a person entering a number. If they accidentally -enter a number that's too large and your program gets a `None` value, you could -tell the user how many items are in the current `Vec` and give them another -chance to enter a valid value. That would be more user-friendly than crashing -the program for a typo! +When we run this code, the first `[]` method will cause the program to panic +because it references a nonexistent element. This method is best used when you +want your program to crash if there’s an attempt to access an element past the +end of the vector. -#### Invalid References +When the `get` method is passed an index that is outside the vector, it returns +`None` without panicking. You would use this method if accessing an element +beyond the range of the vector happens occasionally under normal circumstances. +Your code will then have logic to handle having either `Some(&element)` or +`None`, as discussed in Chapter 6. For example, the index could be coming from +a person entering a number. If they accidentally enter a number that’s too +large and the program gets a `None` value, you could tell the user how many +items are in the current vector and give them another chance to enter a valid +value. That would be more user-friendly than crashing the program due to a typo! -Once the program has a valid reference, the borrow checker will enforce the -ownership and borrowing rules covered in Chapter 4 to ensure this reference and -any other references to the contents of the vector stay valid. Recall the rule -that says we can't have mutable and immutable references in the same scope. -That rule applies in this example, where we hold an immutable reference to the -first element in a vector and try to add an element to the end: +When the program has a valid reference, the borrow checker enforces the +ownership and borrowing rules (covered in Chapter 4) to ensure this reference +and any other references to the contents of the vector remain valid. Recall the +rule that states you can’t have mutable and immutable references in the same +scope. That rule applies in Listing 8-7, where we hold an immutable reference to +the first element in a vector and try to add an element to the end, which won’t +work if we also try to refer to that element later in the function: -```rust,ignore -let mut v = vec![1, 2, 3, 4, 5]; - -let first = &v[0]; - -v.push(6); +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-07/src/main.rs:here}} ``` -Compiling this will give us this error: +Listing 8-7: Attempting to add an element to a vector +while holding a reference to an item -```text -error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable - | -4 | let first = &v[0]; - | - immutable borrow occurs here -5 | -6 | v.push(6); - | ^ mutable borrow occurs here -7 | } - | - immutable borrow ends here +Compiling this code will result in this error: + +```console +{{#include ../listings/ch08-common-collections/listing-08-07/output.txt}} ``` -This code might look like it should work: why should a reference to the first -element care about what changes about the end of the vector? The reason why -this code isn't allowed is due to the way vectors work. Adding a new element -onto the end of the vector might require allocating new memory and copying the -old elements over to the new space, in the circumstance that there isn't enough -room to put all the elements next to each other where the vector was. In that -case, the reference to the first element would be pointing to deallocated -memory. The borrowing rules prevent programs from ending up in that situation. +The code in Listing 8-7 might look like it should work: why should a reference +to the first element care about what changes at the end of the vector? This +error is due to the way vectors work: adding a new element onto the end of the +vector might require allocating new memory and copying the old elements to the +new space, if there isn’t enough room to put all the elements next to each +other where the vector currently is. In that case, the reference to the first +element would be pointing to deallocated memory. The borrowing rules prevent +programs from ending up in that situation. -> Note: For more on this, see [The Nomicon][nomicon]. +> Note: For more on the implementation details of the `Vec` type, see [“The +> Rustonomicon”][nomicon]. -[nomicon]: https://doc.rust-lang.org/stable/nomicon/vec.html +### Iterating over the Values in a Vector + +If we want to access each element in a vector in turn, we can iterate through +all of the elements rather than use indices to access one at a time. Listing +8-8 shows how to use a `for` loop to get immutable references to each element +in a vector of `i32` values and print them. + +```rust +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-08/src/main.rs:here}} +``` + +Listing 8-8: Printing each element in a vector by +iterating over the elements using a `for` loop + +We can also iterate over mutable references to each element in a mutable vector +in order to make changes to all the elements. The `for` loop in Listing 8-9 +will add `50` to each element. + +```rust +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-09/src/main.rs:here}} +``` + +Listing 8-9: Iterating over mutable references to +elements in a vector + +To change the value that the mutable reference refers to, we have to use the +dereference operator (`*`) to get to the value in `i` before we can use the +`+=` operator. We’ll talk more about the dereference operator in the +[“Following the Pointer to the Value with the Dereference Operator”][deref] +section of Chapter 15. ### Using an Enum to Store Multiple Types At the beginning of this chapter, we said that vectors can only store values -that are all the same type. This can be inconvenient; there are definitely use -cases for needing to store a list of things of different types. Luckily, the -variants of an enum are all defined under the same enum type, so when we need to +that are the same type. This can be inconvenient; there are definitely use +cases for needing to store a list of items of different types. Fortunately, the +variants of an enum are defined under the same enum type, so when we need to store elements of a different type in a vector, we can define and use an enum! -For example, let's say we want to get values from a row in a spreadsheet, where -some of the columns in the row contain integers, some floating point numbers, +For example, say we want to get values from a row in a spreadsheet in which +some of the columns in the row contain integers, some floating-point numbers, and some strings. We can define an enum whose variants will hold the different -value types, and then all of the enum variants will be considered the same -type, that of the enum. Then we can create a vector that holds that enum and -so, ultimately, holds different types: +value types, and then all the enum variants will be considered the same type: +that of the enum. Then we can create a vector that holds that enum and so, +ultimately, holds different types. We’ve demonstrated this in Listing 8-10. ```rust -enum SpreadsheetCell { - Int(i32), - Float(f64), - Text(String), -} - -let row = vec![ - SpreadsheetCell::Int(3), - SpreadsheetCell::Text(String::from("blue")), - SpreadsheetCell::Float(10.12), -]; +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-10/src/main.rs:here}} ``` -The reason Rust needs to know exactly what types will be in the vector at -compile time is so that it knows exactly how much memory on the heap will be -needed to store each element. A secondary advantage to this is that we can be -explicit about what types are allowed in this vector. If Rust allowed a vector -to hold any type, there would be a chance that one or more of the types would -cause errors with the operations performed on the elements of the vector. Using -an enum plus a `match` means that Rust will ensure at compile time that we -always handle every possible case, as we discussed in Chapter 6. +Listing 8-10: Defining an `enum` to store values of +different types in one vector - - +Rust needs to know what types will be in the vector at compile time so it knows +exactly how much memory on the heap will be needed to store each element. A +secondary advantage is that we can be explicit about what types are allowed in +this vector. If Rust allowed a vector to hold any type, there would be a chance +that one or more of the types would cause errors with the operations performed +on the elements of the vector. Using an enum plus a `match` expression means +that Rust will ensure at compile time that every possible case is handled, as +discussed in Chapter 6. -If you don't know at the time that you're writing a program the exhaustive set -of types the program will get at runtime to store in a vector, the enum -technique won't work. Instead, you can use a trait object, which we'll cover in -Chapter 13. +When you’re writing a program, if you don’t know the exhaustive set of types +the program will get at runtime to store in a vector, the enum technique won’t +work. Instead, you can use a trait object, which we’ll cover in Chapter 17. -Now that we've gone over some of the most common ways to use vectors, be sure -to take a look at the API documentation for all of the many useful methods -defined on `Vec` by the standard library. For example, in addition to `push` -there's a `pop` method that will remove and return the last element. Let's move -on to the next collection type: `String`! +Now that we’ve discussed some of the most common ways to use vectors, be sure +to review [the API documentation][vec-api] for all the many useful methods defined on +`Vec` by the standard library. For example, in addition to `push`, a `pop` +method removes and returns the last element. Let’s move on to the next +collection type: `String`! - - - +[data-types]: ch03-02-data-types.html#data-types +[nomicon]: ../nomicon/vec.html +[vec-api]: ../std/vec/struct.Vec.html +[deref]: ch15-02-deref.html#following-the-pointer-to-the-value-with-the-dereference-operator diff --git a/src/ch08-02-strings.md b/src/ch08-02-strings.md index 7e499f8..18314e9 100644 --- a/src/ch08-02-strings.md +++ b/src/ch08-02-strings.md @@ -1,152 +1,161 @@ -## Strings +## Storing UTF-8 Encoded Text with Strings -We've already talked about strings a bunch in Chapter 4, but let's take a more -in-depth look at them now. Strings are an area that new Rustaceans commonly get -stuck on. This is due to a combination of three things: Rust's propensity for -making sure to expose possible errors, strings being a more complicated data -structure than many programmers give them credit for, and UTF-8. These things -combine in a way that can seem difficult when coming from other languages. +We talked about strings in Chapter 4, but we’ll look at them in more depth now. +New Rustaceans commonly get stuck on strings for a combination of three +reasons: Rust’s propensity for exposing possible errors, strings being a more +complicated data structure than many programmers give them credit for, and +UTF-8. These factors combine in a way that can seem difficult when you’re +coming from other programming languages. -The reason Strings are in the collections chapter is that strings are -implemented as a collection of bytes plus some methods to provide useful -functionality when those bytes are interpreted as text. In this section, we'll -talk about the operations on `String` that every collection type has, like -creating, updating, and reading. We'll also discuss the ways in which `String` -is different than the other collections, namely how indexing into a `String` is -complicated by the differences in which people and computers interpret `String` -data. +It’s useful to discuss strings in the context of collections because strings +are implemented as a collection of bytes, plus some methods to provide useful +functionality when those bytes are interpreted as text. In this section, we’ll +talk about the operations on `String` that every collection type has, such as +creating, updating, and reading. We’ll also discuss the ways in which `String` +is different from the other collections, namely how indexing into a `String` is +complicated by the differences between how people and computers interpret +`String` data. -### What is a String? +### What Is a String? -Before we can dig into those aspects, we need to talk about what exactly we -mean by the term 'string'. Rust actually only has one string type in the core -language itself: `str`, the string slice, which is usually seen in its borrowed -form, `&str`. We talked about *string slices* in Chapter 4: these are a -reference to some UTF-8 encoded string data stored elsewhere. String literals, -for example, are stored in the binary output of the program, and are therefore +We’ll first define what we mean by the term *string*. Rust has only one string +type in the core language, which is the string slice `str` that is usually seen +in its borrowed form `&str`. In Chapter 4, we talked about *string slices*, +which are references to some UTF-8 encoded string data stored elsewhere. String +literals, for example, are stored in the program’s binary and are therefore string slices. -The type called `String` is provided in Rust's standard library rather than -coded into the core language, and is a growable, mutable, owned, UTF-8 encoded -string type. When Rustaceans talk about 'strings' in Rust, they usually mean -both the `String` and the string slice `&str` types, not just one of those. -This section is largely about `String`, but both these types are used heavily -in Rust's standard library. Both `String` and string slices are UTF-8 encoded. +The `String` type, which is provided by Rust’s standard library rather than +coded into the core language, is a growable, mutable, owned, UTF-8 encoded +string type. When Rustaceans refer to “strings” in Rust, they usually mean the +`String` and the string slice `&str` types, not just one of those types. +Although this section is largely about `String`, both types are used heavily in +Rust’s standard library, and both `String` and string slices are UTF-8 encoded. -Rust's standard library also includes a number of other string types, such as -`OsString`, `OsStr`, `CString`, and `CStr`. Library crates may provide even -more options for storing string data. Similar to the `*String`/`*Str` naming, -they often provide an owned and borrowed variant, just like `String`/`&str`. -These string types may store different encodings or be represented in memory in -a different way, for example. We won't be talking about these other string -types in this chapter; see their API documentation for more about how to use -them and when each is appropriate. +Rust’s standard library also includes a number of other string types, such as +`OsString`, `OsStr`, `CString`, and `CStr`. Library crates can provide even +more options for storing string data. See how those names all end in `String` +or `Str`? They refer to owned and borrowed variants, just like the `String` and +`str` types you’ve seen previously. These string types can store text in +different encodings or be represented in memory in a different way, for +example. We won’t discuss these other string types in this chapter; see their +API documentation for more about how to use them and when each is appropriate. ### Creating a New String -Many of the same operations available with `Vec` are available with `String` as -well, starting with the `new` function to create a string, like so: +Many of the same operations available with `Vec` are available with `String` +as well, starting with the `new` function to create a string, shown in Listing +8-11. ```rust -let s = String::new(); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-11/src/main.rs:here}} ``` -This creates a new empty string called `s` that we can then load data into. +Listing 8-11: Creating a new, empty `String` -Often, we'll have some initial data that we'd like to start the string off +This line creates a new empty string called `s`, which we can then load data +into. Often, we’ll have some initial data that we want to start the string with. For that, we use the `to_string` method, which is available on any type -that implements the `Display` trait, which string literals do: +that implements the `Display` trait, as string literals do. Listing 8-12 shows +two examples. ```rust -let data = "initial contents"; - -let s = data.to_string(); - -// the method also works on a literal directly: -let s = "initial contents".to_string(); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-12/src/main.rs:here}} ``` -This creates a string containing `initial contents`. +Listing 8-12: Using the `to_string` method to create a +`String` from a string literal + +This code creates a string containing `initial contents`. We can also use the function `String::from` to create a `String` from a string -literal. This is equivalent to using `to_string`: +literal. The code in Listing 8-13 is equivalent to the code from Listing 8-12 +that uses `to_string`. ```rust -let s = String::from("initial contents"); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-13/src/main.rs:here}} ``` -Because strings are used for so many things, there are many different generic -APIs that can be used for strings, so there are a lot of options. Some of them -can feel redundant, but they all have their place! In this case, `String::from` -and `.to_string` end up doing the exact same thing, so which you choose is a -matter of style. +Listing 8-13: Using the `String::from` function to create +a `String` from a string literal + +Because strings are used for so many things, we can use many different generic +APIs for strings, providing us with a lot of options. Some of them can seem +redundant, but they all have their place! In this case, `String::from` and +`to_string` do the same thing, so which you choose is a matter of style. Remember that strings are UTF-8 encoded, so we can include any properly encoded -data in them: +data in them, as shown in Listing 8-14. ```rust -let hello = "السلام عليكم"; -let hello = "Dobrý den"; -let hello = "Hello"; -let hello = "שָׁלוֹם"; -let hello = "नमस्ते"; -let hello = "こんにちは"; -let hello = "안녕하세요"; -let hello = "你好"; -let hello = "Olá"; -let hello = "Здравствуйте"; -let hello = "Hola"; +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-14/src/main.rs:here}} ``` +Listing 8-14: Storing greetings in different languages in +strings + +All of these are valid `String` values. + ### Updating a String -A `String` can grow in size and its contents can change just like the -contents of a `Vec`, by pushing more data into it. In addition, `String` has -concatenation operations implemented with the `+` operator for convenience. +A `String` can grow in size and its contents can change, just like the contents +of a `Vec`, if you push more data into it. In addition, you can conveniently +use the `+` operator or the `format!` macro to concatenate `String` values. -#### Appending to a String with Push +#### Appending to a String with `push_str` and `push` -We can grow a `String` by using the `push_str` method to append a string slice: +We can grow a `String` by using the `push_str` method to append a string slice, +as shown in Listing 8-15. ```rust -let mut s = String::from("foo"); -s.push_str("bar"); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-15/src/main.rs:here}} ``` -`s` will contain "foobar" after these two lines. The `push_str` method takes a -string slice because we don't necessarily want to take ownership of the -parameter. For example, it would be unfortunate if we weren't able to use `s2` -after appending its contents to `s1`: +Listing 8-15: Appending a string slice to a `String` +using the `push_str` method + +After these two lines, `s` will contain `foobar`. The `push_str` method takes a +string slice because we don’t necessarily want to take ownership of the +parameter. For example, the code in Listing 8-16 shows that it would be +unfortunate if we weren’t able to use `s2` after appending its contents to `s1`. ```rust -let mut s1 = String::from("foo"); -let s2 = String::from("bar"); -s1.push_str(&s2); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-16/src/main.rs:here}} ``` -The `push` method is defined to have a single character as a parameter and add -it to the `String`: +Listing 8-16: Using a string slice after appending its +contents to a `String` + +If the `push_str` method took ownership of `s2`, we wouldn’t be able to print +its value on the last line. However, this code works as we’d expect! + +The `push` method takes a single character as a parameter and adds it to the +`String`. Listing 8-17 shows code that adds the letter "l" to a `String` using +the `push` method. ```rust -let mut s = String::from("lo"); -s.push('l'); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-17/src/main.rs:here}} ``` -After this, `s` will contain "lol". +Listing 8-17: Adding one character to a `String` value +using `push` -#### Concatenation with the + Operator or the `format!` Macro +As a result of this code, `s` will contain `lol`. -Often, we'll want to combine two existing strings together. One way is to use -the `+` operator like this: +#### Concatenation with the `+` Operator or the `format!` Macro + +Often, you’ll want to combine two existing strings. One way is to use the `+` +operator, as shown in Listing 8-18. ```rust -let s1 = String::from("Hello, "); -let s2 = String::from("world!"); -let s3 = s1 + &s2; // Note that s1 has been moved here and can no longer be used +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-18/src/main.rs:here}} ``` -After this code the String `s3` will contain `Hello, world!`. The reason that -`s1` is no longer valid after the addition and the reason that we used a +Listing 8-18: Using the `+` operator to combine two +`String` values into a new `String` value + +The string `s3` will contain `Hello, world!` as a result of this code. The +reason `s1` is no longer valid after the addition and the reason we used a reference to `s2` has to do with the signature of the method that gets called when we use the `+` operator. The `+` operator uses the `add` method, whose signature looks something like this: @@ -155,163 +164,146 @@ signature looks something like this: fn add(self, s: &str) -> String { ``` -This isn't the exact signature that's in the standard library; there `add` is -defined using generics. Here, we're looking at the signature of `add` with -concrete types substituted for the generic ones, which is what happens when we -call this method with `String` values. This signature gives us the clues we -need to understand the tricky bits of the `+` operator. +This isn’t the exact signature that’s in the standard library: in the standard +library, `add` is defined using generics. Here, we’re looking at the signature +of `add` with concrete types substituted for the generic ones, which is what +happens when we call this method with `String` values. We’ll discuss generics +in Chapter 10. This signature gives us the clues we need to understand the +tricky bits of the `+` operator. -First of all, `s2` has an `&`, meaning that we are adding a *reference* of the -second string to the first string. This is because of the `s` parameter in the -`add` function: we can only add a `&str` to a `String`, we can't add two -`String`s together. Remember back in Chapter 4 when we talked about how -`&String` will coerce to `&str`: we write `&s2` so that the `String` will -coerce to the proper type, `&str`. Because this method does not take ownership -of the parameter, `s2` will still be valid after this operation. +First, `s2` has an `&`, meaning that we’re adding a *reference* of the second +string to the first string because of the `s` parameter in the `add` function: +we can only add a `&str` to a `String`; we can’t add two `String` values +together. But wait—the type of `&s2` is `&String`, not `&str`, as specified in +the second parameter to `add`. So why does Listing 8-18 compile? + +The reason we’re able to use `&s2` in the call to `add` is that the compiler +can *coerce* the `&String` argument into a `&str`. When we call the `add` +method, Rust uses a *deref coercion*, which here turns `&s2` into `&s2[..]`. +We’ll discuss deref coercion in more depth in Chapter 15. Because `add` does +not take ownership of the `s` parameter, `s2` will still be a valid `String` +after this operation. Second, we can see in the signature that `add` takes ownership of `self`, -because `self` does *not* have an `&`. This means `s1` in the above example -will be moved into the `add` call and no longer be valid after that. So while -`let s3 = s1 + &s2;` looks like it will copy both strings and create a new one, -this statement actually takes ownership of `s1`, appends a copy of `s2`'s -contents, then returns ownership of the result. In other words, it looks like -it's making a lot of copies, but isn't: the implementation is more efficient +because `self` does *not* have an `&`. This means `s1` in Listing 8-18 will be +moved into the `add` call and no longer be valid after that. So although `let +s3 = s1 + &s2;` looks like it will copy both strings and create a new one, this +statement actually takes ownership of `s1`, appends a copy of the contents of +`s2`, and then returns ownership of the result. In other words, it looks like +it’s making a lot of copies but isn’t; the implementation is more efficient than copying. -If we need to concatenate multiple strings, the behavior of `+` gets unwieldy: +If we need to concatenate multiple strings, the behavior of the `+` operator +gets unwieldy: ```rust -let s1 = String::from("tic"); -let s2 = String::from("tac"); -let s3 = String::from("toe"); - -let s = s1 + "-" + &s2 + "-" + &s3; +{{#rustdoc_include ../listings/ch08-common-collections/no-listing-01-concat-multiple-strings/src/main.rs:here}} ``` -`s` will be "tic-tac-toe" at this point. With all of the `+` and `"` -characters, it gets hard to see what's going on. For more complicated string +At this point, `s` will be `tic-tac-toe`. With all of the `+` and `"` +characters, it’s difficult to see what’s going on. For more complicated string combining, we can use the `format!` macro: ```rust -let s1 = String::from("tic"); -let s2 = String::from("tac"); -let s3 = String::from("toe"); - -let s = format!("{}-{}-{}", s1, s2, s3); +{{#rustdoc_include ../listings/ch08-common-collections/no-listing-02-format/src/main.rs:here}} ``` - - - - -This code will also set `s` to "tic-tac-toe". The `format!` macro works in the -same way as `println!`, but instead of printing the output to the screen, it -returns a `String` with the contents. This version is much easier to read, and -also does not take ownership of any of its parameters. +This code also sets `s` to `tic-tac-toe`. The `format!` macro works in the same +way as `println!`, but instead of printing the output to the screen, it returns +a `String` with the contents. The version of the code using `format!` is much +easier to read and doesn’t take ownership of any of its parameters. ### Indexing into Strings -In many other languages, accessing individual characters in a string by -referencing them by index is a valid and common operation. In Rust, however, if -we try to access parts of a `String` using indexing syntax, we'll get an error. -That is, this code: +In many other programming languages, accessing individual characters in a +string by referencing them by index is a valid and common operation. However, +if you try to access parts of a `String` using indexing syntax in Rust, you’ll +get an error. Consider the invalid code in Listing 8-19. -```rust,ignore -let s1 = String::from("hello"); -let h = s1[0]; +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-19/src/main.rs:here}} ``` -will result in this error: +Listing 8-19: Attempting to use indexing syntax with a +String -```text -error: the trait bound `std::string::String: std::ops::Index<_>` is not -satisfied [--explain E0277] - |> - |> let h = s1[0]; - |> ^^^^^ -note: the type `std::string::String` cannot be indexed by `_` +This code will result in the following error: + +```console +{{#include ../listings/ch08-common-collections/listing-08-19/output.txt}} ``` -The error and the note tell the story: Rust strings don't support indexing. So -the follow-up question is, why not? In order to answer that, we have to talk a -bit about how Rust stores strings in memory. +The error and the note tell the story: Rust strings don’t support indexing. But +why not? To answer that question, we need to discuss how Rust stores strings in +memory. #### Internal Representation -A `String` is a wrapper over a `Vec`. Let's take a look at some of our -properly-encoded UTF-8 example strings from before. First, this one: +A `String` is a wrapper over a `Vec`. Let’s look at some of our properly +encoded UTF-8 example strings from Listing 8-14. First, this one: ```rust -let len = String::from("Hola").len(); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-14/src/main.rs:spanish}} ``` -In this case, `len` will be four, which means the `Vec` storing the string -"Hola" is four bytes long: each of these letters takes one byte when encoded in -UTF-8. What about this example, though? +In this case, `len` will be 4, which means the vector storing the string “Hola” +is 4 bytes long. Each of these letters takes 1 byte when encoded in UTF-8. But +what about the following line? (Note that this string begins with the capital +Cyrillic letter Ze, not the Arabic number 3.) ```rust -let len = String::from("Здравствуйте").len(); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-14/src/main.rs:russian}} ``` -A person asked how long the string is might say 12. However, Rust's answer -is 24. This is the number of bytes that it takes to encode "Здравствуйте" in -UTF-8, since each character takes two bytes of storage. Therefore, an index -into the string's bytes will not always correlate to a valid character. +Asked how long the string is, you might say 12. However, Rust’s answer is 24: +that’s the number of bytes it takes to encode “Здравствуйте” in UTF-8, because +each Unicode scalar value in that string takes 2 bytes of storage. Therefore, +an index into the string’s bytes will not always correlate to a valid Unicode +scalar value. To demonstrate, consider this invalid Rust code: -To demonstrate, consider this invalid Rust code: - -```rust,ignore +```rust,ignore,does_not_compile let hello = "Здравствуйте"; let answer = &hello[0]; ``` What should the value of `answer` be? Should it be `З`, the first letter? When -encoded in UTF-8, the first byte of `З` is `208`, and the second is `151`, so +encoded in UTF-8, the first byte of `З` is `208` and the second is `151`, so `answer` should in fact be `208`, but `208` is not a valid character on its -own. Returning `208` is likely not what a person would want if they asked for -the first letter of this string, but that's the only data that Rust has at byte -index 0. Returning the byte value is probably not what people want, even with -only Latin letters: `&"hello"[0]` would return `104`, not `h`. To avoid -returning an unexpected value and causing bugs that might not be discovered -immediately, Rust chooses to not compile this code at all and prevent -misunderstandings earlier. +own. Returning `208` is likely not what a user would want if they asked for the +first letter of this string; however, that’s the only data that Rust has at +byte index 0. Users generally don’t want the byte value returned, even if the +string contains only Latin letters: if `&"hello"[0]` were valid code that +returned the byte value, it would return `104`, not `h`. To avoid returning an +unexpected value and causing bugs that might not be discovered immediately, +Rust doesn’t compile this code at all and prevents misunderstandings early in +the development process. -#### Bytes and Scalar Values and Grapheme Clusters! Oh my! +#### Bytes and Scalar Values and Grapheme Clusters! Oh My! -This leads to another point about UTF-8: there are really three relevant ways -to look at strings, from Rust's perspective: as bytes, scalar values, and -grapheme clusters (the closest thing to what people would call 'letters'). +Another point about UTF-8 is that there are actually three relevant ways to +look at strings from Rust’s perspective: as bytes, scalar values, and grapheme +clusters (the closest thing to what we would call *letters*). -If we look at the Hindi word "नमस्ते" written in the Devanagari script, it is -ultimately stored as a `Vec` of `u8` values that looks like this: +If we look at the Hindi word “नमस्ते” written in the Devanagari script, it is +stored as a vector of `u8` values that looks like this: ```text -[224, 164, 168, 224, 164, 174, 224, 164, 184, 224, 165, 141, 224, 164, 164, 224, 165, 135] +[224, 164, 168, 224, 164, 174, 224, 164, 184, 224, 165, 141, 224, 164, 164, +224, 165, 135] ``` -That's 18 bytes, and is how computers ultimately store this data. If we look at -them as Unicode scalar values, which are what Rust's `char` type is, those +That’s 18 bytes and is how computers ultimately store this data. If we look at +them as Unicode scalar values, which are what Rust’s `char` type is, those bytes look like this: ```text ['न', 'म', 'स', '्', 'त', 'े'] ``` -There are six `char` values here, but the fourth and sixth are not letters, -they're diacritics that don't make sense on their own. Finally, if we look at -them as grapheme clusters, we'd get what a person would call the four letters -that make up this word: +There are six `char` values here, but the fourth and sixth are not letters: +they’re diacritics that don’t make sense on their own. Finally, if we look at +them as grapheme clusters, we’d get what a person would call the four letters +that make up the Hindi word: ```text ["न", "म", "स्", "ते"] @@ -321,20 +313,21 @@ Rust provides different ways of interpreting the raw string data that computers store so that each program can choose the interpretation it needs, no matter what human language the data is in. -A final reason Rust does not allow you to index into a `String` to get a +A final reason Rust doesn’t allow us to index into a `String` to get a character is that indexing operations are expected to always take constant time -(O(1)). It isn't possible to guarantee that performance with a `String`, -though, since Rust would have to walk through the contents from the beginning -to the index to determine how many valid characters there were. - -All of these problems mean that Rust does not implement `[]` for `String`, so -we cannot directly do this. +(O(1)). But it isn’t possible to guarantee that performance with a `String`, +because Rust would have to walk through the contents from the beginning to the +index to determine how many valid characters there were. ### Slicing Strings -However, indexing the *bytes* of a string is very useful, and is not expected -to be fast. While we can't use `[]` with a single number, we _can_ use `[]` -with a range to create a string slice containing particular bytes: +Indexing into a string is often a bad idea because it’s not clear what the +return type of the string-indexing operation should be: a byte value, a +character, a grapheme cluster, or a string slice. Therefore, Rust asks you to +be more specific if you really need to use indices to create string slices. To +be more specific in your indexing and indicate that you want a string slice, +rather than indexing using `[]` with a single number, you can use `[]` with a +range to create a string slice containing particular bytes: ```rust let hello = "Здравствуйте"; @@ -342,27 +335,27 @@ let hello = "Здравствуйте"; let s = &hello[0..4]; ``` -Here, `s` will be a `&str` that contains the first four bytes of the string. -Earlier, we mentioned that each of these characters was two bytes, so that -means that `s` will be "Зд". +Here, `s` will be a `&str` that contains the first 4 bytes of the string. +Earlier, we mentioned that each of these characters was 2 bytes, which means +`s` will be `Зд`. -What would happen if we did `&hello[0..1]`? The answer: it will panic at -runtime, in the same way that accessing an invalid index in a vector does: +What would happen if we used `&hello[0..1]`? The answer: Rust would panic at +runtime in the same way as if an invalid index were accessed in a vector: -```text -thread 'main' panicked at 'index 0 and/or 1 in `Здравствуйте` do not lie on -character boundary', ../src/libcore/str/mod.rs:1694 +```console +{{#include ../listings/ch08-common-collections/output-only-01-not-char-boundary/output.txt}} ``` -You should use this with caution, since it can cause your program to crash. +You should use ranges to create string slices with caution, because doing so +can crash your program. ### Methods for Iterating Over Strings -Luckily, there are other ways we can access elements in a String. +Fortunately, you can access elements in a string in other ways. -If we need to perform operations on individual characters, the best way to do -so is to use the `chars` method. Calling `chars` on "नमस्ते" separates out and -returns six values of type `char`, and you can iterate over the result in order +If you need to perform operations on individual Unicode scalar values, the best +way to do so is to use the `chars` method. Calling `chars` on “नमस्ते” separates +out and returns six values of type `char`, and you can iterate over the result to access each element: ```rust @@ -371,7 +364,7 @@ for c in "नमस्ते".chars() { } ``` -This code will print: +This code will print the following: ```text न @@ -391,40 +384,32 @@ for b in "नमस्ते".bytes() { } ``` -This code will print the 18 bytes that make up this `String`, starting with: +This code will print the 18 bytes that make up this `String`: ```text 224 164 -168 -224 -// ... etc +// --snip-- +165 +135 ``` -But make sure to remember that valid UTF-8 characters may be made up of more -than one byte. +But be sure to remember that valid Unicode scalar values may be made up of more +than 1 byte. -Getting grapheme clusters from `String`s is complex, so this functionality is -not provided by the standard library. There are crates available on crates.io -if this is the functionality you need. +Getting grapheme clusters from strings is complex, so this functionality is not +provided by the standard library. Crates are available on +[crates.io](https://crates.io/) if this is the functionality you need. - - - - -### Strings are Not so Simple +### Strings Are Not So Simple To summarize, strings are complicated. Different programming languages make different choices about how to present this complexity to the programmer. Rust has chosen to make the correct handling of `String` data the default behavior -for all Rust programs, which does mean programmers have to put more thought -into handling UTF-8 data upfront. This tradeoff exposes more of the complexity -of strings than other programming languages do, but this will prevent you from -having to handle errors involving non-ASCII characters later in your -development lifecycle. +for all Rust programs, which means programmers have to put more thought into +handling UTF-8 data upfront. This trade-off exposes more of the complexity of +strings than is apparent in other programming languages, but it prevents you +from having to handle errors involving non-ASCII characters later in your +development life cycle. -Let's switch to something a bit less complex: hash map! +Let’s switch to something a bit less complex: hash maps! diff --git a/src/ch08-03-hash-maps.md b/src/ch08-03-hash-maps.md index 4721f71..12f6b6e 100644 --- a/src/ch08-03-hash-maps.md +++ b/src/ch08-03-hash-maps.md @@ -1,137 +1,122 @@ -## Hash Maps +## Storing Keys with Associated Values in Hash Maps -The last of our fundamental collections is the *hash map*. The type `HashMap` stores a mapping of keys of type `K` to values of type `V`. It does this -via a *hashing function*, which determines how it places these keys and values -into memory. Many different programming languages support this kind of data -structure, but often with a different name: hash, map, object, hash table, or -associative array, just to name a few. +The last of our common collections is the *hash map*. The type `HashMap` +stores a mapping of keys of type `K` to values of type `V`. It does this via a +*hashing function*, which determines how it places these keys and values into +memory. Many programming languages support this kind of data structure, but +they often use a different name, such as hash, map, object, hash table, +dictionary, or associative array, just to name a few. -Hash maps are useful for when you want to be able to look up data not by an -index, as you can with vectors, but by using a key that can be of any type. For -example, in a game, you could keep track of each team's score in a hash map -where each key is a team's name and the values are each team's score. Given a -team name, you can retrieve their score. +Hash maps are useful when you want to look up data not by using an index, as +you can with vectors, but by using a key that can be of any type. For example, +in a game, you could keep track of each team’s score in a hash map in which +each key is a team’s name and the values are each team’s score. Given a team +name, you can retrieve its score. -We'll go over the basic API of hash maps in this chapter, but there are many -more goodies hiding in the functions defined on `HashMap` by the standard -library. As always, check the standard library documentation for more -information. +We’ll go over the basic API of hash maps in this section, but many more goodies +are hiding in the functions defined on `HashMap` by the standard library. +As always, check the standard library documentation for more information. ### Creating a New Hash Map -We can create an empty `HashMap` with `new`, and add elements with `insert`. -Here we're keeping track of the scores of two teams whose names are Blue and -Yellow. The Blue team will start with 10 points and the Yellow team starts with -50: +You can create an empty hash map with `new` and add elements with `insert`. In +Listing 8-20, we’re keeping track of the scores of two teams whose names are +Blue and Yellow. The Blue team starts with 10 points, and the Yellow team +starts with 50. ```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Yellow"), 50); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-20/src/main.rs:here}} ``` +Listing 8-20: Creating a new hash map and inserting some +keys and values + Note that we need to first `use` the `HashMap` from the collections portion of -the standard library. Of our three fundamental collections, this one is the -least often used, so it's not included in the features imported automatically -in the prelude. Hash maps also have less support from the standard library; -there's no built-in macro to construct them, for example. +the standard library. Of our three common collections, this one is the least +often used, so it’s not included in the features brought into scope +automatically in the prelude. Hash maps also have less support from the +standard library; there’s no built-in macro to construct them, for example. Just like vectors, hash maps store their data on the heap. This `HashMap` has keys of type `String` and values of type `i32`. Like vectors, hash maps are -homogeneous: all of the keys must have the same type, and all of the values must -have the same type. +homogeneous: all of the keys must have the same type, and all of the values +must have the same type. -Another way of constructing a hash map is by using the `collect` method on a -vector of tuples, where each tuple consists of a key and its value. The -`collect` method gathers up data into a number of collection types, including -`HashMap`. For example, if we had the team names and initial scores in two -separate vectors, we can use the `zip` method to create a vector of tuples -where "Blue" is paired with 10, and so forth. Then we can use the `collect` -method to turn that vector of tuples into a `HashMap`: +Another way of constructing a hash map is by using iterators and the `collect` +method on a vector of tuples, where each tuple consists of a key and its value. +We’ll be going into more detail about iterators and their associated methods in +the [”Processing a Series of Items with Iterators” section of Chapter +13][iterators]. The `collect` method gathers data into a number +of collection types, including `HashMap`. For example, if we had the team names +and initial scores in two separate vectors, we could use the `zip` method to +create a vector of tuples where “Blue” is paired with 10, and so forth. Then we +could use the `collect` method to turn that vector of tuples into a hash map, +as shown in Listing 8-21. ```rust -use std::collections::HashMap; - -let teams = vec![String::from("Blue"), String::from("Yellow")]; -let initial_scores = vec![10, 50]; - -let scores: HashMap<_, _> = teams.iter().zip(initial_scores.iter()).collect(); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-21/src/main.rs:here}} ``` -The type annotation `HashMap<_, _>` is needed here because it's possible to -`collect` into many different data structures, and Rust doesn't know which you -want unless you specify. For the type parameters for the key and value types, -however, we use underscores and Rust can infer the types that the hash map -contains based on the types of the data in the vector. +Listing 8-21: Creating a hash map from a list of teams +and a list of scores + +The type annotation `HashMap<_, _>` is needed here because it’s possible to +`collect` into many different data structures and Rust doesn’t know which you +want unless you specify. For the parameters for the key and value types, +however, we use underscores, and Rust can infer the types that the hash map +contains based on the types of the data in the vectors. In Listing 8-21, the +key type will be `String` and the value type will be `i32`, just as the types +were in Listing 8-20. ### Hash Maps and Ownership For types that implement the `Copy` trait, like `i32`, the values are copied into the hash map. For owned values like `String`, the values will be moved and -the hash map will be the owner of those values: +the hash map will be the owner of those values, as demonstrated in Listing 8-22. ```rust -use std::collections::HashMap; - -let field_name = String::from("Favorite color"); -let field_value = String::from("Blue"); - -let mut map = HashMap::new(); -map.insert(field_name, field_value); -// field_name and field_value are invalid at this point +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-22/src/main.rs:here}} ``` -We would not be able to use the bindings `field_name` and `field_value` after -they have been moved into the hash map with the call to `insert`. +Listing 8-22: Showing that keys and values are owned by +the hash map once they’re inserted -If we insert references to values into the hash map, the values themselves will -not be moved into the hash map. The values that the references point to must be -valid for at least as long as the hash map is valid, though. We will talk more -about these issues in the Lifetimes section of Chapter 10. +We aren’t able to use the variables `field_name` and `field_value` after +they’ve been moved into the hash map with the call to `insert`. + +If we insert references to values into the hash map, the values won’t be moved +into the hash map. The values that the references point to must be valid for at +least as long as the hash map is valid. We’ll talk more about these issues in +the [“Validating References with +Lifetimes”][validating-references-with-lifetimes] section in +Chapter 10. ### Accessing Values in a Hash Map -We can get a value out of the hash map by providing its key to the `get` method: +We can get a value out of the hash map by providing its key to the `get` +method, as shown in Listing 8-23. ```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Yellow"), 50); - -let team_name = String::from("Blue"); -let score = scores.get(&team_name); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-23/src/main.rs:here}} ``` -Here, `score` will have the value that's associated with the Blue team, and the -result will be `Some(10)`. The result is wrapped in `Some` because `get` -returns an `Option`; if there's no value for that key in the hash map, `get` -will return `None`. The program will need to handle the `Option` in one of -the ways that we covered in Chapter 6. +Listing 8-23: Accessing the score for the Blue team +stored in the hash map + +Here, `score` will have the value that’s associated with the Blue team, and the +result will be `Some(&10)`. The result is wrapped in `Some` because `get` +returns an `Option<&V>`; if there’s no value for that key in the hash map, +`get` will return `None`. The program will need to handle the `Option` in one +of the ways that we covered in Chapter 6. We can iterate over each key/value pair in a hash map in a similar manner as we do with vectors, using a `for` loop: ```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Yellow"), 50); - -for (key, value) in &scores { - println!("{}: {}", key, value); -} +{{#rustdoc_include ../listings/ch08-common-collections/no-listing-03-iterate-over-hashmap/src/main.rs:here}} ``` -This will print each pair, in an arbitrary order: +This code will print each pair in an arbitrary order: ```text Yellow: 50 @@ -140,137 +125,127 @@ Blue: 10 ### Updating a Hash Map - - - -While the number of keys and values is growable, each individual key can only -have one value associated with it at a time. When we want to change the data in -a hash map, we have to decide how to handle the case when a key already has a -value assigned. We could choose to replace the old value with the new value, -completely disregarding the old value. We could choose to keep the old value -and ignore the new value, and only add the new value if the key *doesn't* -already have a value. Or we could combine the old value and the new value. -Let's look at how to do each of these! +Although the number of keys and values is growable, each key can only have one +value associated with it at a time. When you want to change the data in a hash +map, you have to decide how to handle the case when a key already has a value +assigned. You could replace the old value with the new value, completely +disregarding the old value. You could keep the old value and ignore the new +value, only adding the new value if the key *doesn’t* already have a value. Or +you could combine the old value and the new value. Let’s look at how to do each +of these! #### Overwriting a Value -If we insert a key and a value into a hash map, then insert that same key with a -different value, the value associated with that key will be replaced. Even -though this following code calls `insert` twice, the hash map will only contain -one key/value pair because we're inserting the value for the Blue team's key -both times: +If we insert a key and a value into a hash map and then insert that same key +with a different value, the value associated with that key will be replaced. +Even though the code in Listing 8-24 calls `insert` twice, the hash map will +only contain one key/value pair because we’re inserting the value for the Blue +team’s key both times. ```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); - -scores.insert(String::from("Blue"), 10); -scores.insert(String::from("Blue"), 25); - -println!("{:?}", scores); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-24/src/main.rs:here}} ``` -This will print `{"Blue": 25}`. The original value of 10 has been overwritten. +Listing 8-24: Replacing a value stored with a particular +key +This code will print `{"Blue": 25}`. The original value of `10` has been +overwritten. -#### Only Insert If the Key Has No Value +#### Only Inserting a Value If the Key Has No Value -It's common to want to check if a particular key has a value and, if it does -not, insert a value for it. Hash maps have a special API for this, called -`entry`, that takes the key we want to check as an argument. The return value -of the `entry` function is an enum, `Entry`, that represents a value that might -or might not exist. Let's say that we want to check if the key for the Yellow -team has a value associated with it. If it doesn't, we want to insert the value -50, and the same for the Blue team. With the entry API, the code for this -looks like: +It’s common to check whether a particular key has a value and, if it doesn’t, +insert a value for it. Hash maps have a special API for this called `entry` +that takes the key you want to check as a parameter. The return value of the +`entry` method is an enum called `Entry` that represents a value that might or +might not exist. Let’s say we want to check whether the key for the Yellow team +has a value associated with it. If it doesn’t, we want to insert the value 50, +and the same for the Blue team. Using the `entry` API, the code looks like +Listing 8-25. ```rust -use std::collections::HashMap; - -let mut scores = HashMap::new(); -scores.insert(String::from("Blue"), 10); - -scores.entry(String::from("Yellow")).or_insert(50); -scores.entry(String::from("Blue")).or_insert(50); - -println!("{:?}", scores); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-25/src/main.rs:here}} ``` -The `or_insert` method on `Entry` returns the value for the `Entry`'s key if it -exists, and if not, inserts its argument as the new value for the `Entry`'s key -and returns that. This is much cleaner than writing the logic ourselves, and in -addition, plays more nicely with the borrow checker. +Listing 8-25: Using the `entry` method to only insert if +the key does not already have a value -This code will print `{"Yellow": 50, "Blue": 10}`. The first call to `entry` -will insert the key for the Yellow team with the value 50, since the Yellow -team doesn't have a value already. The second call to `entry` will not change -the hash map since the Blue team already has the value 10. +The `or_insert` method on `Entry` is defined to return a mutable reference to +the value for the corresponding `Entry` key if that key exists, and if not, +inserts the parameter as the new value for this key and returns a mutable +reference to the new value. This technique is much cleaner than writing the +logic ourselves and, in addition, plays more nicely with the borrow checker. -#### Update a Value Based on the Old Value +Running the code in Listing 8-25 will print `{"Yellow": 50, "Blue": 10}`. The +first call to `entry` will insert the key for the Yellow team with the value +50 because the Yellow team doesn’t have a value already. The second call to +`entry` will not change the hash map because the Blue team already has the +value 10. -Another common use case for hash maps is to look up a key's value then update -it, based on the old value. For instance, if we wanted to count how many times -each word appeared in some text, we could use a hash map with the words as keys -and increment the value to keep track of how many times we've seen that word. -If this is the first time we've seen a word, we'll first insert the value `0`. +#### Updating a Value Based on the Old Value + +Another common use case for hash maps is to look up a key’s value and then +update it based on the old value. For instance, Listing 8-26 shows code that +counts how many times each word appears in some text. We use a hash map with +the words as keys and increment the value to keep track of how many times we’ve +seen that word. If it’s the first time we’ve seen a word, we’ll first insert +the value 0. ```rust -use std::collections::HashMap; - -let text = "hello world wonderful world"; - -let mut map = HashMap::new(); - -for word in text.split_whitespace() { - let count = map.entry(word).or_insert(0); - *count += 1; -} - -println!("{:?}", map); +{{#rustdoc_include ../listings/ch08-common-collections/listing-08-26/src/main.rs:here}} ``` -This will print `{"world": 2, "hello": 1, "wonderful": 1}`. The `or_insert` -method actually returns a mutable reference (`&mut V`) to the value for this -key. Here we store that mutable reference in the `count` variable, so in order -to assign to that value we must first dereference `count` using the asterisk -(`*`). The mutable reference goes out of scope at the end of the `for` loop, so -all of these changes are safe and allowed by the borrowing rules. +Listing 8-26: Counting occurrences of words using a hash +map that stores words and counts -### Hashing Function +This code will print `{"world": 2, "hello": 1, "wonderful": 1}`. The +`or_insert` method actually returns a mutable reference (`&mut V`) to the value +for this key. Here we store that mutable reference in the `count` variable, so +in order to assign to that value, we must first dereference `count` using the +asterisk (`*`). The mutable reference goes out of scope at the end of the `for` +loop, so all of these changes are safe and allowed by the borrowing rules. -By default, `HashMap` uses a cryptographically secure hashing function that can -provide resistance to Denial of Service (DoS) attacks. This is not the fastest -hashing algorithm out there, but the tradeoff for better security that comes -with the drop in performance is worth it. If you profile your code and find -that the default hash function is too slow for your purposes, you can switch to -another function by specifying a different *hasher*. A hasher is a type that -implements the `BuildHasher` trait. We'll be talking about traits and how to -implement them in Chapter 10. +### Hashing Functions + +By default, `HashMap` uses a hashing function called SipHash that can provide +resistance to Denial of Service (DoS) attacks involving hash tables[^siphash]. This +is not the fastest hashing algorithm available, but the trade-off for better +security that comes with the drop in performance is worth it. If you profile +your code and find that the default hash function is too slow for your +purposes, you can switch to another function by specifying a different +*hasher*. A hasher is a type that implements the `BuildHasher` trait. We’ll +talk about traits and how to implement them in Chapter 10. You don’t +necessarily have to implement your own hasher from scratch; +[crates.io](https://crates.io/) has libraries shared by other Rust users that +provide hashers implementing many common hashing algorithms. + +[^siphash]: [https://en.wikipedia.org/wiki/SipHash](https://en.wikipedia.org/wiki/SipHash) ## Summary -Vectors, strings, and hash maps will take you far in programs where you need to -store, access, and modify data. Here are some exercises you should now be -equipped to solve: +Vectors, strings, and hash maps will provide a large amount of functionality +necessary in programs when you need to store, access, and modify data. Here are +some exercises you should now be equipped to solve: -1. Given a list of integers, use a vector and return the mean (average), median - (when sorted, the value in the middle position), and mode (the value that - occurs most often; a hash map will be helpful here) of the list. -2. Convert strings to Pig Latin, where the first consonant of each word is - moved to the end of the word with an added "ay", so "first" becomes - "irst-fay". Words that start with a vowel get "hay" added to the end instead - ("apple" becomes "apple-hay"). Remember about UTF-8 encoding! -3. Using a hash map and vectors, create a text interface to allow a user to add - employee names to a department in the company. For example, "Add Sally to - Engineering" or "Add Amir to Sales". Then let the user retrieve a list of all - people in a department or all people in the company by department, sorted - alphabetically. +* Given a list of integers, use a vector and return the mean (the average + value), median (when sorted, the value in the middle position), and mode (the + value that occurs most often; a hash map will be helpful here) of the list. +* Convert strings to pig latin. The first consonant of each word is moved to + the end of the word and “ay” is added, so “first” becomes “irst-fay.” Words + that start with a vowel have “hay” added to the end instead (“apple” becomes + “apple-hay”). Keep in mind the details about UTF-8 encoding! +* Using a hash map and vectors, create a text interface to allow a user to add + employee names to a department in a company. For example, “Add Sally to + Engineering” or “Add Amir to Sales.” Then let the user retrieve a list of all + people in a department or all people in the company by department, sorted + alphabetically. -The standard library API documentation describes methods these types have that -will be helpful for these exercises! +The standard library API documentation describes methods that vectors, strings, +and hash maps have that will be helpful for these exercises! -We're getting into more complex programs where operations can fail, which means -it's a perfect time to go over error handling next! +We’re getting into more complex programs in which operations can fail, so, it’s +a perfect time to discuss error handling. We’ll do that next! + +[iterators]: ch13-02-iterators.html +[validating-references-with-lifetimes]: +ch10-03-lifetime-syntax.html#validating-references-with-lifetimes diff --git a/src/ch09-00-error-handling.md b/src/ch09-00-error-handling.md index 97b2600..a4c3583 100644 --- a/src/ch09-00-error-handling.md +++ b/src/ch09-00-error-handling.md @@ -1,23 +1,24 @@ # Error Handling -Rust's commitment to reliability extends to error handling. Errors are a fact +Rust’s commitment to reliability extends to error handling. Errors are a fact of life in software, so Rust has a number of features for handling situations -in which something goes wrong. In many cases, Rust will require you to -acknowledge the possibility of an error occurring and take some action before -your code will compile. This makes your program more robust by ensuring that you -won't only discover errors after you've deployed your code to production. +in which something goes wrong. In many cases, Rust requires you to acknowledge +the possibility of an error and take some action before your code will compile. +This requirement makes your program more robust by ensuring that you’ll +discover errors and handle them appropriately before you’ve deployed your code +to production! Rust groups errors into two major categories: *recoverable* and *unrecoverable* -errors. Recoverable errors are situations when it's usually reasonable to -report the problem to the user and retry the operation, like a file not being -found. Unrecoverable errors are always symptoms of bugs, like trying to access -a location beyond the end of an array. +errors. For a recoverable error, such as a file not found error, it’s +reasonable to report the problem to the user and retry the operation. +Unrecoverable errors are always symptoms of bugs, like trying to access a +location beyond the end of an array. -Most languages don't distinguish between the two kinds of errors, and handle -both in the same way using mechanisms like exceptions. Rust doesn't have -exceptions. Instead, it has the value `Result` for recoverable errors and -the `panic!` macro that stops execution when it encounters unrecoverable -errors. This chapter will cover calling `panic!` first, then talk about -returning `Result` values. Finally, we'll discuss considerations to take -into account when deciding whether to try to recover from an error or to stop +Most languages don’t distinguish between these two kinds of errors and handle +both in the same way, using mechanisms such as exceptions. Rust doesn’t have +exceptions. Instead, it has the type `Result` for recoverable errors and +the `panic!` macro that stops execution when the program encounters an +unrecoverable error. This chapter covers calling `panic!` first and then talks +about returning `Result` values. Additionally, we’ll explore +considerations when deciding whether to try to recover from an error or to stop execution. diff --git a/src/ch09-01-unrecoverable-errors-with-panic.md b/src/ch09-01-unrecoverable-errors-with-panic.md index ac50432..ede7cc6 100644 --- a/src/ch09-01-unrecoverable-errors-with-panic.md +++ b/src/ch09-01-unrecoverable-errors-with-panic.md @@ -1,183 +1,161 @@ ## Unrecoverable Errors with `panic!` -Sometimes, bad things happen, and there's nothing that you can do about it. For -these cases, Rust has the `panic!` macro. When this macro executes, your -program will print a failure message, unwind and clean up the stack, and then -quit. The most common situation this occurs in is when a bug of some kind has -been detected and it's not clear to the programmer how to handle the error. +Sometimes, bad things happen in your code, and there’s nothing you can do about +it. In these cases, Rust has the `panic!` macro. When the `panic!` macro +executes, your program will print a failure message, unwind and clean up the +stack, and then quit. This most commonly occurs when a bug of some kind has +been detected and it’s not clear to the programmer how to handle the error. - - -> #### Unwinding -> By default, when a `panic!` occurs, the program starts -> *unwinding*, which means Rust walks back up the stack and cleans up the data -> from each function it encounters, but this walking and cleanup is a lot of -> work. The alternative is to immediately `abort`, which ends the program -> without cleaning up. Memory that the program was using will then need to be -> cleaned up by the operating system. If in your program you need to make -> the resulting binary as small as possible, you can switch from unwinding to -> aborting on panic by adding `panic = 'abort'` to the appropriate `[profile]` -> sections in your `Cargo.toml`. For example, if you want to abort on panic in -> release mode: +> ### Unwinding the Stack or Aborting in Response to a Panic +> +> By default, when a panic occurs, the program starts *unwinding*, which +> means Rust walks back up the stack and cleans up the data from each function +> it encounters. But this walking back and cleanup is a lot of work. The +> alternative is to immediately *abort*, which ends the program without +> cleaning up. Memory that the program was using will then need to be cleaned +> up by the operating system. If in your project you need to make the resulting +> binary as small as possible, you can switch from unwinding to aborting upon a +> panic by adding `panic = 'abort'` to the appropriate `[profile]` sections in +> your *Cargo.toml* file. For example, if you want to abort on panic in release +> mode, add this: > > ```toml > [profile.release] > panic = 'abort' > ``` - - -Let's try calling `panic!()` with a simple program: +Let’s try calling `panic!` in a simple program: Filename: src/main.rs -```rust,should_panic -fn main() { - panic!("crash and burn"); -} +```rust,should_panic,panics +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-01-panic/src/main.rs}} ``` -If you run it, you'll see something like this: +When you run the program, you’ll see something like this: -```text -$ cargo run - Compiling panic v0.1.0 (file:///projects/panic) - Finished debug [unoptimized + debuginfo] target(s) in 0.25 secs - Running `target/debug/panic` -thread 'main' panicked at 'crash and burn', src/main.rs:2 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/panic` (exit code: 101) +```console +{{#include ../listings/ch09-error-handling/no-listing-01-panic/output.txt}} ``` -The last three lines contain the error message caused by the call to `panic!`. +The call to `panic!` causes the error message contained in the last two lines. The first line shows our panic message and the place in our source code where -the panic occurred: `src/main.rs:2` indicates that it's the second like of our -*main.rs* file. +the panic occurred: *src/main.rs:2:5* indicates that it’s the second line, +fifth character of our *src/main.rs* file. -In this case, the line indicated is part of our code, and if we go to that line -we see the `panic!` macro call. In other cases, the `panic!` call might be in -code that our code calls. The filename and line number reported by the error -message will be someone else's code where the `panic!` macro is called, not the -line of our code that eventually led to the `panic!`. We can use the backtrace -of the functions the `panic!` call came from to figure this out. +In this case, the line indicated is part of our code, and if we go to that +line, we see the `panic!` macro call. In other cases, the `panic!` call might +be in code that our code calls, and the filename and line number reported by +the error message will be someone else’s code where the `panic!` macro is +called, not the line of our code that eventually led to the `panic!` call. We +can use the backtrace of the functions the `panic!` call came from to figure +out the part of our code that is causing the problem. We’ll discuss what a +backtrace is in more detail next. ### Using a `panic!` Backtrace -Let's look at another example to see what it's like when a `panic!` call comes +Let’s look at another example to see what it’s like when a `panic!` call comes from a library because of a bug in our code instead of from our code calling -the macro directly: +the macro directly. Listing 9-1 has some code that attempts to access an +element by index in a vector. Filename: src/main.rs -```rust,should_panic -fn main() { - let v = vec![1, 2, 3]; - - v[100]; -} +```rust,should_panic,panics +{{#rustdoc_include ../listings/ch09-error-handling/listing-09-01/src/main.rs}} ``` -We're attempting to access the hundredth element of our vector, but it only has -three elements. In this situation, Rust will panic. Using `[]` is supposed to -return an element, but if you pass an invalid index, there's no element that -Rust could return here that would be correct. +Listing 9-1: Attempting to access an element beyond the +end of a vector, which will cause a call to `panic!` -Other languages like C will attempt to give you exactly what you asked for in -this situation, even though it isn't what you want: you'll get whatever is at -the location in memory that would correspond to that element in the vector, -even though the memory doesn't belong to the vector. This is called a *buffer -overread*, and can lead to security vulnerabilities if an attacker can -manipulate the index in such a way as to read data they shouldn't be allowed to -that is stored after the array. +Here, we’re attempting to access the 100th element of our vector (which is at +index 99 because indexing starts at zero), but it has only 3 elements. In this +situation, Rust will panic. Using `[]` is supposed to return an element, but if +you pass an invalid index, there’s no element that Rust could return here that +would be correct. -In order to protect your program from this sort of vulnerability, if you try to -read an element at an index that doesn't exist, Rust will stop execution and -refuse to continue. Let's try it and see: +In C, attempting to read beyond the end of a data structure is undefined +behavior. You might get whatever is at the location in memory that would +correspond to that element in the data structure, even though the memory +doesn’t belong to that structure. This is called a *buffer overread* and can +lead to security vulnerabilities if an attacker is able to manipulate the index +in such a way as to read data they shouldn’t be allowed to that is stored after +the data structure. -```text -$ cargo run - Compiling panic v0.1.0 (file:///projects/panic) - Finished debug [unoptimized + debuginfo] target(s) in 0.27 secs - Running `target/debug/panic` -thread 'main' panicked at 'index out of bounds: the len is 3 but the index is -100', ../src/libcollections/vec.rs:1265 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -error: Process didn't exit successfully: `target/debug/panic` (exit code: 101) +To protect your program from this sort of vulnerability, if you try to read an +element at an index that doesn’t exist, Rust will stop execution and refuse to +continue. Let’s try it and see: + +```console +{{#include ../listings/ch09-error-handling/listing-09-01/output.txt}} ``` -This points at a file we didn't write, *../src/libcollections/vec.rs*. That's -the implementation of `Vec` in the standard library. The code that gets run -when we use `[]` on our vector `v` is in *../src/libcollections/vec.rs*, and -that is where the `panic!` is actually happening. +This error points at line 4 of our `main.rs` where we attempt to access index +99. The next note line tells us that we can set the `RUST_BACKTRACE` +environment variable to get a backtrace of exactly what happened to cause the +error. A *backtrace* is a list of all the functions that have been called to +get to this point. Backtraces in Rust work as they do in other languages: the +key to reading the backtrace is to start from the top and read until you see +files you wrote. That’s the spot where the problem originated. The lines above +the lines mentioning your files are code that your code called; the lines below +are code that called your code. These lines might include core Rust code, +standard library code, or crates that you’re using. Let’s try getting a +backtrace by setting the `RUST_BACKTRACE` environment variable to any value +except 0. Listing 9-2 shows output similar to what you’ll see. -The next `note` line tells us that we can set the `RUST_BACKTRACE` environment -variable to get a backtrace of exactly what happened to cause the error. Let's -try that. Listing 9-1 shows the output: + -
- -```text +```console $ RUST_BACKTRACE=1 cargo run - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target/debug/panic` -thread 'main' panicked at 'index out of bounds: the len is 3 but the index is -100', ../src/libcollections/vec.rs:1265 +thread 'main' panicked at 'index out of bounds: the len is 3 but the index is 99', src/main.rs:4:5 stack backtrace: - 1: 0x560956150ae9 - -std::sys::backtrace::tracing::imp::write::h482d45d91246faa2 - 2: 0x56095615345c - -std::panicking::default_hook::_{{closure}}::h89158f66286b674e - 3: 0x56095615291e - std::panicking::default_hook::h9e30d428ee3b0c43 - 4: 0x560956152f88 - -std::panicking::rust_panic_with_hook::h2224f33fb7bf2f4c - 5: 0x560956152e22 - std::panicking::begin_panic::hcb11a4dc6d779ae5 - 6: 0x560956152d50 - std::panicking::begin_panic_fmt::h310416c62f3935b3 - 7: 0x560956152cd1 - rust_begin_unwind - 8: 0x560956188a2f - core::panicking::panic_fmt::hc5789f4e80194729 - 9: 0x5609561889d3 - -core::panicking::panic_bounds_check::hb2d969c3cc11ed08 - 10: 0x56095614c075 - _ as -core..ops..Index>::index::hb9f10d3dadbe8101 - at ../src/libcollections/vec.rs:1265 - 11: 0x56095614c134 - panic::main::h2d7d3751fb8705e2 - at /projects/panic/src/main.rs:4 - 12: 0x56095615af46 - __rust_maybe_catch_panic - 13: 0x560956152082 - std::rt::lang_start::h352a66f5026f54bd - 14: 0x56095614c1b3 - main - 15: 0x7f75b88ed72f - __libc_start_main - 16: 0x56095614b3c8 - _start - 17: 0x0 - -error: Process didn't exit successfully: `target/debug/panic` (exit code: 101) + 0: rust_begin_unwind + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:483 + 1: core::panicking::panic_fmt + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/panicking.rs:85 + 2: core::panicking::panic_bounds_check + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/panicking.rs:62 + 3: >::index + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/slice/index.rs:255 + 4: core::slice::index:: for [T]>::index + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/slice/index.rs:15 + 5: as core::ops::index::Index>::index + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/alloc/src/vec.rs:1982 + 6: panic::main + at ./src/main.rs:4 + 7: core::ops::function::FnOnce::call_once + at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/ops/function.rs:227 +note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace. ``` -
+Listing 9-2: The backtrace generated by a call to +`panic!` displayed when the environment variable `RUST_BACKTRACE` is set -Listing 9-1: The backtrace generated by a call to `panic!` displayed when -the environment variable `RUST_BACKTRACE` is set +That’s a lot of output! The exact output you see might be different depending +on your operating system and Rust version. In order to get backtraces with this +information, debug symbols must be enabled. Debug symbols are enabled by +default when using `cargo build` or `cargo run` without the `--release` flag, +as we have here. -
-
+In the output in Listing 9-2, line 6 of the backtrace points to the line in +our project that’s causing the problem: line 4 of *src/main.rs*. If we don’t +want our program to panic, the location pointed to by the first line mentioning +a file we wrote is where we should start investigating. In Listing 9-1, where +we deliberately wrote code that would panic in order to demonstrate how to use +backtraces, the way to fix the panic is to not request an element at index 99 +from a vector that only contains 3 items. When your code panics in the future, +you’ll need to figure out what action the code is taking with what values to +cause the panic and what the code should do instead. -That's a lot of output! Line 11 of the backtrace points to the line in our -project causing the problem: `src/main.rs`, line four. A backtrace is a list of -all the functions that have been called to get to this point. Backtraces in -Rust work like they do in other languages: the key to reading the backtrace is -to start from the top and read until you see files you wrote. That's the spot -where the problem originated. The lines above the lines mentioning your files -are code that your code called; the lines below are code that called your code. -These lines might include core Rust code, standard library code, or crates that -you're using. +We’ll come back to `panic!` and when we should and should not use `panic!` to +handle error conditions in the [“To `panic!` or Not to +`panic!`”][to-panic-or-not-to-panic] section later in this +chapter. Next, we’ll look at how to recover from an error using `Result`. -If we don't want our program to panic, the location pointed to by the first -line mentioning a file we wrote is where we should start investigating in order -to figure out how we got to this location with values that caused the panic. In -our example where we deliberately wrote code that would panic in order to -demonstrate how to use backtraces, the way to fix the panic is to not try to -request an element at index 100 from a vector that only contains three items. -When your code panics in the future, you'll need to figure out for your -particular case what action the code is taking with what values that causes the -panic and what the code should do instead. - -We'll come back to `panic!` and when we should and should not use these methods -later in the chapter. Next, we'll now look at how to recover from an error with -`Result`. +[to-panic-or-not-to-panic]: +ch09-03-to-panic-or-not-to-panic.html#to-panic-or-not-to-panic diff --git a/src/ch09-02-recoverable-errors-with-result.md b/src/ch09-02-recoverable-errors-with-result.md index 44639ae..ba8168d 100644 --- a/src/ch09-02-recoverable-errors-with-result.md +++ b/src/ch09-02-recoverable-errors-with-result.md @@ -1,14 +1,16 @@ ## Recoverable Errors with `Result` -Most errors aren't serious enough to require the program to stop entirely. -Sometimes, when a function fails, it's for a reason that we can easily -interpret and respond to. For example, if we try to open a file and that -operation fails because the file doesn't exist, we might want to create the +Most errors aren’t serious enough to require the program to stop entirely. +Sometimes, when a function fails, it’s for a reason that you can easily +interpret and respond to. For example, if you try to open a file and that +operation fails because the file doesn’t exist, you might want to create the file instead of terminating the process. -Recall from Chapter 2 the section on "Handling Potential Failure with the -`Result` Type" that the `Result` enum is defined as having two variants, `Ok` -and `Err`, as follows: +Recall from [“Handling Potential Failure with the `Result` +Type”][handle_failure] in Chapter 2 that the `Result` enum is +defined as having two variants, `Ok` and `Err`, as follows: + +[handle_failure]: ch02-00-guessing-game-tutorial.html#handling-potential-failure-with-the-result-type ```rust enum Result { @@ -17,22 +19,7 @@ enum Result { } ``` - - - -The `T` and `E` are generic type parameters; we'll go into generics in more +The `T` and `E` are generic type parameters: we’ll discuss generics in more detail in Chapter 10. What you need to know right now is that `T` represents the type of the value that will be returned in a success case within the `Ok` variant, and `E` represents the type of the error that will be returned in a @@ -41,50 +28,33 @@ parameters, we can use the `Result` type and the functions that the standard library has defined on it in many different situations where the successful value and error value we want to return may differ. -Let's call a function that returns a `Result` value because the function could -fail: opening a file, shown in Listing 9-2. +Let’s call a function that returns a `Result` value because the function could +fail. In Listing 9-3 we try to open a file. -
Filename: src/main.rs ```rust -use std::fs::File; - -fn main() { - let f = File::open("hello.txt"); -} +{{#rustdoc_include ../listings/ch09-error-handling/listing-09-03/src/main.rs}} ``` -
+Listing 9-3: Opening a file -Listing 9-2: Opening a file +How do we know `File::open` returns a `Result`? We could look at the [standard +library API documentation](../std/index.html), or we could ask +the compiler! If we give `f` a type annotation that we know is *not* the return +type of the function and then try to compile the code, the compiler will tell +us that the types don’t match. The error message will then tell us what the +type of `f` *is*. Let’s try it! We know that the return type of `File::open` +isn’t of type `u32`, so let’s change the `let f` statement to this: -
-
- -How do we know `File::open` returns a `Result`? We could look at the standard -library API documentation. We could ask the compiler! If we give `f` a type -annotation of some type that we know the return type of the function is *not*, -then we try to compile the code, the compiler will tell us that the types don't -match. The error message will then tell us what the type of `f` *is*! Let's try -it: we know that the return type of `File::open` isn't of type `u32`, so let's -change the `let f` statement to: - -```rust,ignore -let f: u32 = File::open("hello.txt"); +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/src/main.rs:here}} ``` -Attempting to compile now gives us: +Attempting to compile now gives us the following output: -```text -error[E0308]: mismatched types - --> src/main.rs:4:18 - | -4 | let f: u32 = File::open("hello.txt"); - | ^^^^^^^^^^^^^^^^^^^^^^^ expected u32, found enum `std::result::Result` - | - = note: expected type `u32` - = note: found type `std::result::Result` +```console +{{#include ../listings/ch09-error-handling/no-listing-02-ask-compiler-for-type/output.txt}} ``` This tells us the return type of the `File::open` function is a `Result`. @@ -92,494 +62,374 @@ The generic parameter `T` has been filled in here with the type of the success value, `std::fs::File`, which is a file handle. The type of `E` used in the error value is `std::io::Error`. -This return type means the call to `File::open` might succeed and return to us -a file handle that we can read from or write to. The function call also might -fail: for example, the file might not exist, or we might not have permission to +This return type means the call to `File::open` might succeed and return a file +handle that we can read from or write to. The function call also might fail: +for example, the file might not exist, or we might not have permission to access the file. The `File::open` function needs to have a way to tell us -whether it succeeded or failed, and at the same time give us either the file +whether it succeeded or failed and at the same time give us either the file handle or error information. This information is exactly what the `Result` enum conveys. -In the case where `File::open` succeeds, the value we will have in the variable -`f` will be an instance of `Ok` that contains a file handle. In the case where -it fails, the value in `f` will be an instance of `Err` that contains more -information about the kind of error that happened. +In the case where `File::open` succeeds, the value in the variable `f` will be +an instance of `Ok` that contains a file handle. In the case where it fails, +the value in `f` will be an instance of `Err` that contains more information +about the kind of error that happened. - - - -We need to add to the code from Listing 9-2 to take different actions depending -on the value `File::open` returned. Listing 9-3 shows one way to handle the -`Result` with a basic tool: the `match` expression that we learned about in +We need to add to the code in Listing 9-3 to take different actions depending +on the value `File::open` returns. Listing 9-4 shows one way to handle the +`Result` using a basic tool, the `match` expression that we discussed in Chapter 6. - - -
Filename: src/main.rs ```rust,should_panic -use std::fs::File; - -fn main() { - let f = File::open("hello.txt"); - - let f = match f { - Ok(file) => file, - Err(error) => panic!("There was a problem opening the file: {:?}", -error), - }; -} +{{#rustdoc_include ../listings/ch09-error-handling/listing-09-04/src/main.rs}} ``` -
- -Listing 9-3: Using a `match` expression to handle the `Result` variants we -might have - -
-
- - - +Listing 9-4: Using a `match` expression to handle the +`Result` variants that might be returned Note that, like the `Option` enum, the `Result` enum and its variants have been -imported in the prelude, so we don't need to specify `Result::` before the `Ok` -and `Err` variants in the `match` arms. +brought into scope by the prelude, so we don’t need to specify `Result::` +before the `Ok` and `Err` variants in the `match` arms. Here we tell Rust that when the result is `Ok`, return the inner `file` value out of the `Ok` variant, and we then assign that file handle value to the -variable `f`. After the `match`, we can then use the file handle for reading or +variable `f`. After the `match`, we can use the file handle for reading or writing. The other arm of the `match` handles the case where we get an `Err` value from -`File::open`. In this example, we've chosen to call the `panic!` macro. If -there's no file named `hello.txt` in our current directory and we run this -code, we'll see the following output from the `panic!` macro: +`File::open`. In this example, we’ve chosen to call the `panic!` macro. If +there’s no file named *hello.txt* in our current directory and we run this +code, we’ll see the following output from the `panic!` macro: -```text -thread 'main' panicked at 'There was a problem opening the file: Error { repr: -Os { code: 2, message: "No such file or directory" } }', src/main.rs:8 +```console +{{#include ../listings/ch09-error-handling/listing-09-04/output.txt}} ``` - - +As usual, this output tells us exactly what has gone wrong. ### Matching on Different Errors -The code in Listing 9-3 will `panic!` no matter the reason that `File::open` -failed. What we'd really like to do instead is take different actions for -different failure reasons: if `File::open` failed because the file doesn't -exist, we want to create the file and return the handle to the new file. If -`File::open` failed for any other reason, for example because we didn't have -permission to open the file, we still want to `panic!` in the same way as we -did in Listing 9-3. Let's look at Listing 9-4, which adds another arm to the -`match`: +The code in Listing 9-4 will `panic!` no matter why `File::open` failed. What +we want to do instead is take different actions for different failure reasons: +if `File::open` failed because the file doesn’t exist, we want to create the +file and return the handle to the new file. If `File::open` failed for any +other reason—for example, because we didn’t have permission to open the file—we +still want the code to `panic!` in the same way as it did in Listing 9-4. Look +at Listing 9-5, which adds an inner `match` expression. -
Filename: src/main.rs + + ```rust,ignore -use std::fs::File; -use std::io::ErrorKind; - -fn main() { - let f = File::open("hello.txt"); - - let f = match f { - Ok(file) => file, - Err(ref error) if error.kind() == ErrorKind::NotFound => { - match File::create("hello.txt") { - Ok(fc) => fc, - Err(e) => panic!("Tried to create file but there was a problem: {:?}", e), - } - }, - Err(error) => panic!("There was a problem opening the file: {:?}", -error), - }; -} +{{#rustdoc_include ../listings/ch09-error-handling/listing-09-05/src/main.rs}} ``` -
- -Listing 9-4: Handling different kinds of errors in different ways - -
-
- - +Listing 9-5: Handling different kinds of errors in +different ways The type of the value that `File::open` returns inside the `Err` variant is `io::Error`, which is a struct provided by the standard library. This struct -has a method `kind` that we can call to get an `io::ErrorKind` value. -`io::ErrorKind` is an enum provided by the standard library that has variants +has a method `kind` that we can call to get an `io::ErrorKind` value. The enum +`io::ErrorKind` is provided by the standard library and has variants representing the different kinds of errors that might result from an `io` -operation. The variant we're interested in is `ErrorKind::NotFound`, which -indicates the file we're trying to open doesn't exist yet. +operation. The variant we want to use is `ErrorKind::NotFound`, which indicates +the file we’re trying to open doesn’t exist yet. So we match on `f`, but we +also have an inner match on `error.kind()`. -The condition `if error.kind() == ErrorKind::NotFound` is called a *match -guard*: it's an extra condition on a `match` arm that further refines the arm's -pattern. This condition must be true in order for that arm's code to get run; -otherwise, the pattern matching will move on to consider the next arm in the -`match`. The `ref` in the pattern is needed so that the `error` is not moved -into the guard condition but is merely referenced by it. The reason `ref` is -used to take a reference in a pattern instead of `&` will be covered in detail -in Chapter XX. In short, in the context of a pattern, `&` matches a reference -and give us its value, but `ref` matches a value and gives us a reference to it. - -The condition we want to check in the match guard is whether the value returned +The condition we want to check in the inner match is whether the value returned by `error.kind()` is the `NotFound` variant of the `ErrorKind` enum. If it is, -we try to create the file with 'File::create'. However, since `File::create` -could also fail, we need to add an inner `match` statement as well! When the -file can't be opened, a different error message will be printed. The last arm -of the outer `match` stays the same so that the program panics on any error -besides the missing file error. +we try to create the file with `File::create`. However, because `File::create` +could also fail, we need a second arm in the inner `match` expression. When the +file can’t be created, a different error message is printed. The second arm of +the outer `match` stays the same, so the program panics on any error besides +the missing file error. + +That’s a lot of `match`! The `match` expression is very useful but also very +much a primitive. In Chapter 13, you’ll learn about closures; the `Result` type has many methods that accept a closure and are implemented using +`match` expressions. Using those methods will make your code more concise. A +more seasoned Rustacean might write this code instead of Listing 9-5: + +```rust,ignore +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-03-closures/src/main.rs}} +``` + +Although this code has the same behavior as Listing 9-5, it doesn’t contain any +`match` expressions and is cleaner to read. Come back to this example after +you’ve read Chapter 13, and look up the `unwrap_or_else` method in the standard +library documentation. Many more of these methods can clean up huge nested +`match` expressions when you’re dealing with errors. ### Shortcuts for Panic on Error: `unwrap` and `expect` -Using `match` works well enough, but it can be a bit verbose and doesn't always +Using `match` works well enough, but it can be a bit verbose and doesn’t always communicate intent well. The `Result` type has many helper methods -defined on it to do various things. One of those methods, called `unwrap`, is -a shortcut method that is implemented just like the `match` statement we wrote -in Listing 9-3. If the `Result` value is the `Ok` variant, `unwrap` will return +defined on it to do various tasks. One of those methods, called `unwrap`, is a +shortcut method that is implemented just like the `match` expression we wrote in +Listing 9-4. If the `Result` value is the `Ok` variant, `unwrap` will return the value inside the `Ok`. If the `Result` is the `Err` variant, `unwrap` will -call the `panic!` macro for us. +call the `panic!` macro for us. Here is an example of `unwrap` in action: - - - - +Filename: src/main.rs ```rust,should_panic -use std::fs::File; - -fn main() { - let f = File::open("hello.txt").unwrap(); -} +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-04-unwrap/src/main.rs}} ``` - - - -If we run this code without a *hello.txt* file, we'll see an error message from -the `panic` call that the `unwrap` method makes: +If we run this code without a *hello.txt* file, we’ll see an error message from +the `panic!` call that the `unwrap` method makes: ```text thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error { repr: Os { code: 2, message: "No such file or directory" } }', -../src/libcore/result.rs:837 +src/libcore/result.rs:906:4 ``` -There's another method similar to `unwrap` that lets us also choose the -`panic!` error message: `expect`. Using `expect` instead of `unwrap` and -providing good error messages can convey your intent and make tracking down the -source of a panic easier. The syntax of`expect` looks like this: +Another method, `expect`, which is similar to `unwrap`, lets us also choose the +`panic!` error message. Using `expect` instead of `unwrap` and providing good +error messages can convey your intent and make tracking down the source of a +panic easier. The syntax of `expect` looks like this: - +Filename: src/main.rs ```rust,should_panic -use std::fs::File; - -fn main() { - let f = File::open("hello.txt").expect("Failed to open hello.txt"); -} +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-05-expect/src/main.rs}} ``` We use `expect` in the same way as `unwrap`: to return the file handle or call -the `panic!` macro. The error message that `expect` uses in its call to -`panic!` will be the parameter that we pass to `expect` instead of the default -`panic!` message that `unwrap` uses. Here's what it looks like: +the `panic!` macro. The error message used by `expect` in its call to `panic!` +will be the parameter that we pass to `expect`, rather than the default +`panic!` message that `unwrap` uses. Here’s what it looks like: ```text thread 'main' panicked at 'Failed to open hello.txt: Error { repr: Os { code: -2, message: "No such file or directory" } }', ../src/libcore/result.rs:837 +2, message: "No such file or directory" } }', src/libcore/result.rs:906:4 ``` - - - - - +Because this error message starts with the text we specified, `Failed to open +hello.txt`, it will be easier to find where in the code this error message is +coming from. If we use `unwrap` in multiple places, it can take more time to +figure out exactly which `unwrap` is causing the panic because all `unwrap` +calls that panic print the same message. ### Propagating Errors -When writing a function whose implementation calls something that might fail, -instead of handling the error within this function, you can choose to let your -caller know about the error so they can decide what to do. This is known as -*propagating* the error, and gives more control to the calling code where there +When you’re writing a function whose implementation calls something that might +fail, instead of handling the error within this function, you can return the +error to the calling code so that it can decide what to do. This is known as +*propagating* the error and gives more control to the calling code, where there might be more information or logic that dictates how the error should be handled than what you have available in the context of your code. - - +For example, Listing 9-6 shows a function that reads a username from a file. If +the file doesn’t exist or can’t be read, this function will return those errors +to the code that called this function. -For example, Listing 9-5 shows a function that reads a username from a file. If -the file doesn't exist or can't be read, this function will return those errors -to the code that called this function: +Filename: src/main.rs -
+ ```rust -use std::io; -use std::io::Read; -use std::fs::File; - -fn read_username_from_file() -> Result { - let f = File::open("hello.txt"); - - let mut f = match f { - Ok(file) => file, - Err(e) => return Err(e), - }; - - let mut s = String::new(); - - match f.read_to_string(&mut s) { - Ok(_) => Ok(s), - Err(e) => Err(e), - } -} +{{#include ../listings/ch09-error-handling/listing-09-06/src/main.rs:here}} ``` -
+Listing 9-6: A function that returns errors to the +calling code using `match` -Listing 9-5: A function that returns errors to the calling code using `match` - -
-
- -Let's look at the return type of the function first: `Result`. This means that the function is returning a value of the type -`Result` where the generic parameter `T` has been filled in with the -concrete type `String`, and the generic type `E` has been filled in with the -concrete type `io::Error`. If this function succeeds without any problems, the -caller of this function will receive an `Ok` value that holds a `String`—the -username that this function read from the file. If this function encounters any -problems, the caller of this function will receive an `Err` value that holds an -instance of `io::Error` that contains more information about what the problems -were. We chose `io::Error` as the return type of this function because that -happens to be the type of the error value returned from both of the operations -we're calling in this function's body that might fail: the `File::open` -function and the `read_to_string` method. +This function can be written in a much shorter way, but we’re going to start by +doing a lot of it manually in order to explore error handling; at the end, +we’ll show the shorter way. Let’s look at the return type of the function first: +`Result`. This means the function is returning a value of +the type `Result` where the generic parameter `T` has been filled in +with the concrete type `String` and the generic type `E` has been filled in +with the concrete type `io::Error`. If this function succeeds without any +problems, the code that calls this function will receive an `Ok` value that +holds a `String`—the username that this function read from the file. If this +function encounters any problems, the code that calls this function will +receive an `Err` value that holds an instance of `io::Error` that contains +more information about what the problems were. We chose `io::Error` as the +return type of this function because that happens to be the type of the error +value returned from both of the operations we’re calling in this function’s +body that might fail: the `File::open` function and the `read_to_string` +method. The body of the function starts by calling the `File::open` function. Then we handle the `Result` value returned with a `match` similar to the `match` in -Listing 9-3, only instead of calling `panic!` in the `Err` case, we return +Listing 9-4, only instead of calling `panic!` in the `Err` case, we return early from this function and pass the error value from `File::open` back to the -caller as this function's error value. If `File::open` succeeds, we store the -file handle in the variable `f` and continue. +calling code as this function’s error value. If `File::open` succeeds, we store +the file handle in the variable `f` and continue. Then we create a new `String` in variable `s` and call the `read_to_string` -method on the file handle in `f` in order to read the contents of the file into -`s`. The `read_to_string` method also returns a `Result` because it might fail, -even though `File::open` succeeded. So we need another `match` to handle that +method on the file handle in `f` to read the contents of the file into `s`. The +`read_to_string` method also returns a `Result` because it might fail, even +though `File::open` succeeded. So we need another `match` to handle that `Result`: if `read_to_string` succeeds, then our function has succeeded, and we -return the username from the file that's now in `s` wrapped in an `Ok`. If +return the username from the file that’s now in `s` wrapped in an `Ok`. If `read_to_string` fails, we return the error value in the same way that we returned the error value in the `match` that handled the return value of -`File::open`. We don't need to explicitly say `return`, however, since this is -the last expression in the function. +`File::open`. However, we don’t need to explicitly say `return`, because this +is the last expression in the function. The code that calls this code will then handle getting either an `Ok` value that contains a username or an `Err` value that contains an `io::Error`. We -don't know what the caller will do with those values. If they get an `Err` -value, they could choose to call `panic!` and crash their program, use a +don’t know what the calling code will do with those values. If the calling code +gets an `Err` value, it could call `panic!` and crash the program, use a default username, or look up the username from somewhere other than a file, for -example. We don't have enough information on what the caller is actually trying -to do, so we propagate all the success or error information upwards for them to -handle as they see fit. +example. We don’t have enough information on what the calling code is actually +trying to do, so we propagate all the success or error information upward for +it to handle appropriately. -This pattern of propagating errors is so common in Rust that there is dedicated -syntax to make this easier: `?`. +This pattern of propagating errors is so common in Rust that Rust provides the +question mark operator `?` to make this easier. -### A Shortcut for Propagating Errors: `?` +#### A Shortcut for Propagating Errors: the `?` Operator - +Listing 9-7 shows an implementation of `read_username_from_file` that has the +same functionality as it had in Listing 9-6, but this implementation uses the +`?` operator. -Listing 9-6 shows an implementation of `read_username_from_file` that has the -same functionality as it had in Listing 9-5, but this implementation uses the -question mark: +Filename: src/main.rs - - -
+ ```rust -use std::io; -use std::fs::File; - -fn read_username_from_file() -> Result { - let mut f = File::open("hello.txt")?; - let mut s = String::new(); - f.read_to_string(&mut s)?; - Ok(s) -} +{{#include ../listings/ch09-error-handling/listing-09-07/src/main.rs:here}} ``` -
+Listing 9-7: A function that returns errors to the +calling code using the `?` operator -Listing 9-6: A function that returns errors to the calling code using `?` +The `?` placed after a `Result` value is defined to work in almost the same way +as the `match` expressions we defined to handle the `Result` values in Listing +9-6. If the value of the `Result` is an `Ok`, the value inside the `Ok` will +get returned from this expression, and the program will continue. If the value +is an `Err`, the `Err` will be returned from the whole function as if we had +used the `return` keyword so the error value gets propagated to the calling +code. -
-
+There is a difference between what the `match` expression from Listing 9-6 does +and what the `?` operator does: error values that have the `?` operator called +on them go through the `from` function, defined in the `From` trait in the +standard library, which is used to convert errors from one type into another. +When the `?` operator calls the `from` function, the error type received is +converted into the error type defined in the return type of the current +function. This is useful when a function returns one error type to represent all +the ways a function might fail, even if parts might fail for many different +reasons. As long as each error type implements the `from` function to define how +to convert itself to the returned error type, the `?` operator takes care of the +conversion automatically. - - +In the context of Listing 9-7, the `?` at the end of the `File::open` call will +return the value inside an `Ok` to the variable `f`. If an error occurs, the +`?` operator will return early out of the whole function and give any `Err` +value to the calling code. The same thing applies to the `?` at the end of the +`read_to_string` call. -The `?` placed after a `Result` value is defined to work the exact same way as -the`match` expressions we defined to handle the `Result` values in Listing 9-5. -If the value of the `Result` is an `Ok`, the value inside the `Ok` will get -returned from this expression and the program will continue. If the value is an -`Err`, the value inside the `Err` will be returned from the whole function as -if we had used the `return` keyword so that the error value gets propagated to -the caller. - -In the context of Listing 9-6, the `?` at the end of the `File::open` call will -return the value inside an `Ok` to the binding `f`. If an error occurs, `?` -will return early out of the whole function and give any `Err` value to our -caller. The same thing applies to the `?` at the end of the `read_to_string` -call. - -The `?` eliminates a lot of boilerplate and makes this function's +The `?` operator eliminates a lot of boilerplate and makes this function’s implementation simpler. We could even shorten this code further by chaining -method calls immediately after the `?`: +method calls immediately after the `?`, as shown in Listing 9-8. + +Filename: src/main.rs + + ```rust -use std::io; -use std::io::Read; -use std::fs::File; - -fn read_username_from_file() -> Result { - let mut s = String::new(); - - File::open("hello.txt")?.read_to_string(&mut s)?; - - Ok(s) -} +{{#include ../listings/ch09-error-handling/listing-09-08/src/main.rs:here}} ``` - - +Listing 9-8: Chaining method calls after the `?` +operator -We've moved the creation of the new `String` in `s` to the beginning of the -function; that part hasn't changed. Instead of creating a variable `f`, we've +We’ve moved the creation of the new `String` in `s` to the beginning of the +function; that part hasn’t changed. Instead of creating a variable `f`, we’ve chained the call to `read_to_string` directly onto the result of `File::open("hello.txt")?`. We still have a `?` at the end of the `read_to_string` call, and we still return an `Ok` value containing the username in `s` when both `File::open` and `read_to_string` succeed rather than -returning errors. The functionality is again the same as in Listing 9-5 and -Listing 9-6, this is just a different, more ergonomic way to write it. +returning errors. The functionality is again the same as in Listing 9-6 and +Listing 9-7; this is just a different, more ergonomic way to write it. -#### `?` Can Only Be Used in Functions That Return `Result` +Speaking of different ways to write this function, Listing 9-9 shows that +there’s a way to make this even shorter. - - +Filename: src/main.rs -The `?` can only be used in functions that have a return type of `Result`, -since it is defined to work in exactly the same way as the `match` expression -we defined in Listing 9-5. The part of the `match` that requires a return type -of `Result` is `return Err(e)`, so the return type of the function must be a -`Result` to be compatible with this `return`. + - - +Reading a file into a string is a fairly common operation, so Rust provides the +convenient `fs::read_to_string` function that opens the file, creates a new +`String`, reads the contents of the file, puts the contents into that `String`, +and returns it. Of course, using `fs::read_to_string` doesn’t give us the +opportunity to explain all the error handling, so we did it the longer way +first. -Let's look at what happens if use `try!` in the `main` function, which you'll -recall has a return type of `()`: +#### The `?` Operator Can Be Used in Functions That Return `Result` + +The `?` operator can be used in functions that have a return type of +`Result`, because it is defined to work in the same way as the `match` +expression we defined in Listing 9-6. The part of the `match` that requires a +return type of `Result` is `return Err(e)`, so the return type of the function +has to be a `Result` to be compatible with this `return`. + +Let’s look at what happens if we use the `?` operator in the `main` function, +which you’ll recall has a return type of `()`: + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-06-question-mark-in-main/src/main.rs}} +``` + +When we compile this code, we get the following error message: + +```console +{{#include ../listings/ch09-error-handling/no-listing-06-question-mark-in-main/output.txt}} +``` + +This error points out that we’re only allowed to use the `?` operator in a +function that returns `Result` or `Option` or another type that implements +`std::ops::Try`. When you’re writing code in a function +that doesn’t return one of these types, and you want to use `?` when you call other +functions that return `Result`, you have two choices to fix this problem. +One technique is to change the return type of your function to be `Result` if you have no restrictions preventing that. The other technique is to use +a `match` or one of the `Result` methods to handle the `Result` in +whatever way is appropriate. + +The `main` function is special, and there are restrictions on what its return +type must be. One valid return type for main is `()`, and conveniently, another +valid return type is `Result`, as shown here: ```rust,ignore -fn main() { - let f = File::open("hello.txt")?; -} +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-07-main-returning-result/src/main.rs}} ``` - section in Chapter 17. For now, you can +read `Box` to mean “any kind of error.” Using `?` in a `main` +function with this return type is allowed. -I'm bugging people to try and get -https://github.com/rust-lang/rust/issues/35946 fixed soon, hopefully before this -chapter gets through copy editing-- at that point I'll make sure to update this -error message. /Carol --> - -When we compile this, we get the following error message: - -```text -error[E0308]: mismatched types - --> - | -3 | let f = File::open("hello.txt")?; - | ^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found enum `std::result::Result` - | - = note: expected type `()` - = note: found type `std::result::Result<_, _>` -``` - -This error is pointing out that we have mismatched types: the `main()` function -has a return type of `()`, but the `?` might return a `Result`. In functions -that don't return `Result`, when you call other functions that return `Result`, -you'll need to use a `match` or one of the `Result` methods to handle it, -instead of using `?` to potentially propagate the error to the caller. - -Now that we've discussed the details of calling `panic!` or returning `Result`, -let's return to the topic of how to decide which is appropriate to use in which +Now that we’ve discussed the details of calling `panic!` or returning `Result`, +let’s return to the topic of how to decide which is appropriate to use in which cases. + +[trait-objects]: ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types diff --git a/src/ch09-03-to-panic-or-not-to-panic.md b/src/ch09-03-to-panic-or-not-to-panic.md index c15a165..e5af81d 100644 --- a/src/ch09-03-to-panic-or-not-to-panic.md +++ b/src/ch09-03-to-panic-or-not-to-panic.md @@ -1,276 +1,211 @@ -## To `panic!` or Not To `panic!` +## To `panic!` or Not to `panic!` -So how do you decide when you should `panic!` and when you should return -`Result`? When code panics, there's no way to recover. You could choose to call -`panic!` for any error situation, whether there's a possible way to recover or -not, but then you're making the decision for your callers that a situation is -unrecoverable. When you choose to return a `Result` value, you give your caller -options, rather than making the decision for them. They could choose to attempt -to recover in a way that's appropriate for their situation, or they could -decide that actually, an `Err` value in this case is unrecoverable, so they can -call `panic!` and turn your recoverable error into an unrecoverable one. -Therefore, returning `Result` is a good default choice when you're defining a -function that might fail. +So how do you decide when you should call `panic!` and when you should return +`Result`? When code panics, there’s no way to recover. You could call `panic!` +for any error situation, whether there’s a possible way to recover or not, but +then you’re making the decision on behalf of the code calling your code that a +situation is unrecoverable. When you choose to return a `Result` value, you +give the calling code options rather than making the decision for it. The +calling code could choose to attempt to recover in a way that’s appropriate for +its situation, or it could decide that an `Err` value in this case is +unrecoverable, so it can call `panic!` and turn your recoverable error into an +unrecoverable one. Therefore, returning `Result` is a good default choice when +you’re defining a function that might fail. -There are a few situations in which it's more appropriate to write code that -panics instead of returning a `Result`, but they are less common. Let's discuss -why it's appropriate to panic in examples, prototype code, and tests, then -situations where you as a human can know a method won't fail that the compiler -can't reason about, and conclude with some general guidelines on how to decide -whether to panic in library code. +In rare situations, it’s more appropriate to write code that panics instead of +returning a `Result`. Let’s explore why it’s appropriate to panic in examples, +prototype code, and tests. Then we’ll discuss situations in which the compiler +can’t tell that failure is impossible, but you as a human can. The chapter will +conclude with some general guidelines on how to decide whether to panic in +library code. -### Examples, Prototype Code, and Tests: Perfectly Fine to Panic +### Examples, Prototype Code, and Tests -When you're writing an example to illustrate some concept, having robust error -handling code in the example as well can make the example less clear. In -examples, it's understood that a call to a method like `unwrap` that could -`panic!` is meant as a placeholder for the way that you'd actually like your -application to handle errors, which can differ based on what the rest of your -code is doing. +When you’re writing an example to illustrate some concept, having robust +error-handling code in the example as well can make the example less clear. In +examples, it’s understood that a call to a method like `unwrap` that could +panic is meant as a placeholder for the way you’d want your application to +handle errors, which can differ based on what the rest of your code is doing. Similarly, the `unwrap` and `expect` methods are very handy when prototyping, -before you're ready to decide how to handle errors. They leave clear markers in -your code for when you're ready to make your program more robust. +before you’re ready to decide how to handle errors. They leave clear markers in +your code for when you’re ready to make your program more robust. -If a method call fails in a test, we'd want the whole test to fail, even if that -method isn't the functionality under test. Because `panic!` is how a test gets -marked as a failure, calling `unwrap` or `expect` is exactly what makes sense to -do. +If a method call fails in a test, you’d want the whole test to fail, even if +that method isn’t the functionality under test. Because `panic!` is how a test +is marked as a failure, calling `unwrap` or `expect` is exactly what should +happen. -### Cases When You Have More Information Than The Compiler +### Cases in Which You Have More Information Than the Compiler It would also be appropriate to call `unwrap` when you have some other logic -that ensures the `Result` will have an `Ok` value, but the logic isn't -something the compiler understands. You'll still have a `Result` value that you -need to handle: whatever operation you're calling still has the possibility of -failing in general, even though it's logically impossible in your particular -situation. If you can ensure by manually inspecting the code that you'll never -have an `Err` variant, it is perfectly acceptable to call `unwrap`. Here's an +that ensures the `Result` will have an `Ok` value, but the logic isn’t +something the compiler understands. You’ll still have a `Result` value that you +need to handle: whatever operation you’re calling still has the possibility of +failing in general, even though it’s logically impossible in your particular +situation. If you can ensure by manually inspecting the code that you’ll never +have an `Err` variant, it’s perfectly acceptable to call `unwrap`. Here’s an example: - - - ```rust -use std::net::IpAddr; - -let home = "127.0.0.1".parse::().unwrap(); +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-08-unwrap-that-cant-fail/src/main.rs:here}} ``` -We're creating an `IpAddr` instance by parsing a hardcoded string. We can see -that `"127.0.0.1"` is a valid IP address, so it's acceptable to use `unwrap` -here. However, having a hardcoded, valid string doesn't change the return type +We’re creating an `IpAddr` instance by parsing a hardcoded string. We can see +that `127.0.0.1` is a valid IP address, so it’s acceptable to use `unwrap` +here. However, having a hardcoded, valid string doesn’t change the return type of the `parse` method: we still get a `Result` value, and the compiler will -still make us handle the `Result` as if the `Err` variant is still a possibility -since the compiler isn't smart enough to see that this string is always a -valid IP address. If the IP address string came from a user instead of being -hardcoded into the program, and therefore *did* have a possibility of failure, -we'd definitely want to handle the `Result` in a more robust way instead. +still make us handle the `Result` as if the `Err` variant is a possibility +because the compiler isn’t smart enough to see that this string is always a +valid IP address. If the IP address string came from a user rather than being +hardcoded into the program and therefore *did* have a possibility of failure, +we’d definitely want to handle the `Result` in a more robust way instead. ### Guidelines for Error Handling -It's advisable to have your code `panic!` when it's possible that you could end -up in a *bad state*—in this context, *bad state* is when some assumption, -guarantee, contract, or invariant has been broken, such as when invalid values, -contradictory values, or missing values are passed to your code—plus one or -more of the following: +It’s advisable to have your code panic when it’s possible that your code +could end up in a bad state. In this context, a *bad state* is when some +assumption, guarantee, contract, or invariant has been broken, such as when +invalid values, contradictory values, or missing values are passed to your +code—plus one or more of the following: -* The bad state is not something that's *expected* to happen occasionally -* Your code after this point needs to rely on not being in this bad state -* There's not a good way to encode this information in the types you use +* The bad state is not something that’s *expected* to happen occasionally. +* Your code after this point needs to rely on not being in this bad state. +* There’s not a good way to encode this information in the types you use. -If someone calls your code and passes in values that don't make sense, the best -thing might be to `panic!` and alert the person using your library to the bug -in their code so that they can fix it during development. Similarly, `panic!` -is often appropriate if you're calling external code that is out of your -control, and it returns an invalid state that you have no way of fixing. +If someone calls your code and passes in values that don’t make sense, the best +choice might be to call `panic!` and alert the person using your library to the +bug in their code so they can fix it during development. Similarly, `panic!` is +often appropriate if you’re calling external code that is out of your control +and it returns an invalid state that you have no way of fixing. -When a bad state is reached, but it's expected to happen no matter how well you -write your code, it's still more appropriate to return a `Result` rather than -calling `panic!`. Examples of this include a parser being given malformed data, -or an HTTP request returning a status that indicates you have hit a rate limit. -In these cases, you should indicate that failure is an expected possibility by -returning a `Result` in order to propagate these bad states upwards so that the -caller can decide how they would like to handle the problem. To `panic!` -wouldn't be the best way to handle these cases. +However, when failure is expected, it’s more appropriate to return a `Result` +than to make a `panic!` call. Examples include a parser being given malformed +data or an HTTP request returning a status that indicates you have hit a rate +limit. In these cases, returning a `Result` indicates that failure is an +expected possibility that the calling code must decide how to handle. When your code performs operations on values, your code should verify the -values are valid first, and `panic!` if the values aren't valid. This is mostly -for safety reasons: attempting to operate on invalid data can expose your code -to vulnerabilities. This is the main reason that the standard library will -`panic!` if you attempt an out-of-bounds array access: trying to access memory -that doesn't belong to the current data structure is a common security problem. +values are valid first and panic if the values aren’t valid. This is mostly for +safety reasons: attempting to operate on invalid data can expose your code to +vulnerabilities. This is the main reason the standard library will call +`panic!` if you attempt an out-of-bounds memory access: trying to access memory +that doesn’t belong to the current data structure is a common security problem. Functions often have *contracts*: their behavior is only guaranteed if the inputs meet particular requirements. Panicking when the contract is violated -makes sense because a contract violation always indicates a caller-side bug, -and it is not a kind of error you want callers to have to explicitly handle. In -fact, there's no reasonable way for calling code to recover: the calling -*programmers* need to fix the code. Contracts for a function, especially when a -violation will cause a `panic`, should be explained in the API documentation -for the function. +makes sense because a contract violation always indicates a caller-side bug and +it’s not a kind of error you want the calling code to have to explicitly +handle. In fact, there’s no reasonable way for calling code to recover; the +calling *programmers* need to fix the code. Contracts for a function, +especially when a violation will cause a panic, should be explained in the API +documentation for the function. -Having lots of error checks in all of your functions would be verbose and -annoying, though. Luckily, you can use Rust's type system (and thus the type -checking the compiler does) to do a lot of the checks for you. If your function -has a particular type as a parameter, you can proceed with your code's logic +However, having lots of error checks in all of your functions would be verbose +and annoying. Fortunately, you can use Rust’s type system (and thus the type +checking the compiler does) to do many of the checks for you. If your function +has a particular type as a parameter, you can proceed with your code’s logic knowing that the compiler has already ensured you have a valid value. For example, if you have a type rather than an `Option`, your program expects to -have *something* rather than *nothing*. Your code then doesn't have to handle -two cases for the `Some` and `None` variants, it will only have one case for -definitely having a value. Code trying to pass nothing to your function won't -even compile, so your function doesn't have to check for that case at runtime. -Another example is using an unsigned integer type like `u32`, which ensures the -parameter is never negative. - - - +have *something* rather than *nothing*. Your code then doesn’t have to handle +two cases for the `Some` and `None` variants: it will only have one case for +definitely having a value. Code trying to pass nothing to your function won’t +even compile, so your function doesn’t have to check for that case at runtime. +Another example is using an unsigned integer type such as `u32`, which ensures +the parameter is never negative. ### Creating Custom Types for Validation -Let's take the idea of using Rust's type system to ensure we have a valid value -one step further, and look at creating a custom type for validation. Recall the -guessing game in Chapter 2, where our code asked the user to guess a number -between 1 and 100. We actually never validated that the user's guess was -between those numbers before checking it against our secret number, only that -it was positive. In this case, the consequences were not very dire: our output -of "Too high" or "Too low" would still be correct. It would be a useful -enhancement to guide the user towards valid guesses, though, and have different -behavior when a user guesses a number that's out of range versus when a user +Let’s take the idea of using Rust’s type system to ensure we have a valid value +one step further and look at creating a custom type for validation. Recall the +guessing game in Chapter 2 in which our code asked the user to guess a number +between 1 and 100. We never validated that the user’s guess was between those +numbers before checking it against our secret number; we only validated that +the guess was positive. In this case, the consequences were not very dire: our +output of “Too high” or “Too low” would still be correct. But it would be a +useful enhancement to guide the user toward valid guesses and have different +behavior when a user guesses a number that’s out of range versus when a user types, for example, letters instead. One way to do this would be to parse the guess as an `i32` instead of only a -`u32`, to allow potentially negative numbers, then add a check for the number -being in range: +`u32` to allow potentially negative numbers, and then add a check for the +number being in range, like so: ```rust,ignore -loop { - // snip - - let guess: i32 = match guess.trim().parse() { - Ok(num) => num, - Err(_) => continue, - }; - - if guess < 1 || guess > 100 { - println!("The secret number will be between 1 and 100."); - continue; - } - - match guess.cmp(&secret_number) { - // snip -} +{{#rustdoc_include ../listings/ch09-error-handling/no-listing-09-guess-out-of-range/src/main.rs:here}} ``` - - -The `if` expression checks to see if our value is out of range, tells the user +The `if` expression checks whether our value is out of range, tells the user about the problem, and calls `continue` to start the next iteration of the loop and ask for another guess. After the `if` expression, we can proceed with the -comparisons between `guess` and the secret number knowing that guess is between -1 and 100. +comparisons between `guess` and the secret number knowing that `guess` is +between 1 and 100. However, this is not an ideal solution: if it was absolutely critical that the program only operated on values between 1 and 100, and it had many functions -with this requirement, it would be tedious (and potentially impact performance) -to have a check like this in every function. +with this requirement, having a check like this in every function would be +tedious (and might impact performance). -Instead, we can make a new type and put the validations in the type's -constructor rather than repeating them. That way, it's safe for functions to -use the new type in their signatures and confidently use the values they -receive. Listing 9-8 shows one way to define a `Guess` type that will only -create an instance of `Guess` if the `new` function receives a value between 1 -and 100: +Instead, we can make a new type and put the validations in a function to create +an instance of the type rather than repeating the validations everywhere. That +way, it’s safe for functions to use the new type in their signatures and +confidently use the values they receive. Listing 9-10 shows one way to define a +`Guess` type that will only create an instance of `Guess` if the `new` function +receives a value between 1 and 100. -
+ ```rust -struct Guess { - value: u32, -} - -impl Guess { - pub fn new(value: u32) -> Guess { - if value < 1 || value > 100 { - panic!("Guess value must be between 1 and 100, got {}.", value); - } - - Guess { - value: value, - } - } - - pub fn value(&self) -> u32 { - self.value - } -} +{{#include ../listings/ch09-error-handling/listing-09-10/src/main.rs:here}} ``` -
- -Listing 9-8: A `Guess` type that will only continue with values between 1 and -100 - -
-
- - +Listing 9-10: A `Guess` type that will only continue with +values between 1 and 100 First, we define a struct named `Guess` that has a field named `value` that -holds a `u32`. This is where the number will be stored. +holds an `i32`. This is where the number will be stored. -Then we implement an associated function named `new` on `Guess` that is a -constructor of `Guess` values. The `new` function is defined to have one -parameter named `value` of type `u32` and to return a `Guess`. The code in the -body of the `new` function tests `value` to make sure it is between 1 and 100. -If `value` doesn't pass this test, we call `panic!`, which will alert the -programmer who is calling this code that they have a bug they need to fix, -since creating a `Guess` with a `value` outside this range would violate the -contract that `Guess::new` is relying on. The conditions in which `Guess::new` -might panic should be discussed in its public-facing API documentation; we'll -cover documentation conventions around indicating the possibility of a `panic!` -in the API documentation that you create in Chapter 14. If `value` does pass -the test, we create a new `Guess` with its `value` field set to the `value` -parameter, and return the `Guess`. +Then we implement an associated function named `new` on `Guess` that creates +instances of `Guess` values. The `new` function is defined to have one +parameter named `value` of type `i32` and to return a `Guess`. The code in the +body of the `new` function tests `value` to make sure it’s between 1 and 100. +If `value` doesn’t pass this test, we make a `panic!` call, which will alert +the programmer who is writing the calling code that they have a bug they need +to fix, because creating a `Guess` with a `value` outside this range would +violate the contract that `Guess::new` is relying on. The conditions in which +`Guess::new` might panic should be discussed in its public-facing API +documentation; we’ll cover documentation conventions indicating the possibility +of a `panic!` in the API documentation that you create in Chapter 14. If +`value` does pass the test, we create a new `Guess` with its `value` field set +to the `value` parameter and return the `Guess`. - - - -Next, we implement a method named `value` that borrows `self`, doesn't have any -other parameters, and returns a `u32`. This is a kind of method sometimes called -a *getter*, since its purpose is to get some data from its fields and return +Next, we implement a method named `value` that borrows `self`, doesn’t have any +other parameters, and returns an `i32`. This kind of method is sometimes called +a *getter*, because its purpose is to get some data from its fields and return it. This public method is necessary because the `value` field of the `Guess` -struct is private. It's important that the `value` field is private so that -code using the `Guess` struct is not allowed to set `value` directly: callers -*must* use the `Guess::new` constructor function to create an instance of -`Guess`, which ensures there's no way for a `Guess` to have a `value` that -hasn't been checked by the conditions in the constructor. +struct is private. It’s important that the `value` field be private so code +using the `Guess` struct is not allowed to set `value` directly: code outside +the module *must* use the `Guess::new` function to create an instance of +`Guess`, thereby ensuring there’s no way for a `Guess` to have a `value` that +hasn’t been checked by the conditions in the `Guess::new` function. A function that has a parameter or returns only numbers between 1 and 100 could -then declare in its signature that it takes or returns a `Guess` rather than a -`u32`, and wouldn't need to do any additional checks in its body. +then declare in its signature that it takes or returns a `Guess` rather than an +`i32` and wouldn’t need to do any additional checks in its body. ## Summary -Rust's error handling features are designed to help you write more robust code. -The `panic!` macro signals that your program is in a state it can't handle, and +Rust’s error handling features are designed to help you write more robust code. +The `panic!` macro signals that your program is in a state it can’t handle and lets you tell the process to stop instead of trying to proceed with invalid or -incorrect values. The `Result` enum uses Rust's type system to indicate that +incorrect values. The `Result` enum uses Rust’s type system to indicate that operations might fail in a way that your code could recover from. You can use `Result` to tell code that calls your code that it needs to handle potential success or failure as well. Using `panic!` and `Result` in the appropriate situations will make your code more reliable in the face of inevitable problems. -Now that we've seen useful ways that the standard library uses generics with -the `Option` and `Result` enums, let's talk about how generics work and how you -can make use of them in your code. +Now that you’ve seen useful ways that the standard library uses generics with +the `Option` and `Result` enums, we’ll talk about how generics work and how you +can use them in your code. diff --git a/src/ch10-00-generics.md b/src/ch10-00-generics.md index 71259be..c0375a1 100644 --- a/src/ch10-00-generics.md +++ b/src/ch10-00-generics.md @@ -1,134 +1,120 @@ -# Generics +# Generic Types, Traits, and Lifetimes -One of the core tools a programming language gives you is the ability to deal -effectively with duplication of code. It's important to minimize the amount of -code that is duplicated throughout a program to make maintenance easier and -minimize logic errors. Maintenance will be easier if there's only one place -that you need to change the code if you change your mind about how the program -should work, rather than multiple places in the code. If your program's logic -is duplicated in different places and those places don't match, you'll get -errors or unexpected and undesired behavior from your program that could be -hard to track down. Rust has the concept of *generics* as one way to eliminate -duplicate code. Generics come in the form of generic types, traits that those -generic types have, and generic lifetimes. We'll cover how to use all of these -in this chapter. +Every programming language has tools for effectively handling the duplication +of concepts. In Rust, one such tool is *generics*. Generics are abstract +stand-ins for concrete types or other properties. When we’re writing code, we +can express the behavior of generics or how they relate to other generics +without knowing what will be in their place when compiling and running the code. + +Similar to the way a function takes parameters with unknown values to run the +same code on multiple concrete values, functions can take parameters of some +generic type instead of a concrete type, like `i32` or `String`. In fact, we’ve +already used generics in Chapter 6 with `Option`, Chapter 8 with `Vec` +and `HashMap`, and Chapter 9 with `Result`. In this chapter, you’ll +explore how to define your own types, functions, and methods with generics! + +First, we’ll review how to extract a function to reduce code duplication. Next, +we’ll use the same technique to make a generic function from two functions that +differ only in the types of their parameters. We’ll also explain how to use +generic types in struct and enum definitions. + +Then you’ll learn how to use *traits* to define behavior in a generic way. You +can combine traits with generic types to constrain a generic type to only +those types that have a particular behavior, as opposed to just any type. + +Finally, we’ll discuss *lifetimes*, a variety of generics that give the +compiler information about how references relate to each other. Lifetimes allow +us to borrow values in many situations while still enabling the compiler to +check that the references are valid. ## Removing Duplication by Extracting a Function -Let's first go through a technique for dealing with duplication that you're -probably familiar with: extracting a function. Consider a small program that -finds the largest number in a list, shown in Listing 10-1: +Before diving into generics syntax, let’s first look at how to remove +duplication that doesn’t involve generic types by extracting a function. Then +we’ll apply this technique to extract a generic function! In the same way that +you recognize duplicated code to extract into a function, you’ll start to +recognize duplicated code that can use generics. -
-Filename: src/main.rs - -```rust -fn main() { - let numbers = vec![34, 50, 25, 100, 65]; - - let mut largest = numbers[0]; - - for number in numbers { - if number > largest { - largest = number; - } - } - - println!("The largest number is {}", largest); -} -``` - -
- -Listing 10-1: Code to find the largest number in a list of numbers - -
-
- -If we needed to find the largest number in two different lists of numbers, we -could duplicate the code in Listing 10-1 and have the same logic exist in two -places in the program: +Consider a short program that finds the largest number in a list, as shown in +Listing 10-1. Filename: src/main.rs ```rust -fn main() { - let numbers = vec![34, 50, 25, 100, 65]; - - let mut largest = numbers[0]; - - for number in numbers { - if number > largest { - largest = number; - } - } - - println!("The largest number is {}", largest); - - let numbers = vec![102, 34, 6000, 89, 54, 2, 43, 8]; - - let mut largest = numbers[0]; - - for number in numbers { - if number > largest { - largest = number; - } - } - - println!("The largest number is {}", largest); -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-01/src/main.rs:here}} ``` -Copying code is tedious and error-prone, plus now we have two places to update -the logic if we need it to change. Rust, like many languages, gives us a way to -deal with this duplication by creating an abstraction, and in this case the -abstraction we'll use is a function. Here's a program where we've extracted the -code in Listing 10-1 that finds the largest number into a function named -`largest`. This program can find the largest number in two different lists of -numbers, but the code from Listing 10-1 only exists in one spot: +Listing 10-1: Code to find the largest number in a list +of numbers + +This code stores a list of integers in the variable `number_list` and places +the first number in the list in a variable named `largest`. Then it iterates +through all the numbers in the list, and if the current number is greater than +the number stored in `largest`, it replaces the number in that variable. +However, if the current number is less than or equal to the largest number seen +so far, the variable doesn’t change, and the code moves on to the next number +in the list. After considering all the numbers in the list, `largest` should +hold the largest number, which in this case is 100. + +To find the largest number in two different lists of numbers, we can duplicate +the code in Listing 10-1 and use the same logic at two different places in the +program, as shown in Listing 10-2. Filename: src/main.rs ```rust -fn largest(numbers: Vec) { - let mut largest = numbers[0]; - - for number in numbers { - if number > largest { - largest = number; - } - } - - println!("The largest number is {}", largest); -} - -fn main() { - let numbers = vec![34, 50, 25, 100, 65]; - - largest(numbers); - - let numbers = vec![102, 34, 6000, 89, 54, 2, 43, 8]; - - largest(numbers); -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-02/src/main.rs}} ``` -The function defines a parameter, `numbers`, which represents any concrete -`Vec` that we might pass into the function. The code in the function -definition operates on the `numbers` representation of any `Vec`. When -we call the `largest` function, the code actually runs on the specific values -that we pass in. +Listing 10-2: Code to find the largest number in *two* +lists of numbers -Functions aren't the only way to eliminate duplication. For example, our -`largest` function only works for vectors of `i32`. What if we wanted to find -the largest number in a list of floats? Or the largest value in some sort of -custom `struct` or `enum`? We can't solve those kinds of duplication with -regular functions. +Although this code works, duplicating code is tedious and error prone. We also +have to update the code in multiple places when we want to change it. -To solve these kinds of problems, Rust provides a feature called *generics*. In -the same way that functions allow us to abstract over common code, generics -allow us to abstract over types. This ability gives us tremendous power to -write code that works in a large number of situations. First, we'll examine the -syntax of generics. Then, we'll talk about another feature that's used to -augment generics: traits. Finally, we'll discuss one of Rust's most unique uses -of generics: lifetimes. +To eliminate this duplication, we can create an abstraction by defining a +function that operates on any list of integers given to it in a parameter. This +solution makes our code clearer and lets us express the concept of finding the +largest number in a list abstractly. + +In Listing 10-3, we extracted the code that finds the largest number into a +function named `largest`. Unlike the code in Listing 10-1, which can find the +largest number in only one particular list, this program can find the largest +number in two different lists. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-03/src/main.rs:here}} +``` + +Listing 10-3: Abstracted code to find the largest number +in two lists + +The `largest` function has a parameter called `list`, which represents any +concrete slice of `i32` values that we might pass into the function. As a +result, when we call the function, the code runs on the specific values that we +pass in. Don't worry about the syntax of the `for` loop for now. We aren't +referencing a reference to an `i32` here; we're pattern matching and +destructuring each `&i32` that the `for` loop gets so that `item` will be an +`i32` inside the loop body. We'll cover pattern matching in detail in [Chapter +18][ch18]. + +In sum, here are the steps we took to change the code from Listing 10-2 to +Listing 10-3: + +1. Identify duplicate code. +2. Extract the duplicate code into the body of the function and specify the + inputs and return values of that code in the function signature. +3. Update the two instances of duplicated code to call the function instead. + +Next, we’ll use these same steps with generics to reduce code duplication in +different ways. In the same way that the function body can operate on an +abstract `list` instead of specific values, generics allow code to operate on +abstract types. + +For example, say we had two functions: one that finds the largest item in a +slice of `i32` values and one that finds the largest item in a slice of `char` +values. How would we eliminate that duplication? Let’s find out! + +[ch18]: ch18-00-patterns.html diff --git a/src/ch10-01-syntax.md b/src/ch10-01-syntax.md index a4fd597..0eb8b56 100644 --- a/src/ch10-01-syntax.md +++ b/src/ch10-01-syntax.md @@ -1,171 +1,303 @@ -## Generics Syntax +## Generic Data Types -We've already hinted at the idea of generics in previous chapters, but we -never dug into what exactly they are or how to use them. In places where we -specify a type, like function signatures or structs, instead we can use -*generics*. Generics are stand-ins that represent an abstract set instead of something concrete. In this section, we're going to cover generic *data types*. +We can use generics to create definitions for items like function signatures or +structs, which we can then use with many different concrete data types. Let’s +first look at how to define functions, structs, enums, and methods using +generics. Then we’ll discuss how generics affect code performance. -You can recognize when any kind of generics are used by the way that they fit -into Rust's syntax: any time you see angle brackets, `<>`, you're dealing with -generics. Types we've seen before, like in Chapter 8 where we discussed vectors -with types like `Vec`, employ generics. The type that the standard library -defines for vectors is `Vec`. That `T` is called a *type parameter*, and it -serves a similar function as parameters to functions: you fill in the parameter -with a concrete type, and that determines how the overall type works. In the -same way that a function like `foo(x: i32)` can be called with a specific value -such as `foo(5)`, a `Vec` can be created with a specific type, like -`Vec`. +### In Function Definitions -### Duplicated Enum Definitions +When defining a function that uses generics, we place the generics in the +signature of the function where we would usually specify the data types of the +parameters and return value. Doing so makes our code more flexible and provides +more functionality to callers of our function while preventing code duplication. -Let's dive into generic data types in more detail. We learned about how to use -the `Option` enum in Chapter 6, but we never examined its definition. Let's -try to imagine how we'd write it! We'll start from duplicated code like we did -in the "Removing Duplication by Extracting a Function" section. This time, -we'll remove the duplication by extracting a generic data type instead of -extracting a function, but the mechanics of doing the extraction will be -similar. First, let's consider an `Option` enum with a `Some` variant that can -only hold an `i32`. We'll call this enum `OptionalNumber`: +Continuing with our `largest` function, Listing 10-4 shows two functions that +both find the largest value in a slice. Filename: src/main.rs ```rust -enum OptionalNumber { - Some(i32), - None, -} - -fn main() { - let number = OptionalNumber::Some(5); - let no_number = OptionalNumber::None; -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-04/src/main.rs:here}} ``` -This works just fine for `i32`s. But what if we also wanted to store `f64`s? We -would have to duplicate code to define a separate `Option` enum type for each -type we wanted to be able to hold in the `Some` variants. For example, here is -how we could define and use `OptionalFloatingPointNumber`: +Listing 10-4: Two functions that differ only in their +names and the types in their signatures + +The `largest_i32` function is the one we extracted in Listing 10-3 that finds +the largest `i32` in a slice. The `largest_char` function finds the largest +`char` in a slice. The function bodies have the same code, so let’s eliminate +the duplication by introducing a generic type parameter in a single function. + +To parameterize the types in the new function we’ll define, we need to name the +type parameter, just as we do for the value parameters to a function. You can +use any identifier as a type parameter name. But we’ll use `T` because, by +convention, parameter names in Rust are short, often just a letter, and Rust’s +type-naming convention is CamelCase. Short for “type,” `T` is the default +choice of most Rust programmers. + +When we use a parameter in the body of the function, we have to declare the +parameter name in the signature so the compiler knows what that name means. +Similarly, when we use a type parameter name in a function signature, we have +to declare the type parameter name before we use it. To define the generic +`largest` function, place type name declarations inside angle brackets, `<>`, +between the name of the function and the parameter list, like this: + +```rust,ignore +fn largest(list: &[T]) -> T { +``` + +We read this definition as: the function `largest` is generic over some type +`T`. This function has one parameter named `list`, which is a slice of values +of type `T`. The `largest` function will return a value of the +same type `T`. + +Listing 10-5 shows the combined `largest` function definition using the generic +data type in its signature. The listing also shows how we can call the function +with either a slice of `i32` values or `char` values. Note that this code won’t +compile yet, but we’ll fix it later in this chapter. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/src/main.rs}} +``` + +Listing 10-5: A definition of the `largest` function that +uses generic type parameters but doesn’t compile yet + +If we compile this code right now, we’ll get this error: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/output.txt}} +``` + +The note mentions `std::cmp::PartialOrd`, which is a *trait*. We’ll talk about +traits in the next section. For now, this error states that the body of +`largest` won’t work for all possible types that `T` could be. Because we want +to compare values of type `T` in the body, we can only use types whose values +can be ordered. To enable comparisons, the standard library has the +`std::cmp::PartialOrd` trait that you can implement on types (see Appendix C +for more on this trait). You’ll learn how to specify that a generic type has a +particular trait in the [“Traits as Parameters”][traits-as-parameters] section, but let’s first explore other ways of using generic type +parameters. + +### In Struct Definitions + +We can also define structs to use a generic type parameter in one or more +fields using the `<>` syntax. Listing 10-6 shows how to define a `Point` +struct to hold `x` and `y` coordinate values of any type. Filename: src/main.rs ```rust -enum OptionalFloatingPointNumber { - Some(f64), - None, -} - -fn main() { - let number = OptionalFloatingPointNumber::Some(5.0); - let no_number = OptionalFloatingPointNumber::None; -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-06/src/main.rs}} ``` -We've made the enum's name a bit long in order to drive the point home. With -what we currently know how to do in Rust, we would have to write a unique type -for every single kind of value we wanted to have either `Some` or `None` of. In -other words, the idea of "an optional value" is a more abstract concept than one -specific type. We want it to work for any type at all. +Listing 10-6: A `Point` struct that holds `x` and `y` +values of type `T` -### Removing Duplication by Extracting a Generic Data Type +The syntax for using generics in struct definitions is similar to that used in +function definitions. First, we declare the name of the type parameter inside +angle brackets just after the name of the struct. Then we can use the generic +type in the struct definition where we would otherwise specify concrete data +types. -Let's see how to get from duplicated types to the generic type. Here are the -definitions of our two enums side-by-side: +Note that because we’ve used only one generic type to define `Point`, this +definition says that the `Point` struct is generic over some type `T`, and +the fields `x` and `y` are *both* that same type, whatever that type may be. If +we create an instance of a `Point` that has values of different types, as in +Listing 10-7, our code won’t compile. -```text -enum OptionalNumber { enum OptionalFloatingPointNumber { - Some(i32), Some(f64), - None, None, -} } +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/src/main.rs}} ``` -Aside from the names, we have one line where the two definitions are very -close, but still different: the line with the `Some` definitions. The only -difference is the type of the data in that variant, `i32` and `f64`. +Listing 10-7: The fields `x` and `y` must be the same +type because both have the same generic data type `T`. -Just like we can parameterize arguments to a function by choosing a name, we -can parameterize the type by choosing a name. In this case, we've chosen the -name `T`. We could choose any identifier here, but Rust style has type -parameters follow the same style as types themselves: CamelCase. In addition, -they tend to be short, often one letter. `T` is the traditional default choice, -short for 'type'. Let's use that name in our `Some` variant definitions where -the `i32` and `f64` types were: +In this example, when we assign the integer value 5 to `x`, we let the +compiler know that the generic type `T` will be an integer for this instance of +`Point`. Then when we specify 4.0 for `y`, which we’ve defined to have the +same type as `x`, we’ll get a type mismatch error like this: -```text -enum OptionalNumber { enum OptionalFloatingPointNumber { - Some(T), Some(T), - None, None, -} } +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-07/output.txt}} ``` -There's one problem, though: we've *used* `T`, but not defined it. This would -be similar to using a parameter name in a function body without declaring it -in the signature. We need to tell Rust that we've introduced a generic -parameter. The syntax to do that is the angle brackets, like this: +To define a `Point` struct where `x` and `y` are both generics but could have +different types, we can use multiple generic type parameters. For example, in +Listing 10-8, we can change the definition of `Point` to be generic over types +`T` and `U` where `x` is of type `T` and `y` is of type `U`. -```text -enum OptionalNumber { enum OptionalFloatingPointNumber { - Some(T), Some(T), - None, None, -} } -``` - -The `<>`s after the enum name indicate a list of type parameters, just like -`()` after a function name indicates a list of value parameters. Now the only -difference between our two `enum`s is the name. Since we've made them generic, -they're not specific to integers or floating point numbers anymore, so they can -have the same name: - -```text -enum Option { enum Option { - Some(T), Some(T), - None, None, -} } -``` - -Now they're identical! We've made our type fully generic. This definition is -also how `Option` is defined in the standard library. If we were to read this -definition aloud, we'd say, "`Option` is an `enum` with one type parameter, -`T`. It has two variants: `Some`, which has a value with type `T`, and `None`, -which has no value." We can now use the same `Option` type whether we're holding an `i32` or an `f64`: +Filename: src/main.rs ```rust -let integer = Option::Some(5); -let float = Option::Some(5.0); +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-08/src/main.rs}} ``` -We've left in the `Option::` namespace for consistency with the previous -examples, but since `use Option::*` is in the prelude, it's not needed. Usually -using `Option` looks like this: +Listing 10-8: A `Point` generic over two types so +that `x` and `y` can be values of different types + +Now all the instances of `Point` shown are allowed! You can use as many generic +type parameters in a definition as you want, but using more than a few makes +your code hard to read. When you need lots of generic types in your code, it +could indicate that your code needs restructuring into smaller pieces. + +### In Enum Definitions + +As we did with structs, we can define enums to hold generic data types in their +variants. Let’s take another look at the `Option` enum that the standard +library provides, which we used in Chapter 6: + +```rust +enum Option { + Some(T), + None, +} +``` + +This definition should now make more sense to you. As you can see, `Option` +is an enum that is generic over type `T` and has two variants: `Some`, which +holds one value of type `T`, and a `None` variant that doesn’t hold any value. +By using the `Option` enum, we can express the abstract concept of having an +optional value, and because `Option` is generic, we can use this abstraction +no matter what the type of the optional value is. + +Enums can use multiple generic types as well. The definition of the `Result` +enum that we used in Chapter 9 is one example: + +```rust +enum Result { + Ok(T), + Err(E), +} +``` + +The `Result` enum is generic over two types, `T` and `E`, and has two variants: +`Ok`, which holds a value of type `T`, and `Err`, which holds a value of type +`E`. This definition makes it convenient to use the `Result` enum anywhere we +have an operation that might succeed (return a value of some type `T`) or fail +(return an error of some type `E`). In fact, this is what we used to open a +file in Listing 9-3, where `T` was filled in with the type `std::fs::File` when +the file was opened successfully and `E` was filled in with the type +`std::io::Error` when there were problems opening the file. + +When you recognize situations in your code with multiple struct or enum +definitions that differ only in the types of the values they hold, you can +avoid duplication by using generic types instead. + +### In Method Definitions + +We can implement methods on structs and enums (as we did in Chapter 5) and use +generic types in their definitions, too. Listing 10-9 shows the `Point` +struct we defined in Listing 10-6 with a method named `x` implemented on it. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-09/src/main.rs}} +``` + +Listing 10-9: Implementing a method named `x` on the +`Point` struct that will return a reference to the `x` field of type +`T` + +Here, we’ve defined a method named `x` on `Point` that returns a reference +to the data in the field `x`. + +Note that we have to declare `T` just after `impl` so we can use it to specify +that we’re implementing methods on the type `Point`. By declaring `T` as a +generic type after `impl`, Rust can identify that the type in the angle +brackets in `Point` is a generic type rather than a concrete type. + +We could, for example, implement methods only on `Point` instances rather +than on `Point` instances with any generic type. In Listing 10-10 we use the +concrete type `f32`, meaning we don’t declare any types after `impl`. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-10/src/main.rs:here}} +``` + +Listing 10-10: An `impl` block that only applies to a +struct with a particular concrete type for the generic type parameter `T` + +This code means the type `Point` will have a method named +`distance_from_origin` and other instances of `Point` where `T` is not of +type `f32` will not have this method defined. The method measures how far our +point is from the point at coordinates (0.0, 0.0) and uses mathematical +operations that are available only for floating point types. + +Generic type parameters in a struct definition aren’t always the same as those +you use in that struct’s method signatures. For example, Listing 10-11 defines +the method `mixup` on the `Point` struct from Listing 10-8. The method +takes another `Point` as a parameter, which might have different types from the +`self` `Point` we’re calling `mixup` on. The method creates a new `Point` +instance with the `x` value from the `self` `Point` (of type `T`) and the `y` +value from the passed-in `Point` (of type `W`). + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-11/src/main.rs}} +``` + +Listing 10-11: A method that uses different generic types +from its struct’s definition + +In `main`, we’ve defined a `Point` that has an `i32` for `x` (with value `5`) +and an `f64` for `y` (with value `10.4`). The `p2` variable is a `Point` struct +that has a string slice for `x` (with value `"Hello"`) and a `char` for `y` +(with value `c`). Calling `mixup` on `p1` with the argument `p2` gives us `p3`, +which will have an `i32` for `x`, because `x` came from `p1`. The `p3` variable +will have a `char` for `y`, because `y` came from `p2`. The `println!` macro +call will print `p3.x = 5, p3.y = c`. + +The purpose of this example is to demonstrate a situation in which some generic +parameters are declared with `impl` and some are declared with the method +definition. Here, the generic parameters `T` and `U` are declared after `impl`, +because they go with the struct definition. The generic parameters `V` and `W` +are declared after `fn mixup`, because they’re only relevant to the method. + +### Performance of Code Using Generics + +You might be wondering whether there is a runtime cost when you’re using +generic type parameters. The good news is that Rust implements generics in such +a way that your code doesn’t run any slower using generic types than it would +with concrete types. + +Rust accomplishes this by performing monomorphization of the code that is using +generics at compile time. *Monomorphization* is the process of turning generic +code into specific code by filling in the concrete types that are used when +compiled. + +In this process, the compiler does the opposite of the steps we used to create +the generic function in Listing 10-5: the compiler looks at all the places +where generic code is called and generates code for the concrete types the +generic code is called with. + +Let’s look at how this works with an example that uses the standard library’s +`Option` enum: ```rust let integer = Some(5); let float = Some(5.0); ``` -When you recognize situations with almost-duplicate types like this in your -code, you can follow this process to reduce duplication using generics. +When Rust compiles this code, it performs monomorphization. During that +process, the compiler reads the values that have been used in `Option` +instances and identifies two kinds of `Option`: one is `i32` and the other +is `f64`. As such, it expands the generic definition of `Option` into +`Option_i32` and `Option_f64`, thereby replacing the generic definition with +the specific ones. -### Monomorphization at Compile Time - -Understanding this refactoring process is also useful in understanding how -generics work behind the scenes: the compiler does the exact opposite of this -process when compiling your code. *Monomorphization* means taking code that -uses generic type parameters and generating code that is specific for each -concrete type that is used with the generic code. Monomorphization is why -Rust's generics are extremely efficient at runtime. Consider this code that -uses the standard library's `Option`: - -```rust -let integer = Some(5); -let float = Some(5.0); -``` - -When Rust compiles this code, it will perform monomorphization. What this means -is the compiler will see that we've used two kinds of `Option`: one where -`T` is `i32`, and one where `T` is `f64`. As such, it will expand the generic -definition of `Option` into `Option_i32` and `Option_f64`, thereby replacing -the generic definition with the specific ones. The more specific version looks -like the duplicated code we started with at the beginning of this section: +The monomorphized version of the code looks like the following. The generic +`Option` is replaced with the specific definitions created by the compiler: Filename: src/main.rs @@ -186,196 +318,10 @@ fn main() { } ``` -In other words, we can write the non-duplicated form that uses generics in our -code, but Rust will compile that into code that acts as though we wrote the -specific type out in each instance. This means we pay no runtime cost for using -generics; it's just like we duplicated each particular definition. +Because Rust compiles generic code into code that specifies the type in each +instance, we pay no runtime cost for using generics. When the code runs, it +performs just as it would if we had duplicated each definition by hand. The +process of monomorphization makes Rust’s generics extremely efficient at +runtime. -### Generic Structs - -In a similar fashion as we did with enums, we can use `<>`s with structs as -well in order to define structs that have a generic type parameter in one or -more of their fields. Generic structs also get monomorphized into specialized -types at compile time. Listing 10-2 shows the definition and use of a `Point` -struct that could hold `x` and `y` coordinate values that are any type: - -
-Filename: src/main.rs - -```rust -struct Point { - x: T, - y: T, -} - -fn main() { - let integer = Point { x: 5, y: 10 }; - let float = Point { x: 1.0, y: 4.0 }; -} -``` - -
- -Listing 10-2: A `Point` struct that holds `x` and `y` values of type `T` - -
-
- -The syntax is the same with structs: add a `` after the name of the struct, -then use `T` in the definition where you want to use that generic type instead -of a specific type. - -### Multiple Type Parameters - -Note that in the `Point` definition in Listing 10-2, we've used the same `T` -parameter for both fields. This means `x` and `y` must always be values of the -same type. Trying to instantiate a `Point` that uses an `i32` for `x` and an -`f64` for `y`, like this: - -```rust,ignore -let p = Point { x: 5, y: 20.0 }; -``` - -results in a compile-time error that indicates the type of `y` must match the -type of `x`: - -```text -error[E0308]: mismatched types - | -7 | let p = Point { x: 5, y: 20.0 }; - | ^^^^ expected integral variable, found floating-point variable - | - = note: expected type `{integer}` - = note: found type `{float}` -``` - -If we need to be able to have fields with generic but different types, we can -declare multiple type parameters within the angle brackets, separated by a -comma. Listing 10-3 shows how to define a `Point` that can have different types -for `x` and `y`: - -
-Filename: src/main.rs - -```rust -struct Point { - x: X, - y: Y, -} - -fn main() { - let integer = Point { x: 5, y: 10 }; - let float = Point { x: 1.0, y: 4.0 }; - let p = Point { x: 5, y: 20.0 }; -} -``` - -
- -Listing 10-3: A `Point` struct that holds an `x` value of type `X` and a `y` -value of type `Y` - -
-
- -Now `x` will have the type of `X`, and `y` will have the type of `Y`, and we -can instantiate a `Point` with an `i32` for `x` and an `f64` for `y`. - -We can make `enum`s with multiple type parameters as well. Recall the enum -`Result` from Chapter 9 that we used for recoverable errors. Here's its -definition: - -```rust -enum Result { - Ok(T), - Err(E), -} -``` - -Each variant stores a different kind of information, and they're both generic. - -You can have as many type parameters as you'd like. Similarly to parameters of -values in function signatures, if you have a lot of parameters, the code can -get quite confusing, so try to keep the number of parameters defined in any one -type small if you can. - -### Generic Functions and Methods - -In a similar way to data structures, we can use the `<>` syntax in function or -method definitions. The angle brackets for type parameters go after the -function or method name and before the parameter list in parentheses: - -```rust -fn generic_function(value: T) { - // code goes here -} -``` - -We can use the same process that we used to refactor duplicated type -definitions using generics to refactor duplicated function definitions using -generics. Consider these two side-by-side function signatures that differ in -the type of `value`: - -```text -fn takes_integer(value: i32) { fn takes_float(value: f64) { - // code goes here // code goes here -} } -``` - -We can add a type parameter list that declares the generic type `T` after the -function names, then use `T` where the specific `i32` and `f64` types were: - -```text -fn takes_integer(value: T) { fn takes_float(value: T) { - // code goes here // code goes here -} } -``` - -At this point, only the names differ, so we could unify the two functions into -one: - -```rust,ignore -fn takes(value: T) { - // code goes here -} -``` - -There's one problem though. We've got some function *definitions* that work, -but if we try to use `value` in code in the function body, we'll get an -error. For example, the function definition in Listing 10-4 tries to print out -`value` in its body: - -
-Filename: src/lib.rs - -```rust,ignore -fn show_anything(value: T) { - println!("I have something to show you!"); - println!("It's: {}", value); -} -``` - -
- -Listing 10-4: A `show_anything` function definition that does not yet compile - -
-
- -Compiling this definition results in an error: - -```text - error[E0277]: the trait bound `T: std::fmt::Display` is not satisfied - --> :3:37 - | -3 | println!("It's: {}", value); - | ^^^^^ trait `T: std::fmt::Display` not satisfied - | - = help: consider adding a `where T: std::fmt::Display` bound - = note: required by `std::fmt::Display::fmt` - -error: aborting due to previous error(s) -``` - -This error mentions something we haven't learned about yet: traits. In the next -section, we'll learn how to make this compile. +[traits-as-parameters]: ch10-02-traits.html#traits-as-parameters diff --git a/src/ch10-02-traits.md b/src/ch10-02-traits.md index 25b96ee..abfc001 100644 --- a/src/ch10-02-traits.md +++ b/src/ch10-02-traits.md @@ -1,306 +1,471 @@ -## Traits +## Traits: Defining Shared Behavior -*Traits* are similar to a feature often called 'interfaces' in other languages, -but are also different. Traits let us do another kind of abstraction: they let -us abstract over *behavior* that types can have in common. +A *trait* tells the Rust compiler about functionality a particular type has and +can share with other types. We can use traits to define shared behavior in an +abstract way. We can use trait bounds to specify that a generic can be any type +that has certain behavior. -When we use a generic type parameter, we are telling Rust that any type is -valid in that location. When other code *uses* a value that could be of any -type, we need to also tell Rust that the type has the functionality that we -need. Traits let us specify that, for example, we need any type `T` that has -methods defined on it that allow us to print a value of that type. This is -powerful because we can still leave our definitions generic to allow use of -many different types, but we can constrain the type at compile-time to types -that have the behavior we need to be able to use. +> Note: Traits are similar to a feature often called *interfaces* in other +> languages, although with some differences. -Listing 10-5 has an example definition of a trait named `Printable` with a -method named `print`: +### Defining a Trait + +A type’s behavior consists of the methods we can call on that type. Different +types share the same behavior if we can call the same methods on all of those +types. Trait definitions are a way to group method signatures together to +define a set of behaviors necessary to accomplish some purpose. + +For example, let’s say we have multiple structs that hold various kinds and +amounts of text: a `NewsArticle` struct that holds a news story filed in a +particular location and a `Tweet` that can have at most 280 characters along +with metadata that indicates whether it was a new tweet, a retweet, or a reply +to another tweet. + +We want to make a media aggregator library that can display summaries of data +that might be stored in a `NewsArticle` or `Tweet` instance. To do this, we +need a summary from each type, and we need to request that summary by calling a +`summarize` method on an instance. Listing 10-12 shows the definition of a +`Summary` trait that expresses this behavior. -
Filename: src/lib.rs -```rust -trait Printable { - fn print(&self); -} +```rust,noplayground +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-12/src/lib.rs}} ``` -
+Listing 10-12: A `Summary` trait that consists of the +behavior provided by a `summarize` method -Listing 10-5: A `Printable` trait definition with one method, `print` +Here, we declare a trait using the `trait` keyword and then the trait’s name, +which is `Summary` in this case. Inside the curly brackets, we declare the +method signatures that describe the behaviors of the types that implement this +trait, which in this case is `fn summarize(&self) -> String`. -
-
+After the method signature, instead of providing an implementation within curly +brackets, we use a semicolon. Each type implementing this trait must provide +its own custom behavior for the body of the method. The compiler will enforce +that any type that has the `Summary` trait will have the method `summarize` +defined with this signature exactly. -We declare a trait with the `trait` keyword, then the trait's name. In this -case, our trait will describe types which can be printed. Inside of curly -braces, we declare a method signature, but instead of providing an -implementation inside curly braces, we put a semicolon after the signature. A -trait can have multiple methods in its body, with the method signatures listed -one per line and each line ending in a semicolon. +A trait can have multiple methods in its body: the method signatures are listed +one per line and each line ends in a semicolon. -Implementing a trait for a particular type looks similar to implementing -methods on a type since it's also done with the `impl` keyword, but we specify -the trait name as well. Inside the `impl` block, we specify definitions for the -trait's methods in the context of the specific type. Listing 10-6 has an -example of implementing the `Printable` trait from Listing 10-5 (that only has -the `print` method) for a `Temperature` enum: +### Implementing a Trait on a Type + +Now that we’ve defined the desired behavior using the `Summary` trait, we can +implement it on the types in our media aggregator. Listing 10-13 shows an +implementation of the `Summary` trait on the `NewsArticle` struct that uses the +headline, the author, and the location to create the return value of +`summarize`. For the `Tweet` struct, we define `summarize` as the username +followed by the entire text of the tweet, assuming that tweet content is +already limited to 280 characters. -
Filename: src/lib.rs -```rust -# trait Printable { -# fn print(&self); -# } -# -enum Temperature { - Celsius(i32), - Fahrenheit(i32), -} - -impl Printable for Temperature { - fn print(&self) { - match *self { - Temperature::Celsius(val) => println!("{}°C", val), - Temperature::Fahrenheit(val) => println!("{}°F", val), - } - } -} +```rust,noplayground +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-13/src/lib.rs:here}} ``` -
+Listing 10-13: Implementing the `Summary` trait on the +`NewsArticle` and `Tweet` types -Listing 10-6: Implementing the `Printable` trait on a `Temperature` enum +Implementing a trait on a type is similar to implementing regular methods. The +difference is that after `impl`, we put the trait name that we want to +implement, then use the `for` keyword, and then specify the name of the type we +want to implement the trait for. Within the `impl` block, we put the method +signatures that the trait definition has defined. Instead of adding a semicolon +after each signature, we use curly brackets and fill in the method body with +the specific behavior that we want the methods of the trait to have for the +particular type. -
-
- -In the same way `impl` lets us define methods, we've used it to define methods -that pertain to our trait. We can call methods that our trait has defined just -like we can call other methods: - -Filename: src/main.rs - -```rust -# trait Printable { -# fn print(&self); -# } -# -# enum Temperature { -# Celsius(i32), -# Fahrenheit(i32), -# } -# -# impl Printable for Temperature { -# fn print(&self) { -# match *self { -# Temperature::Celsius(val) => println!("{}°C", val), -# Temperature::Fahrenheit(val) => println!("{}°F", val), -# } -# } -# } -# -fn main() { - let t = Temperature::Celsius(37); - - t.print(); -} -``` - -Note that in order to use a trait's methods, the trait itself must be in scope. -If the definition of `Printable` was in a module, the definition would need to -be defined as `pub` and we would need to `use` the trait in the scope where we -wanted to call the `print` method. This is because it's possible to have two -traits that both define a method named `print`, and our `Temperature` enum might -implement both. Rust wouldn't know which `print` method we wanted unless we -brought the trait we wanted into our current scope with `use`. - -### Trait Bounds - -Defining traits with methods and implementing the trait methods on a particular -type gives Rust more information than just defining methods on a type directly. -The information Rust gets is that the type that implements the trait can be -used in places where the code specifies that it needs some type that implements -a trait. To illustrate this, Listing 10-7 has a `print_anything` function -definition. This is similar to the `show_anything` function from Listing 10-4, -but this function has a *trait bound* on the generic type `T` and uses the -`print` function from the trait. A trait bound constrains the generic type to -be any type that implements the trait specified, instead of any type at all. -With the trait bound, we're then allowed to use the trait method `print` in the -function body: - -
-Filename: src/lib.rs
- -```rust -# trait Printable { -# fn print(&self); -# } -# -fn print_anything(value: T) { - println!("I have something to print for you!"); - value.print(); -} -``` - -
- -Listing 10-7: A `print_anything` function that uses the trait bound `Printable` -on type `T` - -
- - -Trait bounds are specified in the type name declarations within the angle -brackets. After the name of the type that you want to apply the bound to, add a -colon (`:`) and then specify the name of the trait. This function now specifies -that it takes a `value` parameter that can be of any type, as long as that type -implements the trait `Printable`. We need to specify the `Printable` trait in -the type name declarations because we want to be able to call the `print` -method that is part of the `Printable` trait. - -Now we are able to call the `print_anything` function from Listing 10-7 and -pass it a `Temperature` instance as the `value` parameter, since we implemented -the trait `Printable` on `Temperature` in Listing 10-6: - -Filename: src/main.rs - -```rust -# trait Printable { -# fn print(&self); -# } -# -# enum Temperature { -# Celsius(i32), -# Fahrenheit(i32), -# } -# -# impl Printable for Temperature { -# fn print(&self) { -# match *self { -# Temperature::Celsius(val) => println!("{}°C", val), -# Temperature::Fahrenheit(val) => println!("{}°F", val), -# } -# } -# } -# -# fn print_anything(value: T) { -# println!("I have something to print for you!"); -# value.print(); -# } -# -fn main() { - let temperature = Temperature::Fahrenheit(98); - print_anything(temperature); -} -``` - -If we implement the `Printable` trait on other types, we can use them with the -`print_anything` method too. If we try to call `print_anything` with an `i32`, -which does *not* implement the `Printable` trait, we get a compile-time error -that looks like this: - -```text -error[E0277]: the trait bound `{integer}: Printable` is not satisfied - | -29 | print_anything(3); - | ^^^^^^^^^^^^^^ trait `{integer}: Printable` not satisfied - | - = help: the following implementations were found: - = help: - = note: required by `print_anything` -``` - -Traits are an extremely useful feature of Rust. You'll almost never see generic -functions without an accompanying trait bound. There are many traits in the -standard library, and they're used for many, many different things. For -example, our `Printable` trait is similar to one of those traits, `Display`. -And in fact, that's how `println!` decides how to format things with `{}`. The -`Display` trait has a `fmt` method that determines how to format something. - -Listing 10-8 shows our original example from Listing 10-3, but this time using -the standard library's `Display` trait in the trait bound on the generic type -in the `show_anything` function: - -
-Filename: src/lib.rs - -```rust -use std::fmt::Display; - -fn show_anything(value: T) { - println!("I have something to show you!"); - println!("It's: {}", value); -} -``` - -
- -Listing 10-8: The `show_anything` function with trait bounds - -
-
- -Now that this function specifies that `T` can be any type as long as that type -implements the `Display` trait, this code will compile. - -### Multiple Trait Bounds and `where` Syntax - -Each generic type can have its own trait bounds. The signature for a function -that takes a type `T` that implements `Display` and a type `U` that implements -`Printable` looks like: +After implementing the trait, we can call the methods on instances of +`NewsArticle` and `Tweet` in the same way we call regular methods, like this: ```rust,ignore -fn some_function(value: T, other_value: U) { +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-01-calling-trait-method/src/main.rs:here}} ``` -To specify multiple trait bounds on one type, list the trait bounds in a list -with a `+` between each trait. For example, here's the signature of a function -that takes a type `T` that implements `Display` and `Clone` (which is another -standard library trait we have mentioned): +This code prints `1 new tweet: horse_ebooks: of course, as you probably already +know, people`. -```rust,ignore -fn some_function(value: T) { -``` +Note that because we defined the `Summary` trait and the `NewsArticle` and +`Tweet` types in the same *lib.rs* in Listing 10-13, they’re all in the same +scope. Let’s say this *lib.rs* is for a crate we’ve called `aggregator` and +someone else wants to use our crate’s functionality to implement the `Summary` +trait on a struct defined within their library’s scope. They would need to +bring the trait into their scope first. They would do so by specifying `use +aggregator::Summary;`, which then would enable them to implement `Summary` for +their type. The `Summary` trait would also need to be a public trait for +another crate to implement it, which it is because we put the `pub` keyword +before `trait` in Listing 10-12. -When trait bounds start getting complicated, there is another syntax that's a -bit cleaner: `where`. And in fact, the error we got when we ran the code from -Listing 10-3 referred to it: +One restriction to note with trait implementations is that we can implement a +trait on a type only if either the trait or the type is local to our crate. +For example, we can implement standard library traits like `Display` on a +custom type like `Tweet` as part of our `aggregator` crate functionality, +because the type `Tweet` is local to our `aggregator` crate. We can also +implement `Summary` on `Vec` in our `aggregator` crate, because the +trait `Summary` is local to our `aggregator` crate. -```text -help: consider adding a `where T: std::fmt::Display` bound -``` +But we can’t implement external traits on external types. For example, we can’t +implement the `Display` trait on `Vec` within our `aggregator` crate, +because `Display` and `Vec` are defined in the standard library and aren’t +local to our `aggregator` crate. This restriction is part of a property of +programs called *coherence*, and more specifically the *orphan rule*, so named +because the parent type is not present. This rule ensures that other people’s +code can’t break your code and vice versa. Without the rule, two crates could +implement the same trait for the same type, and Rust wouldn’t know which +implementation to use. -The `where` syntax moves the trait bounds after the function parameters list. -This definition of `show_anything` means the exact same thing as the definition -in Listing 10-8, just said a different way: +### Default Implementations + +Sometimes it’s useful to have default behavior for some or all of the methods +in a trait instead of requiring implementations for all methods on every type. +Then, as we implement the trait on a particular type, we can keep or override +each method’s default behavior. + +Listing 10-14 shows how to specify a default string for the `summarize` method +of the `Summary` trait instead of only defining the method signature, as we did +in Listing 10-12. Filename: src/lib.rs -```rust -use std::fmt::Display; +```rust,noplayground +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-14/src/lib.rs:here}} +``` -fn show_anything(value: T) where T: Display { - println!("I have something to show you!"); - println!("It's: {}", value); +Listing 10-14: Definition of a `Summary` trait with a +default implementation of the `summarize` method + +To use a default implementation to summarize instances of `NewsArticle` instead +of defining a custom implementation, we specify an empty `impl` block with +`impl Summary for NewsArticle {}`. + +Even though we’re no longer defining the `summarize` method on `NewsArticle` +directly, we’ve provided a default implementation and specified that +`NewsArticle` implements the `Summary` trait. As a result, we can still call +the `summarize` method on an instance of `NewsArticle`, like this: + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-02-calling-default-impl/src/main.rs:here}} +``` + +This code prints `New article available! (Read more...)`. + +Creating a default implementation for `summarize` doesn’t require us to change +anything about the implementation of `Summary` on `Tweet` in Listing 10-13. The +reason is that the syntax for overriding a default implementation is the same +as the syntax for implementing a trait method that doesn’t have a default +implementation. + +Default implementations can call other methods in the same trait, even if those +other methods don’t have a default implementation. In this way, a trait can +provide a lot of useful functionality and only require implementors to specify +a small part of it. For example, we could define the `Summary` trait to have a +`summarize_author` method whose implementation is required, and then define a +`summarize` method that has a default implementation that calls the +`summarize_author` method: + +```rust,noplayground +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/lib.rs:here}} +``` + +To use this version of `Summary`, we only need to define `summarize_author` +when we implement the trait on a type: + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/lib.rs:impl}} +``` + +After we define `summarize_author`, we can call `summarize` on instances of the +`Tweet` struct, and the default implementation of `summarize` will call the +definition of `summarize_author` that we’ve provided. Because we’ve implemented +`summarize_author`, the `Summary` trait has given us the behavior of the +`summarize` method without requiring us to write any more code. + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-03-default-impl-calls-other-methods/src/main.rs:here}} +``` + +This code prints `1 new tweet: (Read more from @horse_ebooks...)`. + +Note that it isn’t possible to call the default implementation from an +overriding implementation of that same method. + +### Traits as Parameters + +Now that you know how to define and implement traits, we can explore how to use +traits to define functions that accept many different types. + +For example, in Listing 10-13, we implemented the `Summary` trait on the +`NewsArticle` and `Tweet` types. We can define a `notify` function that calls +the `summarize` method on its `item` parameter, which is of some type that +implements the `Summary` trait. To do this, we can use the `impl Trait` +syntax, like this: + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-04-traits-as-parameters/src/lib.rs:here}} +``` + +Instead of a concrete type for the `item` parameter, we specify the `impl` +keyword and the trait name. This parameter accepts any type that implements the +specified trait. In the body of `notify`, we can call any methods on `item` +that come from the `Summary` trait, such as `summarize`. We can call `notify` +and pass in any instance of `NewsArticle` or `Tweet`. Code that calls the +function with any other type, such as a `String` or an `i32`, won’t compile +because those types don’t implement `Summary`. + +#### Trait Bound Syntax + +The `impl Trait` syntax works for straightforward cases but is actually +syntax sugar for a longer form, which is called a *trait bound*; it looks like +this: + +```rust,ignore +pub fn notify(item: &T) { + println!("Breaking news! {}", item.summarize()); } ``` -Instead of `T: Display` going inside the angle brackets, they go after the -`where` keyword at the end of the function signature. This can make complex -signatures easier to read. The `where` clause and its parts can also go on new -lines. Here's the signature of a function that takes three generic type -parameters that each have multiple trait bounds: +This longer form is equivalent to the example in the previous section but is +more verbose. We place trait bounds with the declaration of the generic type +parameter after a colon and inside angle brackets. + +The `impl Trait` syntax is convenient and makes for more concise code in simple +cases. The trait bound syntax can express more complexity in other cases. For +example, we can have two parameters that implement `Summary`. Using the `impl +Trait` syntax looks like this: ```rust,ignore -fn some_function(t: T, u: U, v: V) +pub fn notify(item1: &impl Summary, item2: &impl Summary) { +``` + +If we wanted this function to allow `item1` and `item2` to have different +types, using `impl Trait` would be appropriate (as long as both types implement +`Summary`). If we wanted to force both parameters to have the same type, that’s +only possible to express using a trait bound, like this: + +```rust,ignore +pub fn notify(item1: &T, item2: &T) { +``` + +The generic type `T` specified as the type of the `item1` and `item2` +parameters constrains the function such that the concrete type of the value +passed as an argument for `item1` and `item2` must be the same. + +#### Specifying Multiple Trait Bounds with the `+` Syntax + +We can also specify more than one trait bound. Say we wanted `notify` to use +display formatting on `item` as well as the `summarize` method: we specify in +the `notify` definition that `item` must implement both `Display` and +`Summary`. We can do so using the `+` syntax: + +```rust,ignore +pub fn notify(item: &(impl Summary + Display)) { +``` + +The `+` syntax is also valid with trait bounds on generic types: + +```rust,ignore +pub fn notify(item: &T) { +``` + +With the two trait bounds specified, the body of `notify` can call `summarize` +and use `{}` to format `item`. + +#### Clearer Trait Bounds with `where` Clauses + +Using too many trait bounds has its downsides. Each generic has its own trait +bounds, so functions with multiple generic type parameters can contain lots of +trait bound information between the function’s name and its parameter list, +making the function signature hard to read. For this reason, Rust has alternate +syntax for specifying trait bounds inside a `where` clause after the function +signature. So instead of writing this: + +```rust,ignore +fn some_function(t: &T, u: &U) -> i32 { +``` + +we can use a `where` clause, like this: + +```rust,ignore +fn some_function(t: &T, u: &U) -> i32 where T: Display + Clone, - U: Printable + Debug, - V: Clone + Printable + U: Clone + Debug { ``` -Generic type parameters and trait bounds are part of Rust's rich type system. -Another important kind of generic in Rust interacts with Rust's ownership and -references features, and they're called *lifetimes*. +This function’s signature is less cluttered: the function name, parameter list, +and return type are close together, similar to a function without lots of trait +bounds. + +### Returning Types that Implement Traits + +We can also use the `impl Trait` syntax in the return position to return a +value of some type that implements a trait, as shown here: + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-05-returning-impl-trait/src/lib.rs:here}} +``` + +By using `impl Summary` for the return type, we specify that the +`returns_summarizable` function returns some type that implements the `Summary` +trait without naming the concrete type. In this case, `returns_summarizable` +returns a `Tweet`, but the code calling this function doesn’t know that. + +The ability to return a type that is only specified by the trait it implements +is especially useful in the context of closures and iterators, which we cover +in Chapter 13. Closures and iterators create types that only the compiler knows +or types that are very long to specify. The `impl Trait` syntax lets you +concisely specify that a function returns some type that implements the +`Iterator` trait without needing to write out a very long type. + +However, you can only use `impl Trait` if you’re returning a single type. For +example, this code that returns either a `NewsArticle` or a `Tweet` with the +return type specified as `impl Summary` wouldn’t work: + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-06-impl-trait-returns-one-type/src/lib.rs:here}} +``` + +Returning either a `NewsArticle` or a `Tweet` isn’t allowed due to restrictions +around how the `impl Trait` syntax is implemented in the compiler. We’ll cover +how to write a function with this behavior in the [“Using Trait Objects That +Allow for Values of Different +Types”][using-trait-objects-that-allow-for-values-of-different-types] section of Chapter 17. + +### Fixing the `largest` Function with Trait Bounds + +Now that you know how to specify the behavior you want to use using the generic +type parameter’s bounds, let’s return to Listing 10-5 to fix the definition of +the `largest` function that uses a generic type parameter! Last time we tried +to run that code, we received this error: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-05/output.txt}} +``` + +In the body of `largest` we wanted to compare two values of type `T` using the +greater than (`>`) operator. Because that operator is defined as a default +method on the standard library trait `std::cmp::PartialOrd`, we need to specify +`PartialOrd` in the trait bounds for `T` so the `largest` function can work on +slices of any type that we can compare. We don’t need to bring `PartialOrd` +into scope because it’s in the prelude. Change the signature of `largest` to +look like this: + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/src/main.rs:here}} +``` + +This time when we compile the code, we get a different set of errors: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-07-fixing-listing-10-05/output.txt}} +``` + +The key line in this error is `cannot move out of type [T], a non-copy slice`. +With our non-generic versions of the `largest` function, we were only trying to +find the largest `i32` or `char`. As discussed in the [“Stack-Only Data: +Copy”][stack-only-data-copy] section in Chapter 4, types like +`i32` and `char` that have a known size can be stored on the stack, so they +implement the `Copy` trait. But when we made the `largest` function generic, +it became possible for the `list` parameter to have types in it that don’t +implement the `Copy` trait. Consequently, we wouldn’t be able to move the +value out of `list[0]` and into the `largest` variable, resulting in this +error. + +To call this code with only those types that implement the `Copy` trait, we can +add `Copy` to the trait bounds of `T`! Listing 10-15 shows the complete code of +a generic `largest` function that will compile as long as the types of the +values in the slice that we pass into the function implement the `PartialOrd` +*and* `Copy` traits, like `i32` and `char` do. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-15/src/main.rs}} +``` + +Listing 10-15: A working definition of the `largest` +function that works on any generic type that implements the `PartialOrd` and +`Copy` traits + +If we don’t want to restrict the `largest` function to the types that implement +the `Copy` trait, we could specify that `T` has the trait bound `Clone` instead +of `Copy`. Then we could clone each value in the slice when we want the +`largest` function to have ownership. Using the `clone` function means we’re +potentially making more heap allocations in the case of types that own heap +data like `String`, and heap allocations can be slow if we’re working with +large amounts of data. + +Another way we could implement `largest` is for the function to return a +reference to a `T` value in the slice. If we change the return type to `&T` +instead of `T`, thereby changing the body of the function to return a +reference, we wouldn’t need the `Clone` or `Copy` trait bounds and we could +avoid heap allocations. Try implementing these alternate solutions on your own! + +### Using Trait Bounds to Conditionally Implement Methods + +By using a trait bound with an `impl` block that uses generic type parameters, +we can implement methods conditionally for types that implement the specified +traits. For example, the type `Pair` in Listing 10-16 always implements the +`new` function. But `Pair` only implements the `cmp_display` method if its +inner type `T` implements the `PartialOrd` trait that enables comparison *and* +the `Display` trait that enables printing. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-16/src/lib.rs}} +``` + +Listing 10-16: Conditionally implement methods on a +generic type depending on trait bounds + +We can also conditionally implement a trait for any type that implements +another trait. Implementations of a trait on any type that satisfies the trait +bounds are called *blanket implementations* and are extensively used in the +Rust standard library. For example, the standard library implements the +`ToString` trait on any type that implements the `Display` trait. The `impl` +block in the standard library looks similar to this code: + +```rust,ignore +impl ToString for T { + // --snip-- +} +``` + +Because the standard library has this blanket implementation, we can call the +`to_string` method defined by the `ToString` trait on any type that implements +the `Display` trait. For example, we can turn integers into their corresponding +`String` values like this because integers implement `Display`: + +```rust +let s = 3.to_string(); +``` + +Blanket implementations appear in the documentation for the trait in the +“Implementors” section. + +Traits and trait bounds let us write code that uses generic type parameters to +reduce duplication but also specify to the compiler that we want the generic +type to have particular behavior. The compiler can then use the trait bound +information to check that all the concrete types used with our code provide the +correct behavior. In dynamically typed languages, we would get an error at +runtime if we called a method on a type which didn’t define the method. But Rust +moves these errors to compile time so we’re forced to fix the problems before +our code is even able to run. Additionally, we don’t have to write code that +checks for behavior at runtime because we’ve already checked at compile time. +Doing so improves performance without having to give up the flexibility of +generics. + +Another kind of generic that we’ve already been using is called *lifetimes*. +Rather than ensuring that a type has the behavior we want, lifetimes ensure +that references are valid as long as we need them to be. Let’s look at how +lifetimes do that. + +[stack-only-data-copy]: +ch04-01-what-is-ownership.html#stack-only-data-copy +[using-trait-objects-that-allow-for-values-of-different-types]: +ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types diff --git a/src/ch10-03-lifetime-syntax.md b/src/ch10-03-lifetime-syntax.md index 03f06b0..6cec379 100644 --- a/src/ch10-03-lifetime-syntax.md +++ b/src/ch10-03-lifetime-syntax.md @@ -1,493 +1,618 @@ -## Lifetime Syntax +## Validating References with Lifetimes -Generic type parameters let us abstract over types, and traits let us abstract -over behavior. There's one more way that Rust allows us to do something -similar: *lifetimes* allow us to be generic over scopes of code. +One detail we didn’t discuss in the [“References and +Borrowing”][references-and-borrowing] section in Chapter 4 is +that every reference in Rust has a *lifetime*, which is the scope for which +that reference is valid. Most of the time, lifetimes are implicit and +inferred, just like most of the time, types are inferred. We must annotate +types when multiple types are possible. In a similar way, we must annotate +lifetimes when the lifetimes of references could be related in a few different +ways. Rust requires us to annotate the relationships using generic lifetime +parameters to ensure the actual references used at runtime will definitely be +valid. -Scopes of code? Yes, it's a bit unusual. Lifetimes are, in some ways, Rust's -most distinctive feature. They are a bit different than the tools you have used -in other programming languages. Lifetimes are a big topic, so we're not going -to cover everything about them in this chapter. What we *are* going to do is -talk about the very basics of lifetimes, so that when you see the syntax in -documentation or other places, you'll be familiar with the concepts. Chapter 20 -will contain more advanced information about everything lifetimes can do. +The concept of lifetimes is somewhat different from tools in other programming +languages, arguably making lifetimes Rust’s most distinctive feature. Although +we won’t cover lifetimes in their entirety in this chapter, we’ll discuss +common ways you might encounter lifetime syntax so you can become familiar with +the concepts. -### Core Syntax +### Preventing Dangling References with Lifetimes -We talked about references in Chapter 4, but we left out an important detail. -As it turns out, every reference in Rust has a *lifetime*, which is the scope -for which that reference is valid. Most of the time, lifetimes are implicit, -but just like we can choose to annotate types everywhere, we can choose to -annotate lifetimes. +The main aim of lifetimes is to prevent dangling references, which cause a +program to reference data other than the data it’s intended to reference. +Consider the program in Listing 10-17, which has an outer scope and an inner +scope. -Lifetimes have a slightly unusual syntax: - -```rust,ignore -&i32 // a reference -&'a i32 // a reference with an explicit lifetime +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/src/main.rs:here}} ``` -The `'a` there is a *lifetime* with the name `a`. A single apostrophe indicates -that this name is for a lifetime. Lifetime names need to be declared before -they're used. Here's a function signature with lifetime declarations and -annotations: +Listing 10-17: An attempt to use a reference whose value +has gone out of scope -```rust,ignore -fn some_function<'a>(parameter: &'a i32) { +> Note: The examples in Listings 10-17, 10-18, and 10-24 declare variables +> without giving them an initial value, so the variable name exists in the +> outer scope. At first glance, this might appear to be in conflict with Rust’s +> having no null values. However, if we try to use a variable before giving it +> a value, we’ll get a compile-time error, which shows that Rust indeed does +> not allow null values. + +The outer scope declares a variable named `r` with no initial value, and the +inner scope declares a variable named `x` with the initial value of 5. Inside +the inner scope, we attempt to set the value of `r` as a reference to `x`. Then +the inner scope ends, and we attempt to print the value in `r`. This code won’t +compile because the value `r` is referring to has gone out of scope before we +try to use it. Here is the error message: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-17/output.txt}} ``` -Notice anything? In the same way that generic type declarations go inside angle -brackets after the function name, lifetime declarations also go inside those -same angle brackets. We can even write functions that take both a lifetime -declaration and a generic type declaration: +The variable `x` doesn’t “live long enough.” The reason is that `x` will be out +of scope when the inner scope ends on line 7. But `r` is still valid for the +outer scope; because its scope is larger, we say that it “lives longer.” If +Rust allowed this code to work, `r` would be referencing memory that was +deallocated when `x` went out of scope, and anything we tried to do with `r` +wouldn’t work correctly. So how does Rust determine that this code is invalid? +It uses a borrow checker. -```rust,ignore -fn some_function<'a, T>(parameter: &'a T) { +### The Borrow Checker + +The Rust compiler has a *borrow checker* that compares scopes to determine +whether all borrows are valid. Listing 10-18 shows the same code as Listing +10-17 but with annotations showing the lifetimes of the variables. + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/src/main.rs:here}} ``` -This function takes one parameter, a reference to some type, `T`, and the -reference has the lifetime `'a`. In the same way that we parameterize functions -that take generic types, we parameterize references with lifetimes. +Listing 10-18: Annotations of the lifetimes of `r` and +`x`, named `'a` and `'b`, respectively -So, that's the syntax, but *why*? What does a lifetime do, anyway? +Here, we’ve annotated the lifetime of `r` with `'a` and the lifetime of `x` +with `'b`. As you can see, the inner `'b` block is much smaller than the outer +`'a` lifetime block. At compile time, Rust compares the size of the two +lifetimes and sees that `r` has a lifetime of `'a` but that it refers to memory +with a lifetime of `'b`. The program is rejected because `'b` is shorter than +`'a`: the subject of the reference doesn’t live as long as the reference. -### Lifetimes Prevent Dangling References - -Consider the program in listing 10-8. There's an outer scope and an inner -scope. The outer scope declares a variable named `r` with no initial value, and -the inner scope declares a variable named `x` with the initial value of 5. -Inside the inner scope, we attempt to set the value of `r` to a reference to -`x`. Then the inner scope ends and we attempt to print out the value in `r`: - -
-Filename: src/lib.rs - -```rust,ignore -{ - let r; - - { - let x = 5; - r = &x; - } - - println!("r: {}", r); -} -``` - -
- -Listing 10-8: An attempt to use a reference whose value has gone out of scope - -
-
- -If we compile this code, we get an error: - -```text - error: `x` does not live long enough - --> :6:10 - | -6 | r = &x; - | ^ does not live long enough -7 | } - | - borrowed value only lives until here -... -10 | } - | - borrowed value needs to live until here -``` - -The variable `x` doesn't "live long enough." Why not? Well, `x` is going to go -out of scope when we hit the closing curly brace on line 7, ending the inner -scope. But `r` is valid for the outer scope; its scope is larger and we say -that it "lives longer." If Rust allowed this code to work, `r` would be -referencing memory that was deallocated when `x` went out of scope. That'd be -bad! Once it's deallocated, it's meaningless. - -So how does Rust determine that this code should not be allowed? Part of the -compiler called the *borrow checker* compares scopes to determine that all -borrows are valid. Here's the same example from Listing 10-8 with some -annotations: - -```rust,ignore -{ - let r; // -------+-- 'a - // | - { // | - let x = 5; // -+-----+-- 'b - r = &x; // | | - } // -+ | - // | - println!("r: {}", r); // | - // | - // -------+ -} -``` - -Here, we've annotated the lifetime of `r` with `'a` and the lifetime of `x` -with `'b`. Rust looks at these lifetimes and sees that `r` has a lifetime of -`'a`, but that it refers to something with a lifetime of `'b`. It rejects the -program because the lifetime `'b` is shorter than the lifetime of `'a`—the -value that the reference is referring to does not live as long as the reference -does. - -Let's look at a different example that compiles because it does not try to make -a dangling reference, and see what the lifetimes look like: +Listing 10-19 fixes the code so it doesn’t have a dangling reference and +compiles without any errors. ```rust -{ - let x = 5; // -----+-- 'b - // | - let r = &x; // --+--+-- 'a - // | | - println!("r: {}", r); // | | - // --+ | - // -----+ -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/src/main.rs:here}} ``` -Here, `x` lives for `'b`, which in this case is larger than `'a`. This is -allowed: Rust knows that the reference in `r` will always be valid, as it has a -smaller scope than `x`, the value it refers to. +Listing 10-19: A valid reference because the data has a +longer lifetime than the reference -Note that we didn't have to name any lifetimes in the code itself; Rust figured -it out for us. One situation in which Rust can't figure out the lifetimes is -for a function or method when one of the parameters or return values is a -reference, except for a few scenarios we'll discuss in the lifetime elision -section. +Here, `x` has the lifetime `'b`, which in this case is larger than `'a`. This +means `r` can reference `x` because Rust knows that the reference in `r` will +always be valid while `x` is valid. -### Lifetime Annotations in Struct Definitions +Now that you know where the lifetimes of references are and how Rust analyzes +lifetimes to ensure references will always be valid, let’s explore generic +lifetimes of parameters and return values in the context of functions. -Another time that Rust can't figure out the lifetimes is when structs have a -field that holds a reference. In that case, naming the lifetimes looks like -this: +### Generic Lifetimes in Functions -```rust -struct Ref<'a> { - x: &'a i32, -} +Let’s write a function that returns the longer of two string slices. This +function will take two string slices and return a string slice. After we’ve +implemented the `longest` function, the code in Listing 10-20 should print `The +longest string is abcd`. + +Filename: src/main.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-20/src/main.rs}} ``` -Again, the lifetime names are declared in the angle brackets where generic type -parameters are declared, and this is because lifetimes are a form of generics. -In the examples above, `'a` and `'b` were concrete lifetimes: we knew about `r` -and `x` and how long they would live exactly. However, when we write a -function, we can't know beforehand exactly all of the values that it could be -called with and how long they will be valid for. We have to explain to Rust -what we expect the lifetime of the parameter to be (we'll learn about how to -know what you expect the lifetime to be in a bit). This is similar to writing a -function that has a parameter of a generic type: we don't know what type the -values will actually end up being when the function gets called. Lifetimes are -the same idea, but they are generic over the scope of a reference, rather than -a type. +Listing 10-20: A `main` function that calls the `longest` +function to find the longer of two string slices +Note that we want the function to take string slices, which are references, +because we don’t want the `longest` function to take ownership of its +parameters. Refer to the [“String Slices as +Parameters”][string-slices-as-parameters] section in Chapter 4 +for more discussion about why the parameters we use in Listing 10-20 are the +ones we want. + +If we try to implement the `longest` function as shown in Listing 10-21, it +won’t compile. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/src/main.rs:here}} +``` + +Listing 10-21: An implementation of the `longest` +function that returns the longer of two string slices but does not yet +compile + +Instead, we get the following error that talks about lifetimes: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-21/output.txt}} +``` + +The help text reveals that the return type needs a generic lifetime parameter +on it because Rust can’t tell whether the reference being returned refers to +`x` or `y`. Actually, we don’t know either, because the `if` block in the body +of this function returns a reference to `x` and the `else` block returns a +reference to `y`! + +When we’re defining this function, we don’t know the concrete values that will +be passed into this function, so we don’t know whether the `if` case or the +`else` case will execute. We also don’t know the concrete lifetimes of the +references that will be passed in, so we can’t look at the scopes as we did in +Listings 10-18 and 10-19 to determine whether the reference we return will +always be valid. The borrow checker can’t determine this either, because it +doesn’t know how the lifetimes of `x` and `y` relate to the lifetime of the +return value. To fix this error, we’ll add generic lifetime parameters that +define the relationship between the references so the borrow checker can +perform its analysis. + +### Lifetime Annotation Syntax + +Lifetime annotations don’t change how long any of the references live. Just +as functions can accept any type when the signature specifies a generic type +parameter, functions can accept references with any lifetime by specifying a +generic lifetime parameter. Lifetime annotations describe the relationships of +the lifetimes of multiple references to each other without affecting the +lifetimes. + +Lifetime annotations have a slightly unusual syntax: the names of lifetime +parameters must start with an apostrophe (`'`) and are usually all lowercase and +very short, like generic types. Most people use the name `'a`. We place +lifetime parameter annotations after the `&` of a reference, using a space to +separate the annotation from the reference’s type. + +Here are some examples: a reference to an `i32` without a lifetime parameter, a +reference to an `i32` that has a lifetime parameter named `'a`, and a mutable +reference to an `i32` that also has the lifetime `'a`. + +```rust,ignore +&i32 // a reference +&'a i32 // a reference with an explicit lifetime +&'a mut i32 // a mutable reference with an explicit lifetime +``` + +One lifetime annotation by itself doesn’t have much meaning, because the +annotations are meant to tell Rust how generic lifetime parameters of multiple +references relate to each other. For example, let’s say we have a function with +the parameter `first` that is a reference to an `i32` with lifetime `'a`. The +function also has another parameter named `second` that is another reference to +an `i32` that also has the lifetime `'a`. The lifetime annotations indicate +that the references `first` and `second` must both live as long as that generic +lifetime. ### Lifetime Annotations in Function Signatures -Lifetime annotations for functions go on the function signature, but we don't -have to annotate any of the code in the function body with lifetimes. That's -because Rust can analyze the specific code inside the function without any -help. When a function interacts with references that come from or go to code -outside that function, however, the lifetimes of those parameters or return -values will potentially be different each time that function gets called. Rust -would have to analyze every place the function is called to determine that -there were no dangling references. That would be impossible because a library -that you provide to someone else might be called in code that hasn't been -written yet, at the time that you're compiling your library. - -Lifetime parameters specify generic lifetimes that will apply to any specific -lifetimes the function gets called with. The annotation of lifetime parameters -tell Rust what it needs to know in order to be able to analyze a function -without knowing about all possible calling code. Lifetime annotations do not -change how long any of the references involved live. In the same way that -functions can accept any type when the signature specifies a generic type -parameter, functions can accept references with any lifetime when the signature -specifies a generic lifetime parameter. - -To understand lifetime annotations in context, let's write a function that will -return the longest of two string slices. The way we want to be able to call -this function is by passing two string slices, and we want to get back a string -slice. The code in Listing 10-9 should print `The longest string is abcd` once -we've implemented the `longest` function: - -
-Filename: src/main.rs - -```rust -# fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { -# if x.len() > y.len() { -# x -# } else { -# y -# } -# } -# -fn main() { - let a = String::from("abcd"); - let b = "xyz"; - - let c = longest(a.as_str(), b); - println!("The longest string is {}", c); -} -``` - -
- -Listing 10-9: A `main` function that demonstrates how we'd like to use the -`longest` function - -
-
- -Note that we want the function to take string slices because we don't want the -`longest` function to take ownership of its parameters, and we want the function -to be able to accept slices of a `String` (like `a` is) as well as string -literals (`b`). Refer back to the "String Slices as Parameters" section of -Chapter 4 for more discussion about why these are the parameters we want. - -Here's the start of an implementation of the `longest` function that won't -compile yet: - -Filename: src/main.rs - -```rust,ignore -fn longest(x: &str, y: &str) -> &str { - if x.len() > y.len() { - x - } else { - y - } -} -``` - -If we try to compile this, we get an error that talks about lifetimes: - -```text -error[E0106]: missing lifetime specifier - | -1 | fn longest(x: &str, y: &str) -> &str { - | ^ expected lifetime parameter - | - = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `x` or `y` -``` - -The help text is telling us that the return type needs a generic lifetime -parameter on it because this function is returning a reference and Rust can't -tell if the reference being returned refers to `x` or `y`. Actually, we don't -know either, since in the `if` block in the body of this function returns a -reference to `x` and the `else` block returns a reference to `y`! The way to -specify the lifetime parameters in this case is to have the same lifetime for -all of the input parameters and the return type: +Now let’s examine lifetime annotations in the context of the `longest` +function. As with generic type parameters, we need to declare generic lifetime +parameters inside angle brackets between the function name and the parameter +list. The constraint we want to express in this signature is that all the +references in the parameters and the return value must have the same lifetime. +We’ll name the lifetime `'a` and then add it to each reference, as shown in +Listing 10-22. Filename: src/main.rs ```rust -fn longest<'a>(x: &'a str, y: &'a str) -> &'a str { - if x.len() > y.len() { - x - } else { - y - } -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-22/src/main.rs:here}} ``` -This will compile and will produce the result we want with the `main` function -in Listing 10-9. This function signature is now saying that for some lifetime -named `'a`, it will have two parameters, both which are string slices that live -at least as long as the lifetime `'a`. The function will return a string slice -that also will last at least as long as the lifetime `'a`. This is the contract -we are telling Rust we want it to enforce. By specifying the lifetime -parameters in this function signature, we are not changing the lifetimes of any -values passed in or returned, but we are saying that any values that do not -adhere to this contract should be rejected by the borrow checker. This function -does not know (or need to know) exactly how long `x` and `y` will live since it -knows that there is some scope that can be substituted for `'a` that will -satisfy this signature. +Listing 10-22: The `longest` function definition +specifying that all the references in the signature must have the same lifetime +`'a` -The exact way to specify lifetime parameters depends on what your function is -doing. If the function didn't actually return the longest string slice but -instead always returned the first parameter, we wouldn't need to specify a -lifetime on `y`. This code compiles: +This code should compile and produce the result we want when we use it with the +`main` function in Listing 10-20. + +The function signature now tells Rust that for some lifetime `'a`, the function +takes two parameters, both of which are string slices that live at least as +long as lifetime `'a`. The function signature also tells Rust that the string +slice returned from the function will live at least as long as lifetime `'a`. +In practice, it means that the lifetime of the reference returned by the +`longest` function is the same as the smaller of the lifetimes of the +references passed in. These constraints are what we want Rust to enforce. +Remember, when we specify the lifetime parameters in this function signature, +we’re not changing the lifetimes of any values passed in or returned. Rather, +we’re specifying that the borrow checker should reject any values that don’t +adhere to these constraints. Note that the `longest` function doesn’t need to +know exactly how long `x` and `y` will live, only that some scope can be +substituted for `'a` that will satisfy this signature. + +When annotating lifetimes in functions, the annotations go in the function +signature, not in the function body. Rust can analyze the code within the +function without any help. However, when a function has references to or from +code outside that function, it becomes almost impossible for Rust to figure out +the lifetimes of the parameters or return values on its own. The lifetimes +might be different each time the function is called. This is why we need to +annotate the lifetimes manually. + +When we pass concrete references to `longest`, the concrete lifetime that is +substituted for `'a` is the part of the scope of `x` that overlaps with the +scope of `y`. In other words, the generic lifetime `'a` will get the concrete +lifetime that is equal to the smaller of the lifetimes of `x` and `y`. Because +we’ve annotated the returned reference with the same lifetime parameter `'a`, +the returned reference will also be valid for the length of the smaller of the +lifetimes of `x` and `y`. + +Let’s look at how the lifetime annotations restrict the `longest` function by +passing in references that have different concrete lifetimes. Listing 10-23 is +a straightforward example. Filename: src/main.rs ```rust -fn longest<'a>(x: &'a str, y: &str) -> &'a str { - x -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-23/src/main.rs:here}} ``` -The lifetime parameter for the return type needs to be specified and needs to -match one of the value parameters' lifetime parameters. If the reference -returned does *not* refer to one of the parameters, the only other possibility -is that it refers to a value created within this function, and that would be a -dangling reference since the value will go out of scope at the end of the -function. Consider this attempted implementation of `longest`: +Listing 10-23: Using the `longest` function with +references to `String` values that have different concrete lifetimes + +In this example, `string1` is valid until the end of the outer scope, `string2` +is valid until the end of the inner scope, and `result` references something +that is valid until the end of the inner scope. Run this code, and you’ll see +that the borrow checker approves of this code; it will compile and print `The +longest string is long string is long`. + +Next, let’s try an example that shows that the lifetime of the reference in +`result` must be the smaller lifetime of the two arguments. We’ll move the +declaration of the `result` variable outside the inner scope but leave the +assignment of the value to the `result` variable inside the scope with +`string2`. Then we’ll move the `println!` that uses `result` outside the inner +scope, after the inner scope has ended. The code in Listing 10-24 will not +compile. Filename: src/main.rs -```rust,ignore -fn longest<'a>(x: &str, y: &str) -> &'a str { - let result = String::from("really long string"); - result.as_str() -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/src/main.rs:here}} ``` -Even though we've specified a lifetime for the return type, this function fails -to compile with the following error message: +Listing 10-24: Attempting to use `result` after `string2` +has gone out of scope -```text -error: `result` does not live long enough - | -3 | result.as_str() - | ^^^^^^ does not live long enough -4 | } - | - borrowed value only lives until here - | -note: borrowed value must be valid for the lifetime 'a as defined on the block at 1:44... - | -1 | fn longest<'a>(x: &str, y: &str) -> &'a str { - | ^ +When we try to compile this code, we’ll get this error: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-24/output.txt}} ``` -The problem is that `result` will go out of scope and get cleaned up at the end -of the `longest` function, and we're trying to return a reference to `result` -from the function. There's no way we can specify lifetime parameters that would -change the dangling reference, and Rust won't let us create a dangling +The error shows that for `result` to be valid for the `println!` statement, +`string2` would need to be valid until the end of the outer scope. Rust knows +this because we annotated the lifetimes of the function parameters and return +values using the same lifetime parameter `'a`. + +As humans, we can look at this code and see that `string1` is longer than +`string2` and therefore `result` will contain a reference to `string1`. +Because `string1` has not gone out of scope yet, a reference to `string1` will +still be valid for the `println!` statement. However, the compiler can’t see +that the reference is valid in this case. We’ve told Rust that the lifetime of +the reference returned by the `longest` function is the same as the smaller of +the lifetimes of the references passed in. Therefore, the borrow checker +disallows the code in Listing 10-24 as possibly having an invalid reference. + +Try designing more experiments that vary the values and lifetimes of the +references passed in to the `longest` function and how the returned reference +is used. Make hypotheses about whether or not your experiments will pass the +borrow checker before you compile; then check to see if you’re right! + +### Thinking in Terms of Lifetimes + +The way in which you need to specify lifetime parameters depends on what your +function is doing. For example, if we changed the implementation of the +`longest` function to always return the first parameter rather than the longest +string slice, we wouldn’t need to specify a lifetime on the `y` parameter. The +following code will compile: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-08-only-one-reference-with-lifetime/src/main.rs:here}} +``` + +In this example, we’ve specified a lifetime parameter `'a` for the parameter +`x` and the return type, but not for the parameter `y`, because the lifetime of +`y` does not have any relationship with the lifetime of `x` or the return value. + +When returning a reference from a function, the lifetime parameter for the +return type needs to match the lifetime parameter for one of the parameters. If +the reference returned does *not* refer to one of the parameters, it must refer +to a value created within this function, which would be a dangling reference +because the value will go out of scope at the end of the function. Consider +this attempted implementation of the `longest` function that won’t compile: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/src/main.rs:here}} +``` + +Here, even though we’ve specified a lifetime parameter `'a` for the return +type, this implementation will fail to compile because the return value +lifetime is not related to the lifetime of the parameters at all. Here is the +error message we get: + +```console +{{#include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-09-unrelated-lifetime/output.txt}} +``` + +The problem is that `result` goes out of scope and gets cleaned up at the end +of the `longest` function. We’re also trying to return a reference to `result` +from the function. There is no way we can specify lifetime parameters that +would change the dangling reference, and Rust won’t let us create a dangling reference. In this case, the best fix would be to return an owned data type -rather than a reference so that the calling function is then responsible for +rather than a reference so the calling function is then responsible for cleaning up the value. Ultimately, lifetime syntax is about connecting the lifetimes of various -parameters and return values of functions. Once they're connected, Rust has +parameters and return values of functions. Once they’re connected, Rust has enough information to allow memory-safe operations and disallow operations that would create dangling pointers or otherwise violate memory safety. +### Lifetime Annotations in Struct Definitions + +So far, we’ve only defined structs to hold owned types. It’s possible for +structs to hold references, but in that case we would need to add a lifetime +annotation on every reference in the struct’s definition. Listing 10-25 has a +struct named `ImportantExcerpt` that holds a string slice. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-25/src/main.rs}} +``` + +Listing 10-25: A struct that holds a reference, so its +definition needs a lifetime annotation + +This struct has one field, `part`, that holds a string slice, which is a +reference. As with generic data types, we declare the name of the generic +lifetime parameter inside angle brackets after the name of the struct so we can +use the lifetime parameter in the body of the struct definition. This +annotation means an instance of `ImportantExcerpt` can’t outlive the reference +it holds in its `part` field. + +The `main` function here creates an instance of the `ImportantExcerpt` struct +that holds a reference to the first sentence of the `String` owned by the +variable `novel`. The data in `novel` exists before the `ImportantExcerpt` +instance is created. In addition, `novel` doesn’t go out of scope until after +the `ImportantExcerpt` goes out of scope, so the reference in the +`ImportantExcerpt` instance is valid. + ### Lifetime Elision -If every reference has a lifetime, and we need to provide them for functions -that use references as parameters or return values, then why did this function -from the "String Slices" section of Chapter 4 compile? We haven't annotated any -lifetimes here, yet Rust happily compiles this function: +You’ve learned that every reference has a lifetime and that you need to specify +lifetime parameters for functions or structs that use references. However, in +Chapter 4 we had a function in Listing 4-9, which is shown again in Listing +10-26, that compiled without lifetime annotations. Filename: src/lib.rs ```rust -fn first_word(s: &str) -> &str { - let bytes = s.as_bytes(); - - for (i, &item) in bytes.iter().enumerate() { - if item == b' ' { - return &s[0..i]; - } - } - - &s[..] -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/listing-10-26/src/main.rs:here}} ``` -The answer is historical: in early versions of pre-1.0 Rust, this would not -have compiled. Every reference needed an explicit lifetime. At that time, the -function signature would have been written like this: +Listing 10-26: A function we defined in Listing 4-9 that +compiled without lifetime annotations, even though the parameter and return +type are references + +The reason this function compiles without lifetime annotations is historical: +in early versions (pre-1.0) of Rust, this code wouldn’t have compiled because +every reference needed an explicit lifetime. At that time, the function +signature would have been written like this: ```rust,ignore fn first_word<'a>(s: &'a str) -> &'a str { ``` -After writing a lot of Rust code, some patterns developed. The Rust team -noticed that the vast majority of code followed the pattern, and being forced -to use explicit lifetime syntax on every reference wasn't a very great -developer experience. +After writing a lot of Rust code, the Rust team found that Rust programmers +were entering the same lifetime annotations over and over in particular +situations. These situations were predictable and followed a few deterministic +patterns. The developers programmed these patterns into the compiler’s code so +the borrow checker could infer the lifetimes in these situations and wouldn’t +need explicit annotations. -To make it so that lifetime annotations weren't needed as often, they added -*lifetime elision rules* to Rust's analysis of references. This feature isn't -full inference: Rust doesn't try to guess what you meant in places where there -could be ambiguity. The rules are a very basic set of particular cases, and if -your code fits one of those cases, you don't need to write the lifetimes -explicitly. Here are the rules: +This piece of Rust history is relevant because it’s possible that more +deterministic patterns will emerge and be added to the compiler. In the future, +even fewer lifetime annotations might be required. -Lifetimes on function parameters are called *input lifetimes*, and lifetimes on -return values are called *output lifetimes*. There's one rule related to how -Rust infers input lifetimes in the absence of explicit annotations: +The patterns programmed into Rust’s analysis of references are called the +*lifetime elision rules*. These aren’t rules for programmers to follow; they’re +a set of particular cases that the compiler will consider, and if your code +fits these cases, you don’t need to write the lifetimes explicitly. -1. Each function parameter that is a reference and therefore needs a lifetime - parameter gets its own. In other words, a function with one parameter gets one - lifetime parameter: `fn foo<'a>(x: &'a i32)`, a function with two parameters - gets two separate lifetime parameters: `fn foo<'a, 'b>(x: &'a i32, y: &'b - i32)`, and so on. +The elision rules don’t provide full inference. If Rust deterministically +applies the rules but there is still ambiguity as to what lifetimes the +references have, the compiler won’t guess what the lifetime of the remaining +references should be. In this case, instead of guessing, the compiler will give +you an error that you can resolve by adding the lifetime annotations that +specify how the references relate to each other. -And two rules related to output lifetimes: +Lifetimes on function or method parameters are called *input lifetimes*, and +lifetimes on return values are called *output lifetimes*. -2. If there is exactly one input lifetime parameter, that lifetime is assigned - to all output lifetime parameters: `fn foo<'a>(x: &'a i32) -> &'a i32`. -3. If there are multiple input lifetime parameters, but one of them is `&self` - or `&mut self`, then the lifetime of `self` is the lifetime assigned to all - output lifetime parameters. This makes writing methods much nicer. +The compiler uses three rules to figure out what lifetimes references have when +there aren’t explicit annotations. The first rule applies to input lifetimes, +and the second and third rules apply to output lifetimes. If the compiler gets +to the end of the three rules and there are still references for which it can’t +figure out lifetimes, the compiler will stop with an error. These rules apply +to `fn` definitions as well as `impl` blocks. -If none of these three rules apply, then you must explicitly annotate input and -output lifetimes. These rules do apply in the `first_word` function, which is -why we didn't have to specify any lifetimes. +The first rule is that each parameter that is a reference gets its own lifetime +parameter. In other words, a function with one parameter gets one lifetime +parameter: `fn foo<'a>(x: &'a i32)`; a function with two parameters gets two +separate lifetime parameters: `fn foo<'a, 'b>(x: &'a i32, y: &'b i32)`; and so +on. -These rules cover the vast majority of cases, allowing you to write a lot of -code without needing to specify explicit lifetimes. However, Rust is always -checking these rules and the lifetimes in your program, and cases in which the -lifetime elision rules do not apply are cases where you'll need to add lifetime -parameters to help Rust understand the contracts of your code. +The second rule is if there is exactly one input lifetime parameter, that +lifetime is assigned to all output lifetime parameters: `fn foo<'a>(x: &'a i32) +-> &'a i32`. + +The third rule is if there are multiple input lifetime parameters, but one of +them is `&self` or `&mut self` because this is a method, the lifetime of `self` +is assigned to all output lifetime parameters. This third rule makes methods +much nicer to read and write because fewer symbols are necessary. + +Let’s pretend we’re the compiler. We’ll apply these rules to figure out what +the lifetimes of the references in the signature of the `first_word` function +in Listing 10-26 are. The signature starts without any lifetimes associated +with the references: + +```rust,ignore +fn first_word(s: &str) -> &str { +``` + +Then the compiler applies the first rule, which specifies that each parameter +gets its own lifetime. We’ll call it `'a` as usual, so now the signature is +this: + +```rust,ignore +fn first_word<'a>(s: &'a str) -> &str { +``` + +The second rule applies because there is exactly one input lifetime. The second +rule specifies that the lifetime of the one input parameter gets assigned to +the output lifetime, so the signature is now this: + +```rust,ignore +fn first_word<'a>(s: &'a str) -> &'a str { +``` + +Now all the references in this function signature have lifetimes, and the +compiler can continue its analysis without needing the programmer to annotate +the lifetimes in this function signature. + +Let’s look at another example, this time using the `longest` function that had +no lifetime parameters when we started working with it in Listing 10-21: + +```rust,ignore +fn longest(x: &str, y: &str) -> &str { +``` + +Let’s apply the first rule: each parameter gets its own lifetime. This time we +have two parameters instead of one, so we have two lifetimes: + +```rust,ignore +fn longest<'a, 'b>(x: &'a str, y: &'b str) -> &str { +``` + +You can see that the second rule doesn’t apply because there is more than one +input lifetime. The third rule doesn’t apply either, because `longest` is a +function rather than a method, so none of the parameters are `self`. After +working through all three rules, we still haven’t figured out what the return +type’s lifetime is. This is why we got an error trying to compile the code in +Listing 10-21: the compiler worked through the lifetime elision rules but still +couldn’t figure out all the lifetimes of the references in the signature. + +Because the third rule really only applies in method signatures, we’ll look at +lifetimes in that context next to see why the third rule means we don’t have to +annotate lifetimes in method signatures very often. ### Lifetime Annotations in Method Definitions -Now that we've gone over the lifetime elision rules, defining methods on -structs that hold references will make more sense. The lifetime name needs to -be declared after the `impl` keyword and then used after the struct's name, -since the lifetime is part of the struct's type. The lifetimes can be elided in -any methods where the output type's lifetime is the same as that of the -struct's because of the third elision rule. Here's a struct called `App` that -holds a reference to another struct, `Config`, defined elsewhere. The -`append_to_name` method does not need lifetime annotations even though the -method has a reference as a parameter and is returning a reference; the -lifetime of the return value will be the lifetime of `self`: +When we implement methods on a struct with lifetimes, we use the same syntax as +that of generic type parameters shown in Listing 10-11. Where we declare and +use the lifetime parameters depends on whether they’re related to the struct +fields or the method parameters and return values. -Filename: src/lib.rs +Lifetime names for struct fields always need to be declared after the `impl` +keyword and then used after the struct’s name, because those lifetimes are part +of the struct’s type. + +In method signatures inside the `impl` block, references might be tied to the +lifetime of references in the struct’s fields, or they might be independent. In +addition, the lifetime elision rules often make it so that lifetime annotations +aren’t necessary in method signatures. Let’s look at some examples using the +struct named `ImportantExcerpt` that we defined in Listing 10-25. + +First, we’ll use a method named `level` whose only parameter is a reference to +`self` and whose return value is an `i32`, which is not a reference to anything: ```rust -# struct Config {} -# -struct App<'a> { - name: String, - config: &'a Config, -} - -impl<'a> App<'a> { - fn append_to_name(&mut self, suffix: &str) -> &str { - self.name.push_str(suffix); - self.name.as_str() - } -} +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/src/main.rs:1st}} ``` +The lifetime parameter declaration after `impl` and its use after the type name +are required, but we’re not required to annotate the lifetime of the reference +to `self` because of the first elision rule. + +Here is an example where the third lifetime elision rule applies: + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-10-lifetimes-on-methods/src/main.rs:3rd}} +``` + +There are two input lifetimes, so Rust applies the first lifetime elision rule +and gives both `&self` and `announcement` their own lifetimes. Then, because +one of the parameters is `&self`, the return type gets the lifetime of `&self`, +and all lifetimes have been accounted for. + ### The Static Lifetime -There is *one* special lifetime that Rust knows about: `'static`. The `'static` -lifetime is the entire duration of the program. All string literals have the -`'static` lifetime: +One special lifetime we need to discuss is `'static`, which means that this +reference *can* live for the entire duration of the program. All string +literals have the `'static` lifetime, which we can annotate as follows: ```rust let s: &'static str = "I have a static lifetime."; ``` -The text of this string is stored directly in the binary of your program and -the binary of your program is always available. Therefore, the lifetime of all -string literals is `'static`. You may see suggestions to use the `'static` -lifetime in error message help text, but before adding it, think about whether -the reference you have is one that actually lives the entire lifetime of your -program or not (or even if you want it to live that long, if it could). Most of -the time, the problem in the code is an attempt to create a dangling reference -or a mismatch of the available lifetimes, and the solution is fixing those -problems, not specifying the `'static` lifetime. +The text of this string is stored directly in the program’s binary, which +is always available. Therefore, the lifetime of all string literals is +`'static`. + +You might see suggestions to use the `'static` lifetime in error messages. But +before specifying `'static` as the lifetime for a reference, think about +whether the reference you have actually lives the entire lifetime of your +program or not. You might consider whether you want it to live that long, even +if it could. Most of the time, the problem results from attempting to create a +dangling reference or a mismatch of the available lifetimes. In such cases, the +solution is fixing those problems, not specifying the `'static` lifetime. + +## Generic Type Parameters, Trait Bounds, and Lifetimes Together + +Let’s briefly look at the syntax of specifying generic type parameters, trait +bounds, and lifetimes all in one function! + +```rust +{{#rustdoc_include ../listings/ch10-generic-types-traits-and-lifetimes/no-listing-11-generics-traits-and-lifetimes/src/main.rs:here}} +``` + +This is the `longest` function from Listing 10-22 that returns the longer of +two string slices. But now it has an extra parameter named `ann` of the generic +type `T`, which can be filled in by any type that implements the `Display` +trait as specified by the `where` clause. This extra parameter will be printed +before the function compares the lengths of the string slices, which is why the +`Display` trait bound is necessary. Because lifetimes are a type of generic, +the declarations of the lifetime parameter `'a` and the generic type parameter +`T` go in the same list inside the angle brackets after the function name. ## Summary -We've covered the basics of Rust's system of generics. Generics are the core to -building good abstractions, and can be used in a number of ways. There's more -to learn about them, particularly lifetimes, but we'll cover those in later -chapters. Let's move on to testing. +We covered a lot in this chapter! Now that you know about generic type +parameters, traits and trait bounds, and generic lifetime parameters, you’re +ready to write code without repetition that works in many different situations. +Generic type parameters let you apply the code to different types. Traits and +trait bounds ensure that even though the types are generic, they’ll have the +behavior the code needs. You learned how to use lifetime annotations to ensure +that this flexible code won’t have any dangling references. And all of this +analysis happens at compile time, which doesn’t affect runtime performance! + +Believe it or not, there is much more to learn on the topics we discussed in +this chapter: Chapter 17 discusses trait objects, which are another way to use +traits. There are also more complex scenarios involving lifetime annotations +that you will only need in very advanced scenarios; for those, you should read +the [Rust Reference][reference]. But next, you’ll learn how to write tests in +Rust so you can make sure your code is working the way it should. + +[references-and-borrowing]: +ch04-02-references-and-borrowing.html#references-and-borrowing +[string-slices-as-parameters]: +ch04-03-slices.html#string-slices-as-parameters +[reference]: ../reference/index.html diff --git a/src/ch11-00-testing.md b/src/ch11-00-testing.md index b5b528a..6f79959 100644 --- a/src/ch11-00-testing.md +++ b/src/ch11-00-testing.md @@ -1,30 +1,34 @@ -# Testing +# Writing Automated Tests -> Program testing can be a very effective way to show the presence of bugs, but -> it is hopelessly inadequate for showing their absence. -> -> Edsger W. Dijkstra, "The Humble Programmer" (1972) +In his 1972 essay “The Humble Programmer,” Edsger W. Dijkstra said that +“Program testing can be a very effective way to show the presence of bugs, but +it is hopelessly inadequate for showing their absence.” That doesn’t mean we +shouldn’t try to test as much as we can! -Rust is a programming language that cares a lot about correctness, but -correctness is a complex topic and isn't easy to prove. Rust places a lot of -weight on its type system to help ensure that our programs do what we intend, -but it cannot help with everything. As such, Rust also includes support for -writing software tests in the language itself. +Correctness in our programs is the extent to which our code does what we intend +it to do. Rust is designed with a high degree of concern about the correctness +of programs, but correctness is complex and not easy to prove. Rust’s type +system shoulders a huge part of this burden, but the type system cannot catch +every kind of incorrectness. As such, Rust includes support for writing +automated software tests within the language. -For example, we can write a function called `add_two` with a signature that has -an integer as a parameter and returns an integer as a result. We can implement -and compile that function, and Rust can do all the type checking and borrow -checking that we've seen it's capable of doing. What Rust *can't* check for us -is that we've implemented this function to return the parameter plus two and -not the parameter plus 10 or the parameter minus 50! That's where tests come -in. We can write tests that, for example, pass `3` to the `add_two` function -and check that we get `5` back. We can run the tests whenever we make changes -to our code to make sure we didn't change any existing behavior from what the -tests specify it should be. +As an example, say we write a function called `add_two` that adds 2 to whatever +number is passed to it. This function’s signature accepts an integer as a +parameter and returns an integer as a result. When we implement and compile +that function, Rust does all the type checking and borrow checking that you’ve +learned so far to ensure that, for instance, we aren’t passing a `String` value +or an invalid reference to this function. But Rust *can’t* check that this +function will do precisely what we intend, which is return the parameter plus 2 +rather than, say, the parameter plus 10 or the parameter minus 50! That’s where +tests come in. -Testing is a skill, and we cannot hope to cover everything about how to write -good tests in one chapter of a book. What we can discuss, however, are the -mechanics of Rust's testing facilities. We'll talk about the annotations and -macros available to you when writing your tests, the default behavior and -options provided for running your tests, and how to organize tests into unit -tests and integration tests. +We can write tests that assert, for example, that when we pass `3` to the +`add_two` function, the returned value is `5`. We can run these tests whenever +we make changes to our code to make sure any existing correct behavior has not +changed. + +Testing is a complex skill: although we can’t cover every detail about how to +write good tests in one chapter, we’ll discuss the mechanics of Rust’s testing +facilities. We’ll talk about the annotations and macros available to you when +writing your tests, the default behavior and options provided for running your +tests, and how to organize tests into unit tests and integration tests. diff --git a/src/ch11-01-writing-tests.md b/src/ch11-01-writing-tests.md index 346dd01..47b37f7 100644 --- a/src/ch11-01-writing-tests.md +++ b/src/ch11-01-writing-tests.md @@ -1,289 +1,536 @@ -## Writing Tests +## How to Write Tests -Tests are Rust functions that use particular features and are written in such a -way as to verify that non-test code is functioning in the expected manner. -Everything we've discussed about Rust code applies to Rust tests as well! Let's -look at the features Rust provides specifically for writing tests: the `test` -attribute, a few macros, and the `should_panic` attribute. +Tests are Rust functions that verify that the non-test code is functioning in +the expected manner. The bodies of test functions typically perform these three +actions: -### The `test` attribute +1. Set up any needed data or state. +2. Run the code you want to test. +3. Assert the results are what you expect. -At its simplest, a test in Rust is a function that's annotated with the `test` -attribute. Let's make a new library project with Cargo called `adder`: +Let’s look at the features Rust provides specifically for writing tests that +take these actions, which include the `test` attribute, a few macros, and the +`should_panic` attribute. -```text -$ cargo new adder +### The Anatomy of a Test Function + +At its simplest, a test in Rust is a function that’s annotated with the `test` +attribute. Attributes are metadata about pieces of Rust code; one example is +the `derive` attribute we used with structs in Chapter 5. To change a function +into a test function, add `#[test]` on the line before `fn`. When you run your +tests with the `cargo test` command, Rust builds a test runner binary that runs +the functions annotated with the `test` attribute and reports on whether each +test function passes or fails. + +When we make a new library project with Cargo, a test module with a test +function in it is automatically generated for us. This module helps you start +writing your tests so you don’t have to look up the exact structure and syntax +of test functions every time you start a new project. You can add as many +additional test functions and as many test modules as you want! + +We’ll explore some aspects of how tests work by experimenting with the template +test generated for us without actually testing any code. Then we’ll write some +real-world tests that call some code that we’ve written and assert that its +behavior is correct. + +Let’s create a new library project called `adder`: + +```console +$ cargo new adder --lib Created library `adder` project $ cd adder ``` -Cargo will automatically generate a simple test when you make a new library -project. Here's the contents of `src/lib.rs`: +The contents of the *src/lib.rs* file in your `adder` library should look like +Listing 11-1. Filename: src/lib.rs -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-01/src/lib.rs}} ``` -For now, let's ignore the `tests` module and the `#[cfg(test)]` annotation in -order to focus on just the function. Note the `#[test]` before it: this -attribute indicates this is a test function. The function currently has no -body; that's good enough to pass! We can run the tests with `cargo test`: +Listing 11-1: The test module and function generated +automatically by `cargo new` -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.22 secs - Running target/debug/deps/adder-abcabcabc +For now, let’s ignore the top two lines and focus on the function to see how it +works. Note the `#[test]` annotation before the `fn` line: this attribute +indicates this is a test function, so the test runner knows to treat this +function as a test. We could also have non-test functions in the `tests` module +to help set up common scenarios or perform common operations, so we need to +indicate which functions are tests by using the `#[test]` attribute. -running 1 test -test it_works ... ok +The function body uses the `assert_eq!` macro to assert that 2 + 2 equals 4. +This assertion serves as an example of the format for a typical test. Let’s run +it to see that this test passes. -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured +The `cargo test` command runs all tests in our project, as shown in Listing +11-2. - Doc-tests adder - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-01/output.txt}} ``` -Cargo compiled and ran our tests. There are two sets of output here; we're -going to focus on the first set in this chapter. The second set of output is -for documentation tests, which we'll talk about in Chapter 14. For now, note -this line: +Listing 11-2: The output from running the automatically +generated test -```text -test it_works ... ok -``` +Cargo compiled and ran the test. After the `Compiling`, `Finished`, and +`Running` lines is the line `running 1 test`. The next line shows the name +of the generated test function, called `it_works`, and the result of running +that test, `ok`. The overall summary of running the tests appears next. The +text `test result: ok.` means that all the tests passed, and the portion that +reads `1 passed; 0 failed` totals the number of tests that passed or failed. -The `it_works` text comes from the name of our function. +Because we don’t have any tests we’ve marked as ignored, the summary shows `0 +ignored`. We also haven’t filtered the tests being run, so the end of the +summary shows `0 filtered out`. We’ll talk about ignoring and filtering out +tests in the next section, [“Controlling How Tests Are +Run.”][controlling-how-tests-are-run] -We also get a summary line that tells us the aggregate results of all the -tests that we have: +The `0 measured` statistic is for benchmark tests that measure performance. +Benchmark tests are, as of this writing, only available in nightly Rust. See +[the documentation about benchmark tests][bench] to learn more. -```text -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` +[bench]: ../unstable-book/library-features/test.html -### The `assert!` macro +The next part of the test output, which starts with `Doc-tests adder`, is for +the results of any documentation tests. We don’t have any documentation tests +yet, but Rust can compile any code examples that appear in our API +documentation. This feature helps us keep our docs and our code in sync! We’ll +discuss how to write documentation tests in the [“Documentation Comments as +Tests”][doc-comments] section of Chapter 14. For now, we’ll +ignore the `Doc-tests` output. -The empty test function passes because any test which doesn't `panic!` passes, -and any test that does `panic!` fails. Let's make the test fail by using the -`assert!` macro: +Let’s change the name of our test to see how that changes the test output. +Change the `it_works` function to a different name, such as `exploration`, like +so: Filename: src/lib.rs -```rust -#[test] -fn it_works() { - assert!(false); -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/src/lib.rs}} ``` -The `assert!` macro is provided by the standard library, and it takes one -argument. If the argument is `true`, nothing happens. If the argument is -`false`, the macro will `panic!`. Let's run our tests again: +Then run `cargo test` again. The output now shows `exploration` instead of +`it_works`: -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.22 secs - Running target/debug/deps/adder-abcabcabc - -running 1 test -test it_works ... FAILED - -failures: - ----- it_works stdout ---- - thread 'it_works' panicked at 'assertion failed: false', src/lib.rs:5 -note: Run with `RUST_BACKTRACE=1` for a backtrace. - - -failures: - it_works - -test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured - -error: test failed +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-01-changing-test-name/output.txt}} ``` -Rust indicates that our test failed: +Let’s add another test, but this time we’ll make a test that fails! Tests fail +when something in the test function panics. Each test is run in a new thread, +and when the main thread sees that a test thread has died, the test is marked +as failed. We talked about the simplest way to cause a panic in Chapter 9, +which is to call the `panic!` macro. Enter the new test, `another`, so your +*src/lib.rs* file looks like Listing 11-3. -```text -test it_works ... FAILED +Filename: src/lib.rs + +```rust,panics,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-03/src/lib.rs:here}} ``` -And shows that the test failed because the `assert!` macro in `src/lib.rs` on -line 5 got a `false` value: +Listing 11-3: Adding a second test that will fail because +we call the `panic!` macro -```text -thread 'it_works' panicked at 'assertion failed: false', src/lib.rs:5 +Run the tests again using `cargo test`. The output should look like Listing +11-4, which shows that our `exploration` test passed and `another` failed. + +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-03/output.txt}} ``` -The test failure is also reflected in the summary line: +Listing 11-4: Test results when one test passes and one +test fails -```text -test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured +Instead of `ok`, the line `test tests::another` shows `FAILED`. Two new +sections appear between the individual results and the summary: the first +section displays the detailed reason for each test failure. In this case, +`another` failed because it `panicked at 'Make this test fail'`, which happened +on line 10 in the *src/lib.rs* file. The next section lists just the names of +all the failing tests, which is useful when there are lots of tests and lots of +detailed failing test output. We can use the name of a failing test to run just +that test to more easily debug it; we’ll talk more about ways to run tests in +the [“Controlling How Tests Are Run”][controlling-how-tests-are-run] section. + +The summary line displays at the end: overall, our test result is `FAILED`. +We had one test pass and one test fail. + +Now that you’ve seen what the test results look like in different scenarios, +let’s look at some macros other than `panic!` that are useful in tests. + +### Checking Results with the `assert!` Macro + +The `assert!` macro, provided by the standard library, is useful when you want +to ensure that some condition in a test evaluates to `true`. We give the +`assert!` macro an argument that evaluates to a Boolean. If the value is +`true`, `assert!` does nothing and the test passes. If the value is `false`, +the `assert!` macro calls the `panic!` macro, which causes the test to fail. +Using the `assert!` macro helps us check that our code is functioning in the +way we intend. + +In Chapter 5, Listing 5-15, we used a `Rectangle` struct and a `can_hold` +method, which are repeated here in Listing 11-5. Let’s put this code in the +*src/lib.rs* file and write some tests for it using the `assert!` macro. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-05/src/lib.rs:here}} ``` -### Testing equality with the `assert_eq!` and `assert_ne!` macros +Listing 11-5: Using the `Rectangle` struct and its +`can_hold` method from Chapter 5 + +The `can_hold` method returns a Boolean, which means it’s a perfect use case +for the `assert!` macro. In Listing 11-6, we write a test that exercises the +`can_hold` method by creating a `Rectangle` instance that has a width of 8 and +a height of 7 and asserting that it can hold another `Rectangle` instance that +has a width of 5 and a height of 1. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-06/src/lib.rs:here}} +``` + +Listing 11-6: A test for `can_hold` that checks whether a +larger rectangle can indeed hold a smaller rectangle + +Note that we’ve added a new line inside the `tests` module: `use super::*;`. +The `tests` module is a regular module that follows the usual visibility rules +we covered in Chapter 7 in the [“Paths for Referring to an Item in the Module +Tree”][paths-for-referring-to-an-item-in-the-module-tree] +section. Because the `tests` module is an inner module, we need to bring the +code under test in the outer module into the scope of the inner module. We use +a glob here so anything we define in the outer module is available to this +`tests` module. + +We’ve named our test `larger_can_hold_smaller`, and we’ve created the two +`Rectangle` instances that we need. Then we called the `assert!` macro and +passed it the result of calling `larger.can_hold(&smaller)`. This expression +is supposed to return `true`, so our test should pass. Let’s find out! + +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-06/output.txt}} +``` + +It does pass! Let’s add another test, this time asserting that a smaller +rectangle cannot hold a larger rectangle: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/src/lib.rs:here}} +``` + +Because the correct result of the `can_hold` function in this case is `false`, +we need to negate that result before we pass it to the `assert!` macro. As a +result, our test will pass if `can_hold` returns `false`: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-02-adding-another-rectangle-test/output.txt}} +``` + +Two tests that pass! Now let’s see what happens to our test results when we +introduce a bug in our code. Let’s change the implementation of the `can_hold` +method by replacing the greater than sign with a less than sign when it +compares the widths: + +```rust,not_desired_behavior,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/src/lib.rs:here}} +``` + +Running the tests now produces the following: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-03-introducing-a-bug/output.txt}} +``` + +Our tests caught the bug! Because `larger.width` is 8 and `smaller.width` is +5, the comparison of the widths in `can_hold` now returns `false`: 8 is not +less than 5. + +### Testing Equality with the `assert_eq!` and `assert_ne!` Macros A common way to test functionality is to compare the result of the code under -test to the value you expect it to be, and check that they're equal. You can do -this using the `assert!` macro by passing it an expression using the `==` -macro. This is so common, though, that the standard library provides a pair of -macros to do this for convenience: `assert_eq!` and `assert_ne!`. These macros -compare two arguments for equality or inequality, respectively. The other -advantage of using these macros is they will print out what the two values -actually are if the assertion fails so that it's easier to see *why* the test -failed, whereas the `assert!` macro would just print out that it got a `false` -value for the `==` expression. +test to the value you expect the code to return to make sure they’re equal. You +could do this using the `assert!` macro and passing it an expression using the +`==` operator. However, this is such a common test that the standard library +provides a pair of macros—`assert_eq!` and `assert_ne!`—to perform this test +more conveniently. These macros compare two arguments for equality or +inequality, respectively. They’ll also print the two values if the assertion +fails, which makes it easier to see *why* the test failed; conversely, the +`assert!` macro only indicates that it got a `false` value for the `==` +expression, not the values that lead to the `false` value. -Here's an example test that uses each of these macros and will pass: +In Listing 11-7, we write a function named `add_two` that adds `2` to its +parameter and returns the result. Then we test this function using the +`assert_eq!` macro. Filename: src/lib.rs -```rust -#[test] -fn it_works() { - assert_eq!("Hello", "Hello"); - - assert_ne!("Hello", "world"); -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-07/src/lib.rs}} ``` -You can also specify an optional third argument to each of these macros, which -is a custom message that you'd like to be added to the failure message. The -macros expand to logic similar to this: +Listing 11-7: Testing the function `add_two` using the +`assert_eq!` macro + +Let’s check that it passes! + +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-07/output.txt}} +``` + +The first argument we gave to the `assert_eq!` macro, `4`, is equal to the +result of calling `add_two(2)`. The line for this test is `test +tests::it_adds_two ... ok`, and the `ok` text indicates that our test passed! + +Let’s introduce a bug into our code to see what it looks like when a test that +uses `assert_eq!` fails. Change the implementation of the `add_two` function to +instead add `3`: + +```rust,not_desired_behavior,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/src/lib.rs:here}} +``` + +Run the tests again: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/output.txt}} +``` + +Our test caught the bug! The `it_adds_two` test failed, displaying the message +`` assertion failed: `(left == right)` `` and showing that `left` was `4` and +`right` was `5`. This message is useful and helps us start debugging: it means +the `left` argument to `assert_eq!` was `4` but the `right` argument, where we +had `add_two(2)`, was `5`. + +Note that in some languages and test frameworks, the parameters to the +functions that assert two values are equal are called `expected` and `actual`, +and the order in which we specify the arguments matters. However, in Rust, +they’re called `left` and `right`, and the order in which we specify the value +we expect and the value that the code under test produces doesn’t matter. We +could write the assertion in this test as `assert_eq!(add_two(2), 4)`, which +would result in a failure message that displays `` assertion failed: `(left == +right)` `` and that `left` was `5` and `right` was `4`. + +The `assert_ne!` macro will pass if the two values we give it are not equal and +fail if they’re equal. This macro is most useful for cases when we’re not sure +what a value *will* be, but we know what the value definitely *won’t* be if our +code is functioning as we intend. For example, if we’re testing a function that +is guaranteed to change its input in some way, but the way in which the input +is changed depends on the day of the week that we run our tests, the best thing +to assert might be that the output of the function is not equal to the input. + +Under the surface, the `assert_eq!` and `assert_ne!` macros use the operators +`==` and `!=`, respectively. When the assertions fail, these macros print their +arguments using debug formatting, which means the values being compared must +implement the `PartialEq` and `Debug` traits. All the primitive types and most +of the standard library types implement these traits. For structs and enums +that you define, you’ll need to implement `PartialEq` to assert that values of +those types are equal or not equal. You’ll need to implement `Debug` to print +the values when the assertion fails. Because both traits are derivable traits, +as mentioned in Listing 5-12 in Chapter 5, this is usually as straightforward +as adding the `#[derive(PartialEq, Debug)]` annotation to your struct or enum +definition. See Appendix C, [“Derivable Traits,”][derivable-traits] for more details about these and other derivable traits. + +### Adding Custom Failure Messages + +You can also add a custom message to be printed with the failure message as +optional arguments to the `assert!`, `assert_eq!`, and `assert_ne!` macros. Any +arguments specified after the one required argument to `assert!` or the two +required arguments to `assert_eq!` and `assert_ne!` are passed along to the +`format!` macro (discussed in Chapter 8 in the [“Concatenation with the `+` +Operator or the `format!` +Macro”][concatenation-with-the--operator-or-the-format-macro] +section), so you can pass a format string that contains `{}` placeholders and +values to go in those placeholders. Custom messages are useful to document +what an assertion means; when a test fails, you’ll have a better idea of what +the problem is with the code. + +For example, let’s say we have a function that greets people by name and we +want to test that the name we pass into the function appears in the output: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-05-greeter/src/lib.rs}} +``` + +The requirements for this program haven’t been agreed upon yet, and we’re +pretty sure the `Hello` text at the beginning of the greeting will change. We +decided we don’t want to have to update the test when the requirements change, +so instead of checking for exact equality to the value returned from the +`greeting` function, we’ll just assert that the output contains the text of the +input parameter. + +Let’s introduce a bug into this code by changing `greeting` to not include +`name` to see what this test failure looks like: + +```rust,not_desired_behavior,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/src/lib.rs:here}} +``` + +Running this test produces the following: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-06-greeter-with-bug/output.txt}} +``` + +This result just indicates that the assertion failed and which line the +assertion is on. A more useful failure message in this case would print the +value we got from the `greeting` function. Let’s change the test function, +giving it a custom failure message made from a format string with a placeholder +filled in with the actual value we got from the `greeting` function: ```rust,ignore -// assert_eq! - panic if the values aren't equal -if left_val != right_val { - panic!( - "assertion failed: `(left == right)` (left: `{:?}`, right: `{:?}`): {}" - left_val, - right_val, - optional_custom_message - ) -} - -// assert_ne! - panic if the values are equal -if left_val == right_val { - panic!( - "assertion failed: `(left != right)` (left: `{:?}`, right: `{:?}`): {}" - left_val, - right_val, - optional_custom_message - ) -} +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/src/lib.rs:here}} ``` -Let's take a look at a test that will fail because `hello` is not equal to -`world`. We've also added a custom error message, `greeting operation failed`: +Now when we run the test, we’ll get a more informative error message: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-07-custom-failure-message/output.txt}} +``` + +We can see the value we actually got in the test output, which would help us +debug what happened instead of what we were expecting to happen. + +### Checking for Panics with `should_panic` + +In addition to checking that our code returns the correct values we expect, +it’s also important to check that our code handles error conditions as we +expect. For example, consider the `Guess` type that we created in Chapter 9, +Listing 9-10. Other code that uses `Guess` depends on the guarantee that `Guess` +instances will contain only values between 1 and 100. We can write a test that +ensures that attempting to create a `Guess` instance with a value outside that +range panics. + +We do this by adding another attribute, `should_panic`, to our test function. +This attribute makes a test pass if the code inside the function panics; the +test will fail if the code inside the function doesn’t panic. + +Listing 11-8 shows a test that checks that the error conditions of `Guess::new` +happen when we expect them to. Filename: src/lib.rs -```rust -#[test] -fn a_simple_case() { - let result = "hello"; // this value would come from running your code - assert_eq!(result, "world", "greeting operation failed"); -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-08/src/lib.rs}} ``` -Running this indeed fails, and the output we get explains why the test failed -and includes the custom error message we specified: +Listing 11-8: Testing that a condition will cause a +`panic!` -```text ----- a_simple_case stdout ---- - thread 'a_simple_case' panicked at 'assertion failed: `(left == right)` - (left: `"hello"`, right: `"world"`): greeting operation failed', - src/main.rs:4 +We place the `#[should_panic]` attribute after the `#[test]` attribute and +before the test function it applies to. Let’s look at the result when this test +passes: + +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-08/output.txt}} ``` -The two parameters to `assert_eq!` are named "left" and "right" rather than -"expected" and "actual"; the order of the value that comes from your code and -the value hardcoded into your test isn't important. +Looks good! Now let’s introduce a bug in our code by removing the condition +that the `new` function will panic if the value is greater than 100: -Since these macros use the operators `==` and `!=` and print the values using -debug formatting, the values being compared must implement the `PartialEq` and -`Debug` traits. Types provided by Rust implement these traits, but for structs -and enums that you define, you'll need to add `PartialEq` in order to be able -to assert that values of those types are equal or not equal and `Debug` in -order to be able to print out the values in the case that the assertion fails. -Because both of these traits are derivable traits that we mentioned in Chapter -5, usually this is as straightforward as adding the `#[derive(PartialEq, -Debug)]` annotation to your struct or enum definition. See Appendix C for more -details about these and other derivable traits. +```rust,not_desired_behavior,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/src/lib.rs:here}} +``` -## Test for failure with `should_panic` +When we run the test in Listing 11-8, it will fail: -We can invert our test's failure with another attribute: `should_panic`. This -is useful when we want to test that calling a particular function will cause an -error. For example, let's test something that we know will panic from Chapter -8: attempting to create a slice using range syntax with byte indices that -aren't on character boundaries. Add the `#[should_panic]` attribute before the -function like the `#[test]` attribute, as shown in Listing 11-1: +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-08-guess-with-bug/output.txt}} +``` + +We don’t get a very helpful message in this case, but when we look at the test +function, we see that it’s annotated with `#[should_panic]`. The failure we got +means that the code in the test function did not cause a panic. + +Tests that use `should_panic` can be imprecise because they only indicate that +the code has caused some panic. A `should_panic` test would pass even if the +test panics for a different reason from the one we were expecting to happen. To +make `should_panic` tests more precise, we can add an optional `expected` +parameter to the `should_panic` attribute. The test harness will make sure that +the failure message contains the provided text. For example, consider the +modified code for `Guess` in Listing 11-9 where the `new` function panics with +different messages depending on whether the value is too small or too large. -
Filename: src/lib.rs -```rust -#[test] -#[should_panic] -fn slice_not_on_char_boundaries() { - let s = "Здравствуйте"; - &s[0..1]; -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-09/src/lib.rs:here}} ``` -
+Listing 11-9: Testing that a condition will cause a +`panic!` with a particular panic message -Listing 11-1: A test expecting a `panic!` +This test will pass because the value we put in the `should_panic` attribute’s +`expected` parameter is a substring of the message that the `Guess::new` +function panics with. We could have specified the entire panic message that we +expect, which in this case would be `Guess value must be less than or equal to +100, got 200.` What you choose to specify in the expected parameter for +`should_panic` depends on how much of the panic message is unique or dynamic +and how precise you want your test to be. In this case, a substring of the +panic message is enough to ensure that the code in the test function executes +the `else if value > 100` case. -
-
+To see what happens when a `should_panic` test with an `expected` message +fails, let’s again introduce a bug into our code by swapping the bodies of the +`if value < 1` and the `else if value > 100` blocks: -This test will succeed, since the code panics and we said that it should. If -this code happened to run and did not cause a `panic!`, this test would fail. - -`should_panic` tests can be fragile, as it's hard to guarantee that the test -didn't fail for a different reason than the one you were expecting. To help -with this, an optional `expected` parameter can be added to the `should_panic` -attribute. The test harness will make sure that the failure message contains -the provided text. A more robust version of Listing 11-1 would be the -following, in Listing 11-2: - -
-Filename: src/lib.rs - -```rust -#[test] -#[should_panic(expected = "do not lie on character boundary")] -fn slice_not_on_char_boundaries() { - let s = "Здравствуйте"; - &s[0..1]; -} +```rust,ignore,not_desired_behavior +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/src/lib.rs:here}} ``` - +This time when we run the `should_panic` test, it will fail: -
+```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-09-guess-with-panic-msg-bug/output.txt}} +``` -Listing 11-2: A test expecting a `panic!` with a particular message +The failure message indicates that this test did indeed panic as we expected, +but the panic message did not include the expected string `'Guess value must be +less than or equal to 100'`. The panic message that we did get in this case was +`Guess value must be greater than or equal to 1, got 200.` Now we can start +figuring out where our bug is! -
-
+### Using `Result` in Tests -Try on your own to see what happens when a `should_panic` test panics but -doesn't match the expected message: cause a `panic!` that happens for a -different reason in this test, or change the expected panic message to -something that doesn't match the character boundary panic message. +So far, we’ve written tests that panic when they fail. We can also write tests +that use `Result`! Here’s the test from Listing 11-1, rewritten to use +`Result` and return an `Err` instead of panicking: + +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-10-result-in-tests/src/lib.rs}} +``` + +The `it_works` function now has a return type, `Result<(), String>`. In the +body of the function, rather than calling the `assert_eq!` macro, we return +`Ok(())` when the test passes and an `Err` with a `String` inside when the test +fails. + +Writing tests so they return a `Result` enables you to use the question +mark operator in the body of tests, which can be a convenient way to write +tests that should fail if any operation within them returns an `Err` variant. + +You can’t use the `#[should_panic]` annotation on tests that use `Result`. Instead, you should return an `Err` value directly when the test should +fail. + +Now that you know several ways to write tests, let’s look at what is happening +when we run our tests and explore the different options we can use with `cargo +test`. + +[concatenation-with-the--operator-or-the-format-macro]: +ch08-02-strings.html#concatenation-with-the--operator-or-the-format-macro +[controlling-how-tests-are-run]: +ch11-02-running-tests.html#controlling-how-tests-are-run +[derivable-traits]: appendix-03-derivable-traits.html +[doc-comments]: ch14-02-publishing-to-crates-io.html#documentation-comments-as-tests +[paths-for-referring-to-an-item-in-the-module-tree]: ch07-03-paths-for-referring-to-an-item-in-the-module-tree.html diff --git a/src/ch11-02-running-tests.md b/src/ch11-02-running-tests.md index ea81318..c33280e 100644 --- a/src/ch11-02-running-tests.md +++ b/src/ch11-02-running-tests.md @@ -1,257 +1,183 @@ -## Running tests +## Controlling How Tests Are Run -Just like `cargo run` compiles your code and then runs the resulting binary, +Just as `cargo run` compiles your code and then runs the resulting binary, `cargo test` compiles your code in test mode and runs the resulting test -binary. The default behavior of the binary that `cargo test` produces is to run -all the tests in parallel and to capture output generated during test runs so -that it's easier to read the output about the test results. +binary. You can specify command line options to change the default behavior of +`cargo test`. For example, the default behavior of the binary produced by +`cargo test` is to run all the tests in parallel and capture output generated +during test runs, preventing the output from being displayed and making it +easier to read the output related to the test results. -The default behavior of running tests can be changed by specifying command line -options. Some of these options can be passed to `cargo test`, and some need to -be passed instead to the resulting test binary. The way to separate these -arguments is with `--`: after `cargo test`, list the arguments that go to -`cargo test`, then the separator `--`, and then the arguments that go to the -test binary. +Some command line options go to `cargo test`, and some go to the resulting test +binary. To separate these two types of arguments, you list the arguments that +go to `cargo test` followed by the separator `--` and then the ones that go to +the test binary. Running `cargo test --help` displays the options you can use +with `cargo test`, and running `cargo test -- --help` displays the options you +can use after the separator `--`. -### Tests Run in Parallel +### Running Tests in Parallel or Consecutively -Tests are run in parallel using threads. For this reason, you should take care -that your tests are written in such a way as to not depend on each other or on -any shared state. Shared state can also include the environment, such as the -current working directory or environment variables. +When you run multiple tests, by default they run in parallel using threads. +This means the tests will finish running faster so you can get feedback quicker +on whether or not your code is working. Because the tests are running at the +same time, make sure your tests don’t depend on each other or on any shared +state, including a shared environment, such as the current working directory or +environment variables. -If you don't want this behavior, or if you want more fine-grained control over -the number of threads used, you can send the `--test-threads` flag and the -number of threads to the test binary. Setting the number of test threads to 1 -means to not use any parallelism: +For example, say each of your tests runs some code that creates a file on disk +named *test-output.txt* and writes some data to that file. Then each test reads +the data in that file and asserts that the file contains a particular value, +which is different in each test. Because the tests run at the same time, one +test might overwrite the file between when another test writes and reads the +file. The second test will then fail, not because the code is incorrect but +because the tests have interfered with each other while running in parallel. +One solution is to make sure each test writes to a different file; another +solution is to run the tests one at a time. -```text +If you don’t want to run the tests in parallel or if you want more fine-grained +control over the number of threads used, you can send the `--test-threads` flag +and the number of threads you want to use to the test binary. Take a look at +the following example: + +```console $ cargo test -- --test-threads=1 ``` -### Tests Capture Output +We set the number of test threads to `1`, telling the program not to use any +parallelism. Running the tests using one thread will take longer than running +them in parallel, but the tests won’t interfere with each other if they share +state. -By default, Rust's test library captures and discards output to standard out -and standard error, unless the test fails. For example, if you call `println!` -in a test and the test passes, you won't see the `println!` output in your -terminal. This behavior can be disabled by sending the `--nocapture` flag to -the test binary: +### Showing Function Output -```text -$ cargo test -- --nocapture +By default, if a test passes, Rust’s test library captures anything printed to +standard output. For example, if we call `println!` in a test and the test +passes, we won’t see the `println!` output in the terminal; we’ll see only the +line that indicates the test passed. If a test fails, we’ll see whatever was +printed to standard output with the rest of the failure message. + +As an example, Listing 11-10 has a silly function that prints the value of its +parameter and returns 10, as well as a test that passes and a test that fails. + +Filename: src/lib.rs + +```rust,panics,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-10/src/lib.rs}} +``` + +Listing 11-10: Tests for a function that calls +`println!` + +When we run these tests with `cargo test`, we’ll see the following output: + +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-10/output.txt}} +``` + +Note that nowhere in this output do we see `I got the value 4`, which is what +is printed when the test that passes runs. That output has been captured. The +output from the test that failed, `I got the value 8`, appears in the section +of the test summary output, which also shows the cause of the test failure. + +If we want to see printed values for passing tests as well, we can tell Rust +to also show the output of successful tests at the end with `--show-output`. + +```console +$ cargo test -- --show-output +``` + +When we run the tests in Listing 11-10 again with the `--show-output` flag, we +see the following output: + +```console +{{#include ../listings/ch11-writing-automated-tests/output-only-01-show-output/output.txt}} ``` ### Running a Subset of Tests by Name -Sometimes, running a full test suite can take a long time. If you're only -working on code in a particular area, you might want to only run the tests -having to do with that code. `cargo test` takes an argument that allows you to -only run certain tests, specified by name. +Sometimes, running a full test suite can take a long time. If you’re working on +code in a particular area, you might want to run only the tests pertaining to +that code. You can choose which tests to run by passing `cargo test` the name +or names of the test(s) you want to run as an argument. -Let's create three tests with the following names as shown in Listing 11-3: - -
-Filename: src/lib.rs - -```rust -#[test] -fn add_two_and_two() { - assert_eq!(4, 2 + 2); -} - -#[test] -fn add_three_and_two() { - assert_eq!(5, 3 + 2); -} - -#[test] -fn one_hundred() { - assert_eq!(102, 100 + 2); -} -``` - -
- -Listing 11-3: Three tests with a variety of names - -
-
- -Running with different arguments will run different subsets of the tests. No -arguments, as we've already seen, runs all the tests: - -```text -$ cargo test - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-abcabcabc - -running 3 tests -test add_three_and_two ... ok -test one_hundred ... ok -test add_two_and_two ... ok - -test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured -``` - -We can pass the name of any test function to run only that test: - -```text -$ cargo test one_hundred - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-abcabcabc - -running 1 test -test one_hundred ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -We can also pass part of a name, and `cargo test` will run all tests that match: - -```text -$ cargo test add - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-abcabcabc - -running 2 tests -test add_three_and_two ... ok -test add_two_and_two ... ok - -test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured -``` - -Module names become part of the test name, so module names can be used in a -similar way to run just the tests for a particular module. For example, if our -code was organized into a module named `adding` and a module named -`subtracting` with tests in each, as in Listing 11-4: - -
-Filename: src/lib.rs - -```rust -mod adding { - #[test] - fn add_two_and_two() { - assert_eq!(4, 2 + 2); - } - - #[test] - fn add_three_and_two() { - assert_eq!(5, 3 + 2); - } - - #[test] - fn one_hundred() { - assert_eq!(102, 100 + 2); - } -} - -mod subtracting { - #[test] - fn subtract_three_and_two() { - assert_eq!(1, 3 - 2); - } -} -``` - -
- -Listing 11-4: Tests in two modules named `adding` and `subtracting` - -
-
- -Running `cargo test` will run all of the tests, and the module names will -appear in the test names in the output: - -```text -$ cargo test - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-abcabcabc - -running 4 tests -test adding::add_two_and_two ... ok -test adding::add_three_and_two ... ok -test subtracting::subtract_three_and_two ... ok -test adding::one_hundred ... ok -``` - -Running `cargo test adding` would run just the tests in that module and not any -of the tests in the subtracting module: - -```text -$ cargo test adding - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-abcabcabc - -running 3 tests -test adding::add_three_and_two ... ok -test adding::one_hundred ... ok -test adding::add_two_and_two ... ok - -test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured -``` - -### Ignore Some Tests Unless Specifically Requested - -Sometimes a few specific tests can be very time-consuming to execute, so during -most runs of `cargo test`, we'd like to exclude them. Instead of having to -construct an argument to `cargo test` to run all tests except these and -remember to use that argument every time, we can annotate these tests with the -`ignore` attribute: +To demonstrate how to run a subset of tests, we’ll create three tests for our +`add_two` function, as shown in Listing 11-11, and choose which ones to run. Filename: src/lib.rs -```rust -#[test] -fn it_works() { - assert!(true); -} - -#[test] -#[ignore] -fn expensive_test() { - // code that takes an hour to run -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-11/src/lib.rs}} ``` -Now if we run our tests, we'll see `it_works` is run, but `expensive_test` is -not: +Listing 11-11: Three tests with three different +names -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.24 secs - Running target/debug/deps/adder-abcabcabc +If we run the tests without passing any arguments, as we saw earlier, all the +tests will run in parallel: -running 2 tests -test expensive_test ... ignored -test it_works ... ok - -test result: ok. 1 passed; 0 failed; 1 ignored; 0 measured - - Doc-tests adder - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-11/output.txt}} ``` -We can run only the expensive tests by explicitly asking to run them using -`cargo test -- --ignored`: +#### Running Single Tests -```text -$ cargo test -- --ignored - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/adder-abcabcabc +We can pass the name of any test function to `cargo test` to run only that test: -running 1 test -test expensive_test ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured +```console +{{#include ../listings/ch11-writing-automated-tests/output-only-02-single-test/output.txt}} ``` -This way, most of the time that you run `cargo test` the results would be fast. -When you're at a point that it makes sense to check the results of the -`ignored` tests and you have time to wait for the results, you can choose to -run `cargo test -- --ignored` instead. +Only the test with the name `one_hundred` ran; the other two tests didn’t match +that name. The test output lets us know we had more tests than what this +command ran by displaying `2 filtered out` at the end of the summary line. + +We can’t specify the names of multiple tests in this way; only the first value +given to `cargo test` will be used. But there is a way to run multiple tests. + +#### Filtering to Run Multiple Tests + +We can specify part of a test name, and any test whose name matches that value +will be run. For example, because two of our tests’ names contain `add`, we can +run those two by running `cargo test add`: + +```console +{{#include ../listings/ch11-writing-automated-tests/output-only-03-multiple-tests/output.txt}} +``` + +This command ran all tests with `add` in the name and filtered out the test +named `one_hundred`. Also note that the module in which a test appears becomes +part of the test’s name, so we can run all the tests in a module by filtering +on the module’s name. + +### Ignoring Some Tests Unless Specifically Requested + +Sometimes a few specific tests can be very time-consuming to execute, so you +might want to exclude them during most runs of `cargo test`. Rather than +listing as arguments all tests you do want to run, you can instead annotate the +time-consuming tests using the `ignore` attribute to exclude them, as shown +here: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/src/lib.rs}} +``` + +After `#[test]` we add the `#[ignore]` line to the test we want to exclude. Now +when we run our tests, `it_works` runs, but `expensive_test` doesn’t: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-11-ignore-a-test/output.txt}} +``` + +The `expensive_test` function is listed as `ignored`. If we want to run only +the ignored tests, we can use `cargo test -- --ignored`: + +```console +{{#include ../listings/ch11-writing-automated-tests/output-only-04-running-ignored/output.txt}} +``` + +By controlling which tests run, you can make sure your `cargo test` results +will be fast. When you’re at a point where it makes sense to check the results +of the `ignored` tests and you have time to wait for the results, you can run +`cargo test -- --ignored` instead. diff --git a/src/ch11-03-test-organization.md b/src/ch11-03-test-organization.md index b916623..2110ff1 100644 --- a/src/ch11-03-test-organization.md +++ b/src/ch11-03-test-organization.md @@ -1,305 +1,239 @@ ## Test Organization -As mentioned before, testing is a large discipline, and different people -sometimes use different terminology and organization. The Rust community tends -to think about tests in terms of two main categories: *unit tests* and -*integration tests*. Unit tests tend to be smaller and more focused, testing -one module in isolation at a time. They can also test private interfaces. -Integration tests are entirely external to your library. They use your code in -the same way any other code would, using only the public interface and -exercising multiple modules per test. Both kinds of tests are important to -ensure that the pieces of your library are doing what you expect them to -separately and together. +As mentioned at the start of the chapter, testing is a complex discipline, and +different people use different terminology and organization. The Rust community +thinks about tests in terms of two main categories: *unit tests* and +*integration tests*. Unit tests are small and more focused, testing one module +in isolation at a time, and can test private interfaces. Integration tests are +entirely external to your library and use your code in the same way any other +external code would, using only the public interface and potentially exercising +multiple modules per test. + +Writing both kinds of tests is important to ensure that the pieces of your +library are doing what you expect them to, separately and together. ### Unit Tests The purpose of unit tests is to test each unit of code in isolation from the -rest of the code, in order to be able to quickly pinpoint where code is working -as expected or not. Unit tests live in the *src* directory, in the same files -as the code they are testing. They are separated into their own `tests` module -in each file. +rest of the code to quickly pinpoint where code is and isn’t working as +expected. You’ll put unit tests in the *src* directory in each file with the +code that they’re testing. The convention is to create a module named `tests` +in each file to contain the test functions and to annotate the module with +`cfg(test)`. -#### The Tests Module and `cfg(test)` +#### The Tests Module and `#[cfg(test)]` -By placing tests in their own module and using the `cfg` annotation on the -module, we can tell Rust to only compile and run the test code when we run -`cargo test`. This saves compile time when we only want to build the library -code with `cargo build`, and saves space in the resulting compiled artifact -since the tests are not included. +The `#[cfg(test)]` annotation on the tests module tells Rust to compile and run +the test code only when you run `cargo test`, not when you run `cargo build`. +This saves compile time when you only want to build the library and saves space +in the resulting compiled artifact because the tests are not included. You’ll +see that because integration tests go in a different directory, they don’t need +the `#[cfg(test)]` annotation. However, because unit tests go in the same files +as the code, you’ll use `#[cfg(test)]` to specify that they shouldn’t be +included in the compiled result. -Remember when we generated the new `adder` project in the last section? Cargo -generated this code for us: +Recall that when we generated the new `adder` project in the first section of +this chapter, Cargo generated this code for us: Filename: src/lib.rs -```rust -#[cfg(test)] -mod tests { - #[test] - fn it_works() { - } -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-01/src/lib.rs}} ``` -We ignored the module stuff so we could concentrate on the mechanics of the -test code inside the module, but now let's focus on the code surrounding our -tests. - -First of all, there's a new attribute, `cfg`. The `cfg` attribute lets us -declare that something should only be included given a certain *configuration*. -Rust provides the `test` configuration for compiling and running tests. By -using this attribute, Cargo only compiles our test code if we're currently -trying to run the tests. - -Next, the `tests` module holds all of our test functions, while our code is -outside of the `tests` module. The name of the `tests` module is a convention; -otherwise this is a regular module that follows the usual visibility rules we -covered in Chapter 7. Because we're in an inner module, we need to bring the -code under test into scope. This can be annoying if you have a large module, so -this is a common use of globs. - -Up until now in this chapter, we've been writing tests in our `adder` project -that don't actually call any code we've written. Let's change that now! In -*src/lib.rs*, place this `add_two` function and `tests` module that has a test -function to exercise the code, as shown in Listing 11-5: - -
-Filename: src/lib.rs - -```rust -pub fn add_two(a: i32) -> i32 { - a + 2 -} - -#[cfg(test)] -mod tests { - use add_two; - - #[test] - fn it_works() { - assert_eq!(4, add_two(2)); - } -} -``` - -
- -Listing 11-5: Testing the function `add_two` in a child `tests` module - -
-
- -Notice in addition to the test function, we also added `use add_two;` within -the `tests` module. This brings the code we want to test into the scope of the -inner `tests` module, just like we'd need to do for any inner module. If we run -this test now with `cargo test`, it will pass: - -```text -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured -``` - -If we had forgotten to bring the `add_two` function into scope, we would get an -unresolved name error since the `tests` module wouldn't know anything about the -`add_two` function: - -```text -error[E0425]: unresolved name `add_two` - --> src/lib.rs:9:23 - | -9 | assert_eq!(4, add_two(2)); - | ^^^^^^^ unresolved name -``` - -If this module contained lots of code we wanted to test, it would be annoying -to list everything in the `use` statement in the tests. It's common instead to -put `use super::*;` within a module's `test` submodule in order to bring -everything into the `test` module scope at once. +This code is the automatically generated test module. The attribute `cfg` +stands for *configuration* and tells Rust that the following item should only +be included given a certain configuration option. In this case, the +configuration option is `test`, which is provided by Rust for compiling and +running tests. By using the `cfg` attribute, Cargo compiles our test code only +if we actively run the tests with `cargo test`. This includes any helper +functions that might be within this module, in addition to the functions +annotated with `#[test]`. #### Testing Private Functions -There's controversy within the testing community about whether you should write -unit tests for private functions or not. Regardless of which testing ideology -you adhere to, Rust does allow you to test private functions due to the way -that the privacy rules work. Consider the code in Listing 11-6 with the private -function `internal_adder`: +There’s debate within the testing community about whether or not private +functions should be tested directly, and other languages make it difficult or +impossible to test private functions. Regardless of which testing ideology you +adhere to, Rust’s privacy rules do allow you to test private functions. +Consider the code in Listing 11-12 with the private function `internal_adder`. -
Filename: src/lib.rs -```rust -pub fn add_two(a: i32) -> i32 { - internal_adder(a, 2) -} - -fn internal_adder(a: i32, b: i32) -> i32 { - a + b -} - -#[cfg(test)] -mod tests { - use internal_adder; - - #[test] - fn internal() { - assert_eq!(4, internal_adder(2, 2)); - } -} +```rust,noplayground +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-12/src/lib.rs}} ``` -
+Listing 11-12: Testing a private function -Listing 11-6: Testing a private function - -
-
- -Because tests are just Rust code and the `tests` module is just another module, -we can import and call `internal_adder` in a test just fine. If you don't think -private functions should be tested, there's nothing in Rust that will compel +Note that the `internal_adder` function is not marked as `pub`, but because +tests are just Rust code and the `tests` module is just another module, you can +bring `internal_adder` into a test’s scope and call it. If you don’t think +private functions should be tested, there’s nothing in Rust that will compel you to do so. ### Integration Tests -In Rust, integration tests are tests that are entirely external to your -library. They use your library in the same way any other code would. Their -purpose is to test that many parts of your library work correctly together. -Units of code that work correctly by themselves could have problems when -integrated, so test coverage of the integrated code is important as well. +In Rust, integration tests are entirely external to your library. They use your +library in the same way any other code would, which means they can only call +functions that are part of your library’s public API. Their purpose is to test +whether many parts of your library work together correctly. Units of code that +work correctly on their own could have problems when integrated, so test +coverage of the integrated code is important as well. To create integration +tests, you first need a *tests* directory. #### The *tests* Directory -Cargo has support for integration tests in the *tests* directory. If you make -one and put Rust files inside, Cargo will compile each of the files as an -individual crate. Let's give it a try! +We create a *tests* directory at the top level of our project directory, next +to *src*. Cargo knows to look for integration test files in this directory. We +can then make as many test files as we want to in this directory, and Cargo +will compile each of the files as an individual crate. -First, make a *tests* directory at the top level of your project directory, -next to *src*. Then, make a new file, *tests/integration_test.rs*, and put the -code in Listing 11-7 inside: +Let’s create an integration test. With the code in Listing 11-12 still in the +*src/lib.rs* file, make a *tests* directory, create a new file named +*tests/integration_test.rs*, and enter the code in Listing 11-13. -
Filename: tests/integration_test.rs ```rust,ignore -extern crate adder; - -#[test] -fn it_adds_two() { - assert_eq!(4, adder::add_two(2)); -} +{{#rustdoc_include ../listings/ch11-writing-automated-tests/listing-11-13/tests/integration_test.rs}} ``` -
+Listing 11-13: An integration test of a function in the +`adder` crate -Listing 11-7: An integration test of a function in the `adder` crate +We’ve added `use adder` at the top of the code, which we didn’t need in the +unit tests. The reason is that each file in the `tests` directory is a separate +crate, so we need to bring our library into each test crate’s scope. -
-
+We don’t need to annotate any code in *tests/integration_test.rs* with +`#[cfg(test)]`. Cargo treats the `tests` directory specially and compiles files +in this directory only when we run `cargo test`. Run `cargo test` now: -We now have `extern crate adder` at the top, which we didn't need in the unit -tests. Each test in the `tests` directory is an entirely separate crate, so we -need to import our library into each of them. This is also why `tests` is a -suitable place to write integration-style tests: they use the library like any -other consumer of it would, by importing the crate and using only the public -API. - -We also don't need a `tests` module in this file. The whole directory won't be -compiled unless we're running the tests, so we don't need to annotate any part -of it with `#[cfg(test)]`. Also, each test file is already isolated into its -own crate, so we don't need to separate the test code further. - -Let's run the integration tests, which also get run when we run `cargo test`: - -```text -$ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Running target/debug/deps/adder-abcabcabc - -running 1 test -test tests::it_works ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Running target/debug/integration_test-952a27e0126bb565 - -running 1 test -test it_adds_two ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests adder - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured +```console +{{#include ../listings/ch11-writing-automated-tests/listing-11-13/output.txt}} ``` -Now we have three sections of output: the unit tests, the integration test, and -the doc tests. Note that adding more unit tests in any *src* file will add more -lines to the unit tests section. Adding more test functions to the integration -test file we created will add more lines to that section. If we add more -integration test *files* in the *tests* directory, there will be more -integration test sections: one for each file. +The three sections of output include the unit tests, the integration test, and +the doc tests. The first section for the unit tests is the same as we’ve been +seeing: one line for each unit test (one named `internal` that we added in +Listing 11-12) and then a summary line for the unit tests. -Specifying a test function name argument with `cargo test` will also match -against test function names in any integration test file. To run all of the -tests in only one particular integration test file, use the `--test` argument -of `cargo test`: +The integration tests section starts with the line `Running +target/debug/deps/integration_test-1082c4b063a8fbe6` (the hash at the end of +your output will be different). Next, there is a line for each test function in +that integration test and a summary line for the results of the integration +test just before the `Doc-tests adder` section starts. -```text -$ cargo test --test integration_test - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/integration_test-952a27e0126bb565 +Similarly to how adding more unit test functions adds more result lines to the +unit tests section, adding more test functions to the integration test file +adds more result lines to this integration test file’s section. Each +integration test file has its own section, so if we add more files in the +*tests* directory, there will be more integration test sections. -running 1 test -test it_adds_two ... ok +We can still run a particular integration test function by specifying the test +function’s name as an argument to `cargo test`. To run all the tests in a +particular integration test file, use the `--test` argument of `cargo test` +followed by the name of the file: -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured +```console +{{#include ../listings/ch11-writing-automated-tests/output-only-05-single-integration/output.txt}} ``` +This command runs only the tests in the *tests/integration_test.rs* file. + #### Submodules in Integration Tests -As you add more integration tests, you may want to make more than one file in -the `tests` directory in order to group the test functions by the functionality -they're testing, for example. As we mentioned before, that will work fine, -given that Cargo treats every file as its own crate. +As you add more integration tests, you might want to make more than one file in +the *tests* directory to help organize them; for example, you can group the +test functions by the functionality they’re testing. As mentioned earlier, each +file in the *tests* directory is compiled as its own separate crate. -Eventually, you may have a set of helper functions that are common to all -integration tests, for example, functions that set up common scenarios. If you -extract these into a file in the *tests* directory, like *tests/common.rs* for -example, this file will be compiled into a separate crate just like the Rust -files in this directory that contain test functions are. There will be a -separate section in the test output for this file. Since this is probably not -what you want, it's recommended to instead use a *mod.rs* file in a -subdirectory, like *tests/common/mod.rs*, for helper functions. Files in -subdirectories of the *tests* directory do not get compiled as separate crates -or have sections in the test output. +Treating each integration test file as its own crate is useful to create +separate scopes that are more like the way end users will be using your crate. +However, this means files in the *tests* directory don’t share the same +behavior as files in *src* do, as you learned in Chapter 7 regarding how to +separate code into modules and files. + +The different behavior of files in the *tests* directory is most noticeable +when you have a set of helper functions that would be useful in multiple +integration test files and you try to follow the steps in the [“Separating +Modules into Different Files”][separating-modules-into-files] +section of Chapter 7 to extract them into a common module. For example, if we +create *tests/common.rs* and place a function named `setup` in it, we can add +some code to `setup` that we want to call from multiple test functions in +multiple test files: + +Filename: tests/common.rs + +```rust +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/tests/common.rs}} +``` + +When we run the tests again, we’ll see a new section in the test output for the +*common.rs* file, even though this file doesn’t contain any test functions nor +did we call the `setup` function from anywhere: + +```console +{{#include ../listings/ch11-writing-automated-tests/no-listing-12-shared-test-code-problem/output.txt}} +``` + +Having `common` appear in the test results with `running 0 tests` displayed for +it is not what we wanted. We just wanted to share some code with the other +integration test files. + +To avoid having `common` appear in the test output, instead of creating +*tests/common.rs*, we’ll create *tests/common/mod.rs*. This is an alternate +naming convention that Rust also understands. Naming the file this way tells +Rust not to treat the `common` module as an integration test file. When we move +the `setup` function code into *tests/common/mod.rs* and delete the +*tests/common.rs* file, the section in the test output will no longer appear. +Files in subdirectories of the *tests* directory don’t get compiled as separate +crates or have sections in the test output. + +After we’ve created *tests/common/mod.rs*, we can use it from any of the +integration test files as a module. Here’s an example of calling the `setup` +function from the `it_adds_two` test in *tests/integration_test.rs*: + +Filename: tests/integration_test.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch11-writing-automated-tests/no-listing-13-fix-shared-test-code-problem/tests/integration_test.rs}} +``` + +Note that the `mod common;` declaration is the same as the module declaration +we demonstrated in Listing 7-21. Then in the test function, we can call the +`common::setup()` function. #### Integration Tests for Binary Crates -If your project is a binary crate that only contains a *src/main.rs* and does -not have a *src/lib.rs*, it is not possible to create integration tests in the -*tests* directory and use `extern crate` to import the functions in -*src/main.rs*. This is one of the reasons Rust projects that provide a binary -have a straightforward *src/main.rs* that calls logic that lives in -*src/lib.rs*. With that structure, integration tests *can* test the library -crate by using `extern crate` to cover the important functionality, and if that -works, the small amount of code in *src/main.rs* will work as well and does not +If our project is a binary crate that only contains a *src/main.rs* file and +doesn’t have a *src/lib.rs* file, we can’t create integration tests in the +*tests* directory and bring functions defined in the *src/main.rs* file into +scope with a `use` statement. Only library crates expose functions that other +crates can use; binary crates are meant to be run on their own. + +This is one of the reasons Rust projects that provide a binary have a +straightforward *src/main.rs* file that calls logic that lives in the +*src/lib.rs* file. Using that structure, integration tests *can* test the +library crate with `use` to make the important functionality available. +If the important functionality works, the small amount of code in the +*src/main.rs* file will work as well, and that small amount of code doesn’t need to be tested. ## Summary -Rust's testing features provide a way to specify how code should function to -ensure the code continues to work in the specified ways even as we make -changes. Unit tests exercise different parts of a library separately and can -test private implementation details. Integration tests cover the use of many -parts of the library working together, and use the library's public API to test -the code in the same way other code will use it. Rust's type system and -ownership rules help prevent some kinds of bugs, but tests are an important -part of reducing logic bugs having to do with how your code is expected to -behave. +Rust’s testing features provide a way to specify how code should function to +ensure it continues to work as you expect, even as you make changes. Unit tests +exercise different parts of a library separately and can test private +implementation details. Integration tests check that many parts of the library +work together correctly, and they use the library’s public API to test the code +in the same way external code will use it. Even though Rust’s type system and +ownership rules help prevent some kinds of bugs, tests are still important to +reduce logic bugs having to do with how your code is expected to behave. -Let's put together the knowledge from this chapter and other previous chapters -and work on a project in the next chapter! +Let’s combine the knowledge you learned in this chapter and in previous +chapters to work on a project! + +[separating-modules-into-files]: +ch07-05-separating-modules-into-different-files.html diff --git a/src/ch12-00-an-io-project.md b/src/ch12-00-an-io-project.md index 67a546d..5802d97 100644 --- a/src/ch12-00-an-io-project.md +++ b/src/ch12-00-an-io-project.md @@ -1,50 +1,49 @@ -# An I/O Project +# An I/O Project: Building a Command Line Program -We've learned a lot over the last few chapters. Let's take that new knowledge -and apply it by building a project together. Along the way, we'll learn a bit -more about Rust's standard library. +This chapter is a recap of the many skills you’ve learned so far and an +exploration of a few more standard library features. We’ll build a command line +tool that interacts with file and command line input/output to practice some of +the Rust concepts you now have under your belt. -So what should we build? One that uses Rust's strengths. A great use of Rust is -for command line tools: Rust's speed, safety, 'single binary' output, and -cross-platform support make it a good language choice for this kind of task. So -we'll make our own version of a classic command line tool: `grep`. `grep` is -short for "Globally search a Regular Expression and Print." In the -simplest use case, it does this: +Rust’s speed, safety, single binary output, and cross-platform support make it +an ideal language for creating command line tools, so for our project, we’ll +make our own version of the classic command line tool `grep` (**g**lobally +search a **r**egular **e**xpression and **p**rint). In the simplest use case, +`grep` searches a specified file for a specified string. To do so, `grep` takes +as its arguments a filename and a string. Then it reads the file, finds lines +in that file that contain the string argument, and prints those lines. -1. Takes a filename and a string as arguments. -2. Reads the file. -3. Finds lines in the file that contain the string argument. -4. Prints out those lines. +Along the way, we’ll show how to make our command line tool use features of the +terminal that many command line tools use. We’ll read the value of an +environment variable to allow the user to configure the behavior of our tool. +We’ll also print error messages to the standard error console stream (`stderr`) +instead of standard output (`stdout`), so, for example, the user can redirect +successful output to a file while still seeing error messages onscreen. -In addition, we'll add one extra feature: an environment variable that will -allow us to search for the string argument in a case-insensitive way. +One Rust community member, Andrew Gallant, has already created a fully +featured, very fast version of `grep`, called `ripgrep`. By comparison, our +version of `grep` will be fairly simple, but this chapter will give you some of +the background knowledge you need to understand a real-world project such as +`ripgrep`. -There's another great reason to use `grep` as an example project: a very -fully-featured version of `grep` has already been created in Rust by a -community member, Andrew Gallant. It's called `ripgrep`, and it's very, -very fast. While our version of `grep` will be fairly simple, you'll have -some of the background knowledge to understand that project if you want to see -something more real-world. +Our `grep` project will combine a number of concepts you’ve learned so far: -This project will bring together a number of things we learned previously: +* Organizing code (using what you learned about modules in [Chapter 7][ch7]) +* Using vectors and strings (collections, [Chapter 8][ch8]) +* Handling errors ([Chapter 9][ch9]) +* Using traits and lifetimes where appropriate ([Chapter 10][ch10]) +* Writing tests ([Chapter 11][ch11]) -- Organize code (using what we learned in modules, Chapter 7) -- Use vectors and strings (collections, Chapter 8) -- Handle errors (Chapter 9) -- Use traits and lifetimes where appropriate (Chapter 10) -- Have tests (Chapter 11) +We’ll also briefly introduce closures, iterators, and trait objects, which +Chapters [13][ch13] and [17][ch17] will cover in +detail. -Additionally, we'll briefly introduce closures, iterators, and trait objects, -which Chapters XX, YY, and ZZ respectively are about to cover in detail. - -Let's create a new project with, as always, `cargo new`: - -```text -$ cargo new --bin greprs - Created binary (application) `greprs` project -$ cd greprs -``` - -We're calling our version of `grep` 'greprs', so that we don't confuse any of -our users into thinking that it's the more fully-featured version of `grep` -they may already have installed on their system. +[ch7]: ch07-00-managing-growing-projects-with-packages-crates-and-modules.html +[ch8]: ch08-00-common-collections.html +[ch9]: ch09-00-error-handling.html +[ch10]: ch10-00-generics.html +[ch11]: ch11-00-testing.html +[ch13]: ch13-00-functional-features.html +[ch17]: ch17-00-oop.html diff --git a/src/ch12-01-accepting-command-line-arguments.md b/src/ch12-01-accepting-command-line-arguments.md index 77e4c3f..92c9f4c 100644 --- a/src/ch12-01-accepting-command-line-arguments.md +++ b/src/ch12-01-accepting-command-line-arguments.md @@ -1,129 +1,134 @@ ## Accepting Command Line Arguments -Our first task is to have `greprs` accept its two command line arguments. There -are some existing libraries on crates.io that can help us do this, but since -we're learning, we'll implement this ourselves. +Let’s create a new project with, as always, `cargo new`. We’ll call our project +`minigrep` to distinguish it from the `grep` tool that you might already have +on your system. -We'll need to call a function provided in Rust's standard library: -`std::env::args`. This function returns an *iterator* of the command line -arguments that were given to our program. We haven't discussed iterators yet; -Chapter 13 will cover them fully. For our purposes, though, we don't need to -understand much about how they work in order to use them. We only need to -understand two things: +```console +$ cargo new minigrep + Created binary (application) `minigrep` project +$ cd minigrep +``` -1. Iterators produce a series of values. -2. We can call the `collect` function on an iterator to turn it into a vector - containing all of the elements the iterator produces. +The first task is to make `minigrep` accept its two command line arguments: the +filename and a string to search for. That is, we want to be able to run our +program with `cargo run`, a string to search for, and a path to a file to +search in, like so: -Let's give it a try as shown in Listing 12-1: +```console +$ cargo run searchstring example-filename.txt +``` + +Right now, the program generated by `cargo new` cannot process arguments we +give it. Some existing libraries on [crates.io](https://crates.io/) can help +with writing a program that accepts command line arguments, but because you’re +just learning this concept, let’s implement this capability ourselves. + +### Reading the Argument Values + +To enable `minigrep` to read the values of command line arguments we pass to +it, we’ll need a function provided in Rust’s standard library, which is +`std::env::args`. This function returns an iterator of the command line +arguments that were given to `minigrep`. We’ll cover iterators fully in +[Chapter 13][ch13]. For now, you only need to know two details +about iterators: iterators produce a series of values, and we can call the +`collect` method on an iterator to turn it into a collection, such as a vector, +containing all the elements the iterator produces. + +Use the code in Listing 12-1 to allow your `minigrep` program to read any +command line arguments passed to it and then collect the values into a vector. -
Filename: src/main.rs ```rust -use std::env; - -fn main() { - let args: Vec = env::args().collect(); - println!("{:?}", args); -} +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-01/src/main.rs}} ``` -
+Listing 12-1: Collecting the command line arguments into +a vector and printing them -Listing 12-1: Collect the command line arguments into a vector and print them out +First, we bring the `std::env` module into scope with a `use` statement so we +can use its `args` function. Notice that the `std::env::args` function is +nested in two levels of modules. As we discussed in [Chapter +7][ch7-idiomatic-use], in cases where the desired function is +nested in more than one module, it’s conventional to bring the parent module +into scope rather than the function. By doing so, we can easily use other +functions from `std::env`. It’s also less ambiguous than adding `use +std::env::args` and then calling the function with just `args`, because `args` +might easily be mistaken for a function that’s defined in the current module. -
-
+> ### The `args` Function and Invalid Unicode +> +> Note that `std::env::args` will panic if any argument contains invalid +> Unicode. If your program needs to accept arguments containing invalid +> Unicode, use `std::env::args_os` instead. That function returns an iterator +> that produces `OsString` values instead of `String` values. We’ve chosen to +> use `std::env::args` here for simplicity, because `OsString` values differ +> per platform and are more complex to work with than `String` values. - +On the first line of `main`, we call `env::args`, and we immediately use +`collect` to turn the iterator into a vector containing all the values produced +by the iterator. We can use the `collect` function to create many kinds of +collections, so we explicitly annotate the type of `args` to specify that we +want a vector of strings. Although we very rarely need to annotate types in +Rust, `collect` is one function you do often need to annotate because Rust +isn’t able to infer the kind of collection you want. -First, we have a `use` statement to bring the `std::env` module into scope. -When using a function that's nested in more than one level of module, like -`std::env::args` is, it's conventional to use `use` to bring the parent module -into scope, rather than the function itself. `env::args` is less ambiguous than -a lone `args`. Also, if we end up using more than one function in `std::env`, -we only need a single `use`. +Finally, we print the vector using the debug formatter, `:?`. Let’s try running +the code first with no arguments and then with two arguments: -On the first line of `main`, we call `env::args`, and immediately use `collect` -to create a vector out of it. We're also explicitly annotating the type of -`args` here: `collect` can be used to create many kinds of collections. Rust -won't be able to infer what kind of type we want, so the annotation is -required. We very rarely need to annotate types in Rust, but `collect` is one -function where you often need to. - -Finally, we print out the vector with the debug formatter, `:?`. Let's try -running our code with no arguments, and then with two arguments: - -```text -$ cargo run -["target/debug/greprs"] - -$ cargo run needle haystack -...snip... -["target/debug/greprs", "needle", "haystack"] +```console +{{#include ../listings/ch12-an-io-project/listing-12-01/output.txt}} ``` -You'll notice one interesting thing: the name of the binary is the first -argument. The reasons for this are out of the scope of this chapter, but it's -something we'll have to remember to account for. +```console +{{#include ../listings/ch12-an-io-project/output-only-01-with-args/output.txt}} +``` -Now that we have a way to access all of the arguments, let's find the ones we -care about and save them in variables as shown in Listing 12-2: +Notice that the first value in the vector is `"target/debug/minigrep"`, which +is the name of our binary. This matches the behavior of the arguments list in +C, letting programs use the name by which they were invoked in their execution. +It’s often convenient to have access to the program name in case you want to +print it in messages or change behavior of the program based on what command +line alias was used to invoke the program. But for the purposes of this +chapter, we’ll ignore it and save only the two arguments we need. + +### Saving the Argument Values in Variables + +Printing the value of the vector of arguments illustrated that the program is +able to access the values specified as command line arguments. Now we need to +save the values of the two arguments in variables so we can use the values +throughout the rest of the program. We do that in Listing 12-2. -
Filename: src/main.rs -```rust -use std::env; - -fn main() { - let args: Vec = env::args().collect(); - - let search = &args[1]; - let filename = &args[2]; - - println!("Searching for {}", search); - println!("In file {}", filename); -} +```rust,should_panic,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-02/src/main.rs}} ``` -
+Listing 12-2: Creating variables to hold the query +argument and filename argument -Listing 12-2: Create variables to hold the search argument and filename argument +As we saw when we printed the vector, the program’s name takes up the first +value in the vector at `args[0]`, so we’re starting at index `1`. The first +argument `minigrep` takes is the string we’re searching for, so we put a +reference to the first argument in the variable `query`. The second argument +will be the filename, so we put a reference to the second argument in the +variable `filename`. -
-
+We temporarily print the values of these variables to prove that the code is +working as we intend. Let’s run this program again with the arguments `test` +and `sample.txt`: - - -Remember, the program's name is the first argument, so we don't need `args[0]`. -We've decided that the first argument will be the string we're searching for, -so we put a reference to the first argument in the variable `search`. The -second argument will be the filename, so we put a reference to the second -argument in the variable `filename`. Let's try running this program again: - -```text -$ cargo run test sample.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe test sample.txt` -Searching for test -In file sample.txt +```console +{{#include ../listings/ch12-an-io-project/listing-12-02/output.txt}} ``` -Great! There's one problem, though. Let's try giving it no arguments: +Great, the program is working! The values of the arguments we need are being +saved into the right variables. Later we’ll add some error handling to deal +with certain potential erroneous situations, such as when the user provides no +arguments; for now, we’ll ignore that situation and work on adding file-reading +capabilities instead. -```text -$ cargo run - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe` -thread 'main' panicked at 'index out of bounds: the len is 1 -but the index is 1', ../src/libcollections\vec.rs:1307 -note: Run with `RUST_BACKTRACE=1` for a backtrace. -``` - -Because our vector only has one element, the program's name, but we tried to -access the second element, our program panics with a message about the -out-of-bound access. While this error message is _accurate_, it's not -meaningful to users of our program at all. We could fix this problem right now, -but let's push forward: we'll improve this situation before we're finished. +[ch13]: ch13-00-functional-features.html +[ch7-idiomatic-use]: ch07-04-bringing-paths-into-scope-with-the-use-keyword.html#creating-idiomatic-use-paths diff --git a/src/ch12-02-reading-a-file.md b/src/ch12-02-reading-a-file.md index 2e18123..7ba7d92 100644 --- a/src/ch12-02-reading-a-file.md +++ b/src/ch12-02-reading-a-file.md @@ -1,108 +1,58 @@ ## Reading a File -Now that we have some variables containing the information that we need, let's -try using them. The next step is to open the file that we want to search. To do -that, we need a file. Create one called `poem.txt` at the root level of your -project, and fill it up with some Emily Dickinson: +Now we’ll add functionality to read the file that is specified in the +`filename` command line argument. First, we need a sample file to test it with: +the best kind of file to use to make sure `minigrep` is working is one with a +small amount of text over multiple lines with some repeated words. Listing 12-3 +has an Emily Dickinson poem that will work well! Create a file called +*poem.txt* at the root level of your project, and enter the poem “I’m Nobody! +Who are you?” Filename: poem.txt ```text -I'm nobody! Who are you? -Are you nobody, too? -Then there's a pair of us — don't tell! -They'd banish us, you know. - -How dreary to be somebody! -How public, like a frog -To tell your name the livelong day -To an admiring bog! +{{#include ../listings/ch12-an-io-project/listing-12-03/poem.txt}} ``` - +Listing 12-3: A poem by Emily Dickinson makes a good test +case -With that in place, let's edit *src/main.rs* and add code to open the file as -shown in Listing 12-3: +With the text in place, edit *src/main.rs* and add code to read the file, as +shown in Listing 12-4. -
Filename: src/main.rs -```rust -use std::env; -use std::fs::File; -use std::io::prelude::*; - -fn main() { - let args: Vec = env::args().collect(); - - let search = &args[1]; - let filename = &args[2]; - - println!("Searching for {}", search); - println!("In file {}", filename); - - let mut f = File::open(filename).expect("file not found"); - - let mut contents = String::new(); - f.read_to_string(&mut contents).expect("something went wrong reading the file"); - - println!("With text:\n{}", contents); -} +```rust,should_panic,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-04/src/main.rs:here}} ``` -
+Listing 12-4: Reading the contents of the file specified +by the second argument -Listing 12-3: Read the contents of the file specified by the second argument +First, we add another `use` statement to bring in a relevant part of the +standard library: we need `std::fs` to handle files. -
-
+In `main`, we’ve added a new statement: `fs::read_to_string` takes the +`filename`, opens that file, and returns a `Result` of the file’s +contents. - +After that statement, we’ve again added a temporary `println!` statement that +prints the value of `contents` after the file is read, so we can check that the +program is working so far. -We've added a few things. First of all, we need some more `use` statements to -bring in the relevant parts of the standard library: we need `std::fs::File` -for dealing with files, and `std::io::prelude::*` contains various traits that -are useful when doing I/O, including file I/O. In the same way that Rust has a -general prelude that brings certain things into scope automatically, the -`std::io` module has its own prelude of common things you'll need when working -with I/O. Unlike the default prelude, we must explicitly `use` the prelude in -`std::io`. - -In `main`, we've added three things: first, we get a handle to the file and -open it by using the `File::open` function and passing it the name of the file -specified in the second argument. Second, we create a mutable, empty `String` -in the variable `contents`, then call `read_to_string` on our file handle with -our `contents` string as the argument; `contents` is where `read_to_string` -will place the data it reads. Finally, we print out the entire file contents, -which is a way for us to be sure our program is working so far. - -Let's try running this code, specifying any string for the first argument (since -we haven't implemented the searching part yet) and our *poem.txt* file as the +Let’s run this code with any string as the first command line argument (because +we haven’t implemented the searching part yet) and the *poem.txt* file as the second argument: -```text -$ cargo run the poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe the poem.txt` -Searching for the -In file poem.txt -With text: -I'm nobody! Who are you? -Are you nobody, too? -Then there's a pair of us — don't tell! -They'd banish us, you know. - -How dreary to be somebody! -How public, like a frog -To tell your name the livelong day -To an admiring bog! +```console +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-04/output.txt}} ``` -Great! Our code is working. However, it's got a few flaws. Because our program -is still small, these flaws aren't a huge deal, but as our program grows, it -will be harder and harder to fix them in a clean way. Let's do the refactoring -now, instead of waiting. The refactoring will be much easier to do with only -this small amount of code. +Great! The code read and then printed the contents of the file. But the code +has a few flaws. The `main` function has multiple responsibilities: generally, +functions are clearer and easier to maintain if each function is responsible +for only one idea. The other problem is that we’re not handling errors as well +as we could. The program is still small, so these flaws aren’t a big problem, +but as the program grows, it will be harder to fix them cleanly. It’s good +practice to begin refactoring early on when developing a program, because it’s +much easier to refactor smaller amounts of code. We’ll do that next. diff --git a/src/ch12-03-improving-error-handling-and-modularity.md b/src/ch12-03-improving-error-handling-and-modularity.md index abc3b65..32f0e57 100644 --- a/src/ch12-03-improving-error-handling-and-modularity.md +++ b/src/ch12-03-improving-error-handling-and-modularity.md @@ -1,876 +1,503 @@ -## Improving Error Handling and Modularity +## Refactoring to Improve Modularity and Error Handling -There are four problems that we'd like to fix to improve our program, and they -all have to do with potential errors and the way the program is structured. The -first problem is where we open the file: we've used `expect` to print out an -error message if opening the file fails, but the error message only says "file -not found". There are a number of ways that opening a file can fail, but we're -always assuming that it's due to the file being missing. For example, the file -could exist, but we might not have permission to open it: right now, we print -an error message that says the wrong thing! +To improve our program, we’ll fix four problems that have to do with the +program’s structure and how it’s handling potential errors. -Secondly, our use of `expect` over and over is similar to the earlier issue we -noted with the `panic!` on indexing if we don't pass any command line -arguments: while it _works_, it's a bit unprincipled, and we're doing it all -throughout our program. It would be nice to put our error handling in one spot. +First, our `main` function now performs two tasks: it parses arguments and +reads files. For such a small function, this isn’t a major problem. However, if +we continue to grow our program inside `main`, the number of separate tasks the +`main` function handles will increase. As a function gains responsibilities, it +becomes more difficult to reason about, harder to test, and harder to change +without breaking one of its parts. It’s best to separate functionality so each +function is responsible for one task. -The third problem is that our `main` function now does two things: it parses -arguments, and it opens up files. For such a small function, this isn't a huge -problem. However, as we keep growing our program inside of `main`, the number of -separate tasks in the `main` function will get larger and larger. As one -function gains many responsibilities, it gets harder to reason about, harder to -test, and harder to change without breaking one of its parts. +This issue also ties into the second problem: although `query` and `filename` +are configuration variables to our program, variables like `contents` are used +to perform the program’s logic. The longer `main` becomes, the more variables +we’ll need to bring into scope; the more variables we have in scope, the harder +it will be to keep track of the purpose of each. It’s best to group the +configuration variables into one structure to make their purpose clear. -This also ties into our fourth problem: while `search` and `filename` are -configuration variables to our program, variables like `f` and `contents` are -used to perform our program's logic. The longer `main` gets, the more variables -we're going to bring into scope, and the more variables we have in scope, the -harder it is to keep track of which ones we need for which purpose. It would be -better if we grouped the configuration variables into one structure to make -their purpose clear. +The third problem is that we’ve used `expect` to print an error message when +reading the file fails, but the error message just prints `Something went wrong +reading the file`. Reading a file can fail in a number of ways: for example, +the file could be missing, or we might not have permission to open it. Right +now, regardless of the situation, we’d print the `Something went wrong reading +the file` error message, which wouldn’t give the user any information! -Let's address these problems by restructuring our project. +Fourth, we use `expect` repeatedly to handle different errors, and if the user +runs our program without specifying enough arguments, they’ll get an `index out +of bounds` error from Rust that doesn’t clearly explain the problem. It would +be best if all the error-handling code were in one place so future maintainers +had only one place to consult in the code if the error-handling logic needed to +change. Having all the error-handling code in one place will also ensure that +we’re printing messages that will be meaningful to our end users. + +Let’s address these four problems by refactoring our project. ### Separation of Concerns for Binary Projects -These kinds of organizational problems are common to many similar kinds of -projects, so the Rust community has developed a pattern for organizing the -separate concerns. This pattern is useful for organizing any binary project -you'll build in Rust, so we can justify doing this refactoring a bit earlier, -since we know that our project fits the pattern. The pattern looks like this: +The organizational problem of allocating responsibility for multiple tasks to +the `main` function is common to many binary projects. As a result, the Rust +community has developed a process to use as a guideline for splitting the +separate concerns of a binary program when `main` starts getting large. The +process has the following steps: -1. Split your program into both a *main.rs* and a *lib.rs*. -2. Place your command line parsing logic into *main.rs*. -3. Place your program's logic into *lib.rs*. -4. The job of the `main` function is: - * parse arguments - * set up any other configuration - * call a `run` function in *lib.rs* - * if `run` returns an error, handle that error +* Split your program into a *main.rs* and a *lib.rs* and move your program’s + logic to *lib.rs*. +* As long as your command line parsing logic is small, it can remain in + *main.rs*. +* When the command line parsing logic starts getting complicated, extract it + from *main.rs* and move it to *lib.rs*. -Whew! The pattern sounds more complicated than it is, honestly. It's all about -separating concerns: *main.rs* handles actually running the program, and -*lib.rs* handles all of the actual logic of the task at hand. Let's re-work our -program into this pattern. First, let's extract a function whose purpose is -only to parse arguments. Listing 12-4 shows the new start of `main` that calls -a new function `parse_config`, which we're still going to define in -*src/main.rs*: +The responsibilities that remain in the `main` function after this process +should be limited to the following: + +* Calling the command line parsing logic with the argument values +* Setting up any other configuration +* Calling a `run` function in *lib.rs* +* Handling the error if `run` returns an error + +This pattern is about separating concerns: *main.rs* handles running the +program, and *lib.rs* handles all the logic of the task at hand. Because you +can’t test the `main` function directly, this structure lets you test all of +your program’s logic by moving it into functions in *lib.rs*. The only code +that remains in *main.rs* will be small enough to verify its correctness by +reading it. Let’s rework our program by following this process. + +#### Extracting the Argument Parser + +We’ll extract the functionality for parsing arguments into a function that +`main` will call to prepare for moving the command line parsing logic to +*src/lib.rs*. Listing 12-5 shows the new start of `main` that calls a new +function `parse_config`, which we’ll define in *src/main.rs* for the moment. -
Filename: src/main.rs -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# -fn main() { - let args: Vec = env::args().collect(); - - let (search, filename) = parse_config(&args); - - println!("Searching for {}", search); - println!("In file {}", filename); - - // ...snip... -# -# let mut f = File::open(filename).expect("file not found"); -# -# let mut contents = String::new(); -# f.read_to_string(&mut contents).expect("something went wrong reading the file"); -# -# println!("With text:\n{}", contents); -} - -fn parse_config(args: &[String]) -> (&str, &str) { - let search = &args[1]; - let filename = &args[2]; - - (search, filename) -} +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-05/src/main.rs:here}} ``` -
+Listing 12-5: Extracting a `parse_config` function from +`main` -Listing 12-4: Extract a `parse_config` function from `main` +We’re still collecting the command line arguments into a vector, but instead of +assigning the argument value at index 1 to the variable `query` and the +argument value at index 2 to the variable `filename` within the `main` +function, we pass the whole vector to the `parse_config` function. The +`parse_config` function then holds the logic that determines which argument +goes in which variable and passes the values back to `main`. We still create +the `query` and `filename` variables in `main`, but `main` no longer has the +responsibility of determining how the command line arguments and variables +correspond. -
-
+This rework may seem like overkill for our small program, but we’re refactoring +in small, incremental steps. After making this change, run the program again to +verify that the argument parsing still works. It’s good to check your progress +often, to help identify the cause of problems when they occur. - +#### Grouping Configuration Values -This may seem like overkill, but we're working in small steps. After making -this change, run the program again to verify that the argument parsing still -works. It's good to check your progress often, so that you have a better idea -of which change caused a problem, should you encounter one. +We can take another small step to improve the `parse_config` function further. +At the moment, we’re returning a tuple, but then we immediately break that +tuple into individual parts again. This is a sign that perhaps we don’t have +the right abstraction yet. -### Grouping Configuration Values +Another indicator that shows there’s room for improvement is the `config` part +of `parse_config`, which implies that the two values we return are related and +are both part of one configuration value. We’re not currently conveying this +meaning in the structure of the data other than by grouping the two values into +a tuple; we could put the two values into one struct and give each of the +struct fields a meaningful name. Doing so will make it easier for future +maintainers of this code to understand how the different values relate to each +other and what their purpose is. -Now that we have a function, let's improve it. Our code still has an indication -that there's a better design possible: we return a tuple, but then immediately -break that tuple up into individual parts again. This code isn't bad on its -own, but there's one other sign we have room for improvement: we called our -function `parse_config`. The `config` part of the name is saying the two values -we return should really be bound together, since they're both part of one -configuration value. +> Note: Using primitive values when a complex type would be more appropriate is +> an anti-pattern known as *primitive obsession*. -> Note: some people call this anti-pattern of using primitive values when a -> complex type would be more appropriate *primitive obsession*. +Listing 12-6 shows the improvements to the `parse_config` function. -Let's introduce a struct to hold all of our configuration. Listing 12-5 shows -the addition of the `Config` struct definition, the refactoring of -`parse_config`, and updates to `main`: - -
Filename: src/main.rs -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# -fn main() { - let args: Vec = env::args().collect(); - - let config = parse_config(&args); - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - let mut f = File::open(config.filename).expect("file not found"); - - // ...snip... -# let mut contents = String::new(); -# f.read_to_string(&mut contents).expect("something went wrong reading the file"); -# -# println!("With text:\n{}", contents); -} - -struct Config { - search: String, - filename: String, -} - -fn parse_config(args: &[String]) -> Config { - let search = args[1].clone(); - let filename = args[2].clone(); - - Config { - search: search, - filename: filename, - } -} +```rust,should_panic,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-06/src/main.rs:here}} ``` -
+Listing 12-6: Refactoring `parse_config` to return an +instance of a `Config` struct -Listing 12-5: Refactoring `parse_config` to return an instance of a `Config` -struct +We’ve added a struct named `Config` defined to have fields named `query` and +`filename`. The signature of `parse_config` now indicates that it returns a +`Config` value. In the body of `parse_config`, where we used to return string +slices that reference `String` values in `args`, we now define `Config` to +contain owned `String` values. The `args` variable in `main` is the owner of +the argument values and is only letting the `parse_config` function borrow +them, which means we’d violate Rust’s borrowing rules if `Config` tried to take +ownership of the values in `args`. -
-
+We could manage the `String` data in a number of different ways, but the +easiest, though somewhat inefficient, route is to call the `clone` method on +the values. This will make a full copy of the data for the `Config` instance to +own, which takes more time and memory than storing a reference to the string +data. However, cloning the data also makes our code very straightforward +because we don’t have to manage the lifetimes of the references; in this +circumstance, giving up a little performance to gain simplicity is a worthwhile +trade-off. - - -The signature of `parse_config` now indicates that it returns a `Config` value. -In the body of `parse_config`, we used to be returning string slices that were -references to `String` values in `args`, but we've defined `Config` to contain -owned `String` values. Because the argument to `parse_config` is a slice of -`String` values, the `Config` instance can't take ownership of the `String` -values: that violates Rust's borrowing rules, since the `args` variable in -`main` owns the `String` values and is only letting the `parse_config` function -borrow them. - -There are a number of different ways we could manage the `String` data; for -now, we'll take the easy but less efficient route, and call the `clone` method -on the string slices. The call to `clone` will make a full copy of the string's -data for the `Config` instance to own, which does take more time and memory -than storing a reference to the string data, but cloning the data makes our -code very straightforward. - - - -> #### The Tradeoffs of Using `clone` +> ### The Trade-Offs of Using `clone` > -> There's a tendency amongst many Rustaceans to prefer not to use `clone` to fix -> ownership problems due to its runtime cost. In Chapter XX on iterators, we'll -> learn how to make this situation more efficient. For now, it's okay to copy a -> few strings to keep making progress. We're only going to be making these -> copies once, and our filename and search string are both very small. It's -> better to have a working program that's a bit inefficient than try to -> hyper-optimize code on your first pass. As you get more experienced with Rust, -> it'll be easier to skip this step, but for now, it's perfectly acceptable to -> call `clone`. +> There’s a tendency among many Rustaceans to avoid using `clone` to fix +> ownership problems because of its runtime cost. In +> [Chapter 13][ch13], you’ll learn how to use more efficient +> methods in this type of situation. But for now, it’s okay to copy a few +> strings to continue making progress because you’ll make these copies only +> once and your filename and query string are very small. It’s better to have +> a working program that’s a bit inefficient than to try to hyperoptimize code +> on your first pass. As you become more experienced with Rust, it’ll be +> easier to start with the most efficient solution, but for now, it’s +> perfectly acceptable to call `clone`. - +We’ve updated `main` so it places the instance of `Config` returned by +`parse_config` into a variable named `config`, and we updated the code that +previously used the separate `query` and `filename` variables so it now uses +the fields on the `Config` struct instead. -We've updated `main` to put the instance of `Config` that `parse_config` -returns in a variable named `config`, and we've updated the code that was using -the separate `search` and `filename` variables to use the fields on the -`Config` struct instead. +Now our code more clearly conveys that `query` and `filename` are related and +that their purpose is to configure how the program will work. Any code that +uses these values knows to find them in the `config` instance in the fields +named for their purpose. -### Creating a Constructor for `Config` +#### Creating a Constructor for `Config` -Let's now think about the purpose of `parse_config`: it's a function that -creates a `Config` instance. We've already seen a convention for functions that -create instances: a `new` function, like `String::new`. Listing 12-6 shows the -result of transforming `parse_config` into a `new` function associated with our -`Config` struct: +So far, we’ve extracted the logic responsible for parsing the command line +arguments from `main` and placed it in the `parse_config` function. Doing so +helped us to see that the `query` and `filename` values were related and that +relationship should be conveyed in our code. We then added a `Config` struct to +name the related purpose of `query` and `filename` and to be able to return the +values’ names as struct field names from the `parse_config` function. + +So now that the purpose of the `parse_config` function is to create a `Config` +instance, we can change `parse_config` from a plain function to a function +named `new` that is associated with the `Config` struct. Making this change +will make the code more idiomatic. We can create instances of types in the +standard library, such as `String`, by calling `String::new`. Similarly, by +changing `parse_config` into a `new` function associated with `Config`, we’ll +be able to create instances of `Config` by calling `Config::new`. Listing 12-7 +shows the changes we need to make. -
Filename: src/main.rs -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args); - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - // ...snip... - -# let mut f = File::open(config.filename).expect("file not found"); -# -# let mut contents = String::new(); -# f.read_to_string(&mut contents).expect("something went wrong reading the file"); -# -# println!("With text:\n{}", contents); - -} - -# struct Config { -# search: String, -# filename: String, -# } -# -// ...snip... - -impl Config { - fn new(args: &[String]) -> Config { - let search = args[1].clone(); - let filename = args[2].clone(); - - Config { - search: search, - filename: filename, - } - } -} +```rust,should_panic,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-07/src/main.rs:here}} ``` -
+Listing 12-7: Changing `parse_config` into +`Config::new` -Listing 12-6: Changing `parse_config` into `Config::new` +We’ve updated `main` where we were calling `parse_config` to instead call +`Config::new`. We’ve changed the name of `parse_config` to `new` and moved it +within an `impl` block, which associates the `new` function with `Config`. Try +compiling this code again to make sure it works. -
-
+### Fixing the Error Handling - +Now we’ll work on fixing our error handling. Recall that attempting to access +the values in the `args` vector at index 1 or index 2 will cause the program to +panic if the vector contains fewer than three items. Try running the program +without any arguments; it will look like this: -We've changed the name of `parse_config` to `new` and moved it within an `impl` -block. We've also updated the callsite in `main`. Try compiling this again to -make sure it works. +```console +{{#include ../listings/ch12-an-io-project/listing-12-07/output.txt}} +``` -### Returning a `Result` from the Constructor +The line `index out of bounds: the len is 1 but the index is 1` is an error +message intended for programmers. It won’t help our end users understand what +happened and what they should do instead. Let’s fix that now. -Here's our last refactoring of this method: remember how accessing the vector -with indices 1 and 2 panics when it contains fewer than 3 items and gives a bad -error message? Let's fix that! Listing 12-7 shows how we can check that our -slice is long enough before accessing those locations, and panic with a better -error message: +#### Improving the Error Message + +In Listing 12-8, we add a check in the `new` function that will verify that the +slice is long enough before accessing index 1 and 2. If the slice isn’t long +enough, the program panics and displays a better error message than the `index +out of bounds` message. -
Filename: src/main.rs -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# -# fn main() { -# let args: Vec = env::args().collect(); -# -# let config = Config::new(&args); -# -# println!("Searching for {}", config.search); -# println!("In file {}", config.filename); -# -# let mut f = File::open(config.filename).expect("file not found"); -# -# let mut contents = String::new(); -# f.read_to_string(&mut contents).expect("something went wrong reading the file"); -# -# println!("With text:\n{}", contents); -# } -# -# struct Config { -# search: String, -# filename: String, -# } -# -# impl Config { -// ...snip... -fn new(args: &[String]) -> Config { - if args.len() < 3 { - panic!("not enough arguments"); - } - - let search = args[1].clone(); - // ...snip... -# let filename = args[2].clone(); -# -# Config { -# search: search, -# filename: filename, -# } -} -# } +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-08/src/main.rs:here}} ``` -
+Listing 12-8: Adding a check for the number of +arguments -Listing 12-7: Adding a check for the number of arguments +This code is similar to [the `Guess::new` function we wrote in Listing +9-10][ch9-custom-types], where we called `panic!` when the +`value` argument was out of the range of valid values. Instead of checking for +a range of values here, we’re checking that the length of `args` is at least 3 +and the rest of the function can operate under the assumption that this +condition has been met. If `args` has fewer than three items, this condition +will be true, and we call the `panic!` macro to end the program immediately. -
-
+With these extra few lines of code in `new`, let’s run the program without any +arguments again to see what the error looks like now: - - -With these extra few lines of code in `new`, let's try running our program -without any arguments: - -```text -$ cargo run - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe` -thread 'main' panicked at 'not enough arguments', src\main.rs:29 -note: Run with `RUST_BACKTRACE=1` for a backtrace. +```console +{{#include ../listings/ch12-an-io-project/listing-12-08/output.txt}} ``` -This is a bit better! We at least have a reasonable error message here. -However, we also have a bunch of extra information that we don't want to give -to our users. We can do better by changing the type signature of `new`. Right -now, it returns only a `Config`, so there's no way to indicate that an error -happened while creating our `Config`. Instead, we can return a `Result`, as -shown in Listing 12-8: +This output is better: we now have a reasonable error message. However, we also +have extraneous information we don’t want to give to our users. Perhaps using +the technique we used in Listing 9-10 isn’t the best to use here: a call to +`panic!` is more appropriate for a programming problem than a usage problem, +[as discussed in Chapter 9][ch9-error-guidelines]. Instead, we +can use the other technique you learned about in Chapter 9—[returning a +`Result`][ch9-result] that indicates either success or an error. + +#### Returning a `Result` from `new` Instead of Calling `panic!` + +We can instead return a `Result` value that will contain a `Config` instance in +the successful case and will describe the problem in the error case. When +`Config::new` is communicating to `main`, we can use the `Result` type to +signal there was a problem. Then we can change `main` to convert an `Err` +variant into a more practical error for our users without the surrounding text +about `thread 'main'` and `RUST_BACKTRACE` that a call to `panic!` causes. + +Listing 12-9 shows the changes we need to make to the return value of +`Config::new` and the body of the function needed to return a `Result`. Note +that this won’t compile until we update `main` as well, which we’ll do in the +next listing. -
Filename: src/main.rs -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# use std::process; -# -# fn main() { -# let args: Vec = env::args().collect(); -# -# let config = Config::new(&args).unwrap_or_else(|err| { -# println!("Problem parsing arguments: {}", err); -# process::exit(1); -# }); -# -# println!("Searching for {}", config.search); -# println!("In file {}", config.filename); -# -# let mut f = File::open(config.filename).expect("file not found"); -# -# let mut contents = String::new(); -# f.read_to_string(&mut contents).expect("something went wrong reading the file"); -# -# println!("With text:\n{}", contents); -# } -# struct Config { -# search: String, -# filename: String, -# } -# -impl Config { - fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - Ok(Config { - search: search, - filename: filename, - }) - } -} +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-09/src/main.rs:here}} ``` -
+Listing 12-9: Returning a `Result` from +`Config::new` -Listing 12-8: Return a `Result` from `Config::new` +Our `new` function now returns a `Result` with a `Config` instance in the +success case and a `&str` in the error case. -
-
+We’ve made two changes in the body of the `new` function: instead of calling +`panic!` when the user doesn’t pass enough arguments, we now return an `Err` +value, and we’ve wrapped the `Config` return value in an `Ok`. These changes +make the function conform to its new type signature. - +Returning an `Err` value from `Config::new` allows the `main` function to +handle the `Result` value returned from the `new` function and exit the process +more cleanly in the error case. -Our `new` function now returns a `Result`, with a `Config` instance in the -success case and a `&'static str` when an error happens. Recall from "The -Static Lifetime" section in Chapter 10 `&'static str` is the type of string -literals, which is what our error message is for now. +#### Calling `Config::new` and Handling Errors -We've made two changes in the body of the `new` function: instead of calling -`panic!` if there aren't enough arguments, we now return an `Err` value. We -wrapped the `Config` return value in an `Ok`. These changes make the function -conform to its new type signature. +To handle the error case and print a user-friendly message, we need to update +`main` to handle the `Result` being returned by `Config::new`, as shown in +Listing 12-10. We’ll also take the responsibility of exiting the command line +tool with a nonzero error code from `panic!` and implement it by hand. A +nonzero exit status is a convention to signal to the process that called our +program that the program exited with an error state. -### Calling `Config::new` and Handling Errors - -Now we need to make some changes to `main` as shown in Listing 12-9: - -
Filename: src/main.rs -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -// ...snip... -use std::process; - -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args).unwrap_or_else(|err| { - println!("Problem parsing arguments: {}", err); - process::exit(1); - }); - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - // ...snip... -# -# let mut f = File::open(config.filename).expect("file not found"); -# -# let mut contents = String::new(); -# f.read_to_string(&mut contents).expect("something went wrong reading the file"); -# -# println!("With text:\n{}", contents); -# } -# -# struct Config { -# search: String, -# filename: String, -# } -# -# impl Config { -# fn new(args: &[String]) -> Result { -# if args.len() < 3 { -# return Err("not enough arguments"); -# } -# -# let search = args[1].clone(); -# let filename = args[2].clone(); -# -# Ok(Config { -# search: search, -# filename: filename, -# }) -# } -# } +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-10/src/main.rs:here}} ``` -
+Listing 12-10: Exiting with an error code if creating a +new `Config` fails -Listing 12-9: Exiting with an error code if creating a new `Config` fails +In this listing, we’ve used a method we haven’t covered in detail yet: +`unwrap_or_else`, which is defined on `Result` by the standard library. +Using `unwrap_or_else` allows us to define some custom, non-`panic!` error +handling. If the `Result` is an `Ok` value, this method’s behavior is similar +to `unwrap`: it returns the inner value `Ok` is wrapping. However, if the value +is an `Err` value, this method calls the code in the *closure*, which is an +anonymous function we define and pass as an argument to `unwrap_or_else`. We’ll +cover closures in more detail in [Chapter 13][ch13]. For now, +you just need to know that `unwrap_or_else` will pass the inner value of the +`Err`, which in this case is the static string `"not enough arguments"` that we +added in Listing 12-9, to our closure in the argument `err` that appears +between the vertical pipes. The code in the closure can then use the `err` +value when it runs. -
-
+We’ve added a new `use` line to bring `process` from the standard library into +scope. The code in the closure that will be run in the error case is only two +lines: we print the `err` value and then call `process::exit`. The +`process::exit` function will stop the program immediately and return the +number that was passed as the exit status code. This is similar to the +`panic!`-based handling we used in Listing 12-8, but we no longer get all the +extra output. Let’s try it: - - -We've added a new `use` line to import `process` from the standard library. -In the `main` function itself, we'll handle the `Result` value returned -from the `new` function and exit the process in a cleaner way if `Config::new` -returns an `Err` value. - -We're using a method we haven't covered before that's defined on `Result` -by the standard library: `unwrap_or_else`. This method has similar behavior as -`unwrap` if the `Result` is an `Ok` value: it returns the inner value `Ok` is -wrapping. Unlike `unwrap`, if the value is an `Err` value, this method calls a -*closure* which is an anonymous function that we define and pass as an argument -to `unwrap_or_else`. We'll be covering closures in more detail in Chapter XX; -the important part to understand in this case is that `unwrap_or_else` will -pass the inner value of the `Err` to our closure in the parameter `err` that -appears between the vertical pipes. Using `unwrap_or_else` lets us do some -custom, non-`panic!` error handling. - -Said error handling is only two lines: we print out the error, then call -`std::process::exit`. That function will stop our program's execution -immediately and return the number passed to it as a return code. By convention, -a zero means success and any other value means failure. In the end, this has -similar characteristics to our `panic!`-based handling we had in Listing 12-7, -but we no longer get all the extra output. Let's try it: - -```text -$ cargo run - Compiling greprs v0.1.0 (file:///projects/greprs) - Finished debug [unoptimized + debuginfo] target(s) in 0.48 secs - Running `target\debug\greprs.exe` -Problem parsing arguments: not enough arguments +```console +{{#include ../listings/ch12-an-io-project/listing-12-10/output.txt}} ``` Great! This output is much friendlier for our users. -### Handling Errors from the `run` Function +### Extracting Logic from `main` -Now that we're done refactoring our configuration parsing, let's improve our -program's logic. Listing 12-10 shows the code after extracting a function named -`run` that we'll call from `main`. The `run` function contains the code that -was in `main`: +Now that we’ve finished refactoring the configuration parsing, let’s turn to +the program’s logic. As we stated in [“Separation of Concerns for Binary +Projects”](#separation-of-concerns-for-binary-projects), we’ll +extract a function named `run` that will hold all the logic currently in the +`main` function that isn’t involved with setting up configuration or handling +errors. When we’re done, `main` will be concise and easy to verify by +inspection, and we’ll be able to write tests for all the other logic. -
-Filename: src/main.rs - -```rust -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# use std::process; -# -fn main() { -# let args: Vec = env::args().collect(); -# -# let config = Config::new(&args).unwrap_or_else(|err| { -# println!("Problem parsing arguments: {}", err); -# process::exit(1); -# }); - // ...snip... - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - run(config); -} - -fn run(config: Config) { - let mut f = File::open(config.filename).expect("file not found"); - - let mut contents = String::new(); - f.read_to_string(&mut contents).expect("something went wrong reading the file"); - - println!("With text:\n{}", contents); -} - -// ...snip... -# -# struct Config { -# search: String, -# filename: String, -# } -# -# impl Config { -# fn new(args: &[String]) -> Result { -# if args.len() < 3 { -# return Err("not enough arguments"); -# } -# -# let search = args[1].clone(); -# let filename = args[2].clone(); -# -# Ok(Config { -# search: search, -# filename: filename, -# }) -# } -# } -``` - -
- -Listing 12-10: Extracting a `run` functionality for the rest of the program logic - -
-
- - - -The contents of `run` are the previous lines that were in `main`, and the `run` -function takes a `Config` as an argument. Now that we have a separate function, -we can make a similar improvement to the one we made to `Config::new` in -Listing 12-8: let's return a `Result` instead of calling `panic!` via -`expect`. Listing 12-11 shows the addition of a `use` statement to bring -`std::error::Error` struct into scope and the changes to the `run` function -to return a `Result`: - -
-Filename: src/main.rs - -```rust -use std::error::Error; -# use std::env; -# use std::fs::File; -# use std::io::prelude::*; -# use std::process; - -// ...snip... -# fn main() { -# let args: Vec = env::args().collect(); -# -# let config = Config::new(&args).unwrap_or_else(|err| { -# println!("Problem parsing arguments: {}", err); -# process::exit(1); -# }); -# -# println!("Searching for {}", config.search); -# println!("In file {}", config.filename); -# -# run(config); -# -# } - -fn run(config: Config) -> Result<(), Box> { - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - println!("With text:\n{}", contents); - - Ok(()) -} -# -# struct Config { -# search: String, -# filename: String, -# } -# -# impl Config { -# fn new(args: &[String]) -> Result { -# if args.len() < 3 { -# return Err("not enough arguments"); -# } -# -# let search = args[1].clone(); -# let filename = args[2].clone(); -# -# Ok(Config { -# search: search, -# filename: filename, -# }) -# } -# } -``` - -
- -Listing 12-11: Changing the `run` function to return `Result` - -
-
- - - -We've made three big changes here. The first is the return type of the `run` -function is now `Result<(), Box>`. Previously, our function returned the -unit type, `()`, so that's still the value returned in the `Ok` case. For our -error type, we're going to use `Box`. This is called a *trait object*, -which we'll be covering in Chapter XX. For now, think of it like this: -`Box` means the function will return some kind of type that implements -the `Error` trait, but we're not specifying what particular type the return -value will be. This gives us flexibility to return error values that may be of -different types in different error cases. `Box` is a smart pointer to heap -data, and we'll be going into detail about `Box` in Chapter YY. - -The second change is that we've removed our calls to `expect` in favor of `?`, -like we talked about in Chapter 9. Rather than `panic!` on an error, this will -return the error value from the function we're in for the caller to handle. - -The third change is that we're now returning an `Ok` value from this function -in the success case. Because we've declared the `run` function's success type -as `()` in the signature, we need to wrap the unit type value in the `Ok` -value. `Ok(())` looks a bit strange at first, but using `()` in this way is the -idiomatic way to indicate that we're calling `run` for its side effects only; -it doesn't return anything interesting. - -This will compile, but with a warning: - -```text -warning: unused result which must be used, #[warn(unused_must_use)] on by default - --> src\main.rs:39:5 - | -39 | run(config); - | ^^^^^^^^^^^^ -``` - -Rust is trying to tell us that we're ignoring our `Result`, which might be an -error value. Let's handle that now. We'll use a similar technique as the way we -handled failure with `Config::new` in Listing 12-9, but with a slight -difference: +Listing 12-11 shows the extracted `run` function. For now, we’re just making +the small, incremental improvement of extracting the function. We’re still +defining the function in *src/main.rs*. Filename: src/main.rs ```rust,ignore -fn main() { - // ...snip... - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - if let Err(e) = run(config) { - println!("Application error: {}", e); - - process::exit(1); - } -} - -fn run(config: Config) -> Result<(), Box> { - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - println!("With text:\n{}", contents); - - Ok(()) -} +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-11/src/main.rs:here}} ``` - +Listing 12-11: Extracting a `run` function containing the +rest of the program logic -Instead of `unwrap_or_else`, we use `if let` to see if `run` returns an `Err` -value and call `process::exit(1)` if so. Why? The distinction between this case -and the `Config::new` case is a bit subtle. With `Config::new`, we cared about -two things: +The `run` function now contains all the remaining logic from `main`, starting +from reading the file. The `run` function takes the `Config` instance as an +argument. -1. Detecting any errors that happen -2. Getting a `Config` if no errors happened +#### Returning Errors from the `run` Function -In this case, because `run` returns a `()` in the success case, the only thing -we care about is the first case: detecting an error. If we used -`unwrap_or_else`, we'd get its return value, which would be `()`. That's not -very useful. +With the remaining program logic separated into the `run` function, we can +improve the error handling, as we did with `Config::new` in Listing 12-9. +Instead of allowing the program to panic by calling `expect`, the `run` +function will return a `Result` when something goes wrong. This will let +us further consolidate into `main` the logic around handling errors in a +user-friendly way. Listing 12-12 shows the changes we need to make to the +signature and body of `run`. -The bodies of the `if let` and of the `unwrap_or_else` are the same in both -cases though: we print out an error and exit. +Filename: src/main.rs -### Split Code into a Library Crate +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-12/src/main.rs:here}} +``` -This is looking pretty good! There's one more thing we haven't done yet: split -the *src/main.rs* up and put some code into *src/lib.rs* Let's do that now: -move the `run` function from *src/main.rs* to a new file, *src/lib.rs*. You'll -also need to move the relevant `use` statements and the definition of `Config` -and its `new` method as well. Your *src/lib.rs* should now look like Listing -12-12: +Listing 12-12: Changing the `run` function to return +`Result` + +We’ve made three significant changes here. First, we changed the return type of +the `run` function to `Result<(), Box>`. This function previously +returned the unit type, `()`, and we keep that as the value returned in the +`Ok` case. + +For the error type, we used the *trait object* `Box` (and we’ve +brought `std::error::Error` into scope with a `use` statement at the top). +We’ll cover trait objects in [Chapter 17][ch17]. For now, just +know that `Box` means the function will return a type that +implements the `Error` trait, but we don’t have to specify what particular type +the return value will be. This gives us flexibility to return error values that +may be of different types in different error cases. The `dyn` keyword is short +for “dynamic.” + +Second, we’ve removed the call to `expect` in favor of the `?` operator, as we +talked about in [Chapter 9][ch9-question-mark]. Rather than +`panic!` on an error, `?` will return the error value from the current function +for the caller to handle. + +Third, the `run` function now returns an `Ok` value in the success case. We’ve +declared the `run` function’s success type as `()` in the signature, which +means we need to wrap the unit type value in the `Ok` value. This `Ok(())` +syntax might look a bit strange at first, but using `()` like this is the +idiomatic way to indicate that we’re calling `run` for its side effects only; +it doesn’t return a value we need. + +When you run this code, it will compile but will display a warning: + +```console +{{#include ../listings/ch12-an-io-project/listing-12-12/output.txt}} +``` + +Rust tells us that our code ignored the `Result` value and the `Result` value +might indicate that an error occurred. But we’re not checking to see whether or +not there was an error, and the compiler reminds us that we probably meant to +have some error-handling code here! Let’s rectify that problem now. + +#### Handling Errors Returned from `run` in `main` + +We’ll check for errors and handle them using a technique similar to one we used +with `Config::new` in Listing 12-10, but with a slight difference: + +Filename: src/main.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/src/main.rs:here}} +``` + +We use `if let` rather than `unwrap_or_else` to check whether `run` returns an +`Err` value and call `process::exit(1)` if it does. The `run` function doesn’t +return a value that we want to `unwrap` in the same way that `Config::new` +returns the `Config` instance. Because `run` returns `()` in the success case, +we only care about detecting an error, so we don’t need `unwrap_or_else` to +return the unwrapped value because it would only be `()`. + +The bodies of the `if let` and the `unwrap_or_else` functions are the same in +both cases: we print the error and exit. + +### Splitting Code into a Library Crate + +Our `minigrep` project is looking good so far! Now we’ll split the +*src/main.rs* file and put some code into the *src/lib.rs* file so we can test +it and have a *src/main.rs* file with fewer responsibilities. + +Let’s move all the code that isn’t the `main` function from *src/main.rs* to +*src/lib.rs*: + +* The `run` function definition +* The relevant `use` statements +* The definition of `Config` +* The `Config::new` function definition + +The contents of *src/lib.rs* should have the signatures shown in Listing 12-13 +(we’ve omitted the bodies of the functions for brevity). Note that this won’t +compile until we modify *src/main.rs* in Listing 12-14. -
Filename: src/lib.rs -```rust -use std::error::Error; -use std::fs::File; -use std::io::prelude::*; - -pub struct Config { - pub search: String, - pub filename: String, -} - -impl Config { - pub fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - Ok(Config { - search: search, - filename: filename, - }) - } -} - -pub fn run(config: Config) -> Result<(), Box>{ - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - println!("With text:\n{}", contents); - - Ok(()) -} +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-13/src/lib.rs:here}} ``` -
+Listing 12-13: Moving `Config` and `run` into +*src/lib.rs* -Listing 12-12: Moving `Config` and `run` into *src/lib.rs* +We’ve made liberal use of the `pub` keyword: on `Config`, on its fields and its +`new` method, and on the `run` function. We now have a library crate that has a +public API that we can test! -
-
+Now we need to bring the code we moved to *src/lib.rs* into the scope of the +binary crate in *src/main.rs*, as shown in Listing 12-14. - - -Notice we also made liberal use of `pub`: on `Config`, its fields and its `new` -method, and on the `run` function. - -Now in *src/main.rs*, we need to bring in the code that's now in *src/lib.rs* -through `extern crate greprs`. Then we need to add a `use greprs::Config` line -to bring `Config` into scope, and prefix the `run` function with our crate name -as shown in Listing 12-13: - -
Filename: src/main.rs ```rust,ignore -extern crate greprs; - -use std::env; -use std::process; - -use greprs::Config; - -fn main() { - let args: Vec = env::args().collect(); - - let config = Config::new(&args).unwrap_or_else(|err| { - println!("Problem parsing arguments: {}", err); - process::exit(1); - }); - - println!("Searching for {}", config.search); - println!("In file {}", config.filename); - - if let Err(e) = greprs::run(config) { - println!("Application error: {}", e); - - process::exit(1); - } -} +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-14/src/main.rs:here}} ``` -
+Listing 12-14: Using the `minigrep` library crate in +*src/main.rs* -Listing 12-13: Bringing the `greprs` crate into the scope of *src/main.rs* +We add a `use minigrep::Config` line to bring the `Config` type from the +library crate into the binary crate’s scope, and we prefix the `run` function +with our crate name. Now all the functionality should be connected and should +work. Run the program with `cargo run` and make sure everything works +correctly. -
-
+Whew! That was a lot of work, but we’ve set ourselves up for success in the +future. Now it’s much easier to handle errors, and we’ve made the code more +modular. Almost all of our work will be done in *src/lib.rs* from here on out. - +Let’s take advantage of this newfound modularity by doing something that would +have been difficult with the old code but is easy with the new code: we’ll +write some tests! -With that, everything should work again. Give it a few `cargo run`s and make -sure you haven't broken anything. Whew! That all was a lot of work, but we've -set ourselves up for success in the future. We've set up a way to handle errors -in a much nicer fashion, and we've made our code slightly more modular. Almost -all of our work will be done in *src/lib.rs* from here on out. - -Let's take advantage of this newfound modularity by doing something that would -have been hard with our old code, but is easy with our new code: write some -tests! +[ch13]: ch13-00-functional-features.html +[ch9-custom-types]: ch09-03-to-panic-or-not-to-panic.html#creating-custom-types-for-validation +[ch9-error-guidelines]: ch09-03-to-panic-or-not-to-panic.html#guidelines-for-error-handling +[ch9-result]: ch09-02-recoverable-errors-with-result.html +[ch17]: ch17-00-oop.html +[ch9-question-mark]: ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator diff --git a/src/ch12-04-testing-the-librarys-functionality.md b/src/ch12-04-testing-the-librarys-functionality.md index 6cca791..d079439 100644 --- a/src/ch12-04-testing-the-librarys-functionality.md +++ b/src/ch12-04-testing-the-librarys-functionality.md @@ -1,295 +1,240 @@ -## Testing the Library's Functionality +## Developing the Library’s Functionality with Test-Driven Development -Writing tests for the core functionality of our code is now easier since we -extracted the logic into *src/lib.rs* and left all the argument parsing and -error handling in *src/main.rs*. We can now call our code directly with various -arguments and check return values without having to call our binary from the -command line. +Now that we’ve extracted the logic into *src/lib.rs* and left the argument +collecting and error handling in *src/main.rs*, it’s much easier to write tests +for the core functionality of our code. We can call functions directly with +various arguments and check return values without having to call our binary +from the command line. Feel free to write some tests for the functionality in +the `Config::new` and `run` functions on your own. -We're going to write a function named `grep` that takes our search term and the -text to search and produces a list of search results. Let's remove that -`println!` from `run` (and from *src/main.rs* as well, as we don't really need -those anymore either), and call the new `grep` function with the options we've -collected. We'll add a placeholder implementation of the function for now, and -a test that specifies the behavior we'd like the `grep` function to have. The -test will fail with our placeholder implementation, of course, but we can make -sure the code compiles and that we get the failure message we expect. Listing -12-14 shows these modifications: +In this section, we’ll add the searching logic to the `minigrep` program by +using the Test-driven development (TDD) process. This software development +technique follows these steps: + +1. Write a test that fails and run it to make sure it fails for the reason you + expect. +2. Write or modify just enough code to make the new test pass. +3. Refactor the code you just added or changed and make sure the tests + continue to pass. +4. Repeat from step 1! + +This process is just one of many ways to write software, but TDD can help drive +code design as well. Writing the test before you write the code that makes the +test pass helps to maintain high test coverage throughout the process. + +We’ll test drive the implementation of the functionality that will actually do +the searching for the query string in the file contents and produce a list of +lines that match the query. We’ll add this functionality in a function called +`search`. + +### Writing a Failing Test + +Because we don’t need them anymore, let’s remove the `println!` statements from +*src/lib.rs* and *src/main.rs* that we used to check the program’s behavior. +Then, in *src/lib.rs*, we’ll add a `tests` module with a test function, as we +did in [Chapter 11][ch11-anatomy]. The test function specifies +the behavior we want the `search` function to have: it will take a query and +the text to search for the query in, and it will return only the lines from the +text that contain the query. Listing 12-15 shows this test, which won’t compile +yet. -
Filename: src/lib.rs -```rust -# use std::error::Error; -# use std::fs::File; -# use std::io::prelude::*; -# -# pub struct Config { -# pub search: String, -# pub filename: String, -# } -# -// ...snip... - -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - vec![] -} - -pub fn run(config: Config) -> Result<(), Box>{ - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - grep(&config.search, &contents); - - Ok(()) -} - -#[cfg(test)] -mod test { - use grep; - - #[test] - fn one_result() { - let search = "duct"; - let contents = "\ -Rust: -safe, fast, productive. -Pick three."; - - assert_eq!( - vec!["safe, fast, productive."], - grep(search, contents) - ); - } -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-15/src/lib.rs:here}} ``` -
+Listing 12-15: Creating a failing test for the `search` +function we wish we had -Listing 12-14: Creating a function where our logic will go and a failing test -for that function +This test searches for the string `"duct"`. The text we’re searching is three +lines, only one of which contains `"duct"`. We assert that the value returned +from the `search` function contains only the line we expect. -
-
+We aren’t able to run this test and watch it fail because the test doesn’t even +compile: the `search` function doesn’t exist yet! So now we’ll add just enough +code to get the test to compile and run by adding a definition of the `search` +function that always returns an empty vector, as shown in Listing 12-16. Then +the test should compile and fail because an empty vector doesn’t match a vector +containing the line `"safe, fast, productive."` - +Filename: src/lib.rs -Notice that we need an explicit lifetime `'a` declared in the signature of -`grep` and used with the `contents` parameter and the return value. Remember, -lifetime parameters are used to specify which function parameters' lifetimes -connect to the lifetime of the return value. In this case, we're indicating that -the vector we're returning is going to contain string slices that reference -slices of the parameter `contents`, as opposed to referencing slices of the -parameter `search`. Another way to think about what we're telling Rust is that -the data returned by the `grep` function will live as long as the data passed -into this function in the `contents` parameter. This is important! Given that -the data a slice references needs to be valid in order for the reference to be -valid, if the compiler thought that we were making string slices of `search` -rather than `contents`, it would do its safety checking incorrectly. If we tried -to compile this function without lifetimes, we would get this error: - -```text -error[E0106]: missing lifetime specifier - --> src\lib.rs:37:46 - | -37 | fn grep(search: &str, contents: &str) -> Vec<&str> { - | ^ expected lifetime parameter - | - = help: this function's return type contains a borrowed value, but the - signature does not say whether it is borrowed from `search` or - `contents` +```rust,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-16/src/lib.rs:here}} ``` -Rust can't possibly know which of the two parameters we need, so it needs us to -tell it. Because `contents` is the parameter that contains all of our text and -we want to return the parts of that text that match, we know `contents` is the -parameter that should be connected to the return value using the lifetime -syntax. +Listing 12-16: Defining just enough of the `search` +function so our test will compile -Connecting parameters to return values in the signature is something that other -programming languages don't make you do, so don't worry if this still feels -strange! Knowing how to specify lifetimes gets easier over time, and practice -makes perfect. You may want to re-read the above section or go back and compare -this example with the Lifetime Syntax section in Chapter 10. +Notice that we need an explicit lifetime `'a` defined in the signature of +`search` and used with the `contents` argument and the return value. Recall in +[Chapter 10][ch10-lifetimes] that the lifetime parameters +specify which argument lifetime is connected to the lifetime of the return +value. In this case, we indicate that the returned vector should contain string +slices that reference slices of the argument `contents` (rather than the +argument `query`). -Now let's try running our test: +In other words, we tell Rust that the data returned by the `search` function +will live as long as the data passed into the `search` function in the +`contents` argument. This is important! The data referenced *by* a slice needs +to be valid for the reference to be valid; if the compiler assumes we’re making +string slices of `query` rather than `contents`, it will do its safety checking +incorrectly. -```text -$ cargo test -...warnings... - Finished debug [unoptimized + debuginfo] target(s) in 0.43 secs - Running target/debug/deps/greprs-abcabcabc +If we forget the lifetime annotations and try to compile this function, we’ll +get this error: -running 1 test -test test::one_result ... FAILED - -failures: - ----- test::one_result stdout ---- - thread 'test::one_result' panicked at 'assertion failed: `(left == right)` -(left: `["safe, fast, productive."]`, right: `[]`)', src/lib.rs:16 -note: Run with `RUST_BACKTRACE=1` for a backtrace. - - -failures: - test::one_result - -test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured - -error: test failed +```console +{{#include ../listings/ch12-an-io-project/output-only-02-missing-lifetimes/output.txt}} ``` -Great, our test fails, exactly as we expected. Let's get the test to pass! It's -failing because we always return an empty vector. Here's what we're going to do -to implement `grep`: +Rust can’t possibly know which of the two arguments we need, so we need to tell +it. Because `contents` is the argument that contains all of our text and we +want to return the parts of that text that match, we know `contents` is the +argument that should be connected to the return value using the lifetime syntax. -1. Iterate through each line of the contents. -2. Check if the line contains our search string. - * If it does, add it to the list of values we're returning. - * If not, do nothing. -3. Return the list of results that match. +Other programming languages don’t require you to connect arguments to return +values in the signature. Although this might seem strange, it will get easier +over time. You might want to compare this example with the [“Validating +References with Lifetimes”][validating-references-with-lifetimes] section in Chapter 10. -Let's take each step at a time, starting with iterating through lines. Strings -have a helpful method to handle this, conveniently named `lines`: +Now let’s run the test: + +```console +{{#include ../listings/ch12-an-io-project/listing-12-16/output.txt}} +``` + +Great, the test fails, exactly as we expected. Let’s get the test to pass! + +### Writing Code to Pass the Test + +Currently, our test is failing because we always return an empty vector. To fix +that and implement `search`, our program needs to follow these steps: + +* Iterate through each line of the contents. +* Check whether the line contains our query string. +* If it does, add it to the list of values we’re returning. +* If it doesn’t, do nothing. +* Return the list of results that match. + +Let’s work through each step, starting with iterating through lines. + +#### Iterating Through Lines with the `lines` Method + +Rust has a helpful method to handle line-by-line iteration of strings, +conveniently named `lines`, that works as shown in Listing 12-17. Note this +won’t compile yet. + +Filename: src/lib.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-17/src/lib.rs:here}} +``` + +Listing 12-17: Iterating through each line in `contents` + + +The `lines` method returns an iterator. We’ll talk about iterators in depth in +[Chapter 13][ch13-iterators], but recall that you saw this way of using an +iterator in [Listing 3-5][ch3-iter], where we used a `for` loop +with an iterator to run some code on each item in a collection. + +#### Searching Each Line for the Query + +Next, we’ll check whether the current line contains our query string. +Fortunately, strings have a helpful method named `contains` that does this for +us! Add a call to the `contains` method in the `search` function, as shown in +Listing 12-18. Note this still won’t compile yet. + +Filename: src/lib.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-18/src/lib.rs:here}} +``` + +Listing 12-18: Adding functionality to see whether the +line contains the string in `query` + +#### Storing Matching Lines + +We also need a way to store the lines that contain our query string. For that, +we can make a mutable vector before the `for` loop and call the `push` method +to store a `line` in the vector. After the `for` loop, we return the vector, as +shown in Listing 12-19. Filename: src/lib.rs ```rust,ignore -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - for line in contents.lines() { - // do something with line - } -} +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-19/src/lib.rs:here}} ``` - +Listing 12-19: Storing the lines that match so we can +return them -We're using a `for` loop along with the `lines` method to get each line in turn. -Next, let's see if our line contains the search string. Luckily, strings have a -helpful method named `contains` that does this for us! Using the `contains` -method looks like this: +Now the `search` function should return only the lines that contain `query`, +and our test should pass. Let’s run the test: + +```console +{{#include ../listings/ch12-an-io-project/listing-12-19/output.txt}} +``` + +Our test passed, so we know it works! + +At this point, we could consider opportunities for refactoring the +implementation of the search function while keeping the tests passing to +maintain the same functionality. The code in the search function isn’t too bad, +but it doesn’t take advantage of some useful features of iterators. We’ll +return to this example in [Chapter 13][ch13-iterators], where we’ll +explore iterators in detail, and look at how to improve it. + +#### Using the `search` Function in the `run` Function + +Now that the `search` function is working and tested, we need to call `search` +from our `run` function. We need to pass the `config.query` value and the +`contents` that `run` reads from the file to the `search` function. Then `run` +will print each line returned from `search`: Filename: src/lib.rs ```rust,ignore -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - for line in contents.lines() { - if line.contains(search) { - // do something with line - } - } -} +{{#rustdoc_include ../listings/ch12-an-io-project/no-listing-02-using-search-in-run/src/lib.rs:here}} ``` - +We’re still using a `for` loop to return each line from `search` and print it. -Finally, we need a way to store the lines that contain our search string. For -that, we can make a mutable vector before the `for` loop and call the `push` -method to store a `line` in the vector. After the `for` loop, we return the -vector. Listing 12-15 has the full implementation: +Now the entire program should work! Let’s try it out, first with a word that +should return exactly one line from the Emily Dickinson poem, “frog”: -
-Filename: src/lib.rs - -```rust -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let mut results = Vec::new(); - - for line in contents.lines() { - if line.contains(search) { - results.push(line); - } - } - - results -} +```console +{{#include ../listings/ch12-an-io-project/no-listing-02-using-search-in-run/output.txt}} ``` -
+Cool! Now let’s try a word that will match multiple lines, like “body”: -Listing 12-15: Fully functioning implementation of the `grep` function - -
-
- - - -Let's give it a try: - -```text -$ cargo test -running 1 test -test test::one_result ... ok - -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured - - Running target/debug/greprs-2f55ee8cd1721808 - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests greprs - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured +```console +{{#include ../listings/ch12-an-io-project/output-only-03-multiple-matches/output.txt}} ``` -Great! It works. Now that our test is passing, we could consider opportunities -for refactoring the implementation of `grep` and be certain we maintain the -same functionality while we do so. This code isn't bad, but it isn't taking -advantage of some useful features of iterators. We'll be coming back to this -example in Chapter 13 where we'll explore iterators in detail and see how to -improve it. +And finally, let’s make sure that we don’t get any lines when we search for a +word that isn’t anywhere in the poem, such as “monomorphization”: -Now that the `grep` function is working, we need to do one last thing inside of -the `run` function: we never printed out the results! We'll do that by adding -a `for` loop that prints each line returned from the `grep` function: - -Filename: src/lib.rs - -```rust,ignore -pub fn run(config: Config) -> Result<(), Box> { - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - for line in grep(&config.search, &contents) { - println!("{}", line); - } - - Ok(()) -} +```console +{{#include ../listings/ch12-an-io-project/output-only-04-no-matches/output.txt}} ``` - - -Now our whole program should be working! Let's try it out: - -```text -$ cargo run the poem.txt - Compiling greprs v0.1.0 (file:///projects/greprs) - Finished debug [unoptimized + debuginfo] target(s) in 0.38 secs - Running `target\debug\greprs.exe the poem.txt` -Then there's a pair of us - don't tell! -To tell your name the livelong day - -$ cargo run a poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe a poem.txt` -I'm nobody! Who are you? -Then there's a pair of us - don't tell! -They'd banish us, you know. -How dreary to be somebody! -How public, like a frog -To tell your name the livelong day -To an admiring bog! -``` - -Excellent! We've built our own version of a classic tool, and learned a lot -about how to structure applications. We've also learned a bit about file input +Excellent! We’ve built our own mini version of a classic tool and learned a lot +about how to structure applications. We’ve also learned a bit about file input and output, lifetimes, testing, and command line parsing. + +To round out this project, we’ll briefly demonstrate how to work with +environment variables and how to print to standard error, both of which are +useful when you’re writing command line programs. + +[validating-references-with-lifetimes]: +ch10-03-lifetime-syntax.html#validating-references-with-lifetimes +[ch11-anatomy]: ch11-01-writing-tests.html#the-anatomy-of-a-test-function +[ch10-lifetimes]: ch10-03-lifetime-syntax.html +[ch3-iter]: ch03-05-control-flow.html#looping-through-a-collection-with-for +[ch13-iterators]: ch13-02-iterators.html diff --git a/src/ch12-05-working-with-environment-variables.md b/src/ch12-05-working-with-environment-variables.md index 7dc5ff9..86457e8 100644 --- a/src/ch12-05-working-with-environment-variables.md +++ b/src/ch12-05-working-with-environment-variables.md @@ -1,256 +1,206 @@ ## Working with Environment Variables -Let's add one more feature: case insensitive searching. In addition, this -setting won't be a command line option: it'll be an environment variable -instead. We could choose to make case insensitivity a command line option, but -our users have requested an environment variable that they could set once and -make all their searches case insensitive in that terminal session. +We’ll improve `minigrep` by adding an extra feature: an option for +case-insensitive searching that the user can turn on via an environment +variable. We could make this feature a command line option and require that +users enter it each time they want it to apply, but instead we’ll use an +environment variable. Doing so allows our users to set the environment variable +once and have all their searches be case insensitive in that terminal session. -### Implement and Test a Case-Insensitive `grep` Function +### Writing a Failing Test for the Case-Insensitive `search` Function -First, let's add a new function that we will call when the environment variable -is on. Let's start by adding a new test and re-naming our existing one: - -```rust,ignore -#[cfg(test)] -mod test { - use {grep, grep_case_insensitive}; - - #[test] - fn case_sensitive() { - let search = "duct"; - let contents = "\ -Rust: -safe, fast, productive. -Pick three. -Duct tape."; - - assert_eq!( - vec!["safe, fast, productive."], - grep(search, contents) - ); - } - - #[test] - fn case_insensitive() { - let search = "rust"; - let contents = "\ -Rust: -safe, fast, productive. -Pick three. -Trust me."; - - assert_eq!( - vec!["Rust:", "Trust me."], - grep_case_insensitive(search, contents) - ); - } -} -``` - - - -We're going to define a new function named `grep_case_insensitive`. Its -implementation will be almost the same as the `grep` function, but with some -minor changes as shown in Listing 12-16: - -
-Filename: src/lib.rs - -```rust -fn grep_case_insensitive<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let search = search.to_lowercase(); - let mut results = Vec::new(); - - for line in contents.lines() { - if line.to_lowercase().contains(&search) { - results.push(line); - } - } - - results -} -``` - -
- -Listing 12-16: Implementing a `grep_case_insensitive` function by changing the -search string and the lines of the contents to lowercase before comparing them - -
-
- - - -First, we lowercase the `search` string, and store it in a shadowed variable -with the same name. Note that `search` is now a `String` rather than a string -slice, so we need to add an ampersand when we pass `search` to `contains` since -`contains` takes a string slice. - -Second, we add a call to `to_lowercase` each `line` before we check if it -contains `search`. Since we've converted both `line` and `search` into all -lowercase, we'll find matches no matter what case they used in the file and the -command line arguments, respectively. Let's see if this passes the tests: - -```text - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target\debug\deps\greprs-e58e9b12d35dc861.exe - -running 2 tests -test test::case_insensitive ... ok -test test::case_sensitive ... ok - -test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured - - Running target\debug\greprs-8a7faa2662b5030a.exe - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured - - Doc-tests greprs - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Great! Now, we have to actually use the new `grep_case_insensitive` function. -First, let's add a configuration option for it to the `Config` struct: +We want to add a new `search_case_insensitive` function that we’ll call when +the environment variable is on. We’ll continue to follow the TDD process, so +the first step is again to write a failing test. We’ll add a new test for the +new `search_case_insensitive` function and rename our old test from +`one_result` to `case_sensitive` to clarify the differences between the two +tests, as shown in Listing 12-20. Filename: src/lib.rs -```rust -pub struct Config { - pub search: String, - pub filename: String, - pub case_sensitive: bool, -} +```rust,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-20/src/lib.rs:here}} ``` - +Listing 12-20: Adding a new failing test for the +case-insensitive function we’re about to add -And then check for that option inside of the `run` function, and decide which -function to call based on the value of the `case_sensitive` function: +Note that we’ve edited the old test’s `contents` too. We’ve added a new line +with the text `"Duct tape."` using a capital D that shouldn’t match the query +`"duct"` when we’re searching in a case-sensitive manner. Changing the old test +in this way helps ensure that we don’t accidentally break the case-sensitive +search functionality that we’ve already implemented. This test should pass now +and should continue to pass as we work on the case-insensitive search. + +The new test for the case-*insensitive* search uses `"rUsT"` as its query. In +the `search_case_insensitive` function we’re about to add, the query `"rUsT"` +should match the line containing `"Rust:"` with a capital R and match the line +`"Trust me."` even though both have different casing from the query. This is +our failing test, and it will fail to compile because we haven’t yet defined +the `search_case_insensitive` function. Feel free to add a skeleton +implementation that always returns an empty vector, similar to the way we did +for the `search` function in Listing 12-16 to see the test compile and fail. + +### Implementing the `search_case_insensitive` Function + +The `search_case_insensitive` function, shown in Listing 12-21, will be almost +the same as the `search` function. The only difference is that we’ll lowercase +the `query` and each `line` so whatever the case of the input arguments, +they’ll be the same case when we check whether the line contains the query. Filename: src/lib.rs -```rust,ignore -pub fn run(config: Config) -> Result<(), Box>{ - let mut f = File::open(config.filename)?; - - let mut contents = String::new(); - f.read_to_string(&mut contents)?; - - let results = if config.case_sensitive { - grep(&config.search, &contents) - } else { - grep_case_insensitive(&config.search, &contents) - }; - - for line in results { - println!("{}", line); - } - - Ok(()) -} +```rust,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-21/src/lib.rs:here}} ``` - +Listing 12-21: Defining the `search_case_insensitive` +function to lowercase the query and the line before comparing them -Finally, we need to actually check the environment for the variable. To bring -the `env` module from the standard library into our project, we add a `use` line -at the top of *src/lib.rs*: +First, we lowercase the `query` string and store it in a shadowed variable with +the same name. Calling `to_lowercase` on the query is necessary so no matter +whether the user’s query is `"rust"`, `"RUST"`, `"Rust"`, or `"rUsT"`, we’ll +treat the query as if it were `"rust"` and be insensitive to the case. While +`to_lowercase` will handle basic Unicode, it won't be 100% accurate. If we were +writing a real application, we'd want to do a bit more work here, but this section +is about environment variables, not Unicode, so we'll leave it at that here. + +Note that `query` is now a `String` rather than a string slice, because calling +`to_lowercase` creates new data rather than referencing existing data. Say the +query is `"rUsT"`, as an example: that string slice doesn’t contain a lowercase +`u` or `t` for us to use, so we have to allocate a new `String` containing +`"rust"`. When we pass `query` as an argument to the `contains` method now, we +need to add an ampersand because the signature of `contains` is defined to take +a string slice. + +Next, we add a call to `to_lowercase` on each `line` before we check whether it +contains `query` to lowercase all characters. Now that we’ve converted `line` +and `query` to lowercase, we’ll find matches no matter what the case of the +query is. + +Let’s see if this implementation passes the tests: + +```console +{{#include ../listings/ch12-an-io-project/listing-12-21/output.txt}} +``` + +Great! They passed. Now, let’s call the new `search_case_insensitive` function +from the `run` function. First, we’ll add a configuration option to the +`Config` struct to switch between case-sensitive and case-insensitive search. +Adding this field will cause compiler errors because we aren’t initializing +this field anywhere yet: Filename: src/lib.rs -```rust -use std::env; +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-22/src/lib.rs:here}} ``` -And then use the `vars` method from the `env` module inside of `Config::new`: +Note that we added the `case_sensitive` field that holds a Boolean. Next, we +need the `run` function to check the `case_sensitive` field’s value and use +that to decide whether to call the `search` function or the +`search_case_insensitive` function, as shown in Listing 12-22. Note this still +won’t compile yet. Filename: src/lib.rs -```rust -# use std::env; -# -# struct Config { -# search: String, -# filename: String, -# case_sensitive: bool, -# } -# -impl Config { - pub fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - let mut case_sensitive = true; - - for (name, _) in env::vars() { - if name == "CASE_INSENSITIVE" { - case_sensitive = false; - } - } - - Ok(Config { - search: search, - filename: filename, - case_sensitive: case_sensitive, - }) - } -} +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-22/src/lib.rs:there}} ``` - +Listing 12-22: Calling either `search` or +`search_case_insensitive` based on the value in `config.case_sensitive` -Here, we call `env::vars`, which works in a similar way as `env::args`. The -difference is `env::vars` returns an iterator of environment variables rather -than command line arguments. Instead of using `collect` to create a vector of -all of the environment variables, we're using a `for` loop. `env::vars` returns -tuples: the name of the environment variable and its value. We never care about -the values, only if the variable is set at all, so we use the `_` placeholder -instead of a name to let Rust know that it shouldn't warn us about an unused -variable. Finally, we have a `case_sensitive` variable, which is set to true by -default. If we ever find a `CASE_INSENSITIVE` environment variable, we set the -`case_sensitive` variable to false instead. Then we return the value as part of -the `Config`. +Finally, we need to check for the environment variable. The functions for +working with environment variables are in the `env` module in the standard +library, so we want to bring that module into scope with a `use std::env;` line +at the top of *src/lib.rs*. Then we’ll use the `var` function from the `env` +module to check for an environment variable named `CASE_INSENSITIVE`, as shown +in Listing 12-23. -Let's give it a try! +Filename: src/lib.rs -```text -$ cargo run to poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe to poem.txt` -Are you nobody, too? -How dreary to be somebody! +```rust,noplayground +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-23/src/lib.rs:here}} ``` -```text +Listing 12-23: Checking for an environment variable named +`CASE_INSENSITIVE` + +Here, we create a new variable `case_sensitive`. To set its value, we call the +`env::var` function and pass it the name of the `CASE_INSENSITIVE` environment +variable. The `env::var` function returns a `Result` that will be the successful +`Ok` variant that contains the value of the environment variable if the +environment variable is set. It will return the `Err` variant if the +environment variable is not set. + +We’re using the `is_err` method on the `Result` to check whether it’s an error +and therefore unset, which means it *should* do a case-sensitive search. If the +`CASE_INSENSITIVE` environment variable is set to anything, `is_err` will +return false and the program will perform a case-insensitive search. We don’t +care about the *value* of the environment variable, just whether it’s set or +unset, so we’re checking `is_err` rather than using `unwrap`, `expect`, or any +of the other methods we’ve seen on `Result`. + +We pass the value in the `case_sensitive` variable to the `Config` instance so +the `run` function can read that value and decide whether to call `search` or +`search_case_insensitive`, as we implemented in Listing 12-22. + +Let’s give it a try! First, we’ll run our program without the environment +variable set and with the query `to`, which should match any line that contains +the word “to” in all lowercase: + +```console +{{#include ../listings/ch12-an-io-project/listing-12-23/output.txt}} +``` + +Looks like that still works! Now, let’s run the program with `CASE_INSENSITIVE` +set to `1` but with the same query `to`. + +If you're using PowerShell, you will need to set the environment +variable and run the program as separate commands: + +```console +PS> $Env:CASE_INSENSITIVE=1; cargo run to poem.txt +``` + +This will make `CASE_INSENSITIVE` persist for the remainder of your shell +session. It can be unset with the `Remove-Item` cmdlet: + +```console +PS> Remove-Item Env:CASE_INSENSITIVE +``` + +We should get lines that contain “to” that might have uppercase letters: + + + +```console $ CASE_INSENSITIVE=1 cargo run to poem.txt - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running `target\debug\greprs.exe to poem.txt` + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/minigrep to poem.txt` Are you nobody, too? How dreary to be somebody! To tell your name the livelong day To an admiring bog! ``` -Excellent! Our `greprs` program can now do case insensitive searching controlled -by an environment variable. Now you know how to manage options set using -either command line arguments or environment variables! +Excellent, we also got lines containing “To”! Our `minigrep` program can now do +case-insensitive searching controlled by an environment variable. Now you know +how to manage options set using either command line arguments or environment +variables. -Some programs allow both arguments _and_ environment variables for the same -configuration. In those cases, the programs decide that one or the other of -arguments or environment variables take precedence. For another exercise on -your own, try controlling case insensitivity through a command line argument as -well, and decide which should take precedence if you run the program with -contradictory values. +Some programs allow arguments *and* environment variables for the same +configuration. In those cases, the programs decide that one or the other takes +precedence. For another exercise on your own, try controlling case +insensitivity through either a command line argument or an environment +variable. Decide whether the command line argument or the environment variable +should take precedence if the program is run with one set to case sensitive and +one set to case insensitive. The `std::env` module contains many more useful features for dealing with -environment variables; check out its documentation to see what's available. +environment variables: check out its documentation to see what is available. diff --git a/src/ch12-06-writing-to-stderr-instead-of-stdout.md b/src/ch12-06-writing-to-stderr-instead-of-stdout.md index b68964f..0d6a45a 100644 --- a/src/ch12-06-writing-to-stderr-instead-of-stdout.md +++ b/src/ch12-06-writing-to-stderr-instead-of-stdout.md @@ -1,105 +1,88 @@ -## Write to `stderr` Instead of `stdout` +## Writing Error Messages to Standard Error Instead of Standard Output -Right now, we're writing all of our output to the terminal with `println!`. -This works, but most terminals provide two kinds of output: "standard out" is -used for most information, but "standard error" is used for error messages. This -makes it easier to do things like "Print error messages to my terminal, but -write other output to a file." +At the moment, we’re writing all of our output to the terminal using the +`println!` macro. Most terminals provide two kinds of output: *standard +output* (`stdout`) for general information and *standard error* (`stderr`) +for error messages. This distinction enables users to choose to direct the +successful output of a program to a file but still print error messages to the +screen. -We can see that our program is only capable of printing to `stdout` by -redirecting it to a file using `>` on the command line, and running our program -without any arguments, which causes an error: +The `println!` macro is only capable of printing to standard output, so we +have to use something else to print to standard error. -```text +### Checking Where Errors Are Written + +First, let’s observe how the content printed by `minigrep` is currently being +written to standard output, including any error messages we want to write to +standard error instead. We’ll do that by redirecting the standard output stream +to a file while also intentionally causing an error. We won’t redirect the +standard error stream, so any content sent to standard error will continue to +display on the screen. + +Command line programs are expected to send error messages to the standard error +stream so we can still see error messages on the screen even if we redirect the +standard output stream to a file. Our program is not currently well-behaved: +we’re about to see that it saves the error message output to a file instead! + +The way to demonstrate this behavior is by running the program with `>` and the +filename, *output.txt*, that we want to redirect the standard output stream to. +We won’t pass any arguments, which should cause an error: + +```console $ cargo run > output.txt ``` -The `>` syntax tells the shell to write the contents of standard out to -*output.txt* instead of the screen. However, if we open *output.txt* after -running we'll see our error message: +The `>` syntax tells the shell to write the contents of standard output to +*output.txt* instead of the screen. We didn’t see the error message we were +expecting printed to the screen, so that means it must have ended up in the +file. This is what *output.txt* contains: ```text Problem parsing arguments: not enough arguments ``` -We'd like this to be printed to the screen instead, and only have the output -from a successful run end up in the file if we run our program this way. Let's -change how error messages are printed as shown in Listing 12-17: +Yup, our error message is being printed to standard output. It’s much more +useful for error messages like this to be printed to standard error so only +data from a successful run ends up in the file. We’ll change that. + +### Printing Errors to Standard Error + +We’ll use the code in Listing 12-24 to change how error messages are printed. +Because of the refactoring we did earlier in this chapter, all the code that +prints error messages is in one function, `main`. The standard library provides +the `eprintln!` macro that prints to the standard error stream, so let’s change +the two places we were calling `println!` to print errors to use `eprintln!` +instead. -
Filename: src/main.rs ```rust,ignore -extern crate greprs; - -use std::env; -use std::process; -use std::io::prelude::*; - -use greprs::Config; - -fn main() { - let mut stderr = std::io::stderr(); - let args: Vec = env::args().collect(); - - let config = Config::new(&args).unwrap_or_else(|err| { - writeln!( - &mut stderr, - "Problem parsing arguments: {}", - err - ).expect("Could not write to stderr"); - - process::exit(1); - }); - - if let Err(e) = greprs::run(config) { - - writeln!( - &mut stderr, - "Application error: {}", - e - ).expect("Could not write to stderr"); - - process::exit(1); - } -} +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-24/src/main.rs:here}} ``` -
+Listing 12-24: Writing error messages to standard error +instead of standard output using `eprintln!` -Listing 12-17: Writing error messages to `stderr` instead of `stdout` +After changing `println!` to `eprintln!`, let’s run the program again in the +same way, without any arguments and redirecting standard output with `>`: -
-
- - - -Rust does not have a convenient function like `println!` for writing to -standard error. Instead, we use the `writeln!` macro, which is sort of like -`println!`, but it takes an extra argument. The first thing we pass to it is -what to write to. We can acquire a handle to standard error through the -`std::io::stderr` function. We give a mutable reference to `stderr` to -`writeln!`; we need it to be mutable so we can write to it! The second and -third arguments to `writeln!` are like the first and second arguments to -`println!`: a format string and any variables we're interpolating. - -Let's try running the program again in the same way, without any arguments and -redirecting `stdout` with `>`: - -```text +```console $ cargo run > output.txt Problem parsing arguments: not enough arguments ``` -Now we see our error on the screen, but `output.txt` contains nothing. If we -try it again with arguments that work: +Now we see the error onscreen and *output.txt* contains nothing, which is the +behavior we expect of command line programs. -```text +Let’s run the program again with arguments that don’t cause an error but still +redirect standard output to a file, like so: + +```console $ cargo run to poem.txt > output.txt ``` -We'll see no output to our terminal, but `output.txt` will contain -our results: +We won’t see any output to the terminal, and *output.txt* will contain our +results: Filename: output.txt @@ -108,16 +91,18 @@ Are you nobody, too? How dreary to be somebody! ``` +This demonstrates that we’re now using standard output for successful output +and standard error for error output as appropriate. + ## Summary -In this chapter, we've covered how to do common I/O operations in a Rust -context. By using command line arguments, files, environment variables, and the -ability to write to `stderr`, you're now prepared to write command line -applications. By using the concepts from previous chapters, your code will be -well-organized, be able to store data effectively in the appropriate data -structures, handle errors nicely, and be well tested. We also saw a real-world -scenario where lifetime annotations are needed to ensure references are -always valid. +This chapter recapped some of the major concepts you’ve learned so far and +covered how to perform common I/O operations in Rust. By using command line +arguments, files, environment variables, and the `eprintln!` macro for printing +errors, you’re now prepared to write command line applications. By using the +concepts in previous chapters, your code will be well organized, store data +effectively in the appropriate data structures, handle errors nicely, and be +well tested. -Next, let's explore how to make use of some features of Rust that were -influenced by functional languages: closures and iterators. +Next, we’ll explore some Rust features that were influenced by functional +languages: closures and iterators. diff --git a/src/ch13-00-functional-features.md b/src/ch13-00-functional-features.md index 55cce67..f743a7b 100644 --- a/src/ch13-00-functional-features.md +++ b/src/ch13-00-functional-features.md @@ -1,21 +1,24 @@ -# Functional Language features in Rust - Iterators and Closures +# Functional Language Features: Iterators and Closures -Rust's design has taken inspiration from a lot of previous work. One of Rust's -influences is functional programming, where functions are values that can be -used as arguments or return values to other functions, assigned to variables, -and so forth. We're going to sidestep the issue of what, exactly, functional -programming is or is not, and instead show off some features of Rust that -are similar to features in many languages referred to as functional. +Rust’s design has taken inspiration from many existing languages and +techniques, and one significant influence is *functional programming*. +Programming in a functional style often includes using functions as values by +passing them in arguments, returning them from other functions, assigning them +to variables for later execution, and so forth. -More specifically, we're going to cover: +In this chapter, we won’t debate the issue of what functional programming is or +isn’t but will instead discuss some features of Rust that are similar to +features in many languages often referred to as functional. -* *Closures*, a function-like construct you can store in a variable. -* *Iterators*, a way of processing series of elements. -* How to use these features to improve upon the project from the last chapter. -* The performance of these features. Spoiler alert: they're faster than you - might think! +More specifically, we’ll cover: -This is not a complete list of Rust's influence from the functional style: -pattern matching, enums, and many other features are too. But mastering -closures and iterators are an important part of writing idiomatic, fast Rust -code. +* *Closures*, a function-like construct you can store in a variable +* *Iterators*, a way of processing a series of elements +* How to use these two features to improve the I/O project in Chapter 12 +* The performance of these two features (Spoiler alert: they’re faster than you + might think!) + +Other Rust features, such as pattern matching and enums, which we’ve covered in +other chapters, are influenced by the functional style as well. Mastering +closures and iterators is an important part of writing idiomatic, fast Rust +code, so we’ll devote this entire chapter to them. diff --git a/src/ch13-01-closures.md b/src/ch13-01-closures.md index 082fdac..26e0075 100644 --- a/src/ch13-01-closures.md +++ b/src/ch13-01-closures.md @@ -1,256 +1,557 @@ -## Closures +## Closures: Anonymous Functions that Can Capture Their Environment -Rust gives you the ability to define *closures*, which are similar to -functions. Instead of starting with a technical definition, let's see what -closures look like, syntactically, and then we'll return to defining what they -are. Listing 13-1 shows a small closure whose definition is assigned to the -variable `add_one`, which we can then use to call the closure: +Rust’s closures are anonymous functions you can save in a variable or pass as +arguments to other functions. You can create the closure in one place and then +call the closure to evaluate it in a different context. Unlike functions, +closures can capture values from the scope in which they’re defined. We’ll +demonstrate how these closure features allow for code reuse and behavior +customization. + +### Creating an Abstraction of Behavior with Closures + +Let’s work on an example of a situation in which it’s useful to store a closure +to be executed later. Along the way, we’ll talk about the syntax of closures, +type inference, and traits. + +Consider this hypothetical situation: we work at a startup that’s making an app +to generate custom exercise workout plans. The backend is written in Rust, and +the algorithm that generates the workout plan takes into account many factors, +such as the app user’s age, body mass index, exercise preferences, recent +workouts, and an intensity number they specify. The actual algorithm used isn’t +important in this example; what’s important is that this calculation takes a +few seconds. We want to call this algorithm only when we need to and only call +it once so we don’t make the user wait more than necessary. + +We’ll simulate calling this hypothetical algorithm with the function +`simulated_expensive_calculation` shown in Listing 13-1, which will print +`calculating slowly...`, wait for two seconds, and then return whatever number +we passed in. -
Filename: src/main.rs ```rust -fn main() { - let add_one = |x| x + 1; - - let five = add_one(4); - - assert_eq!(5, five); -} +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-01/src/main.rs:here}} ``` -
+Listing 13-1: A function to stand in for a hypothetical +calculation that takes about 2 seconds to run -Listing 13-1: A closure that takes one parameter and adds one to it, assigned to -the variable `add_one` +Next is the `main` function, which contains the parts of the workout app +important for this example. This function represents the code that the app will +call when a user asks for a workout plan. Because the interaction with the +app’s frontend isn’t relevant to the use of closures, we’ll hardcode values +representing inputs to our program and print the outputs. -
-
+The required inputs are these: -The closure definition, on the first line, shows that the closure takes one -parameter named `x`. Parameters to closures go in between vertical pipes (`|`). +* An intensity number from the user, which is specified when they request + a workout to indicate whether they want a low-intensity workout or a + high-intensity workout +* A random number that will generate some variety in the workout plans -This is a minimal closure with only one expression as its body. Listing 13-2 has -a closure with a bit more complexity: +The output will be the recommended workout plan. Listing 13-2 shows the `main` +function we’ll use. -
Filename: src/main.rs ```rust -fn main() { - let calculate = |a, b| { - let mut result = a * 2; - - result += b; - - result - }; - - assert_eq!(7, calculate(2, 3)); // 2 * 2 + 3 == 7 - assert_eq!(13, calculate(4, 5)); // 4 * 2 + 5 == 13 -} +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-02/src/main.rs:here}} ``` -
+Listing 13-2: A `main` function with hardcoded values to +simulate user input and random number generation -Listing 13-2: A closure with two parameters and multiple expressions in its body +We’ve hardcoded the variable `simulated_user_specified_value` as 10 and the +variable `simulated_random_number` as 7 for simplicity’s sake; in an actual +program, we’d get the intensity number from the app frontend, and we’d use the +`rand` crate to generate a random number, as we did in the Guessing Game +example in Chapter 2. The `main` function calls a `generate_workout` function +with the simulated input values. -
-
+Now that we have the context, let’s get to the algorithm. The function +`generate_workout` in Listing 13-3 contains the business logic of the +app that we’re most concerned with in this example. The rest of the code +changes in this example will be made to this function. -We can use curly brackets to define a closure body with more than one -expression. - -You'll notice a few things about closures that are different from functions -defined with the `fn` keyword. The first difference is that we did not need to -annotate the types of the parameters the closure takes or the value it returns. -We can choose to add type annotations if we want; Listing 13-3 shows the -closure from Listing 13-1 with annotations for the parameter's and return -value's types: - -
Filename: src/main.rs ```rust -fn main() { - let add_one = |x: i32| -> i32 { x + 1 }; - - assert_eq!(2, add_one(1)); -} +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-03/src/main.rs:here}} ``` -
+Listing 13-3: The business logic that prints the workout +plans based on the inputs and calls to the `simulated_expensive_calculation` +function -Listing 13-3: A closure definition with optional parameter and return value -type annotations +The code in Listing 13-3 has multiple calls to the slow calculation function. +The first `if` block calls `simulated_expensive_calculation` twice, the `if` +inside the outer `else` doesn’t call it at all, and the code inside the +second `else` case calls it once. -
-
+The desired behavior of the `generate_workout` function is to first check +whether the user wants a low-intensity workout (indicated by a number less than +25) or a high-intensity workout (a number of 25 or greater). -The syntax of closures and functions looks more similar with type annotations. -Let's compare the different ways we can specify closures with the syntax for -defining a function more directly. We've added some spaces here to line up the -relevant parts: +Low-intensity workout plans will recommend a number of push-ups and sit-ups +based on the complex algorithm we’re simulating. + +If the user wants a high-intensity workout, there’s some additional logic: if +the value of the random number generated by the app happens to be 3, the app +will recommend a break and hydration. If not, the user will get a number of +minutes of running based on the complex algorithm. + +This code works the way the business wants it to now, but let’s say the data +science team decides that we need to make some changes to the way we call the +`simulated_expensive_calculation` function in the future. To simplify the +update when those changes happen, we want to refactor this code so it calls the +`simulated_expensive_calculation` function only once. We also want to cut the +place where we’re currently unnecessarily calling the function twice without +adding any other calls to that function in the process. That is, we don’t want +to call it if the result isn’t needed, and we still want to call it only once. + +#### Refactoring Using Functions + +We could restructure the workout program in many ways. First, we’ll try +extracting the duplicated call to the `simulated_expensive_calculation` +function into a variable, as shown in Listing 13-4. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-04/src/main.rs:here}} +``` + +Listing 13-4: Extracting the calls to +`simulated_expensive_calculation` to one place and storing the result in the +`expensive_result` variable + +This change unifies all the calls to `simulated_expensive_calculation` and +solves the problem of the first `if` block unnecessarily calling the function +twice. Unfortunately, we’re now calling this function and waiting for the +result in all cases, which includes the inner `if` block that doesn’t use the +result value at all. + +We want to refer to `simulated_expensive_calculation` only once in +`generate_workout`, but defer the expensive calculation to only where +we actually need the result. This is a use case for closures! + +#### Refactoring with Closures to Store Code + +Instead of always calling the `simulated_expensive_calculation` function before +the `if` blocks, we can define a closure and store the *closure* in a variable +rather than storing the result of the function call, as shown in Listing 13-5. +We can actually move the whole body of `simulated_expensive_calculation` within +the closure we’re introducing here. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-05/src/main.rs:here}} +``` + +Listing 13-5: Defining a closure and storing it in the +`expensive_closure` variable + +The closure definition comes after the `=` to assign it to the variable +`expensive_closure`. To define a closure, we start with a pair of vertical +pipes (`|`), inside which we specify the parameters to the closure; this syntax +was chosen because of its similarity to closure definitions in Smalltalk and +Ruby. This closure has one parameter named `num`: if we had more than one +parameter, we would separate them with commas, like `|param1, param2|`. + +After the parameters, we place curly brackets that hold the body of the +closure—these are optional if the closure body is a single expression. The end +of the closure, after the curly brackets, needs a semicolon to complete the +`let` statement. The value returned from the last line in the closure body +(`num`) will be the value returned from the closure when it’s called, because +that line doesn’t end in a semicolon; just as in function bodies. + +Note that this `let` statement means `expensive_closure` contains the +*definition* of an anonymous function, not the *resulting value* of calling the +anonymous function. Recall that we’re using a closure because we want to define +the code to call at one point, store that code, and call it at a later point; +the code we want to call is now stored in `expensive_closure`. + +With the closure defined, we can change the code in the `if` blocks to call the +closure to execute the code and get the resulting value. We call a closure like +we do a function: we specify the variable name that holds the closure +definition and follow it with parentheses containing the argument values we +want to use, as shown in Listing 13-6. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-06/src/main.rs:here}} +``` + +Listing 13-6: Calling the `expensive_closure` we’ve +defined + +Now how to perform the expensive calculation is defined in only one +place, and we’re only executing that code where we need the results. + +However, we’ve reintroduced one of the problems from Listing 13-3: we’re still +calling the closure twice in the first `if` block, which will call the +expensive code twice and make the user wait twice as long as they need to. We +could fix this problem by creating a variable local to that `if` block to hold +the result of calling the closure, but closures provide us with another +solution. We’ll talk about that solution in a bit. But first let’s talk about +why there aren’t type annotations in the closure definition and the traits +involved with closures. + +### Closure Type Inference and Annotation + +Closures don’t require you to annotate the types of the parameters or the +return value like `fn` functions do. Type annotations are required on functions +because they’re part of an explicit interface exposed to your users. Defining +this interface rigidly is important for ensuring that everyone agrees on what +types of values a function uses and returns. But closures aren’t used in an +exposed interface like this: they’re stored in variables and used without +naming them and exposing them to users of our library. + +Closures are usually short and relevant only within a narrow context rather +than in any arbitrary scenario. Within these limited contexts, the compiler is +reliably able to infer the types of the parameters and the return type, similar +to how it’s able to infer the types of most variables. + +Making programmers annotate the types in these small, anonymous functions would +be annoying and largely redundant with the information the compiler already has +available. + +As with variables, we can add type annotations if we want to increase +explicitness and clarity at the cost of being more verbose than is strictly +necessary. Annotating the types for the closure we defined in Listing 13-5 +would look like the definition shown in Listing 13-7. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-07/src/main.rs:here}} +``` + +Listing 13-7: Adding optional type annotations of the +parameter and return value types in the closure + +With type annotations added, the syntax of closures looks more similar to the +syntax of functions. The following is a vertical comparison of the syntax for +the definition of a function that adds 1 to its parameter and a closure that +has the same behavior. We’ve added some spaces to line up the relevant parts. +This illustrates how closure syntax is similar to function syntax except for +the use of pipes and the amount of syntax that is optional: ```rust,ignore -fn add_one_v1 (x: i32) -> i32 { x + 1 } // a function -let add_one_v2 = |x: i32| -> i32 { x + 1 }; // the full syntax for a closure -let add_one_v3 = |x| { x + 1 }; // a closure eliding types -let add_one_v4 = |x| x + 1 ; // without braces +fn add_one_v1 (x: u32) -> u32 { x + 1 } +let add_one_v2 = |x: u32| -> u32 { x + 1 }; +let add_one_v3 = |x| { x + 1 }; +let add_one_v4 = |x| x + 1 ; ``` -The reason type annotations are not required for defining a closure but are -required for defining a function is that functions are part of an explicit -interface exposed to your users, so defining this interface rigidly is -important for ensuring that everyone agrees on what types of values a function -uses and returns. Closures aren't used in an exposed interface like this, -though: they're stored in bindings and called directly. Being forced to -annotate the types would be a significant ergonomic loss for little advantage. +The first line shows a function definition, and the second line shows a fully +annotated closure definition. The third line removes the type annotations from +the closure definition, and the fourth line removes the brackets, which are +optional because the closure body has only one expression. These are all valid +definitions that will produce the same behavior when they’re called. Calling +the closures is required for `add_one_v3` and `add_one_v4` to be able to +compile because the types will be inferred from their usage. -Closure definitions do have one type inferred for each of their parameters and -for their return value. For instance, if we call the closure without type -annotations from Listing 13-1 using an `i8`, we'll get an error if we then try -to call the same closure with an `i32`: +Closure definitions will have one concrete type inferred for each of their +parameters and for their return value. For instance, Listing 13-8 shows the +definition of a short closure that just returns the value it receives as a +parameter. This closure isn’t very useful except for the purposes of this +example. Note that we haven’t added any type annotations to the definition: if +we then try to call the closure twice, using a `String` as an argument the +first time and a `u32` the second time, we’ll get an error. Filename: src/main.rs -```rust,ignore -let add_one = |x| x + 1; - -let five = add_one(4i8); -assert_eq!(5i8, five); - -let three = add_one(2i32); +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-08/src/main.rs:here}} ``` +Listing 13-8: Attempting to call a closure whose types +are inferred with two different types + The compiler gives us this error: -```text -error[E0308]: mismatched types - --> - | -7 | let three = add_one(2i32); - | ^^^^ expected i8, found i32 +```console +{{#include ../listings/ch13-functional-features/listing-13-08/output.txt}} ``` -Since closures' types can be inferred reliably since they're called directly, -it would be tedious if we were required to annotate their types. +The first time we call `example_closure` with the `String` value, the compiler +infers the type of `x` and the return type of the closure to be `String`. Those +types are then locked into the closure in `example_closure`, and we get a type +error if we try to use a different type with the same closure. -Another reason to have a different syntax from functions for closures is that -they have different behavior than functions: closures possess an *environment*. +### Storing Closures Using Generic Parameters and the `Fn` Traits -### Closures Can Reference Their Environment +Let’s return to our workout generation app. In Listing 13-6, our code was still +calling the expensive calculation closure more times than it needed to. One +option to solve this issue is to save the result of the expensive closure in a +variable for reuse and use the variable in each place we need the result, +instead of calling the closure again. However, this method could result in a +lot of repeated code. -We've learned that functions can only use variables that are in scope, either -by being `const` or being declared as parameters. Closures can do more: they're -allowed to access variables from their enclosing scope. Listing 13-4 has an -example of a closure in the variable `equal_to_x` that uses the variable `x` -from the closure's surrounding environment: +Fortunately, another solution is available to us. We can create a struct that +will hold the closure and the resulting value of calling the closure. The +struct will execute the closure only if we need the resulting value, and it +will cache the resulting value so the rest of our code doesn’t have to be +responsible for saving and reusing the result. You may know this pattern as +*memoization* or *lazy evaluation*. + +To make a struct that holds a closure, we need to specify the type of the +closure, because a struct definition needs to know the types of each of its +fields. Each closure instance has its own unique anonymous type: that is, even +if two closures have the same signature, their types are still considered +different. To define structs, enums, or function parameters that use closures, +we use generics and trait bounds, as we discussed in Chapter 10. + +The `Fn` traits are provided by the standard library. All closures implement at +least one of the traits: `Fn`, `FnMut`, or `FnOnce`. We’ll discuss the +difference between these traits in the [“Capturing the Environment with +Closures”](#capturing-the-environment-with-closures) section; in +this example, we can use the `Fn` trait. + +We add types to the `Fn` trait bound to represent the types of the parameters +and return values the closures must have to match this trait bound. In this +case, our closure has a parameter of type `u32` and returns a `u32`, so the +trait bound we specify is `Fn(u32) -> u32`. + +Listing 13-9 shows the definition of the `Cacher` struct that holds a closure +and an optional result value. -
Filename: src/main.rs ```rust -fn main() { - let x = 4; - - let equal_to_x = |z| z == x; - - let y = 4; - - assert!(equal_to_x(y)); -} +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-09/src/main.rs:here}} ``` -
+Listing 13-9: Defining a `Cacher` struct that holds a +closure in `calculation` and an optional result in `value` -Listing 13-4: Example of a closure that refers to a variable in its enclosing -scope +The `Cacher` struct has a `calculation` field of the generic type `T`. The +trait bounds on `T` specify that it’s a closure by using the `Fn` trait. Any +closure we want to store in the `calculation` field must have one `u32` +parameter (specified within the parentheses after `Fn`) and must return a +`u32` (specified after the `->`). -
-
+> Note: Functions can implement all three of the `Fn` traits too. If what we +> want to do doesn’t require capturing a value from the environment, we can use +> a function rather than a closure where we need something that implements an +> `Fn` trait. -Here, even though `x` is not one of the parameters of `equal_to_x`, the -`equal_to_x` closure is allowed to use `x`, since `x` is a variable defined in -the scope that `equal_to_x` is defined. We aren't allowed to do the same thing -that Listing 13-4 does with functions; let's see what happens if we try: +The `value` field is of type `Option`. Before we execute the closure, +`value` will be `None`. When code using a `Cacher` asks for the *result* of the +closure, the `Cacher` will execute the closure at that time and store the +result within a `Some` variant in the `value` field. Then if the code asks for +the result of the closure again, instead of executing the closure again, the +`Cacher` will return the result held in the `Some` variant. + +The logic around the `value` field we’ve just described is defined in Listing +13-10. Filename: src/main.rs -```rust,ignore -fn main() { - let x = 4; +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-10/src/main.rs:here}} +``` - fn equal_to_x(z: i32) -> bool { z == x } +Listing 13-10: The caching logic of `Cacher` - let y = 4; +We want `Cacher` to manage the struct fields’ values rather than letting the +calling code potentially change the values in these fields directly, so these +fields are private. - assert!(equal_to_x(y)); -} +The `Cacher::new` function takes a generic parameter `T`, which we’ve defined +as having the same trait bound as the `Cacher` struct. Then `Cacher::new` +returns a `Cacher` instance that holds the closure specified in the +`calculation` field and a `None` value in the `value` field, because we haven’t +executed the closure yet. + +When the calling code needs the result of evaluating the closure, instead of +calling the closure directly, it will call the `value` method. This method +checks whether we already have a resulting value in `self.value` in a `Some`; +if we do, it returns the value within the `Some` without executing the closure +again. + +If `self.value` is `None`, the code calls the closure stored in +`self.calculation`, saves the result in `self.value` for future use, and +returns the value as well. + +Listing 13-11 shows how we can use this `Cacher` struct in the function +`generate_workout` from Listing 13-6. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-11/src/main.rs:here}} +``` + +Listing 13-11: Using `Cacher` in the `generate_workout` +function to abstract away the caching logic + +Instead of saving the closure in a variable directly, we save a new instance of +`Cacher` that holds the closure. Then, in each place we want the result, we +call the `value` method on the `Cacher` instance. We can call the `value` +method as many times as we want, or not call it at all, and the expensive +calculation will be run a maximum of once. + +Try running this program with the `main` function from Listing 13-2. Change the +values in the `simulated_user_specified_value` and `simulated_random_number` +variables to verify that in all the cases in the various `if` and `else` +blocks, `calculating slowly...` appears only once and only when needed. The +`Cacher` takes care of the logic necessary to ensure we aren’t calling the +expensive calculation more than we need to so `generate_workout` can focus on +the business logic. + +### Limitations of the `Cacher` Implementation + +Caching values is a generally useful behavior that we might want to use in +other parts of our code with different closures. However, there are two +problems with the current implementation of `Cacher` that would make reusing it +in different contexts difficult. + +The first problem is that a `Cacher` instance assumes it will always get the +same value for the parameter `arg` to the `value` method. That is, this test of +`Cacher` will fail: + +```rust,ignore,panics +{{#rustdoc_include ../listings/ch13-functional-features/no-listing-01-failing-cacher-test/src/lib.rs:here}} +``` + +This test creates a new `Cacher` instance with a closure that returns the value +passed into it. We call the `value` method on this `Cacher` instance with an +`arg` value of 1 and then an `arg` value of 2, and we expect the call to +`value` with the `arg` value of 2 to return 2. + +Run this test with the `Cacher` implementation in Listing 13-9 and Listing +13-10, and the test will fail on the `assert_eq!` with this message: + +```console +{{#include ../listings/ch13-functional-features/no-listing-01-failing-cacher-test/output.txt}} +``` + +The problem is that the first time we called `c.value` with 1, the `Cacher` +instance saved `Some(1)` in `self.value`. Thereafter, no matter what we pass into +the `value` method, it will always return 1. + +Try modifying `Cacher` to hold a hash map rather than a single value. The keys +of the hash map will be the `arg` values that are passed in, and the values of +the hash map will be the result of calling the closure on that key. Instead of +looking at whether `self.value` directly has a `Some` or a `None` value, the +`value` function will look up the `arg` in the hash map and return the value if +it’s present. If it’s not present, the `Cacher` will call the closure and save +the resulting value in the hash map associated with its `arg` value. + +The second problem with the current `Cacher` implementation is that it only +accepts closures that take one parameter of type `u32` and return a `u32`. We +might want to cache the results of closures that take a string slice and return +`usize` values, for example. To fix this issue, try introducing more generic +parameters to increase the flexibility of the `Cacher` functionality. + +### Capturing the Environment with Closures + +In the workout generator example, we only used closures as inline anonymous +functions. However, closures have an additional capability that functions don’t +have: they can capture their environment and access variables from the scope in +which they’re defined. + +Listing 13-12 has an example of a closure stored in the `equal_to_x` variable +that uses the `x` variable from the closure’s surrounding environment. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-12/src/main.rs}} +``` + +Listing 13-12: Example of a closure that refers to a +variable in its enclosing scope + +Here, even though `x` is not one of the parameters of `equal_to_x`, the +`equal_to_x` closure is allowed to use the `x` variable that’s defined in the +same scope that `equal_to_x` is defined in. + +We can’t do the same with functions; if we try with the following example, our +code won’t compile: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch13-functional-features/no-listing-02-functions-cant-capture/src/main.rs}} ``` We get an error: -```text -error[E0434]: can't capture dynamic environment in a fn item; use the || { ... } -closure form instead - --> - | -4 | fn equal_to_x(z: i32) -> bool { z == x } - | ^ +```console +{{#include ../listings/ch13-functional-features/no-listing-02-functions-cant-capture/output.txt}} ``` The compiler even reminds us that this only works with closures! -Creating closures that capture values from their environment is mostly used in -the context of starting new threads. We'll show some more examples and explain -more detail about this feature of closures in Chapter 16 when we talk about -concurrency. +When a closure captures a value from its environment, it uses memory to store +the values for use in the closure body. This use of memory is overhead that we +don’t want to pay in more common cases where we want to execute code that +doesn’t capture its environment. Because functions are never allowed to capture +their environment, defining and using functions will never incur this overhead. -### Closures as Function Parameters Using the `Fn` Traits +Closures can capture values from their environment in three ways, which +directly map to the three ways a function can take a parameter: taking +ownership, borrowing mutably, and borrowing immutably. These are encoded in the +three `Fn` traits as follows: -While we can bind closures to variables, that's not the most useful thing we -can do with them. We can also define functions that have closures as parameters -by using the `Fn` traits. Here's an example of a function named `call_with_one` -whose signature has a closure as a parameter: +* `FnOnce` consumes the variables it captures from its enclosing scope, known + as the closure’s *environment*. To consume the captured variables, the + closure must take ownership of these variables and move them into the closure + when it is defined. The `Once` part of the name represents the fact that the + closure can’t take ownership of the same variables more than once, so it can + be called only once. +* `FnMut` can change the environment because it mutably borrows values. +* `Fn` borrows values from the environment immutably. -```rust -fn call_with_one(some_closure: F) -> i32 - where F: Fn(i32) -> i32 { +When you create a closure, Rust infers which trait to use based on how the +closure uses the values from the environment. All closures implement `FnOnce` +because they can all be called at least once. Closures that don’t move the +captured variables also implement `FnMut`, and closures that don’t need mutable +access to the captured variables also implement `Fn`. In Listing 13-12, the +`equal_to_x` closure borrows `x` immutably (so `equal_to_x` has the `Fn` trait) +because the body of the closure only needs to read the value in `x`. - some_closure(1) -} +If you want to force the closure to take ownership of the values it uses in the +environment, you can use the `move` keyword before the parameter list. This +technique is mostly useful when passing a closure to a new thread to move the +data so it’s owned by the new thread. -let answer = call_with_one(|x| x + 2); +> Note: `move` closures may still implement `Fn` or `FnMut`, even though +> they capture variables by move. This is because the traits implemented by a +> closure type are determined by what the closure does with captured values, +> not how it captures them. The `move` keyword only specifies the latter. -assert_eq!(3, answer); +We’ll have more examples of `move` closures in Chapter 16 when we talk about +concurrency. For now, here’s the code from Listing 13-12 with the `move` +keyword added to the closure definition and using vectors instead of integers, +because integers can be copied rather than moved; note that this code will not +yet compile. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch13-functional-features/no-listing-03-move-closures/src/main.rs}} ``` -We pass the closure `|x| x + 2`, to `call_with_one`, and `call_with_one` calls -that closure with `1` as an argument. The return value of the call to -`some_closure` is then returned from `call_with_one`. +We receive the following error: -The signature of `call_with_one` is using the `where` syntax discussed in the -Traits section of Chapter 10. The `some_closure` parameter has the generic type -`F`, which in the `where` clause is defined as having the trait bounds -`Fn(i32) -> i32`. The `Fn` trait represents a closure, and we can add types to -the `Fn` trait to represent a specific type of closure. In this case, our -closure has a parameter of type `i32` and returns an `i32`, so the generic bound -we specify is `Fn(i32) -> i32`. +```console +{{#include ../listings/ch13-functional-features/no-listing-03-move-closures/output.txt}} +``` -Specifying a function signature that contains a closure requires the use of -generics and trait bounds. Each closure has a unique type, so we can't write -the type of a closure directly, we have to use generics. +The `x` value is moved into the closure when the closure is defined, because we +added the `move` keyword. The closure then has ownership of `x`, and `main` +isn’t allowed to use `x` anymore in the `println!` statement. Removing +`println!` will fix this example. -`Fn` isn't the only trait bound available for specifying closures, however. -There are three: `Fn`, `FnMut`, and `FnOnce`. This continues the patterns of -threes we've seen elsewhere in Rust: borrowing, borrowing mutably, and -ownership. Using `Fn` specifies that the closure used may only borrow values in -its environment. To specify a closure that mutates the environment, use -`FnMut`, and if the closure takes ownership of the environment, `FnOnce`. Most -of the time, you can start with `Fn`, and the compiler will tell you if you -need `FnMut` or `FnOnce` based on what happens when the function calls the -closure. +Most of the time when specifying one of the `Fn` trait bounds, you can start +with `Fn` and the compiler will tell you if you need `FnMut` or `FnOnce` based +on what happens in the closure body. -To illustrate a situation where it's useful for a function to have a parameter -that's a closure, let's move on to our next topic: iterators. +To illustrate situations where closures that can capture their environment are +useful as function parameters, let’s move on to our next topic: iterators. diff --git a/src/ch13-02-iterators.md b/src/ch13-02-iterators.md index b7e4c03..070a330 100644 --- a/src/ch13-02-iterators.md +++ b/src/ch13-02-iterators.md @@ -1,251 +1,328 @@ -## Iterators +## Processing a Series of Items with Iterators -Iterators are a pattern in Rust that allows you to do some processing on a -sequence of items. For example, the code in Listing 13-5 adds one to each -number in a vector: +The iterator pattern allows you to perform some task on a sequence of items in +turn. An iterator is responsible for the logic of iterating over each item and +determining when the sequence has finished. When you use iterators, you don’t +have to reimplement that logic yourself. -
+In Rust, iterators are *lazy*, meaning they have no effect until you call +methods that consume the iterator to use it up. For example, the code in +Listing 13-13 creates an iterator over the items in the vector `v1` by calling +the `iter` method defined on `Vec`. This code by itself doesn’t do anything +useful. ```rust -let v1 = vec![1, 2, 3]; - -let v2: Vec = v1.iter().map(|x| x + 1).collect(); - -assert_eq!(v2, [2, 3, 4]); +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-13/src/main.rs:here}} ``` -
+Listing 13-13: Creating an iterator -Listing 13-5: Using an iterator, `map`, and `collect` to add one to each number -in a vector +Once we’ve created an iterator, we can use it in a variety of ways. In Listing +3-5 in Chapter 3, we used iterators with `for` loops to execute some code on +each item, although we glossed over what the call to `iter` did until now. -
-
- - - -The `iter` method on vectors allows us to produce an *iterator* from the -vector. Next, the `map` method called on the iterator allows us to process each -element: in this case, we've passed a closure to `map` that specifies for every -element `x`, add one to it. `map` is one of the most basic ways of interacting -with an iterator, as processing each element in turn is very useful! Finally, -the `collect` method consumes the iterator and puts the iterator's elements -into a new data structure. In this case, since we've said that `v2` has the -type `Vec`, `collect` will create a new vector out of the `i32` values. - -Methods on iterators like `map` are sometimes called *iterator adaptors* -because they take one iterator and produce a new iterator. That is, `map` -builds on top of our previous iterator and produces another iterator by calling -the closure it's passed to create the new sequence of values. - -So, to recap, this line of code does the following: - -1. Creates an iterator from the vector. -2. Uses the `map` adaptor with a closure argument to add one to each element. -3. Uses the `collect` adaptor to consume the iterator and make a new vector. - -That's how we end up with `[2, 3, 4]`. As you can see, closures are a very -important part of using iterators: they provide a way of customizing the -behavior of an iterator adaptor like `map`. - -### Iterators are Lazy - -In the previous section, you may have noticed a subtle difference in wording: -we said that `map` *adapts* an iterator, but `collect` *consumes* one. That was -intentional. By themselves, iterators won't do anything; they're lazy. That is, -if we write code like Listing 13-5 except we don't call `collect`: +The example in Listing 13-14 separates the creation of the iterator from the +use of the iterator in the `for` loop. The iterator is stored in the `v1_iter` +variable, and no iteration takes place at that time. When the `for` loop is +called using the iterator in `v1_iter`, each element in the iterator is used in +one iteration of the loop, which prints out each value. ```rust -let v1: Vec = vec![1, 2, 3]; - -v1.iter().map(|x| x + 1); // without collect +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-14/src/main.rs:here}} ``` -It will compile, but it will give us a warning: +Listing 13-14: Using an iterator in a `for` loop -```text -warning: unused result which must be used: iterator adaptors are lazy and do -nothing unless consumed, #[warn(unused_must_use)] on by default - --> src/main.rs:4:1 - | -4 | v1.iter().map(|x| x + 1); // without collect - | ^^^^^^^^^^^^^^^^^^^^^^^^^ -``` +In languages that don’t have iterators provided by their standard libraries, +you would likely write this same functionality by starting a variable at index +0, using that variable to index into the vector to get a value, and +incrementing the variable value in a loop until it reached the total number of +items in the vector. -We get this warning because iterator adaptors won't start actually doing the -processing on their own. They need some other method that causes the iterator -chain to evaluate. We call those *consuming adaptors*, and `collect` is one of -them. +Iterators handle all that logic for you, cutting down on repetitive code you +could potentially mess up. Iterators give you more flexibility to use the same +logic with many different kinds of sequences, not just data structures you can +index into, like vectors. Let’s examine how iterators do that. -So how do we tell which iterator methods consume the iterator or not? And what -adaptors are available? For that, let's look at the `Iterator` trait. +### The `Iterator` Trait and the `next` Method -### The `Iterator` trait - -Iterators all implement a trait named `Iterator` that is defined in the standard -library. The definition of the trait looks like this: +All iterators implement a trait named `Iterator` that is defined in the +standard library. The definition of the trait looks like this: ```rust -trait Iterator { +pub trait Iterator { type Item; fn next(&mut self) -> Option; + + // methods with default implementations elided } ``` -There's some new syntax that we haven't covered here yet: `type Item` and -`Self::Item` are defining an *associated type* with this trait, and we'll talk -about associated types in depth in Chapter XX. For now, all you need to know is -that this code says the `Iterator` trait requires that you also define an -`Item` type, and this `Item` type is used in the return type of the `next` -method. In other words, the `Item` type will be the type of element that's -returned from the iterator. - -Let's make an iterator named `Counter` that will count from `1` to `5`, using -the `Iterator` trait. First, we need to create a struct that holds the current -state of the iterator, which is one field named `count` that will hold a `u32`. -We'll also define a `new` method, which isn't strictly necessary. We want our -`Counter` to go from one to five, though, so we're always going to have it -holding a zero to start: - -```rust -struct Counter { - count: u32, -} - -impl Counter { - fn new() -> Counter { - Counter { count: 0 } - } -} -``` - -Next, we're going to implement the `Iterator` trait for our `Counter` type by -defining the body of the `next` method. The way we want our iterator to work -is to add one to the state (which is why we initialized `count` to 0, since we -want our iterator to return one first). If `count` is still less than six, we'll -return the current value, but if `count` is six or higher, our iterator will -return `None`, as shown in Listing 13-6: - -
- -```rust -# struct Counter { -# count: u32, -# } -# -impl Iterator for Counter { - // Our iterator will produce u32s - type Item = u32; - - fn next(&mut self) -> Option { - // increment our count. This is why we started at zero. - self.count += 1; - - // check to see if we've finished counting or not. - if self.count < 6 { - Some(self.count) - } else { - None - } - } -} -``` - -
- -Listing 13-6: Implementing the `Iterator` trait on our `Counter` struct - -
-
- - - -The `type Item = u32` line is saying that the associated `Item` type will be -a `u32` for our iterator. Again, don't worry about associated types yet, because -we'll be covering them in Chapter XX. - -The `next` method is the main interface into an iterator, and it returns an -`Option`. If the option is `Some(value)`, we have gotten another value from the -iterator. If it's `None`, iteration is finished. Inside of the `next` method, -we do whatever kind of calculation our iterator needs to do. In this case, we -add one, then check to see if we're still below six. If we are, we can return -`Some(self.count)` to produce the next value. If we're at six or more, -iteration is over, so we return `None`. - -The iterator trait specifies that when an iterator returns `None`, that -indicates iteration is finished. The trait does not mandate anything about the -behavior an iterator must have if the `next` method is called again after -having returned one `None` value. In this case, every time we call `next` after -getting the first `None` value will still return `None`, but the internal -`count` field will continue to be incremented by one each time. If we call -`next` as many times as the maximum value a `u32` value can hold, `count` will -overflow (which will `panic!` in debug mode and wrap in release mode). Other -iterator implementations choose to start iterating again. If you need to be -sure to have an iterator that will always return `None` on subsequent calls to -the `next` method after the first `None` value is returned, you can use the -`fuse` method to create an iterator with that characteristic out of any other +Notice this definition uses some new syntax: `type Item` and `Self::Item`, +which are defining an *associated type* with this trait. We’ll talk about +associated types in depth in Chapter 19. For now, all you need to know is that +this code says implementing the `Iterator` trait requires that you also define +an `Item` type, and this `Item` type is used in the return type of the `next` +method. In other words, the `Item` type will be the type returned from the iterator. -Once we've implemented the `Iterator` trait, we have an iterator! We can use -the iterator functionality that our `Counter` struct now has by calling the -`next` method on it repeatedly: +The `Iterator` trait only requires implementors to define one method: the +`next` method, which returns one item of the iterator at a time wrapped in +`Some` and, when iteration is over, returns `None`. -```rust,ignore -let mut counter = Counter::new(); +We can call the `next` method on iterators directly; Listing 13-15 demonstrates +what values are returned from repeated calls to `next` on the iterator created +from the vector. -let x = counter.next(); -println!("{:?}", x); +Filename: src/lib.rs -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); - -let x = counter.next(); -println!("{:?}", x); +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-15/src/lib.rs:here}} ``` -This will print `Some(1)` through `Some(5)` and then `None`, each on their own -line. +Listing 13-15: Calling the `next` method on an +iterator -### All Sorts of `Iterator` Adaptors +Note that we needed to make `v1_iter` mutable: calling the `next` method on an +iterator changes internal state that the iterator uses to keep track of where +it is in the sequence. In other words, this code *consumes*, or uses up, the +iterator. Each call to `next` eats up an item from the iterator. We didn’t need +to make `v1_iter` mutable when we used a `for` loop because the loop took +ownership of `v1_iter` and made it mutable behind the scenes. -In Listing 13-5, we had iterators and we called methods like `map` and -`collect` on them. In Listing 13-6, however, we only implemented the `next` -method on our `Counter`. How do we get methods like `map` and `collect` on our -`Counter`? +Also note that the values we get from the calls to `next` are immutable +references to the values in the vector. The `iter` method produces an iterator +over immutable references. If we want to create an iterator that takes +ownership of `v1` and returns owned values, we can call `into_iter` instead of +`iter`. Similarly, if we want to iterate over mutable references, we can call +`iter_mut` instead of `iter`. -Well, when we told you about the definition of `Iterator`, we committed a small -lie of omission. The `Iterator` trait has a number of other useful methods -defined on it that come with default implementations that call the `next` -method. Since `next` is the only method of the `Iterator` trait that does not -have a default implementation, once you've done that, you get all of the other -`Iterator` adaptors for free. There are a lot of them! +### Methods that Consume the Iterator -For example, if for some reason we wanted to take the first five values that -an instance of `Counter` produces, pair those values with values produced by -another `Counter` instance after skipping the first value that instance -produces, multiply each pair together, keep only those results that are -divisible by three, and add all the resulting values together, we could do: +The `Iterator` trait has a number of different methods with default +implementations provided by the standard library; you can find out about these +methods by looking in the standard library API documentation for the `Iterator` +trait. Some of these methods call the `next` method in their definition, which +is why you’re required to implement the `next` method when implementing the +`Iterator` trait. -```rust,ignore -let sum: u32 = Counter::new().take(5) - .zip(Counter::new().skip(1)) - .map(|(a, b)| a * b) - .filter(|x| x % 3 == 0) - .sum(); -assert_eq!(48, sum); +Methods that call `next` are called *consuming adaptors*, because calling them +uses up the iterator. One example is the `sum` method, which takes ownership of +the iterator and iterates through the items by repeatedly calling `next`, thus +consuming the iterator. As it iterates through, it adds each item to a running +total and returns the total when iteration is complete. Listing 13-16 has a +test illustrating a use of the `sum` method: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-16/src/lib.rs:here}} ``` -All of these method calls are possible because we implemented the `Iterator` -trait by specifying how the `next` method works. Use the standard library -documentation to find more useful methods that will come in handy when you're -working with iterators. +Listing 13-16: Calling the `sum` method to get the total +of all items in the iterator + +We aren’t allowed to use `v1_iter` after the call to `sum` because `sum` takes +ownership of the iterator we call it on. + +### Methods that Produce Other Iterators + +Other methods defined on the `Iterator` trait, known as *iterator adaptors*, +allow you to change iterators into different kinds of iterators. You can chain +multiple calls to iterator adaptors to perform complex actions in a readable +way. But because all iterators are lazy, you have to call one of the consuming +adaptor methods to get results from calls to iterator adaptors. + +Listing 13-17 shows an example of calling the iterator adaptor method `map`, +which takes a closure to call on each item to produce a new iterator. The +closure here creates a new iterator in which each item from the vector has been +incremented by 1. However, this code produces a warning: + +Filename: src/main.rs + +```rust,not_desired_behavior +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-17/src/main.rs:here}} +``` + +Listing 13-17: Calling the iterator adaptor `map` to +create a new iterator + +The warning we get is this: + +```console +{{#include ../listings/ch13-functional-features/listing-13-17/output.txt}} +``` + +The code in Listing 13-17 doesn’t do anything; the closure we’ve specified +never gets called. The warning reminds us why: iterator adaptors are lazy, and +we need to consume the iterator here. + +To fix this and consume the iterator, we’ll use the `collect` method, which we +used in Chapter 12 with `env::args` in Listing 12-1. This method consumes the +iterator and collects the resulting values into a collection data type. + +In Listing 13-18, we collect the results of iterating over the iterator that’s +returned from the call to `map` into a vector. This vector will end up +containing each item from the original vector incremented by 1. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-18/src/main.rs:here}} +``` + +Listing 13-18: Calling the `map` method to create a new +iterator and then calling the `collect` method to consume the new iterator and +create a vector + +Because `map` takes a closure, we can specify any operation we want to perform +on each item. This is a great example of how closures let you customize some +behavior while reusing the iteration behavior that the `Iterator` trait +provides. + +### Using Closures that Capture Their Environment + +Now that we’ve introduced iterators, we can demonstrate a common use of +closures that capture their environment by using the `filter` iterator adaptor. +The `filter` method on an iterator takes a closure that takes each item from +the iterator and returns a Boolean. If the closure returns `true`, the value +will be included in the iterator produced by `filter`. If the closure returns +`false`, the value won’t be included in the resulting iterator. + +In Listing 13-19, we use `filter` with a closure that captures the `shoe_size` +variable from its environment to iterate over a collection of `Shoe` struct +instances. It will return only shoes that are the specified size. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-19/src/lib.rs}} +``` + +Listing 13-19: Using the `filter` method with a closure +that captures `shoe_size` + +The `shoes_in_size` function takes ownership of a vector of shoes and a shoe +size as parameters. It returns a vector containing only shoes of the specified +size. + +In the body of `shoes_in_size`, we call `into_iter` to create an iterator +that takes ownership of the vector. Then we call `filter` to adapt that +iterator into a new iterator that only contains elements for which the closure +returns `true`. + +The closure captures the `shoe_size` parameter from the environment and +compares the value with each shoe’s size, keeping only shoes of the size +specified. Finally, calling `collect` gathers the values returned by the +adapted iterator into a vector that’s returned by the function. + +The test shows that when we call `shoes_in_size`, we get back only shoes +that have the same size as the value we specified. + +### Creating Our Own Iterators with the `Iterator` Trait + +We’ve shown that you can create an iterator by calling `iter`, `into_iter`, or +`iter_mut` on a vector. You can create iterators from the other collection +types in the standard library, such as hash map. You can also create iterators +that do anything you want by implementing the `Iterator` trait on your own +types. As previously mentioned, the only method you’re required to provide a +definition for is the `next` method. Once you’ve done that, you can use all +other methods that have default implementations provided by the `Iterator` +trait! + +To demonstrate, let’s create an iterator that will only ever count from 1 to 5. +First, we’ll create a struct to hold some values. Then we’ll make this struct +into an iterator by implementing the `Iterator` trait and using the values in +that implementation. + +Listing 13-20 has the definition of the `Counter` struct and an associated +`new` function to create instances of `Counter`: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-20/src/lib.rs}} +``` + +Listing 13-20: Defining the `Counter` struct and a `new` +function that creates instances of `Counter` with an initial value of 0 for +`count` + +The `Counter` struct has one field named `count`. This field holds a `u32` +value that will keep track of where we are in the process of iterating from 1 +to 5. The `count` field is private because we want the implementation of +`Counter` to manage its value. The `new` function enforces the behavior of +always starting new instances with a value of 0 in the `count` field. + +Next, we’ll implement the `Iterator` trait for our `Counter` type by defining +the body of the `next` method to specify what we want to happen when this +iterator is used, as shown in Listing 13-21: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-21/src/lib.rs:here}} +``` + +Listing 13-21: Implementing the `Iterator` trait on our +`Counter` struct + +We set the associated `Item` type for our iterator to `u32`, meaning the +iterator will return `u32` values. Again, don’t worry about associated types +yet, we’ll cover them in Chapter 19. + +We want our iterator to add 1 to the current state, so we initialized `count` +to 0 so it would return 1 first. If the value of `count` is less than 5, `next` +will increment `count` and return the current value wrapped in `Some`. Once +`count` is 5, our iterator will stop incrementing `count` and always return +`None`. + +#### Using Our `Counter` Iterator’s `next` Method + +Once we’ve implemented the `Iterator` trait, we have an iterator! Listing 13-22 +shows a test demonstrating that we can use the iterator functionality of our +`Counter` struct by calling the `next` method on it directly, just as we did +with the iterator created from a vector in Listing 13-15. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-22/src/lib.rs:here}} +``` + +Listing 13-22: Testing the functionality of the `next` +method implementation + +This test creates a new `Counter` instance in the `counter` variable and then +calls `next` repeatedly, verifying that we have implemented the behavior we +want this iterator to have: returning the values from 1 to 5. + +#### Using Other `Iterator` Trait Methods + +We implemented the `Iterator` trait by defining the `next` method, so we +can now use any `Iterator` trait method’s default implementations as defined in +the standard library, because they all use the `next` method’s functionality. + +For example, if for some reason we wanted to take the values produced by an +instance of `Counter`, pair them with values produced by another `Counter` +instance after skipping the first value, multiply each pair together, keep only +those results that are divisible by 3, and add all the resulting values +together, we could do so, as shown in the test in Listing 13-23: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-23/src/lib.rs:here}} +``` + +Listing 13-23: Using a variety of `Iterator` trait +methods on our `Counter` iterator + +Note that `zip` produces only four pairs; the theoretical fifth pair `(5, +None)` is never produced because `zip` returns `None` when either of its input +iterators return `None`. + +All of these method calls are possible because we specified how the `next` +method works, and the standard library provides default implementations for +other methods that call `next`. diff --git a/src/ch13-03-improving-our-io-project.md b/src/ch13-03-improving-our-io-project.md index b10a054..28a4945 100644 --- a/src/ch13-03-improving-our-io-project.md +++ b/src/ch13-03-improving-our-io-project.md @@ -1,190 +1,179 @@ -## Improving our I/O Project +## Improving Our I/O Project -In our I/O project implementing `grep` in the last chapter, there are some -places where the code could be made clearer and more concise using iterators. -Let's take a look at how iterators can improve our implementation of the -`Config::new` function and the `grep` function. +With this new knowledge about iterators, we can improve the I/O project in +Chapter 12 by using iterators to make places in the code clearer and more +concise. Let’s look at how iterators can improve our implementation of the +`Config::new` function and the `search` function. -### Removing a `clone` by Using an Iterator +### Removing a `clone` Using an Iterator -Back in listing 12-8, we had this code that took a slice of `String` values and -created an instance of the `Config` struct by checking for the right number of -arguments, indexing into the slice, and cloning the values so that the `Config` -struct could own those values: +In Listing 12-6, we added code that took a slice of `String` values and created +an instance of the `Config` struct by indexing into the slice and cloning the +values, allowing the `Config` struct to own those values. In Listing 13-24, +we’ve reproduced the implementation of the `Config::new` function as it was in +Listing 12-23: + +Filename: src/lib.rs ```rust,ignore -impl Config { - fn new(args: &[String]) -> Result { - if args.len() < 3 { - return Err("not enough arguments"); - } - - let search = args[1].clone(); - let filename = args[2].clone(); - - Ok(Config { - search: search, - filename: filename, - }) - } -} +{{#rustdoc_include ../listings/ch13-functional-features/listing-12-23-reproduced/src/lib.rs:ch13}} ``` -At the time, we said not to worry about the `clone` calls here, and that we -could remove them in the future. Well, that time is now! So, why do we need -`clone` here? The issue is that we have a slice with `String` elements in the -parameter `args`, and the `new` function does not own `args`. In order to be -able to return ownership of a `Config` instance, we need to clone the values -that we put in the `search` and `filename` fields of `Config`, so that the -`Config` instance can own its values. +Listing 13-24: Reproduction of the `Config::new` function +from Listing 12-23 -Now that we know more about iterators, we can change the `new` function to -instead take ownership of an iterator as its argument. We'll use the iterator -functionality instead of having to check the length of the slice and index into -specific locations. Since we've taken ownership of the iterator, and we won't be -using indexing operations that borrow anymore, we can move the `String` values -from the iterator into `Config` instead of calling `clone` and making a new -allocation. +At the time, we said not to worry about the inefficient `clone` calls because +we would remove them in the future. Well, that time is now! -First, let's take `main` as it was in Listing 12-6, and change it to pass the -return value of `env::args` to `Config::new`, instead of calling `collect` and -passing a slice: +We needed `clone` here because we have a slice with `String` elements in the +parameter `args`, but the `new` function doesn’t own `args`. To return +ownership of a `Config` instance, we had to clone the values from the `query` +and `filename` fields of `Config` so the `Config` instance can own its values. + +With our new knowledge about iterators, we can change the `new` function to +take ownership of an iterator as its argument instead of borrowing a slice. +We’ll use the iterator functionality instead of the code that checks the length +of the slice and indexes into specific locations. This will clarify what the +`Config::new` function is doing because the iterator will access the values. + +Once `Config::new` takes ownership of the iterator and stops using indexing +operations that borrow, we can move the `String` values from the iterator into +`Config` rather than calling `clone` and making a new allocation. + +#### Using the Returned Iterator Directly + +Open your I/O project’s *src/main.rs* file, which should look like this: + +Filename: src/main.rs ```rust,ignore -fn main() { - let config = Config::new(env::args()); - // ...snip... +{{#rustdoc_include ../listings/ch13-functional-features/listing-12-24-reproduced/src/main.rs:ch13}} ``` - - -If we look in the standard library documentation for the `env::args` function, -we'll see that its return type is `std::env::Args`. So next we'll update the -signature of the `Config::new` function so that the parameter `args` has the -type `std::env::Args` instead of `&[String]`: +We’ll change the start of the `main` function that we had in Listing 12-24 to +the code in Listing 13-25. This won’t compile until we update `Config::new` as +well. +Filename: src/main.rs ```rust,ignore -impl Config { - fn new(args: std::env::Args) -> Result { - // ...snip... +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-25/src/main.rs:here}} ``` - +Listing 13-25: Passing the return value of `env::args` to +`Config::new` -Next, we'll fix the body of `Config::new`. As we can also see in the standard -library documentation, `std::env::Args` implements the `Iterator` trait, so we -know we can call the `next` method on it! Here's the new code: +The `env::args` function returns an iterator! Rather than collecting the +iterator values into a vector and then passing a slice to `Config::new`, now +we’re passing ownership of the iterator returned from `env::args` to +`Config::new` directly. -```rust -# struct Config { -# search: String, -# filename: String, -# } -# -impl Config { - fn new(mut args: std::env::Args) -> Result { - args.next(); +Next, we need to update the definition of `Config::new`. In your I/O project’s +*src/lib.rs* file, let’s change the signature of `Config::new` to look like +Listing 13-26. This still won’t compile because we need to update the function +body. - let search = match args.next() { - Some(arg) => arg, - None => return Err("Didn't get a search string"), - }; +Filename: src/lib.rs - let filename = match args.next() { - Some(arg) => arg, - None => return Err("Didn't get a file name"), - }; - - Ok(Config { - search: search, - filename: filename, - }) - } -} +```rust,ignore +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-26/src/lib.rs:here}} ``` - +Listing 13-26: Updating the signature of `Config::new` to +expect an iterator + +The standard library documentation for the `env::args` function shows that the +type of the iterator it returns is `std::env::Args`. We’ve updated the +signature of the `Config::new` function so the parameter `args` has the type +`std::env::Args` instead of `&[String]`. Because we’re taking ownership of +`args` and we’ll be mutating `args` by iterating over it, we can add the `mut` +keyword into the specification of the `args` parameter to make it mutable. + +We also needed to specify that the string slice error type can now only have +the `'static` lifetime. Because we’re only ever returning string literals, this +was true before. However, when we had a reference in the parameters, there was +the possibility that the reference in the return type could have had the same +lifetime as the reference in the parameters. The rules that we discussed in the +[“Lifetime Elision”][lifetime-elision] section of Chapter 10 applied, and we +weren’t required to annotate the lifetime of `&str`. With the change to `args`, +the lifetime elision rules no longer apply, and we must specify the `'static` +lifetime. + +#### Using `Iterator` Trait Methods Instead of Indexing + +Next, we’ll fix the body of `Config::new`. The standard library documentation +also mentions that `std::env::Args` implements the `Iterator` trait, so we know +we can call the `next` method on it! Listing 13-27 updates the code from +Listing 12-23 to use the `next` method: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-27/src/lib.rs:here}} +``` + +Listing 13-27: Changing the body of `Config::new` to use +iterator methods Remember that the first value in the return value of `env::args` is the name of -the program. We want to ignore that, so first we'll call `next` and not do -anything with the return value. The second time we call `next` should be the -value we want to put in the `search` field of `Config`. We use a `match` to -extract the value if `next` returns a `Some`, and we return early with an `Err` -value if there weren't enough arguments (which would cause this call to `next` -to return `None`). - -We do the same thing for the `filename` value. It's slightly unfortunate that -the `match` expressions for `search` and `filename` are so similar. It would be -nice if we could use `?` on the `Option` returned from `next`, but `?` only -works with `Result` values currently. Even if we could use `?` on `Option` like -we can on `Result`, the value we would get would be borrowed, and we want to -move the `String` from the iterator into `Config`. +the program. We want to ignore that and get to the next value, so first we call +`next` and do nothing with the return value. Second, we call `next` to get the +value we want to put in the `query` field of `Config`. If `next` returns a +`Some`, we use a `match` to extract the value. If it returns `None`, it means +not enough arguments were given and we return early with an `Err` value. We do +the same thing for the `filename` value. ### Making Code Clearer with Iterator Adaptors -The other bit of code where we could take advantage of iterators was in the -`grep` function as implemented in Listing 12-15: +We can also take advantage of iterators in the `search` function in our I/O +project, which is reproduced here in Listing 13-28 as it was in Listing 12-19: - +Filename: src/lib.rs -```rust -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let mut results = Vec::new(); - - for line in contents.lines() { - if line.contains(search) { - results.push(line); - } - } - - results -} +```rust,ignore +{{#rustdoc_include ../listings/ch12-an-io-project/listing-12-19/src/lib.rs:ch13}} ``` -We can write this code in a much shorter way, and avoiding having to have a -mutable intermediate `results` vector, by using iterator adaptor methods like -this instead: +Listing 13-28: The implementation of the `search` +function from Listing 12-19 -```rust -fn grep<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - contents.lines() - .filter(|line| line.contains(search)) - .collect() -} +We can write this code in a more concise way using iterator adaptor methods. +Doing so also lets us avoid having a mutable intermediate `results` vector. The +functional programming style prefers to minimize the amount of mutable state to +make code clearer. Removing the mutable state might enable a future enhancement +to make searching happen in parallel, because we wouldn’t have to manage +concurrent access to the `results` vector. Listing 13-29 shows this change: + +Filename: src/lib.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch13-functional-features/listing-13-29/src/lib.rs:here}} ``` -Here, we use the `filter` adaptor to only keep the lines that -`line.contains(search)` returns true for. We then collect them up into another -vector with `collect`. Much simpler! +Listing 13-29: Using iterator adaptor methods in the +implementation of the `search` function -We can use the same technique in the `grep_case_insensitive` function that we -defined in Listing 12-16 as follows: +Recall that the purpose of the `search` function is to return all lines in +`contents` that contain the `query`. Similar to the `filter` example in Listing +13-19, this code uses the `filter` adaptor to keep only the lines that +`line.contains(query)` returns `true` for. We then collect the matching lines +into another vector with `collect`. Much simpler! Feel free to make the same +change to use iterator methods in the `search_case_insensitive` function as +well. - +The next logical question is which style you should choose in your own code and +why: the original implementation in Listing 13-28 or the version using +iterators in Listing 13-29. Most Rust programmers prefer to use the iterator +style. It’s a bit tougher to get the hang of at first, but once you get a feel +for the various iterator adaptors and what they do, iterators can be easier to +understand. Instead of fiddling with the various bits of looping and building +new vectors, the code focuses on the high-level objective of the loop. This +abstracts away some of the commonplace code so it’s easier to see the concepts +that are unique to this code, such as the filtering condition each element in +the iterator must pass. -```rust -fn grep_case_insensitive<'a>(search: &str, contents: &'a str) -> Vec<&'a str> { - let search = search.to_lowercase(); +But are the two implementations truly equivalent? The intuitive assumption +might be that the more low-level loop will be faster. Let’s talk about +performance. - contents.lines() - .filter(|line| { - line.to_lowercase().contains(&search) - }).collect() -} -``` - -Not too bad! So which style should you choose? Most Rust programmers prefer to -use the iterator style. It's a bit tougher to understand at first, but once you -gain an intuition for what the various iterator adaptors do, this is much -easier to understand. Instead of fiddling with the various bits of looping -and building a new vector, the code focuses on the high-level objective of the -loop, abstracting some of the commonplace code so that it's easier to see the -concepts that are unique to this usage of the code, like the condition on which -the code is filtering each element in the iterator. - -But are they truly equivalent? Surely the more low-level loop will be faster. -Let's talk about performance. +[lifetime-elision]: ch10-03-lifetime-syntax.html#lifetime-elision diff --git a/src/ch13-04-performance.md b/src/ch13-04-performance.md index 3582089..eacb1ba 100644 --- a/src/ch13-04-performance.md +++ b/src/ch13-04-performance.md @@ -1,42 +1,47 @@ -## Performance +## Comparing Performance: Loops vs. Iterators -Which version of our `grep` functions is faster: the version with an explicit -`for` loop or the version with iterators? We ran a benchmark by loading the -entire contents of "The Adventures of Sherlock Holmes" by Sir Arthur Conan -Doyle into a `String` and looking for the word "the" in the contents. Here were -the results of the benchmark on the version of grep using the `for` loop and the -version using iterators: +To determine whether to use loops or iterators, you need to know which version +of our `search` functions is faster: the version with an explicit `for` loop or +the version with iterators. + +We ran a benchmark by loading the entire contents of *The Adventures of +Sherlock Holmes* by Sir Arthur Conan Doyle into a `String` and looking for the +word *the* in the contents. Here are the results of the benchmark on the +version of `search` using the `for` loop and the version using iterators: ```text -test bench_grep_for ... bench: 19,620,300 ns/iter (+/- 915,700) -test bench_grep_iter ... bench: 19,234,900 ns/iter (+/- 657,200) +test bench_search_for ... bench: 19,620,300 ns/iter (+/- 915,700) +test bench_search_iter ... bench: 19,234,900 ns/iter (+/- 657,200) ``` -The iterator version ended up slightly faster! We're not going to go through -the benchmark code here, as the point is not to prove that they're exactly -equivalent, but to get a general sense of how these two implementations -compare. For a *real* benchmark, you'd want to check various texts of various -sizes, different words, words of different lengths, and all kinds of other -variations. The point is this: iterators, while a high-level abstraction, get -compiled down to roughly the same code as if you'd written the lower-level code -yourself. Iterators are one of Rust's *zero-cost abstractions*, by which we mean -using the abstraction imposes no additional runtime overhead in the same way -that Bjarne Stroustrup, the original designer and implementer of C++, defines -*zero-overhead*: +The iterator version was slightly faster! We won’t explain the benchmark code +here, because the point is not to prove that the two versions are equivalent +but to get a general sense of how these two implementations compare +performance-wise. + +For a more comprehensive benchmark, you should check using various texts of +various sizes as the `contents`, different words and words of different lengths +as the `query`, and all kinds of other variations. The point is this: +iterators, although a high-level abstraction, get compiled down to roughly the +same code as if you’d written the lower-level code yourself. Iterators are one +of Rust’s *zero-cost abstractions*, by which we mean using the abstraction +imposes no additional runtime overhead. This is analogous to how Bjarne +Stroustrup, the original designer and implementor of C++, defines +*zero-overhead* in “Foundations of C++” (2012): > In general, C++ implementations obey the zero-overhead principle: What you > don’t use, you don’t pay for. And further: What you do use, you couldn’t hand > code any better. -> -> - Bjarne Stroustrup "Foundations of C++" -As another example, here is some code taken from an audio decoder. This code -uses an iterator chain to do some math on three variables in scope: a `buffer` -slice of data, an array of 12 `coefficients`, and an amount by which to shift -data in `qlp_shift`. We've declared the variables within this example but not -given them any values; while this code doesn't have much meaning outside of its -context, it's still a concise, real-world example of how Rust translates -high-level ideas to low-level code: +As another example, the following code is taken from an audio decoder. The +decoding algorithm uses the linear prediction mathematical operation to +estimate future values based on a linear function of the previous samples. This +code uses an iterator chain to do some math on three variables in scope: a +`buffer` slice of data, an array of 12 `coefficients`, and an amount by which +to shift data in `qlp_shift`. We’ve declared the variables within this example +but not given them any values; although this code doesn’t have much meaning +outside of its context, it’s still a concise, real-world example of how Rust +translates high-level ideas to low-level code. ```rust,ignore let buffer: &mut [i32]; @@ -53,33 +58,37 @@ for i in 12..buffer.len() { } ``` -In order to calculate the value of `prediction`, this code iterates through -each of the 12 values in `coefficients`, uses the `zip` method to pair the -coefficient values with the previous 12 values in `buffer`. Then for each pair, +To calculate the value of `prediction`, this code iterates through each of the +12 values in `coefficients` and uses the `zip` method to pair the coefficient +values with the previous 12 values in `buffer`. Then, for each pair, we multiply the values together, sum all the results, and shift the bits in the -sum `qlp_shift` bits to the right +sum `qlp_shift` bits to the right. Calculations in applications like audio decoders often prioritize performance -most highly. Here, we're creating an iterator, using two adaptors, then +most highly. Here, we’re creating an iterator, using two adaptors, and then consuming the value. What assembly code would this Rust code compile to? Well, -as of this writing, it compiles down to the same assembly you'd write by hand. -There's no loop at all corresponding to the iteration over the values in -`coefficients`: Rust knows that there are twelve iterations, so it "unrolls" -the loop. All of the coefficients get stored in registers (which means -accessing the values is very fast). There are no bounds checks on the array -access. It's extremely efficient. +as of this writing, it compiles down to the same assembly you’d write by hand. +There’s no loop at all corresponding to the iteration over the values in +`coefficients`: Rust knows that there are 12 iterations, so it “unrolls” the +loop. *Unrolling* is an optimization that removes the overhead of the loop +controlling code and instead generates repetitive code for each iteration of +the loop. -Now that you know this, go use iterators and closures without fear! They make -code feel higher-level, but don't impose a runtime performance penalty for -doing so. +All of the coefficients get stored in registers, which means accessing the +values is very fast. There are no bounds checks on the array access at runtime. +All these optimizations that Rust is able to apply make the resulting code +extremely efficient. Now that you know this, you can use iterators and closures +without fear! They make code seem like it’s higher level but don’t impose a +runtime performance penalty for doing so. ## Summary Closures and iterators are Rust features inspired by functional programming -language ideas. They contribute to Rust's ability to clearly express high-level -ideas. The implementations of closures and iterators, as well as other zero-cost -abstractions in Rust, are such that runtime performance is not affected. +language ideas. They contribute to Rust’s capability to clearly express +high-level ideas at low-level performance. The implementations of closures and +iterators are such that runtime performance is not affected. This is part of +Rust’s goal to strive to provide zero-cost abstractions. -Now that we've improved the expressiveness of our I/O project, let's look at -some more features of `cargo` that would help us get ready to share the project -with the world. +Now that we’ve improved the expressiveness of our I/O project, let’s look at +some more features of `cargo` that will help us share the project with the +world. diff --git a/src/ch14-00-more-about-cargo.md b/src/ch14-00-more-about-cargo.md index 6796a1e..d08d8cc 100644 --- a/src/ch14-00-more-about-cargo.md +++ b/src/ch14-00-more-about-cargo.md @@ -1,15 +1,15 @@ -# More about Cargo and Crates.io +# More About Cargo and Crates.io -We've used some features of Cargo in this book so far, but only the most basic -ones. We've used Cargo to build, run, and test our code, but it can do a lot -more. Let's go over some of its other features now. Cargo can do even more than -what we will cover in this chapter; for a full explanation, see its -documentation. +So far we’ve used only the most basic features of Cargo to build, run, and test +our code, but it can do a lot more. In this chapter, we’ll discuss some of its +other, more advanced features to show you how to do the following: -We're going to cover: +* Customize your build through release profiles +* Publish libraries on [crates.io](https://crates.io/) +* Organize large projects with workspaces +* Install binaries from [crates.io](https://crates.io/) +* Extend Cargo using custom commands -* Customizing your build through release profiles -* Publishing libraries on crates.io -* Organizing larger projects with workspaces -* Installing binaries from crates.io -* Extending Cargo with your own custom commands +Cargo can do even more than what we cover in this chapter, so for a full +explanation of all its features, see [its +documentation](https://doc.rust-lang.org/cargo/). diff --git a/src/ch14-01-release-profiles.md b/src/ch14-01-release-profiles.md index b24acb8..66f611c 100644 --- a/src/ch14-01-release-profiles.md +++ b/src/ch14-01-release-profiles.md @@ -1,28 +1,41 @@ -## Release profiles +## Customizing Builds with Release Profiles -Cargo supports a notion of *release profiles*. These profiles control various -options for compiling your code and let you configure each profile -independently of the others. You've seen a hint of this feature in the output -of your builds: +In Rust, *release profiles* are predefined and customizable profiles with +different configurations that allow a programmer to have more control over +various options for compiling code. Each profile is configured independently of +the others. -```text +Cargo has two main profiles: the `dev` profile Cargo uses when you run `cargo +build` and the `release` profile Cargo uses when you run `cargo build +--release`. The `dev` profile is defined with good defaults for development, +and the `release` profile has good defaults for release builds. + +These profile names might be familiar from the output of your builds: + + + +```console $ cargo build - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs + Finished dev [unoptimized + debuginfo] target(s) in 0.0s $ cargo build --release - Finished release [optimized] target(s) in 0.0 secs + Finished release [optimized] target(s) in 0.0s ``` -The "debug" and "release" notifications here indicate that the compiler is -using different profiles. Cargo supports four profiles: +The `dev` and `release` shown in this build output indicate that the compiler +is using different profiles. -* `dev`: used for `cargo build` -* `release` used for `cargo build --release` -* `test` used for `cargo test` -* `doc` used for `cargo doc` +Cargo has default settings for each of the profiles that apply when there +aren’t any `[profile.*]` sections in the project’s *Cargo.toml* file. By adding +`[profile.*]` sections for any profile you want to customize, you can override +any subset of the default settings. For example, here are the default values +for the `opt-level` setting for the `dev` and `release` profiles: -We can customize our `Cargo.toml` file with `[profile.*]` sections to tweak -various compiler options for these profiles. For example, here's one of the -default options for the `dev` and `release` profiles: +Filename: Cargo.toml ```toml [profile.dev] @@ -32,26 +45,32 @@ opt-level = 0 opt-level = 3 ``` -The `opt-level` setting controls how many optimizations Rust will apply to your -code. The setting goes from zero to three. Applying more optimizations takes -more time. When you're compiling very often in development, you'd usually want -compiling to be fast at the expense of the resulting code running slower. When -you're ready to release, it's better to spend more time compiling the one time -that you build your code to trade off for code that will run faster every time -you use that compiled code. +The `opt-level` setting controls the number of optimizations Rust will apply to +your code, with a range of 0 to 3. Applying more optimizations extends +compiling time, so if you’re in development and compiling your code often, +you’ll want faster compiling even if the resulting code runs slower. That is +the reason the default `opt-level` for `dev` is `0`. When you’re ready to +release your code, it’s best to spend more time compiling. You’ll only compile +in release mode once, but you’ll run the compiled program many times, so +release mode trades longer compile time for code that runs faster. That is why +the default `opt-level` for the `release` profile is `3`. -We could override these defaults by changing them in `Cargo.toml`. For example, -if we wanted to use optimization level 1 in development: +You can override any default setting by adding a different value for it in +*Cargo.toml*. For example, if we want to use optimization level 1 in the +development profile, we can add these two lines to our project’s *Cargo.toml* +file: + +Filename: Cargo.toml ```toml [profile.dev] opt-level = 1 ``` -This overrides the default setting of `0`, and now our development builds will -use more optimizations. Not as much as a release build, but a little bit more. +This code overrides the default setting of `0`. Now when we run `cargo build`, +Cargo will use the defaults for the `dev` profile plus our customization to +`opt-level`. Because we set `opt-level` to `1`, Cargo will apply more +optimizations than the default, but not as many as in a release build. -For the full list of settings and the defaults for each profile, see [Cargo's -documentation.][cargodoc] - -[cargodoc]: http://doc.crates.io/ +For the full list of configuration options and defaults for each profile, see +[Cargo’s documentation](https://doc.rust-lang.org/cargo/reference/profiles.html). diff --git a/src/ch14-02-publishing-to-crates-io.md b/src/ch14-02-publishing-to-crates-io.md index ff6b8f8..b9f43fb 100644 --- a/src/ch14-02-publishing-to-crates-io.md +++ b/src/ch14-02-publishing-to-crates-io.md @@ -1,410 +1,461 @@ ## Publishing a Crate to Crates.io -We've added crates from crates.io as dependencies of our project. We can choose -to share our code for other people to use as well. Crates.io distributes the -source code of your packages, so it is primarily used to distribute code that's -open source. +We’ve used packages from [crates.io](https://crates.io/) as +dependencies of our project, but you can also share your code with other people +by publishing your own packages. The crate registry at +[crates.io](https://crates.io/) distributes the source code of +your packages, so it primarily hosts code that is open source. -Rust and Cargo have some features that can make your published package easier -for people to find and use. We'll talk about some of those features, then cover -how to publish a package. +Rust and Cargo have features that help make your published package easier for +people to use and to find in the first place. We’ll talk about some of these +features next and then explain how to publish a package. -### Documentation Comments +### Making Useful Documentation Comments -In Chapter 3, we saw comments in Rust that start with `//`. Rust also has a -second kind of comment: the *documentation comment*. While comments can be -useful if someone is reading your code, you can generate HTML documentation -that displays the contents of documentation comments for public API items meant -for someone who's interested in knowing how to *use* your crate, as opposed to -how your crate is *implemented*. Note that documentation is only generated for -library crates, since binary crates don't have a public API that people need to -know how to use. +Accurately documenting your packages will help other users know how and when to +use them, so it’s worth investing the time to write documentation. In Chapter +3, we discussed how to comment Rust code using two slashes, `//`. Rust also has +a particular kind of comment for documentation, known conveniently as a +*documentation comment*, that will generate HTML documentation. The HTML +displays the contents of documentation comments for public API items intended +for programmers interested in knowing how to *use* your crate as opposed to how +your crate is *implemented*. -Documentation comments use `///` instead of `//` and support Markdown notation -inside. They go just before the item they are documenting. Here's documentation -comments for an `add_one` function: - -
+Documentation comments use three slashes, `///`, instead of two and support +Markdown notation for formatting the text. Place documentation comments just +before the item they’re documenting. Listing 14-1 shows documentation comments +for an `add_one` function in a crate named `my_crate`: Filename: src/lib.rs -````rust -/// Adds one to the number given. -/// -/// # Examples -/// -/// ``` -/// let five = 5; -/// -/// assert_eq!(6, add_one(5)); -/// # fn add_one(x: i32) -> i32 { -/// # x + 1 -/// # } -/// ``` -pub fn add_one(x: i32) -> i32 { - x + 1 -} -```` +```rust,ignore +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-01/src/lib.rs}} +``` -
+Listing 14-1: A documentation comment for a +function -Listing 14-1: A documentation comment for a function +Here, we give a description of what the `add_one` function does, start a +section with the heading `Examples`, and then provide code that demonstrates +how to use the `add_one` function. We can generate the HTML documentation from +this documentation comment by running `cargo doc`. This command runs the +`rustdoc` tool distributed with Rust and puts the generated HTML documentation +in the *target/doc* directory. -
-
+For convenience, running `cargo doc --open` will build the HTML for your +current crate’s documentation (as well as the documentation for all of your +crate’s dependencies) and open the result in a web browser. Navigate to the +`add_one` function and you’ll see how the text in the documentation comments is +rendered, as shown in Figure 14-1: -`cargo doc` runs a tool distributed with Rust, `rustdoc`, to generate HTML -documentation from these comments. To try this out locally, you can run `cargo -doc --open`, which will build the documentation for your current crate (as well -as all of your crate's dependencies) and open it in a web browser. Navigate to -the `add_one` function and you'll see how the text in the documentation -comments gets rendered. +Rendered HTML documentation for the `add_one` function of `my_crate` -Adding examples in code blocks in your documentation comments is a way to -clearly demonstrate how to use your library. There's an additional bonus reason -to do this: `cargo test` will run the code examples in your documentation as -tests! Nothing is better than documentation with examples. Nothing is worse -than examples that don't actually work because the code has changed since the -documentation has been written. Try running `cargo test` with the documentation -for the `add_one` function in Listing 14-1; you'll see a section in the test -results like this: +Figure 14-1: HTML documentation for the `add_one` +function -```test - Doc-tests add-one +#### Commonly Used Sections + +We used the `# Examples` Markdown heading in Listing 14-1 to create a section +in the HTML with the title “Examples.” Here are some other sections that crate +authors commonly use in their documentation: + +* **Panics**: The scenarios in which the function being documented could + panic. Callers of the function who don’t want their programs to panic should + make sure they don’t call the function in these situations. +* **Errors**: If the function returns a `Result`, describing the kinds of + errors that might occur and what conditions might cause those errors to be + returned can be helpful to callers so they can write code to handle the + different kinds of errors in different ways. +* **Safety**: If the function is `unsafe` to call (we discuss unsafety in + Chapter 19), there should be a section explaining why the function is unsafe + and covering the invariants that the function expects callers to uphold. + +Most documentation comments don’t need all of these sections, but this is a +good checklist to remind you of the aspects of your code that people calling +your code will be interested in knowing about. + +#### Documentation Comments as Tests + +Adding example code blocks in your documentation comments can help demonstrate +how to use your library, and doing so has an additional bonus: running `cargo +test` will run the code examples in your documentation as tests! Nothing is +better than documentation with examples. But nothing is worse than examples +that don’t work because the code has changed since the documentation was +written. If we run `cargo test` with the documentation for the `add_one` +function from Listing 14-1, we will see a section in the test results like this: + + + +```text + Doc-tests my_crate running 1 test -test add_one_0 ... ok +test src/lib.rs - add_one (line 5) ... ok -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.27s ``` -Try changing the function or the example to see that `cargo test` will catch -that the example no longer works! +Now if we change either the function or the example so the `assert_eq!` in the +example panics and run `cargo test` again, we’ll see that the doc tests catch +that the example and the code are out of sync with each other! -There's another style of doc comment, `//!`, to comment containing items (e.g. -crates, modules or functions), instead of the items following it. These are -typically used inside the crate root (lib.rs) or a module's root (mod.rs) to -document the crate or the module as a whole, respectively. Here's the -documentation within the `libstd` module that contains the entire standard -library: +#### Commenting Contained Items +Another style of doc comment, `//!`, adds documentation to the item that +contains the comments rather than adding documentation to the items following +the comments. We typically use these doc comments inside the crate root file +(*src/lib.rs* by convention) or inside a module to document the crate or the +module as a whole. + +For example, if we want to add documentation that describes the purpose of the +`my_crate` crate that contains the `add_one` function, we can add documentation +comments that start with `//!` to the beginning of the *src/lib.rs* file, as +shown in Listing 14-2: + +Filename: src/lib.rs + +```rust,ignore +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-02/src/lib.rs:here}} ``` -//! # The Rust Standard Library -//! -//! The Rust Standard Library provides the essential runtime -//! functionality for building portable Rust software. -``` + +Listing 14-2: Documentation for the `my_crate` crate as a +whole + +Notice there isn’t any code after the last line that begins with `//!`. Because +we started the comments with `//!` instead of `///`, we’re documenting the item +that contains this comment rather than an item that follows this comment. In +this case, the item that contains this comment is the *src/lib.rs* file, which +is the crate root. These comments describe the entire crate. + +When we run `cargo doc --open`, these comments will display on the front +page of the documentation for `my_crate` above the list of public items in the +crate, as shown in Figure 14-2: + +Rendered HTML documentation with a comment for the crate as a whole + +Figure 14-2: Rendered documentation for `my_crate`, +including the comment describing the crate as a whole + +Documentation comments within items are useful for describing crates and +modules especially. Use them to explain the overall purpose of the container to +help your users understand the crate’s organization. ### Exporting a Convenient Public API with `pub use` -In Chapter 7, we covered how to organize our code into modules with the `mod` -keyword, how to make items public with the `pub` keyword, and how to bring -items into a scope with the `use` keyword. When publishing a crate for people -unfamiliar with the implementation to use, it's worth taking time to consider -if the structure of your crate that's useful for you as you're developing is -what would be useful for people depending on your crate. If the structure isn't -convenient to use from another library, you don't have to rearrange your -internal organization: you can choose to re-export items to make a different -public structure with `pub use`. +In Chapter 7, we covered how to organize our code into modules using the `mod` +keyword, how to make items public using the `pub` keyword, and how to bring +items into a scope with the `use` keyword. However, the structure that makes +sense to you while you’re developing a crate might not be very convenient for +your users. You might want to organize your structs in a hierarchy containing +multiple levels, but then people who want to use a type you’ve defined deep in +the hierarchy might have trouble finding out that type exists. They might also +be annoyed at having to enter `use` +`my_crate::some_module::another_module::UsefulType;` rather than `use` +`my_crate::UsefulType;`. -For example, say that we made a library named `art` consisting of a `kinds` -module containing an enum named `Color` and a `utils` module containing a -function named `mix` as shown in Listing 14-2: +The structure of your public API is a major consideration when publishing a +crate. People who use your crate are less familiar with the structure than you +are and might have difficulty finding the pieces they want to use if your crate +has a large module hierarchy. + +The good news is that if the structure *isn’t* convenient for others to use +from another library, you don’t have to rearrange your internal organization: +instead, you can re-export items to make a public structure that’s different +from your private structure by using `pub use`. Re-exporting takes a public +item in one location and makes it public in another location, as if it were +defined in the other location instead. + +For example, say we made a library named `art` for modeling artistic concepts. +Within this library are two modules: a `kinds` module containing two enums +named `PrimaryColor` and `SecondaryColor` and a `utils` module containing a +function named `mix`, as shown in Listing 14-3: -
Filename: src/lib.rs -```rust -//! # Art -//! -//! A library for modeling artistic concepts. - -pub mod kinds { - /// The primary colors according to the RYB color model. - pub enum PrimaryColor { - Red, - Yellow, - Blue, - } - - /// The secondary colors according to the RYB color model. - pub enum SecondaryColor { - Orange, - Green, - Purple, - } -} - -pub mod utils { - use kinds::*; - - /// Combines two primary colors in equal amounts to create - /// a secondary color. - pub fn mix(c1: PrimaryColor, c2: PrimaryColor) -> SecondaryColor { - // ...snip... -# SecondaryColor::Green - } -} +```rust,noplayground,test_harness +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-03/src/lib.rs}} ``` -
+Listing 14-3: An `art` library with items organized into +`kinds` and `utils` modules -Listing 14-2: An `art` library with items organized into `kinds` and `utils` -modules +Figure 14-3 shows what the front page of the documentation for this crate +generated by `cargo doc` would look like: -
-
+Rendered documentation for the `art` crate that lists the `kinds` and `utils` modules -In order to use this library, another crate would have `use` statements as in -Listing 14-3: +Figure 14-3: Front page of the documentation for `art` +that lists the `kinds` and `utils` modules + +Note that the `PrimaryColor` and `SecondaryColor` types aren’t listed on the +front page, nor is the `mix` function. We have to click `kinds` and `utils` to +see them. + +Another crate that depends on this library would need `use` statements that +bring the items from `art` into scope, specifying the module structure that’s +currently defined. Listing 14-4 shows an example of a crate that uses the +`PrimaryColor` and `mix` items from the `art` crate: -
Filename: src/main.rs ```rust,ignore -extern crate art; - -use art::kinds::PrimaryColor; -use art::utils::mix; - -fn main() { - let red = PrimaryColor::Red; - let yellow = PrimaryColor::Yellow; - mix(red, yellow); -} +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-04/src/main.rs}} ``` -
+Listing 14-4: A crate using the `art` crate’s items with +its internal structure exported -Listing 14-3: A program using the `art` crate's items with its internal -structure exported +The author of the code in Listing 14-4, which uses the `art` crate, had to +figure out that `PrimaryColor` is in the `kinds` module and `mix` is in the +`utils` module. The module structure of the `art` crate is more relevant to +developers working on the `art` crate than to developers using the `art` crate. +The internal structure that organizes parts of the crate into the `kinds` +module and the `utils` module doesn’t contain any useful information for +someone trying to understand how to use the `art` crate. Instead, the `art` +crate’s module structure causes confusion because developers have to figure out +where to look, and the structure is inconvenient because developers must +specify the module names in the `use` statements. -
-
+To remove the internal organization from the public API, we can modify the +`art` crate code in Listing 14-3 to add `pub use` statements to re-export the +items at the top level, as shown in Listing 14-5: -Users of this crate shouldn't need to know that `PrimaryColor` and -`SecondaryColor` are in the `kinds` module, and `mix` is in the `utils` module; -that structure might be useful for internal organization but doesn't have much -meaning from the outside looking in. - -To change this, we can add the following `pub use` statements to the code from -Listing 14-2 to re-export the types at the top level, as shown in Listing 14-4: - -
Filename: src/lib.rs -```rust -//! # Art -//! -//! A library for modeling artistic concepts. - -pub use kinds::PrimaryColor; -pub use kinds::SecondaryColor; -pub use utils::mix; - -pub mod kinds { - // ...snip... -# pub enum PrimaryColor; -# pub enum SecondaryColor; -# } -# -# pub mod utils { -# pub fn mix() {} -# } +```rust,ignore +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-05/src/lib.rs:here}} ``` -
+Listing 14-5: Adding `pub use` statements to re-export +items -Listing 14-4: Adding `pub use` statements to re-export items +The API documentation that `cargo doc` generates for this crate will now list +and link re-exports on the front page, as shown in Figure 14-4, making the +`PrimaryColor` and `SecondaryColor` types and the `mix` function easier to find. -
-
+Rendered documentation for the `art` crate with the re-exports on the front page - +Figure 14-4: The front page of the documentation for `art` +that lists the re-exports -Re-exports are listed and linked on the front page of the crate's API -documentation. Users of the `art` crate can still see and choose to use the -internal structure as in Listing 14-3, or they can use the more convenient -structure from Listing 14-4, as shown in Listing 14-5: +The `art` crate users can still see and use the internal structure from Listing +14-3 as demonstrated in Listing 14-4, or they can use the more convenient +structure in Listing 14-5, as shown in Listing 14-6: -
Filename: src/main.rs ```rust,ignore -extern crate art; - -use art::PrimaryColor; -use art::mix; - -fn main() { - // ...snip... -} +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-06/src/main.rs:here}} ``` -
+Listing 14-6: A program using the re-exported items from +the `art` crate -Listing 14-5: Using the re-exported items from the `art` crate +In cases where there are many nested modules, re-exporting the types at the top +level with `pub use` can make a significant difference in the experience of +people who use the crate. -
-
+Creating a useful public API structure is more of an art than a science, and +you can iterate to find the API that works best for your users. Choosing `pub +use` gives you flexibility in how you structure your crate internally and +decouples that internal structure from what you present to your users. Look at +some of the code of crates you’ve installed to see if their internal structure +differs from their public API. - +### Setting Up a Crates.io Account -Creating a useful public API structure is more of an art than a science. -Choosing `pub use` gives you flexibility in how you expose your crate's -internal structure to users. Take a look at some of the code of crates you've -installed to see if their internal structure differs from their public API. +Before you can publish any crates, you need to create an account on +[crates.io](https://crates.io/) and get an API token. To do so, +visit the home page at [crates.io](https://crates.io/) and log in +via a GitHub account. (The GitHub account is currently a requirement, but the +site might support other ways of creating an account in the future.) Once +you’re logged in, visit your account settings at +[https://crates.io/me/](https://crates.io/me/) and retrieve your +API key. Then run the `cargo login` command with your API key, like this: -### Before Your First Publish - -Before being able to publish any crates, you'll need to create an account on -[crates.io] and get an API token. To do so, [visit the home page][crates.io] -and log in via a GitHub account. A GitHub account is a requirement for now, but -the site might support other ways of creating an account in the future. Once -you're logged in, visit your [Account Settings] page and run the `cargo login` -command with the API key as the page specifies, which will look something like -this: - -[crates.io]: https://crates.io -[Account Settings]: https://crates.io/me - -```text +```console $ cargo login abcdefghijklmnopqrstuvwxyz012345 ``` This command will inform Cargo of your API token and store it locally in -*~/.cargo/config*. Note that this token is a **secret** and should not be -shared with anyone else. If it gets shared with anyone for any reason, you -should regenerate it immediately. +*~/.cargo/credentials*. Note that this token is a *secret*: do not share it +with anyone else. If you do share it with anyone for any reason, you should +revoke it and generate a new token on [crates.io](https://crates.io/). -### Before Publishing a New Crate +### Adding Metadata to a New Crate -First, your crate will need a unique name. While you're working on a crate -locally, you may name a crate whatever you'd like, but crate names on -[crates.io] are allocated on a first-come-first- serve basis. Once a crate name -is taken, it cannot be used for another crate, so check on the site that the -name you'd like is available. +Now that you have an account, let’s say you have a crate you want to publish. +Before publishing, you’ll need to add some metadata to your crate by adding it +to the `[package]` section of the crate’s *Cargo.toml* file. -If you try to publish a crate as generated by `cargo new`, you'll get a warning -and then an error: +Your crate will need a unique name. While you’re working on a crate locally, +you can name a crate whatever you’d like. However, crate names on +[crates.io](https://crates.io/) are allocated on a first-come, +first-served basis. Once a crate name is taken, no one else can publish a crate +with that name. Before attempting to publish a crate, search for the name you +want to use on the site. If the name has been used by another crate, you will +need to find another name and edit the `name` field in the *Cargo.toml* file +under the `[package]` section to use the new name for publishing, like so: -```text -$ cargo publish - Updating registry `https://github.com/rust-lang/crates.io-index` -warning: manifest has no description, license, license-file, documentation, -homepage or repository. -...snip... -error: api errors: missing or empty metadata fields: description, license. -Please see http://doc.crates.io/manifest.html#package-metadata for how to -upload metadata +Filename: Cargo.toml + +```toml +[package] +name = "guessing_game" ``` -We can include more information about our package in *Cargo.toml*. Some of -these fields are optional, but a description and a license are required in -order to publish so that people will know what your crate does and under what -terms they may use it. +Even if you’ve chosen a unique name, when you run `cargo publish` to publish +the crate at this point, you’ll get a warning and then an error: -The description appears with your crate in search results and on your crate's -page. Descriptions are usually a sentence or two. The `license` field takes a -license identifier value, and the possible values have been specified by the -Linux Foundation's [Software Package Data Exchange (SPDX)][spdx]. If you would -like to use a license that doesn't appear there, instead of the `license` key, -you can use `license-file` to specify the name of a file in your project that -contains the text of the license you want to use. + -Guidance on which license is right for your project is out of scope for this -book. Many people in the Rust community choose to license their projects in the -same way as Rust itself, with a dual license of `MIT/Apache-2.0`, which -demonstrates that you can specify multiple license identifiers separated by a -slash. So the *Cargo.toml* for a project that is ready to publish might look -like this: +```console +$ cargo publish + Updating crates.io index +warning: manifest has no description, license, license-file, documentation, homepage or repository. +See https://doc.rust-lang.org/cargo/reference/manifest.html#package-metadata for more info. +--snip-- +error: api errors (status 200 OK): missing or empty metadata fields: description, license. Please see https://doc.rust-lang.org/cargo/reference/manifest.html for how to upload metadata +``` + +The reason is that you’re missing some crucial information: a description and +license are required so people will know what your crate does and under what +terms they can use it. To rectify this error, you need to include this +information in the *Cargo.toml* file. + +Add a description that is just a sentence or two, because it will appear with +your crate in search results. For the `license` field, you need to give a +*license identifier value*. The [Linux Foundation’s Software Package Data +Exchange (SPDX)][spdx] lists the identifiers you can use for this value. For +example, to specify that you’ve licensed your crate using the MIT License, add +the `MIT` identifier: [spdx]: http://spdx.org/licenses/ +Filename: Cargo.toml + +```toml +[package] +name = "guessing_game" +license = "MIT" +``` + +If you want to use a license that doesn’t appear in the SPDX, you need to place +the text of that license in a file, include the file in your project, and then +use `license-file` to specify the name of that file instead of using the +`license` key. + +Guidance on which license is appropriate for your project is beyond the scope +of this book. Many people in the Rust community license their projects in the +same way as Rust by using a dual license of `MIT OR Apache-2.0`. This practice +demonstrates that you can also specify multiple license identifiers separated +by `OR` to have multiple licenses for your project. + +With a unique name, the version, the author details that `cargo new` added +when you created the crate, your description, and a license added, the +*Cargo.toml* file for a project that is ready to publish might look like this: + +Filename: Cargo.toml + ```toml [package] name = "guessing_game" version = "0.1.0" authors = ["Your Name "] +edition = "2018" description = "A fun game where you guess what number the computer has chosen." -license = "MIT/Apache-2.0" +license = "MIT OR Apache-2.0" [dependencies] ``` -Be sure to check out the [documentation on crates.io][other-metadata] that -describes other metadata you can specify to ensure your crate can be discovered -and used more easily! - -[other-metadata]: http://doc.crates.io/manifest.html#package-metadata +[Cargo’s documentation](https://doc.rust-lang.org/cargo/) describes other +metadata you can specify to ensure others can discover and use your crate more +easily. ### Publishing to Crates.io -Now that we've created an account, saved our API token, chosen a name for our -crate, and specified the required metadata, we're ready to publish! Publishing -a crate is when a specific version is uploaded to be hosted on crates.io. +Now that you’ve created an account, saved your API token, chosen a name for +your crate, and specified the required metadata, you’re ready to publish! +Publishing a crate uploads a specific version to +[crates.io](https://crates.io/) for others to use. -Take care when publishing a crate, because a publish is **permanent**. The -version can never be overwritten, and the code cannot be deleted. However, -there is no limit to the number of versions which can be published. +Be careful when publishing a crate because a publish is *permanent*. The +version can never be overwritten, and the code cannot be deleted. One major +goal of [crates.io](https://crates.io/) is to act as a permanent +archive of code so that builds of all projects that depend on crates from +[crates.io](https://crates.io/) will continue to work. Allowing +version deletions would make fulfilling that goal impossible. However, there is +no limit to the number of crate versions you can publish. -Let's run the `cargo publish` command, which should succeed this time since -we've now specified the required metadata: +Run the `cargo publish` command again. It should succeed now: -```text + + +```console $ cargo publish - Updating registry `https://github.com/rust-lang/crates.io-index` -Packaging guessing_game v0.1.0 (file:///projects/guessing_game) -Verifying guessing_game v0.1.0 (file:///projects/guessing_game) -Compiling guessing_game v0.1.0 + Updating crates.io index + Packaging guessing_game v0.1.0 (file:///projects/guessing_game) + Verifying guessing_game v0.1.0 (file:///projects/guessing_game) + Compiling guessing_game v0.1.0 (file:///projects/guessing_game/target/package/guessing_game-0.1.0) - Finished debug [unoptimized + debuginfo] target(s) in 0.19 secs -Uploading guessing_game v0.1.0 (file:///projects/guessing_game) + Finished dev [unoptimized + debuginfo] target(s) in 0.19s + Uploading guessing_game v0.1.0 (file:///projects/guessing_game) ``` -Congratulations! You've now shared your code with the Rust community, and -anyone can easily add your crate as a dependency to their project. +Congratulations! You’ve now shared your code with the Rust community, and +anyone can easily add your crate as a dependency of their project. ### Publishing a New Version of an Existing Crate -When you've made changes to your crate and are ready to release a new version, -change the `version` value specified in your *Cargo.toml*. Use the [Semantic -Versioning rules][semver] to decide what an appropriate next version number is -based on the kinds of changes you've made. Then run `cargo publish` to upload -the new version. +When you’ve made changes to your crate and are ready to release a new version, +you change the `version` value specified in your *Cargo.toml* file and +republish. Use the [Semantic Versioning rules][semver] to decide what an +appropriate next version number is based on the kinds of changes you’ve made. +Then run `cargo publish` to upload the new version. [semver]: http://semver.org/ ### Removing Versions from Crates.io with `cargo yank` -Occasions may arise where you publish a version of a crate that actually ends -up being broken for one reason or another, such as a syntax error or forgetting -to include a file. For situations such as this, Cargo supports *yanking* a -version of a crate. +Although you can’t remove previous versions of a crate, you can prevent any +future projects from adding them as a new dependency. This is useful when a +crate version is broken for one reason or another. In such situations, Cargo +supports *yanking* a crate version. -Marking a version of a crate as yanked means that no projects will be able to -start depending on that version, but all existing projects that depend on that -version will continue to be allowed to download and depend on that version. One -of the major goals of crates.io is to act as a permanent archive of code so -that builds of all projects will continue to work, and allowing deletion of a -version would go against this goal. Essentially, a yank means that all projects -with a *Cargo.lock* will not break, while any future *Cargo.lock* files -generated will not use the yanked version. - -A yank **does not** delete any code. The yank feature is not intended for -deleting accidentally uploaded secrets, for example. If that happens, you must -reset those secrets immediately. +Yanking a version prevents new projects from starting to depend on that version +while allowing all existing projects that depend on it to continue to download +and depend on that version. Essentially, a yank means that all projects with a +*Cargo.lock* will not break, and any future *Cargo.lock* files generated will +not use the yanked version. To yank a version of a crate, run `cargo yank` and specify which version you want to yank: -```text +```console $ cargo yank --vers 1.0.1 ``` -You can also undo a yank, and allow projects to start depending on a version -again, by adding `--undo` to the command: +By adding `--undo` to the command, you can also undo a yank and allow projects +to start depending on a version again: -```text +```console $ cargo yank --vers 1.0.1 --undo ``` + +A yank *does not* delete any code. For example, the yank feature is not +intended for deleting accidentally uploaded secrets. If that happens, you must +reset those secrets immediately. diff --git a/src/ch14-03-cargo-workspaces.md b/src/ch14-03-cargo-workspaces.md index c53ef85..5d8f834 100644 --- a/src/ch14-03-cargo-workspaces.md +++ b/src/ch14-03-cargo-workspaces.md @@ -1,207 +1,373 @@ ## Cargo Workspaces -In Chapter 12, we built a package that included both a binary crate and a -library crate. But what if the library crate continues to get bigger and we -want to split our package up further into multiple library crates? As packages -grow, separating out major components can be quite useful. In this situation, -Cargo has a feature called *workspaces* that can help us manage multiple -related packages that are developed in tandem. +In Chapter 12, we built a package that included a binary crate and a library +crate. As your project develops, you might find that the library crate +continues to get bigger and you want to split up your package further into +multiple library crates. In this situation, Cargo offers a feature called +*workspaces* that can help manage multiple related packages that are developed +in tandem. -A *workspace* is a set of packages that will all share the same *Cargo.lock* -and output directory. Let's make a project using a workspace where the code -will be trivial so that we can concentrate on the structure of a workspace. -We'll have a binary that uses two libraries: one that will provide an `add_one` -method and a second that will provide an `add_two` method. Let's start by -creating a new crate for the binary: +### Creating a Workspace -```text -$ cargo new --bin adder - Created binary (application) `adder` project -$ cd adder +A *workspace* is a set of packages that share the same *Cargo.lock* and output +directory. Let’s make a project using a workspace—we’ll use trivial code so we +can concentrate on the structure of the workspace. There are multiple ways to +structure a workspace; we’re going to show one common way. We’ll have a +workspace containing a binary and two libraries. The binary, which will provide +the main functionality, will depend on the two libraries. One library will +provide an `add_one` function, and a second library an `add_two` function. +These three crates will be part of the same workspace. We’ll start by creating +a new directory for the workspace: + +```console +$ mkdir add +$ cd add ``` -We need to modify the binary package's *Cargo.toml* to tell Cargo the `adder` -package is a workspace. Add this at the bottom of the file: +Next, in the *add* directory, we create the *Cargo.toml* file that will +configure the entire workspace. This file won’t have a `[package]` section or +the metadata we’ve seen in other *Cargo.toml* files. Instead, it will start +with a `[workspace]` section that will allow us to add members to the workspace +by specifying the path to the package with our binary crate; in this case, +that path is *adder*: + +Filename: Cargo.toml ```toml -[workspace] +{{#include ../listings/ch14-more-about-cargo/no-listing-01-workspace-with-adder-crate/add/Cargo.toml}} ``` -Like many Cargo features, workspaces support convention over configuration: we -don't need to say anything more than this as long as we follow the convention. -The convention is that any crates that we depend on as sub-directories will be -part of the workspace. Let's add a path dependency to the `adder` crate by -changing the `[dependencies]` section of *Cargo.toml* to look like this: +Next, we’ll create the `adder` binary crate by running `cargo new` within the +*add* directory: + + + +```console +$ cargo new adder + Created binary (application) `adder` package +``` + +At this point, we can build the workspace by running `cargo build`. The files +in your *add* directory should look like this: + +```text +├── Cargo.lock +├── Cargo.toml +├── adder +│ ├── Cargo.toml +│ └── src +│ └── main.rs +└── target +``` + +The workspace has one *target* directory at the top level for the compiled +artifacts to be placed into; the `adder` package doesn’t have its own *target* +directory. Even if we were to run `cargo build` from inside the *adder* +directory, the compiled artifacts would still end up in *add/target* rather +than *add/adder/target*. Cargo structures the *target* directory in a workspace +like this because the crates in a workspace are meant to depend on each other. +If each crate had its own *target* directory, each crate would have to +recompile each of the other crates in the workspace to have the artifacts in +its own *target* directory. By sharing one *target* directory, the crates can +avoid unnecessary rebuilding. + +### Creating the Second Package in the Workspace + +Next, let’s create another member package in the workspace and call it `add-one`. +Change the top-level *Cargo.toml* to specify the *add-one* path in the +`members` list: + +Filename: Cargo.toml ```toml -[dependencies] -add-one = { path = "add-one" } +{{#include ../listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/Cargo.toml}} ``` -If we add dependencies that don't have a `path` specified, those will be normal -dependencies that aren't in this workspace. +Then generate a new library crate named `add-one`: -Next, generate the `add-one` crate within the `adder` directory: + -```text -$ cargo new add-one - Created library `add-one` project +```console +$ cargo new add-one --lib + Created library `add-one` package ``` -Your `adder` directory should now have these directories and files: +Your *add* directory should now have these directories and files: ```text +├── Cargo.lock ├── Cargo.toml ├── add-one -│   ├── Cargo.toml -│   └── src -│   └── lib.rs -└── src - └── main.rs +│ ├── Cargo.toml +│ └── src +│ └── lib.rs +├── adder +│ ├── Cargo.toml +│ └── src +│ └── main.rs +└── target ``` -In *add-one/src/lib.rs*, let's add an implementation of an `add_one` function: +In the *add-one/src/lib.rs* file, let’s add an `add_one` function: Filename: add-one/src/lib.rs -```rust -pub fn add_one(x: i32) -> i32 { - x + 1 -} +```rust,noplayground +{{#rustdoc_include ../listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/add-one/src/lib.rs}} ``` -Open up *src/main.rs* for `adder` and add an `extern crate` line to bring the -new `add-one` library crate into scope, and change the `main` function to use -the `add_one` function: +Now that we have another package in the workspace, we can have the `adder` +package with our binary depend on the `add-one` package, that has our +library. First, we’ll need to add a path dependency on `add-one` to +*adder/Cargo.toml*. + +Filename: adder/Cargo.toml + +```toml +{{#include ../listings/ch14-more-about-cargo/no-listing-02-workspace-with-two-crates/add/adder/Cargo.toml:7:9}} +``` + +Cargo doesn’t assume that crates in a workspace will depend on each other, so +we need to be explicit about the dependency relationships between the crates. + +Next, let’s use the `add_one` function from the `add-one` crate in the `adder` +crate. Open the *adder/src/main.rs* file and add a `use` line at the top to +bring the new `add-one` library crate into scope. Then change the `main` +function to call the `add_one` function, as in Listing 14-7. + +Filename: adder/src/main.rs ```rust,ignore -extern crate add_one; - -fn main() { - let num = 10; - println!("Hello, world! {} plus one is {}!", num, add_one::add_one(num)); -} +{{#rustdoc_include ../listings/ch14-more-about-cargo/listing-14-07/add/adder/src/main.rs}} ``` -Let's build it! +Listing 14-7: Using the `add-one` library crate from the + `adder` crate -```text +Let’s build the workspace by running `cargo build` in the top-level *add* +directory! + + + +```console $ cargo build - Compiling add-one v0.1.0 (file:///projects/adder/add-one) - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.68 secs + Compiling add-one v0.1.0 (file:///projects/add/add-one) + Compiling adder v0.1.0 (file:///projects/add/adder) + Finished dev [unoptimized + debuginfo] target(s) in 0.68s ``` -Note that running `cargo build` in the *adder* directory built both that crate -and the `add-one` crate in *adder/add-one*, but created only one *Cargo.lock* -and one *target* directory, both in the *adder* directory. See if you can add -an `add-two` crate in the same way. +To run the binary crate from the *add* directory, we can specify which +package in the workspace we want to run by using the `-p` argument and the +package name with `cargo run`: -Let's now say that we'd like to use the `rand` crate in our `add-one` crate. -As usual, we'll add it to the `[dependencies]` section in the `Cargo.toml` for -that crate: + + +```console +$ cargo run -p adder + Finished dev [unoptimized + debuginfo] target(s) in 0.0s + Running `target/debug/adder` +Hello, world! 10 plus one is 11! +``` + +This runs the code in *adder/src/main.rs*, which depends on the `add-one` crate. + +#### Depending on an External Package in a Workspace + +Notice that the workspace has only one *Cargo.lock* file at the top level of +the workspace rather than having a *Cargo.lock* in each crate’s directory. This +ensures that all crates are using the same version of all dependencies. If we +add the `rand` package to the *adder/Cargo.toml* and *add-one/Cargo.toml* +files, Cargo will resolve both of those to one version of `rand` and record +that in the one *Cargo.lock*. Making all crates in the workspace use the same +dependencies means the crates in the workspace will always be compatible with +each other. Let’s add the `rand` crate to the `[dependencies]` section in the +*add-one/Cargo.toml* file to be able to use the `rand` crate in the `add-one` +crate: + + Filename: add-one/Cargo.toml ```toml -[dependencies] - -rand = "0.3.14" +{{#include ../listings/ch14-more-about-cargo/no-listing-03-workspace-with-external-dependency/add/add-one/Cargo.toml:7:8}} ``` -And if we add `extern crate rand;` to *add-one/src/lib.rs* then run `cargo -build`, it will succeed: +We can now add `use rand;` to the *add-one/src/lib.rs* file, and building the +whole workspace by running `cargo build` in the *add* directory will bring in +and compile the `rand` crate. We will get one warning because we aren’t +referring to the `rand` we brought into scope: -```text + + +```console $ cargo build - Updating registry `https://github.com/rust-lang/crates.io-index` - Downloading rand v0.3.14 - ...snip... - Compiling rand v0.3.14 - Compiling add-one v0.1.0 (file:///projects/adder/add-one) - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 10.18 secs -``` - -The top level *Cargo.lock* now contains information about the dependency -`add-one` has on `rand`. However, even though `rand` is used somewhere in the -workspace, we can't use it in other crates in the workspace unless we add -`rand` to their *Cargo.toml* as well. If we add `extern crate rand;` to -*src/main.rs* for the top level `adder` crate, for example, we'll get an error: - -```text -$ cargo build - Compiling adder v0.1.0 (file:///projects/adder) -error[E0463]: can't find crate for `rand` - --> src/main.rs:1:1 + Updating crates.io index + Downloaded rand v0.8.3 + --snip-- + Compiling rand v0.8.3 + Compiling add-one v0.1.0 (file:///projects/add/add-one) +warning: unused import: `rand` + --> add-one/src/lib.rs:1:5 | -1 | extern crate rand; - | ^^^^^^^^^^^^^^^^^^^ can't find crate +1 | use rand; + | ^^^^ + | + = note: `#[warn(unused_imports)]` on by default + +warning: 1 warning emitted + + Compiling adder v0.1.0 (file:///projects/add/adder) + Finished dev [unoptimized + debuginfo] target(s) in 10.18s ``` -To fix this, edit *Cargo.toml* for the top level and indicate that `rand` is a -dependency for the `adder` crate. +The top-level *Cargo.lock* now contains information about the dependency of +`add-one` on `rand`. However, even though `rand` is used somewhere in the +workspace, we can’t use it in other crates in the workspace unless we add +`rand` to their *Cargo.toml* files as well. For example, if we add `use rand;` +to the *adder/src/main.rs* file for the `adder` package, we’ll get an error: -For another enhancement, let's add a test of the `add_one::add_one` function -within that crate: + + +```console +$ cargo build + --snip-- + Compiling adder v0.1.0 (file:///projects/add/adder) +error[E0432]: unresolved import `rand` + --> adder/src/main.rs:2:5 + | +2 | use rand; + | ^^^^ no external crate `rand` +``` + +To fix this, edit the *Cargo.toml* file for the `adder` package and indicate +that `rand` is a dependency for it as well. Building the `adder` package will +add `rand` to the list of dependencies for `adder` in *Cargo.lock*, but no +additional copies of `rand` will be downloaded. Cargo has ensured that every +crate in every package in the workspace using the `rand` package will be +using the same version. Using the same version of `rand` across the workspace +saves space because we won’t have multiple copies and ensures that the crates +in the workspace will be compatible with each other. + +#### Adding a Test to a Workspace + +For another enhancement, let’s add a test of the `add_one::add_one` function +within the `add_one` crate: Filename: add-one/src/lib.rs -```rust -pub fn add_one(x: i32) -> i32 { - x + 1 -} - -#[cfg(test)] -mod tests { - use super::*; - - #[test] - fn it_works() { - assert_eq!(3, add_one(2)); - } -} +```rust,noplayground +{{#rustdoc_include ../listings/ch14-more-about-cargo/no-listing-04-workspace-with-tests/add/add-one/src/lib.rs}} ``` -Now run `cargo test` in the top-level *adder* directory: +Now run `cargo test` in the top-level *add* directory: -```text + + +```console $ cargo test - Compiling adder v0.1.0 (file:///projects/adder) - Finished debug [unoptimized + debuginfo] target(s) in 0.27 secs - Running target/debug/adder-f0253159197f7841 - -running 0 tests - -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured -``` - -Wait a second, zero tests? We just added one! If we look at the output, we can -see that `cargo test` in a workspace only runs the tests for the top level -crate. To run tests for the other crates, we need to use the `-p` argument to -indicate we want to run tests for a particular package: - -```text -$ cargo test -p add-one - Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs - Running target/debug/deps/add_one-abcabcabc + Compiling add-one v0.1.0 (file:///projects/add/add-one) + Compiling adder v0.1.0 (file:///projects/add/adder) + Finished test [unoptimized + debuginfo] target(s) in 0.27s + Running target/debug/deps/add_one-f0253159197f7841 running 1 test test tests::it_works ... ok -test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Running target/debug/deps/adder-49979ff40686fa8e + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s Doc-tests add-one running 0 tests -test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s ``` -Similarly, if you choose to publish the workspace to crates.io, each crate in -the workspace will get published separately. +The first section of the output shows that the `it_works` test in the `add-one` +crate passed. The next section shows that zero tests were found in the `adder` +crate, and then the last section shows zero documentation tests were found in +the `add-one` crate. Running `cargo test` in a workspace structured like this +one will run the tests for all the crates in the workspace. -As your project grows, consider a workspace: smaller components are easier to -understand individually than one big blob of code. Keeping the crates in a -workspace can make coordination among them easier if they work together and are +We can also run tests for one particular crate in a workspace from the +top-level directory by using the `-p` flag and specifying the name of the crate +we want to test: + + + +```console +$ cargo test -p add-one + Finished test [unoptimized + debuginfo] target(s) in 0.00s + Running target/debug/deps/add_one-b3235fea9a156f74 + +running 1 test +test tests::it_works ... ok + +test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s + + Doc-tests add-one + +running 0 tests + +test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s +``` + +This output shows `cargo test` only ran the tests for the `add-one` crate and +didn’t run the `adder` crate tests. + +If you publish the crates in the workspace to [crates.io](https://crates.io/), +each crate in the workspace will need to be published separately. The `cargo +publish` command does not have an `--all` flag or a `-p` flag, so you must +change to each crate’s directory and run `cargo publish` on each crate in the +workspace to publish the crates. + +For additional practice, add an `add-two` crate to this workspace in a similar +way as the `add-one` crate! + +As your project grows, consider using a workspace: it’s easier to understand +smaller, individual components than one big blob of code. Furthermore, keeping +the crates in a workspace can make coordination between them easier if they are often changed at the same time. diff --git a/src/ch14-04-installing-binaries.md b/src/ch14-04-installing-binaries.md index 3fb59f9..753e3c6 100644 --- a/src/ch14-04-installing-binaries.md +++ b/src/ch14-04-installing-binaries.md @@ -1,29 +1,44 @@ ## Installing Binaries from Crates.io with `cargo install` The `cargo install` command allows you to install and use binary crates -locally. This isn't intended to replace system packages; it's meant to be a +locally. This isn’t intended to replace system packages; it’s meant to be a convenient way for Rust developers to install tools that others have shared on -crates.io. Only packages which have binary targets can be installed, and all -binaries are installed into the installation root's *bin* folder. If you -installed Rust using *rustup.rs* and don't have any custom configurations, this -will be `$HOME/.cargo/bin`. Add that directory to your `$PATH` to be able to -run programs you've gotten through `cargo install`. +[crates.io](https://crates.io/). Note that you can only install +packages that have binary targets. A *binary target* is the runnable program +that is created if the crate has a *src/main.rs* file or another file specified +as a binary, as opposed to a library target that isn’t runnable on its own but +is suitable for including within other programs. Usually, crates have +information in the *README* file about whether a crate is a library, has a +binary target, or both. -For example, we mentioned in Chapter 12 that there's a Rust implementation of -the `grep` tool for searching files called `ripgrep`. If we want to install -`ripgrep`, we can run: +All binaries installed with `cargo install` are stored in the installation +root’s *bin* folder. If you installed Rust using *rustup.rs* and don’t have any +custom configurations, this directory will be *$HOME/.cargo/bin*. Ensure that +directory is in your `$PATH` to be able to run programs you’ve installed with +`cargo install`. -```text +For example, in Chapter 12 we mentioned that there’s a Rust implementation of +the `grep` tool called `ripgrep` for searching files. If we want to install +`ripgrep`, we can run the following: + + + +```console $ cargo install ripgrep -Updating registry `https://github.com/rust-lang/crates.io-index` - Downloading ripgrep v0.3.2 - ...snip... - Compiling ripgrep v0.3.2 - Finished release [optimized + debuginfo] target(s) in 97.91 secs + Updating crates.io index + Downloaded ripgrep v11.0.2 + Downloaded 1 crate (243.3 KB) in 0.88s + Installing ripgrep v11.0.2 +--snip-- + Compiling ripgrep v11.0.2 + Finished release [optimized + debuginfo] target(s) in 3m 10s Installing ~/.cargo/bin/rg + Installed package `ripgrep v11.0.2` (executable `rg`) ``` -The last line of the output shows the location and the name of the installed -binary, which in the case of `ripgrep` is named `rg`. As long as the -installation directory is in our `$PATH` as mentioned above, we can then run -`rg --help` and start using a faster, rustier tool for searching files! +The second-to-last line of the output shows the location and the name of the +installed binary, which in the case of `ripgrep` is `rg`. As long as the +installation directory is in your `$PATH`, as mentioned previously, you can +then run `rg --help` and start using a faster, rustier tool for searching files! diff --git a/src/ch14-05-extending-cargo.md b/src/ch14-05-extending-cargo.md index e1cd1ca..bd22871 100644 --- a/src/ch14-05-extending-cargo.md +++ b/src/ch14-05-extending-cargo.md @@ -1,16 +1,17 @@ ## Extending Cargo with Custom Commands -Cargo is designed to be extensible with new subcommands without having to -modify Cargo itself. If a binary in your `$PATH` is named `cargo-something`, -you can run it as if it were a Cargo subcommand by running `cargo something`. -Custom commands like this are also listed when you run `cargo --list`. It's -convenient to `cargo install` extensions to Cargo then be able to run them just -like the built-in Cargo tools! +Cargo is designed so you can extend it with new subcommands without having to +modify Cargo. If a binary in your `$PATH` is named `cargo-something`, you can +run it as if it was a Cargo subcommand by running `cargo something`. Custom +commands like this are also listed when you run `cargo --list`. Being able to +use `cargo install` to install extensions and then run them just like the +built-in Cargo tools is a super convenient benefit of Cargo’s design! ## Summary -Sharing code with Cargo and crates.io is part of what makes the Rust ecosystem -useful for many different tasks. Rust's standard library is small and stable, -but crates are easy to share, use, and improve on a different timeline than the -language itself. Don't be shy about sharing code that's useful to you on -crates.io; it's likely that it will be useful to someone else as well! +Sharing code with Cargo and [crates.io](https://crates.io/) is +part of what makes the Rust ecosystem useful for many different tasks. Rust’s +standard library is small and stable, but crates are easy to share, use, and +improve on a timeline different from that of the language. Don’t be shy about +sharing code that’s useful to you on [crates.io](https://crates.io/); it’s likely that it will be useful to someone else as well! diff --git a/src/ch15-00-smart-pointers.md b/src/ch15-00-smart-pointers.md index 632993e..cadd547 100644 --- a/src/ch15-00-smart-pointers.md +++ b/src/ch15-00-smart-pointers.md @@ -1,112 +1,56 @@ # Smart Pointers -By smart pointers we mean a reference with more characteristics. +A *pointer* is a general concept for a variable that contains an address in +memory. This address refers to, or “points at,” some other data. The most +common kind of pointer in Rust is a reference, which you learned about in +Chapter 4. References are indicated by the `&` symbol and borrow the value they +point to. They don’t have any special capabilities other than referring to +data. Also, they don’t have any overhead and are the kind of pointer we use +most often. -Example of something that doesn't work +*Smart pointers*, on the other hand, are data structures that not only act like +a pointer but also have additional metadata and capabilities. The concept of +smart pointers isn’t unique to Rust: smart pointers originated in C++ and exist +in other languages as well. In Rust, the different smart pointers defined in +the standard library provide functionality beyond that provided by references. +One example that we’ll explore in this chapter is the *reference counting* +smart pointer type. This pointer enables you to have multiple owners of data by +keeping track of the number of owners and, when no owners remain, cleaning up +the data. -Surprise! Vec and String are technically smart pointers too! +In Rust, which uses the concept of ownership and borrowing, an additional +difference between references and smart pointers is that references are +pointers that only borrow data; in contrast, in many cases, smart pointers +*own* the data they point to. -This chapter is not a comprehensive list, but will give some examples of the -ones in the standard library. +We’ve already encountered a few smart pointers in this book, such as `String` +and `Vec` in Chapter 8, although we didn’t call them smart pointers at the +time. Both these types count as smart pointers because they own some memory and +allow you to manipulate it. They also have metadata (such as their capacity) +and extra capabilities or guarantees (such as with `String` ensuring its data +will always be valid UTF-8). +Smart pointers are usually implemented using structs. The characteristic that +distinguishes a smart pointer from an ordinary struct is that smart pointers +implement the `Deref` and `Drop` traits. The `Deref` trait allows an instance +of the smart pointer struct to behave like a reference so you can write code +that works with either references or smart pointers. The `Drop` trait allows +you to customize the code that is run when an instance of the smart pointer +goes out of scope. In this chapter, we’ll discuss both traits and demonstrate +why they’re important to smart pointers. -## `Box` +Given that the smart pointer pattern is a general design pattern used +frequently in Rust, this chapter won’t cover every existing smart pointer. Many +libraries have their own smart pointers, and you can even write your own. We’ll +cover the most common smart pointers in the standard library: -Don't use very often in your own code -Heap allocated -Express Ownership of a heap allocated thing +* `Box` for allocating values on the heap +* `Rc`, a reference counting type that enables multiple ownership +* `Ref` and `RefMut`, accessed through `RefCell`, a type that enforces + the borrowing rules at runtime instead of compile time -The three situations to use Box +In addition, we’ll cover the *interior mutability* pattern where an immutable +type exposes an API for mutating an interior value. We’ll also discuss +*reference cycles*: how they can leak memory and how to prevent them. -1. Trait objects -2. Recursive data structures -3. Extend the lifetime of something - -How this interacts with the Drop trait - -## `Rc` - -Reference counted. Rc is for *multiple ownership* - this thing should get -deallocated when all of the owners go out of scope. - -Show the data structure: - -```rust -struct Rc { - data: Box, - strong_reference_count: usize, - weak_reference_count: usize, -} -``` - -Talk through this. - -This only works if the data is immutable. - -What happens when you clone an Rc: data isn't cloned, increase the strong count. -When an Rc clone goes out of scope, the count goes down. - -### Rc Cycles - -This is how you leak memory in rust, which btw is totally safe. - -Is this garbage collecting? Well it's not tracing GC... if you use Rc and had -a cycle detector, it would be functionally equivalent to a tracing GC. Different -runtime characteristics tho. - - -#### Solution: turn an Rc into a `Weak` - -Same as Rc, but doesn't count towards the strong ref count. When you do this, the -strong ref count goes down and the weak count goes up. - -Data gets cleaned up when the strong count is 0, no matter what the weak count is. -However, Rc structure is kept until weak reference count also goes to zero, so weak pointers do not become dangling pointers. -At this point, attempt to upgrade Weak pointer will result into None. -Only when weak reference counter also reduces to zero, Rc structure is freed. - -## `RefCell` - -Single owner of mutable data - -The ownership rules checked at runtime instead of compile time. - -Only single threaded. See next chapter. - -### `borrow` and `borrow_mut` methods - -Checks all the rules and panics at runtime if the code violates them. - -1. The borrow checker is conservative and people can know more things. (no you -don't, but if you really want to go back to debugging segfaults, feel free) - -2. For when you're only allowed to have an immutable thing (which could be `Rc`) -but you need to be able to mutate the underlying data. - -## `Cell` - -Same thing as RefCell but for types that are Copy. No borrow checking rules here -anyway. So just reason #2 above. - -## Is this really safe? Yes! - -RefCell is still doing the checks, just at runtime -Cell is safe bc Copy types don't need the ownership rules anyway - -### The Interior Mutability Pattern - -The Interior Mutability Pattern is super unsafe internally but safe to use -from the outside and is totally safe, totally, trust us, seriously, it's safe. - -Allude to `UnsafeCell` maybe. Affects optimizations since &mut T is unique. -UnsafeCell turns off those optimizations so that everything doesn't break. - -This is how you can opt-out of the default of Rust's ownership rules and opt -in to different guarantees. - -## Summary - -If you want to implement your own smart pointer, go read the Nomicon. - -Now let's talk about concurrency, and some smart pointers that can be used -with multiple threads. +Let’s dive in! diff --git a/src/ch15-01-box.md b/src/ch15-01-box.md new file mode 100644 index 0000000..394e4eb --- /dev/null +++ b/src/ch15-01-box.md @@ -0,0 +1,254 @@ +## Using `Box` to Point to Data on the Heap + +The most straightforward smart pointer is a *box*, whose type is written +`Box`. Boxes allow you to store data on the heap rather than the stack. What +remains on the stack is the pointer to the heap data. Refer to Chapter 4 to +review the difference between the stack and the heap. + +Boxes don’t have performance overhead, other than storing their data on the +heap instead of on the stack. But they don’t have many extra capabilities +either. You’ll use them most often in these situations: + +* When you have a type whose size can’t be known at compile time and you want + to use a value of that type in a context that requires an exact size +* When you have a large amount of data and you want to transfer ownership but + ensure the data won’t be copied when you do so +* When you want to own a value and you care only that it’s a type that + implements a particular trait rather than being of a specific type + +We’ll demonstrate the first situation in the [“Enabling Recursive Types with +Boxes”](#enabling-recursive-types-with-boxes) section. In the +second case, transferring ownership of a large amount of data can take a long +time because the data is copied around on the stack. To improve performance in +this situation, we can store the large amount of data on the heap in a box. +Then, only the small amount of pointer data is copied around on the stack, +while the data it references stays in one place on the heap. The third case is +known as a *trait object*, and Chapter 17 devotes an entire section, [“Using +Trait Objects That Allow for Values of Different Types,”][trait-objects] just to that topic. So what you learn here you’ll apply again in +Chapter 17! + +### Using a `Box` to Store Data on the Heap + +Before we discuss this use case for `Box`, we’ll cover the syntax and how to +interact with values stored within a `Box`. + +Listing 15-1 shows how to use a box to store an `i32` value on the heap: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-01/src/main.rs}} +``` + +Listing 15-1: Storing an `i32` value on the heap using a +box + +We define the variable `b` to have the value of a `Box` that points to the +value `5`, which is allocated on the heap. This program will print `b = 5`; in +this case, we can access the data in the box similar to how we would if this +data were on the stack. Just like any owned value, when a box goes out of +scope, as `b` does at the end of `main`, it will be deallocated. The +deallocation happens for the box (stored on the stack) and the data it points +to (stored on the heap). + +Putting a single value on the heap isn’t very useful, so you won’t use boxes by +themselves in this way very often. Having values like a single `i32` on the +stack, where they’re stored by default, is more appropriate in the majority of +situations. Let’s look at a case where boxes allow us to define types that we +wouldn’t be allowed to if we didn’t have boxes. + +### Enabling Recursive Types with Boxes + +At compile time, Rust needs to know how much space a type takes up. One type +whose size can’t be known at compile time is a *recursive type*, where a value +can have as part of itself another value of the same type. Because this nesting +of values could theoretically continue infinitely, Rust doesn’t know how much +space a value of a recursive type needs. However, boxes have a known size, so +by inserting a box in a recursive type definition, you can have recursive types. + +Let’s explore the *cons list*, which is a data type common in functional +programming languages, as an example of a recursive type. The cons list type +we’ll define is straightforward except for the recursion; therefore, the +concepts in the example we’ll work with will be useful any time you get into +more complex situations involving recursive types. + +#### More Information About the Cons List + +A *cons list* is a data structure that comes from the Lisp programming language +and its dialects. In Lisp, the `cons` function (short for “construct function”) +constructs a new pair from its two arguments, which usually are a single value +and another pair. These pairs containing pairs form a list. + +The cons function concept has made its way into more general functional +programming jargon: “to cons *x* onto *y*” informally means to construct a new +container instance by putting the element *x* at the start of this new +container, followed by the container *y*. + +Each item in a cons list contains two elements: the value of the current item +and the next item. The last item in the list contains only a value called `Nil` +without a next item. A cons list is produced by recursively calling the `cons` +function. The canonical name to denote the base case of the recursion is `Nil`. +Note that this is not the same as the “null” or “nil” concept in Chapter 6, +which is an invalid or absent value. + +Although functional programming languages use cons lists frequently, the cons +list isn’t a commonly used data structure in Rust. Most of the time when you +have a list of items in Rust, `Vec` is a better choice to use. Other, more +complex recursive data types *are* useful in various situations, but by +starting with the cons list, we can explore how boxes let us define a recursive +data type without much distraction. + +Listing 15-2 contains an enum definition for a cons list. Note that this code +won’t compile yet because the `List` type doesn’t have a known size, which +we’ll demonstrate. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-02/src/main.rs:here}} +``` + +Listing 15-2: The first attempt at defining an enum to +represent a cons list data structure of `i32` values + +> Note: We’re implementing a cons list that holds only `i32` values for the +> purposes of this example. We could have implemented it using generics, as we +> discussed in Chapter 10, to define a cons list type that could store values of +> any type. + +Using the `List` type to store the list `1, 2, 3` would look like the code in +Listing 15-3: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-03/src/main.rs:here}} +``` + +Listing 15-3: Using the `List` enum to store the list `1, +2, 3` + +The first `Cons` value holds `1` and another `List` value. This `List` value is +another `Cons` value that holds `2` and another `List` value. This `List` value +is one more `Cons` value that holds `3` and a `List` value, which is finally +`Nil`, the non-recursive variant that signals the end of the list. + +If we try to compile the code in Listing 15-3, we get the error shown in +Listing 15-4: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-03/output.txt}} +``` + +Listing 15-4: The error we get when attempting to define +a recursive enum + +The error shows this type “has infinite size.” The reason is that we’ve defined +`List` with a variant that is recursive: it holds another value of itself +directly. As a result, Rust can’t figure out how much space it needs to store a +`List` value. Let’s break down why we get this error a bit. First, let’s look +at how Rust decides how much space it needs to store a value of a non-recursive +type. + +#### Computing the Size of a Non-Recursive Type + +Recall the `Message` enum we defined in Listing 6-2 when we discussed enum +definitions in Chapter 6: + +```rust +{{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-02/src/main.rs:here}} +``` + +To determine how much space to allocate for a `Message` value, Rust goes +through each of the variants to see which variant needs the most space. Rust +sees that `Message::Quit` doesn’t need any space, `Message::Move` needs enough +space to store two `i32` values, and so forth. Because only one variant will be +used, the most space a `Message` value will need is the space it would take to +store the largest of its variants. + +Contrast this with what happens when Rust tries to determine how much space a +recursive type like the `List` enum in Listing 15-2 needs. The compiler starts +by looking at the `Cons` variant, which holds a value of type `i32` and a value +of type `List`. Therefore, `Cons` needs an amount of space equal to the size of +an `i32` plus the size of a `List`. To figure out how much memory the `List` +type needs, the compiler looks at the variants, starting with the `Cons` +variant. The `Cons` variant holds a value of type `i32` and a value of type +`List`, and this process continues infinitely, as shown in Figure 15-1. + +An infinite Cons list + +Figure 15-1: An infinite `List` consisting of infinite +`Cons` variants + +#### Using `Box` to Get a Recursive Type with a Known Size + +Rust can’t figure out how much space to allocate for recursively defined types, +so the compiler gives the error in Listing 15-4. But the error does include +this helpful suggestion: + + + +```text +help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `List` representable + | +2 | Cons(i32, Box), + | ^^^^ ^ +``` + +In this suggestion, “indirection” means that instead of storing a value +directly, we’ll change the data structure to store the value indirectly by +storing a pointer to the value instead. + +Because a `Box` is a pointer, Rust always knows how much space a `Box` +needs: a pointer’s size doesn’t change based on the amount of data it’s +pointing to. This means we can put a `Box` inside the `Cons` variant instead +of another `List` value directly. The `Box` will point to the next `List` +value that will be on the heap rather than inside the `Cons` variant. +Conceptually, we still have a list, created with lists “holding” other lists, +but this implementation is now more like placing the items next to one another +rather than inside one another. + +We can change the definition of the `List` enum in Listing 15-2 and the usage +of the `List` in Listing 15-3 to the code in Listing 15-5, which will compile: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-05/src/main.rs}} +``` + +Listing 15-5: Definition of `List` that uses `Box` in +order to have a known size + +The `Cons` variant will need the size of an `i32` plus the space to store the +box’s pointer data. The `Nil` variant stores no values, so it needs less space +than the `Cons` variant. We now know that any `List` value will take up the +size of an `i32` plus the size of a box’s pointer data. By using a box, we’ve +broken the infinite, recursive chain, so the compiler can figure out the size +it needs to store a `List` value. Figure 15-2 shows what the `Cons` variant +looks like now. + +A finite Cons list + +Figure 15-2: A `List` that is not infinitely sized +because `Cons` holds a `Box` + +Boxes provide only the indirection and heap allocation; they don’t have any +other special capabilities, like those we’ll see with the other smart pointer +types. They also don’t have any performance overhead that these special +capabilities incur, so they can be useful in cases like the cons list where the +indirection is the only feature we need. We’ll look at more use cases for boxes +in Chapter 17, too. + +The `Box` type is a smart pointer because it implements the `Deref` trait, +which allows `Box` values to be treated like references. When a `Box` +value goes out of scope, the heap data that the box is pointing to is cleaned +up as well because of the `Drop` trait implementation. Let’s explore these two +traits in more detail. These two traits will be even more important to the +functionality provided by the other smart pointer types we’ll discuss in the +rest of this chapter. + +[trait-objects]: ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types diff --git a/src/ch15-02-deref.md b/src/ch15-02-deref.md new file mode 100644 index 0000000..9030df0 --- /dev/null +++ b/src/ch15-02-deref.md @@ -0,0 +1,287 @@ +## Treating Smart Pointers Like Regular References with the `Deref` Trait + +Implementing the `Deref` trait allows you to customize the behavior of the +*dereference operator*, `*` (as opposed to the multiplication or glob +operator). By implementing `Deref` in such a way that a smart pointer can be +treated like a regular reference, you can write code that operates on +references and use that code with smart pointers too. + +Let’s first look at how the dereference operator works with regular references. +Then we’ll try to define a custom type that behaves like `Box`, and see why +the dereference operator doesn’t work like a reference on our newly defined +type. We’ll explore how implementing the `Deref` trait makes it possible for +smart pointers to work in ways similar to references. Then we’ll look at +Rust’s *deref coercion* feature and how it lets us work with either references +or smart pointers. + +> Note: there’s one big difference between the `MyBox` type we’re about to +> build and the real `Box`: our version will not store its data on the heap. +> We are focusing this example on `Deref`, so where the data is actually stored +> is less important than the pointer-like behavior. + +### Following the Pointer to the Value with the Dereference Operator + +A regular reference is a type of pointer, and one way to think of a pointer is +as an arrow to a value stored somewhere else. In Listing 15-6, we create a +reference to an `i32` value and then use the dereference operator to follow the +reference to the data: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-06/src/main.rs}} +``` + +Listing 15-6: Using the dereference operator to follow a +reference to an `i32` value + +The variable `x` holds an `i32` value, `5`. We set `y` equal to a reference to +`x`. We can assert that `x` is equal to `5`. However, if we want to make an +assertion about the value in `y`, we have to use `*y` to follow the reference +to the value it’s pointing to (hence *dereference*). Once we dereference `y`, +we have access to the integer value `y` is pointing to that we can compare with +`5`. + +If we tried to write `assert_eq!(5, y);` instead, we would get this compilation +error: + +```console +{{#include ../listings/ch15-smart-pointers/output-only-01-comparing-to-reference/output.txt}} +``` + +Comparing a number and a reference to a number isn’t allowed because they’re +different types. We must use the dereference operator to follow the reference +to the value it’s pointing to. + +### Using `Box` Like a Reference + +We can rewrite the code in Listing 15-6 to use a `Box` instead of a +reference; the dereference operator will work as shown in Listing 15-7: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-07/src/main.rs}} +``` + +Listing 15-7: Using the dereference operator on a +`Box` + +The only difference between Listing 15-7 and Listing 15-6 is that here we set +`y` to be an instance of a box pointing to a copied value of `x` rather than a +reference pointing to the value of `x`. In the last assertion, we can use the +dereference operator to follow the box’s pointer in the same way that we did +when `y` was a reference. Next, we’ll explore what is special about `Box` +that enables us to use the dereference operator by defining our own box type. + +### Defining Our Own Smart Pointer + +Let’s build a smart pointer similar to the `Box` type provided by the +standard library to experience how smart pointers behave differently from +references by default. Then we’ll look at how to add the ability to use the +dereference operator. + +The `Box` type is ultimately defined as a tuple struct with one element, so +Listing 15-8 defines a `MyBox` type in the same way. We’ll also define a +`new` function to match the `new` function defined on `Box`. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-08/src/main.rs:here}} +``` + +Listing 15-8: Defining a `MyBox` type + +We define a struct named `MyBox` and declare a generic parameter `T`, because +we want our type to hold values of any type. The `MyBox` type is a tuple struct +with one element of type `T`. The `MyBox::new` function takes one parameter of +type `T` and returns a `MyBox` instance that holds the value passed in. + +Let’s try adding the `main` function in Listing 15-7 to Listing 15-8 and +changing it to use the `MyBox` type we’ve defined instead of `Box`. The +code in Listing 15-9 won’t compile because Rust doesn’t know how to dereference +`MyBox`. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-09/src/main.rs:here}} +``` + +Listing 15-9: Attempting to use `MyBox` in the same +way we used references and `Box` + +Here’s the resulting compilation error: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-09/output.txt}} +``` + +Our `MyBox` type can’t be dereferenced because we haven’t implemented that +ability on our type. To enable dereferencing with the `*` operator, we +implement the `Deref` trait. + +### Treating a Type Like a Reference by Implementing the `Deref` Trait + +As discussed in Chapter 10, to implement a trait, we need to provide +implementations for the trait’s required methods. The `Deref` trait, provided +by the standard library, requires us to implement one method named `deref` that +borrows `self` and returns a reference to the inner data. Listing 15-10 +contains an implementation of `Deref` to add to the definition of `MyBox`: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-10/src/main.rs:here}} +``` + +Listing 15-10: Implementing `Deref` on `MyBox` + +The `type Target = T;` syntax defines an associated type for the `Deref` trait +to use. Associated types are a slightly different way of declaring a generic +parameter, but you don’t need to worry about them for now; we’ll cover them in +more detail in Chapter 19. + +We fill in the body of the `deref` method with `&self.0` so `deref` returns a +reference to the value we want to access with the `*` operator. The `main` +function in Listing 15-9 that calls `*` on the `MyBox` value now compiles, +and the assertions pass! + +Without the `Deref` trait, the compiler can only dereference `&` references. +The `deref` method gives the compiler the ability to take a value of any type +that implements `Deref` and call the `deref` method to get a `&` reference that +it knows how to dereference. + +When we entered `*y` in Listing 15-9, behind the scenes Rust actually ran this +code: + +```rust,ignore +*(y.deref()) +``` + +Rust substitutes the `*` operator with a call to the `deref` method and then a +plain dereference so we don’t have to think about whether or not we need to +call the `deref` method. This Rust feature lets us write code that functions +identically whether we have a regular reference or a type that implements +`Deref`. + +The reason the `deref` method returns a reference to a value, and that the plain +dereference outside the parentheses in `*(y.deref())` is still necessary, is the +ownership system. If the `deref` method returned the value directly instead of +a reference to the value, the value would be moved out of `self`. We don’t want +to take ownership of the inner value inside `MyBox` in this case or in most +cases where we use the dereference operator. + +Note that the `*` operator is replaced with a call to the `deref` method and +then a call to the `*` operator just once, each time we use a `*` in our code. +Because the substitution of the `*` operator does not recurse infinitely, we +end up with data of type `i32`, which matches the `5` in `assert_eq!` in +Listing 15-9. + +### Implicit Deref Coercions with Functions and Methods + +*Deref coercion* is a convenience that Rust performs on arguments to functions +and methods. Deref coercion works only on types that implement the `Deref` +trait. Deref coercion converts such a type into a reference to another type. +For example, deref coercion can convert `&String` to `&str` because `String` +implements the `Deref` trait such that it returns `str`. Deref coercion happens +automatically when we pass a reference to a particular type’s value as an +argument to a function or method that doesn’t match the parameter type in the +function or method definition. A sequence of calls to the `deref` method +converts the type we provided into the type the parameter needs. + +Deref coercion was added to Rust so that programmers writing function and +method calls don’t need to add as many explicit references and dereferences +with `&` and `*`. The deref coercion feature also lets us write more code that +can work for either references or smart pointers. + +To see deref coercion in action, let’s use the `MyBox` type we defined in +Listing 15-8 as well as the implementation of `Deref` that we added in Listing +15-10. Listing 15-11 shows the definition of a function that has a string slice +parameter: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-11/src/main.rs:here}} +``` + +Listing 15-11: A `hello` function that has the parameter +`name` of type `&str` + +We can call the `hello` function with a string slice as an argument, such as +`hello("Rust");` for example. Deref coercion makes it possible to call `hello` +with a reference to a value of type `MyBox`, as shown in Listing 15-12: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-12/src/main.rs:here}} +``` + +Listing 15-12: Calling `hello` with a reference to a +`MyBox` value, which works because of deref coercion + +Here we’re calling the `hello` function with the argument `&m`, which is a +reference to a `MyBox` value. Because we implemented the `Deref` trait +on `MyBox` in Listing 15-10, Rust can turn `&MyBox` into `&String` +by calling `deref`. The standard library provides an implementation of `Deref` +on `String` that returns a string slice, and this is in the API documentation +for `Deref`. Rust calls `deref` again to turn the `&String` into `&str`, which +matches the `hello` function’s definition. + +If Rust didn’t implement deref coercion, we would have to write the code in +Listing 15-13 instead of the code in Listing 15-12 to call `hello` with a value +of type `&MyBox`. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-13/src/main.rs:here}} +``` + +Listing 15-13: The code we would have to write if Rust +didn’t have deref coercion + +The `(*m)` dereferences the `MyBox` into a `String`. Then the `&` and +`[..]` take a string slice of the `String` that is equal to the whole string to +match the signature of `hello`. The code without deref coercions is harder to +read, write, and understand with all of these symbols involved. Deref coercion +allows Rust to handle these conversions for us automatically. + +When the `Deref` trait is defined for the types involved, Rust will analyze the +types and use `Deref::deref` as many times as necessary to get a reference to +match the parameter’s type. The number of times that `Deref::deref` needs to be +inserted is resolved at compile time, so there is no runtime penalty for taking +advantage of deref coercion! + +### How Deref Coercion Interacts with Mutability + +Similar to how you use the `Deref` trait to override the `*` operator on +immutable references, you can use the `DerefMut` trait to override the `*` +operator on mutable references. + +Rust does deref coercion when it finds types and trait implementations in three +cases: + +* From `&T` to `&U` when `T: Deref` +* From `&mut T` to `&mut U` when `T: DerefMut` +* From `&mut T` to `&U` when `T: Deref` + +The first two cases are the same except for mutability. The first case states +that if you have a `&T`, and `T` implements `Deref` to some type `U`, you can +get a `&U` transparently. The second case states that the same deref coercion +happens for mutable references. + +The third case is trickier: Rust will also coerce a mutable reference to an +immutable one. But the reverse is *not* possible: immutable references will +never coerce to mutable references. Because of the borrowing rules, if you have +a mutable reference, that mutable reference must be the only reference to that +data (otherwise, the program wouldn’t compile). Converting one mutable +reference to one immutable reference will never break the borrowing rules. +Converting an immutable reference to a mutable reference would require that the +initial immutable reference is the only immutable reference to that data, but +the borrowing rules don’t guarantee that. Therefore, Rust can’t make the +assumption that converting an immutable reference to a mutable reference is +possible. diff --git a/src/ch15-03-drop.md b/src/ch15-03-drop.md new file mode 100644 index 0000000..6a61bc9 --- /dev/null +++ b/src/ch15-03-drop.md @@ -0,0 +1,147 @@ +## Running Code on Cleanup with the `Drop` Trait + +The second trait important to the smart pointer pattern is `Drop`, which lets +you customize what happens when a value is about to go out of scope. You can +provide an implementation for the `Drop` trait on any type, and the code you +specify can be used to release resources like files or network connections. +We’re introducing `Drop` in the context of smart pointers because the +functionality of the `Drop` trait is almost always used when implementing a +smart pointer. For example, when a `Box` is dropped it will deallocate the space +on the heap that the box points to. + +In some languages, the programmer must call code to free memory or resources +every time they finish using an instance of a smart pointer. If they forget, +the system might become overloaded and crash. In Rust, you can specify that a +particular bit of code be run whenever a value goes out of scope, and the +compiler will insert this code automatically. As a result, you don’t need to be +careful about placing cleanup code everywhere in a program that an instance of +a particular type is finished with—you still won’t leak resources! + +Specify the code to run when a value goes out of scope by implementing the +`Drop` trait. The `Drop` trait requires you to implement one method named +`drop` that takes a mutable reference to `self`. To see when Rust calls `drop`, +let’s implement `drop` with `println!` statements for now. + +Listing 15-14 shows a `CustomSmartPointer` struct whose only custom +functionality is that it will print `Dropping CustomSmartPointer!` when the +instance goes out of scope. This example demonstrates when Rust runs the `drop` +function. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-14/src/main.rs}} +``` + +Listing 15-14: A `CustomSmartPointer` struct that +implements the `Drop` trait where we would put our cleanup code + +The `Drop` trait is included in the prelude, so we don’t need to bring it into +scope. We implement the `Drop` trait on `CustomSmartPointer` and provide an +implementation for the `drop` method that calls `println!`. The body of the +`drop` function is where you would place any logic that you wanted to run when +an instance of your type goes out of scope. We’re printing some text here to +demonstrate when Rust will call `drop`. + +In `main`, we create two instances of `CustomSmartPointer` and then print +`CustomSmartPointers created`. At the end of `main`, our instances of +`CustomSmartPointer` will go out of scope, and Rust will call the code we put +in the `drop` method, printing our final message. Note that we didn’t need to +call the `drop` method explicitly. + +When we run this program, we’ll see the following output: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-14/output.txt}} +``` + +Rust automatically called `drop` for us when our instances went out of scope, +calling the code we specified. Variables are dropped in the reverse order of +their creation, so `d` was dropped before `c`. This example gives you a visual +guide to how the `drop` method works; usually you would specify the cleanup +code that your type needs to run rather than a print message. + +### Dropping a Value Early with `std::mem::drop` + +Unfortunately, it’s not straightforward to disable the automatic `drop` +functionality. Disabling `drop` isn’t usually necessary; the whole point of the +`Drop` trait is that it’s taken care of automatically. Occasionally, however, +you might want to clean up a value early. One example is when using smart +pointers that manage locks: you might want to force the `drop` method that +releases the lock so that other code in the same scope can acquire the lock. +Rust doesn’t let you call the `Drop` trait’s `drop` method manually; instead +you have to call the `std::mem::drop` function provided by the standard library +if you want to force a value to be dropped before the end of its scope. + +If we try to call the `Drop` trait’s `drop` method manually by modifying the +`main` function from Listing 15-14, as shown in Listing 15-15, we’ll get a +compiler error: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-15/src/main.rs:here}} +``` + +Listing 15-15: Attempting to call the `drop` method from +the `Drop` trait manually to clean up early + +When we try to compile this code, we’ll get this error: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-15/output.txt}} +``` + +This error message states that we’re not allowed to explicitly call `drop`. The +error message uses the term *destructor*, which is the general programming term +for a function that cleans up an instance. A *destructor* is analogous to a +*constructor*, which creates an instance. The `drop` function in Rust is one +particular destructor. + +Rust doesn’t let us call `drop` explicitly because Rust would still +automatically call `drop` on the value at the end of `main`. This would be a +*double free* error because Rust would be trying to clean up the same value +twice. + +We can’t disable the automatic insertion of `drop` when a value goes out of +scope, and we can’t call the `drop` method explicitly. So, if we need to force +a value to be cleaned up early, we can use the `std::mem::drop` function. + +The `std::mem::drop` function is different from the `drop` method in the `Drop` +trait. We call it by passing the value we want to force to be dropped early as +an argument. The function is in the prelude, so we can modify `main` in Listing +15-15 to call the `drop` function, as shown in Listing 15-16: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-16/src/main.rs:here}} +``` + +Listing 15-16: Calling `std::mem::drop` to explicitly +drop a value before it goes out of scope + +Running this code will print the following: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-16/output.txt}} +``` + +The text ```Dropping CustomSmartPointer with data `some data`!``` is printed +between the `CustomSmartPointer created.` and `CustomSmartPointer dropped +before the end of main.` text, showing that the `drop` method code is called to +drop `c` at that point. + +You can use code specified in a `Drop` trait implementation in many ways to +make cleanup convenient and safe: for instance, you could use it to create your +own memory allocator! With the `Drop` trait and Rust’s ownership system, you +don’t have to remember to clean up because Rust does it automatically. + +You also don’t have to worry about problems resulting from accidentally +cleaning up values still in use: the ownership system that makes sure +references are always valid also ensures that `drop` gets called only once when +the value is no longer being used. + +Now that we’ve examined `Box` and some of the characteristics of smart +pointers, let’s look at a few other smart pointers defined in the standard +library. diff --git a/src/ch15-04-rc.md b/src/ch15-04-rc.md new file mode 100644 index 0000000..fb685bc --- /dev/null +++ b/src/ch15-04-rc.md @@ -0,0 +1,165 @@ +## `Rc`, the Reference Counted Smart Pointer + +In the majority of cases, ownership is clear: you know exactly which variable +owns a given value. However, there are cases when a single value might have +multiple owners. For example, in graph data structures, multiple edges might +point to the same node, and that node is conceptually owned by all of the edges +that point to it. A node shouldn’t be cleaned up unless it doesn’t have any +edges pointing to it. + +To enable multiple ownership, Rust has a type called `Rc`, which is an +abbreviation for *reference counting*. The `Rc` type keeps track of the +number of references to a value which determines whether or not a value is +still in use. If there are zero references to a value, the value can be cleaned +up without any references becoming invalid. + +Imagine `Rc` as a TV in a family room. When one person enters to watch TV, +they turn it on. Others can come into the room and watch the TV. When the last +person leaves the room, they turn off the TV because it’s no longer being used. +If someone turns off the TV while others are still watching it, there would be +uproar from the remaining TV watchers! + +We use the `Rc` type when we want to allocate some data on the heap for +multiple parts of our program to read and we can’t determine at compile time +which part will finish using the data last. If we knew which part would finish +last, we could just make that part the data’s owner, and the normal ownership +rules enforced at compile time would take effect. + +Note that `Rc` is only for use in single-threaded scenarios. When we discuss +concurrency in Chapter 16, we’ll cover how to do reference counting in +multithreaded programs. + +### Using `Rc` to Share Data + +Let’s return to our cons list example in Listing 15-5. Recall that we defined +it using `Box`. This time, we’ll create two lists that both share ownership +of a third list. Conceptually, this looks similar to Figure 15-3: + +Two lists that share ownership of a third list + +Figure 15-3: Two lists, `b` and `c`, sharing ownership of +a third list, `a` + +We’ll create list `a` that contains 5 and then 10. Then we’ll make two more +lists: `b` that starts with 3 and `c` that starts with 4. Both `b` and `c` +lists will then continue on to the first `a` list containing 5 and 10. In other +words, both lists will share the first list containing 5 and 10. + +Trying to implement this scenario using our definition of `List` with `Box` +won’t work, as shown in Listing 15-17: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-17/src/main.rs}} +``` + +Listing 15-17: Demonstrating we’re not allowed to have +two lists using `Box` that try to share ownership of a third list + +When we compile this code, we get this error: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-17/output.txt}} +``` + +The `Cons` variants own the data they hold, so when we create the `b` list, `a` +is moved into `b` and `b` owns `a`. Then, when we try to use `a` again when +creating `c`, we’re not allowed to because `a` has been moved. + +We could change the definition of `Cons` to hold references instead, but then +we would have to specify lifetime parameters. By specifying lifetime +parameters, we would be specifying that every element in the list will live at +least as long as the entire list. The borrow checker wouldn’t let us compile +`let a = Cons(10, &Nil);` for example, because the temporary `Nil` value would +be dropped before `a` could take a reference to it. + +Instead, we’ll change our definition of `List` to use `Rc` in place of +`Box`, as shown in Listing 15-18. Each `Cons` variant will now hold a value +and an `Rc` pointing to a `List`. When we create `b`, instead of taking +ownership of `a`, we’ll clone the `Rc` that `a` is holding, thereby +increasing the number of references from one to two and letting `a` and `b` +share ownership of the data in that `Rc`. We’ll also clone `a` when +creating `c`, increasing the number of references from two to three. Every time +we call `Rc::clone`, the reference count to the data within the `Rc` will +increase, and the data won’t be cleaned up unless there are zero references to +it. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-18/src/main.rs}} +``` + +Listing 15-18: A definition of `List` that uses +`Rc` + +We need to add a `use` statement to bring `Rc` into scope because it’s not +in the prelude. In `main`, we create the list holding 5 and 10 and store it in +a new `Rc` in `a`. Then when we create `b` and `c`, we call the +`Rc::clone` function and pass a reference to the `Rc` in `a` as an +argument. + +We could have called `a.clone()` rather than `Rc::clone(&a)`, but Rust’s +convention is to use `Rc::clone` in this case. The implementation of +`Rc::clone` doesn’t make a deep copy of all the data like most types’ +implementations of `clone` do. The call to `Rc::clone` only increments the +reference count, which doesn’t take much time. Deep copies of data can take a +lot of time. By using `Rc::clone` for reference counting, we can visually +distinguish between the deep-copy kinds of clones and the kinds of clones that +increase the reference count. When looking for performance problems in the +code, we only need to consider the deep-copy clones and can disregard calls to +`Rc::clone`. + +### Cloning an `Rc` Increases the Reference Count + +Let’s change our working example in Listing 15-18 so we can see the reference +counts changing as we create and drop references to the `Rc` in `a`. + +In Listing 15-19, we’ll change `main` so it has an inner scope around list `c`; +then we can see how the reference count changes when `c` goes out of scope. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-19/src/main.rs:here}} +``` + +Listing 15-19: Printing the reference count + +At each point in the program where the reference count changes, we print the +reference count, which we can get by calling the `Rc::strong_count` function. +This function is named `strong_count` rather than `count` because the `Rc` +type also has a `weak_count`; we’ll see what `weak_count` is used for in the +[“Preventing Reference Cycles: Turning an `Rc` into a +`Weak`”][preventing-ref-cycles] section. + +This code prints the following: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-19/output.txt}} +``` + +We can see that the `Rc` in `a` has an initial reference count of 1; then +each time we call `clone`, the count goes up by 1. When `c` goes out of scope, +the count goes down by 1. We don’t have to call a function to decrease the +reference count like we have to call `Rc::clone` to increase the reference +count: the implementation of the `Drop` trait decreases the reference count +automatically when an `Rc` value goes out of scope. + +What we can’t see in this example is that when `b` and then `a` go out of scope +at the end of `main`, the count is then 0, and the `Rc` is cleaned up +completely at that point. Using `Rc` allows a single value to have +multiple owners, and the count ensures that the value remains valid as long as +any of the owners still exist. + +Via immutable references, `Rc` allows you to share data between multiple +parts of your program for reading only. If `Rc` allowed you to have multiple +mutable references too, you might violate one of the borrowing rules discussed +in Chapter 4: multiple mutable borrows to the same place can cause data races +and inconsistencies. But being able to mutate data is very useful! In the next +section, we’ll discuss the interior mutability pattern and the `RefCell` +type that you can use in conjunction with an `Rc` to work with this +immutability restriction. + +[preventing-ref-cycles]: ch15-06-reference-cycles.html#preventing-reference-cycles-turning-an-rct-into-a-weakt diff --git a/src/ch15-05-interior-mutability.md b/src/ch15-05-interior-mutability.md new file mode 100644 index 0000000..a42b49f --- /dev/null +++ b/src/ch15-05-interior-mutability.md @@ -0,0 +1,341 @@ +## `RefCell` and the Interior Mutability Pattern + +*Interior mutability* is a design pattern in Rust that allows you to mutate +data even when there are immutable references to that data; normally, this +action is disallowed by the borrowing rules. To mutate data, the pattern uses +`unsafe` code inside a data structure to bend Rust’s usual rules that govern +mutation and borrowing. We haven’t yet covered unsafe code; we will in Chapter +19. We can use types that use the interior mutability pattern when we can +ensure that the borrowing rules will be followed at runtime, even though the +compiler can’t guarantee that. The `unsafe` code involved is then wrapped in a +safe API, and the outer type is still immutable. + +Let’s explore this concept by looking at the `RefCell` type that follows the +interior mutability pattern. + +### Enforcing Borrowing Rules at Runtime with `RefCell` + +Unlike `Rc`, the `RefCell` type represents single ownership over the data +it holds. So, what makes `RefCell` different from a type like `Box`? +Recall the borrowing rules you learned in Chapter 4: + +* At any given time, you can have *either* (but not both of) one mutable + reference or any number of immutable references. +* References must always be valid. + +With references and `Box`, the borrowing rules’ invariants are enforced at +compile time. With `RefCell`, these invariants are enforced *at runtime*. +With references, if you break these rules, you’ll get a compiler error. With +`RefCell`, if you break these rules, your program will panic and exit. + +The advantages of checking the borrowing rules at compile time are that errors +will be caught sooner in the development process, and there is no impact on +runtime performance because all the analysis is completed beforehand. For those +reasons, checking the borrowing rules at compile time is the best choice in the +majority of cases, which is why this is Rust’s default. + +The advantage of checking the borrowing rules at runtime instead is that +certain memory-safe scenarios are then allowed, whereas they are disallowed by +the compile-time checks. Static analysis, like the Rust compiler, is inherently +conservative. Some properties of code are impossible to detect by analyzing the +code: the most famous example is the Halting Problem, which is beyond the scope +of this book but is an interesting topic to research. + +Because some analysis is impossible, if the Rust compiler can’t be sure the +code complies with the ownership rules, it might reject a correct program; in +this way, it’s conservative. If Rust accepted an incorrect program, users +wouldn’t be able to trust in the guarantees Rust makes. However, if Rust +rejects a correct program, the programmer will be inconvenienced, but nothing +catastrophic can occur. The `RefCell` type is useful when you’re sure your +code follows the borrowing rules but the compiler is unable to understand and +guarantee that. + +Similar to `Rc`, `RefCell` is only for use in single-threaded scenarios +and will give you a compile-time error if you try using it in a multithreaded +context. We’ll talk about how to get the functionality of `RefCell` in a +multithreaded program in Chapter 16. + +Here is a recap of the reasons to choose `Box`, `Rc`, or `RefCell`: + +* `Rc` enables multiple owners of the same data; `Box` and `RefCell` + have single owners. +* `Box` allows immutable or mutable borrows checked at compile time; `Rc` + allows only immutable borrows checked at compile time; `RefCell` allows + immutable or mutable borrows checked at runtime. +* Because `RefCell` allows mutable borrows checked at runtime, you can + mutate the value inside the `RefCell` even when the `RefCell` is + immutable. + +Mutating the value inside an immutable value is the *interior mutability* +pattern. Let’s look at a situation in which interior mutability is useful and +examine how it’s possible. + +### Interior Mutability: A Mutable Borrow to an Immutable Value + +A consequence of the borrowing rules is that when you have an immutable value, +you can’t borrow it mutably. For example, this code won’t compile: + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/src/main.rs}} +``` + +If you tried to compile this code, you’d get the following error: + +```console +{{#include ../listings/ch15-smart-pointers/no-listing-01-cant-borrow-immutable-as-mutable/output.txt}} +``` + +However, there are situations in which it would be useful for a value to mutate +itself in its methods but appear immutable to other code. Code outside the +value’s methods would not be able to mutate the value. Using `RefCell` is +one way to get the ability to have interior mutability. But `RefCell` +doesn’t get around the borrowing rules completely: the borrow checker in the +compiler allows this interior mutability, and the borrowing rules are checked +at runtime instead. If you violate the rules, you’ll get a `panic!` instead of +a compiler error. + +Let’s work through a practical example where we can use `RefCell` to mutate +an immutable value and see why that is useful. + +#### A Use Case for Interior Mutability: Mock Objects + +A *test double* is the general programming concept for a type used in place of +another type during testing. *Mock objects* are specific types of test doubles +that record what happens during a test so you can assert that the correct +actions took place. + +Rust doesn’t have objects in the same sense as other languages have objects, +and Rust doesn’t have mock object functionality built into the standard library +as some other languages do. However, you can definitely create a struct that +will serve the same purposes as a mock object. + +Here’s the scenario we’ll test: we’ll create a library that tracks a value +against a maximum value and sends messages based on how close to the maximum +value the current value is. This library could be used to keep track of a +user’s quota for the number of API calls they’re allowed to make, for example. + +Our library will only provide the functionality of tracking how close to the +maximum a value is and what the messages should be at what times. Applications +that use our library will be expected to provide the mechanism for sending the +messages: the application could put a message in the application, send an +email, send a text message, or something else. The library doesn’t need to know +that detail. All it needs is something that implements a trait we’ll provide +called `Messenger`. Listing 15-20 shows the library code: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-20/src/lib.rs}} +``` + +Listing 15-20: A library to keep track of how close a +value is to a maximum value and warn when the value is at certain levels + +One important part of this code is that the `Messenger` trait has one method +called `send` that takes an immutable reference to `self` and the text of the +message. This trait is the interface our mock object needs to implement so that +the mock can be used in the same way a real object is. The other important part +is that we want to test the behavior of the `set_value` method on the +`LimitTracker`. We can change what we pass in for the `value` parameter, but +`set_value` doesn’t return anything for us to make assertions on. We want to be +able to say that if we create a `LimitTracker` with something that implements +the `Messenger` trait and a particular value for `max`, when we pass different +numbers for `value`, the messenger is told to send the appropriate messages. + +We need a mock object that, instead of sending an email or text message when we +call `send`, will only keep track of the messages it’s told to send. We can +create a new instance of the mock object, create a `LimitTracker` that uses the +mock object, call the `set_value` method on `LimitTracker`, and then check that +the mock object has the messages we expect. Listing 15-21 shows an attempt to +implement a mock object to do just that, but the borrow checker won’t allow it: + +Filename: src/lib.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-21/src/lib.rs:here}} +``` + +Listing 15-21: An attempt to implement a `MockMessenger` +that isn’t allowed by the borrow checker + +This test code defines a `MockMessenger` struct that has a `sent_messages` +field with a `Vec` of `String` values to keep track of the messages it’s told +to send. We also define an associated function `new` to make it convenient to +create new `MockMessenger` values that start with an empty list of messages. We +then implement the `Messenger` trait for `MockMessenger` so we can give a +`MockMessenger` to a `LimitTracker`. In the definition of the `send` method, we +take the message passed in as a parameter and store it in the `MockMessenger` +list of `sent_messages`. + +In the test, we’re testing what happens when the `LimitTracker` is told to set +`value` to something that is more than 75 percent of the `max` value. First, we +create a new `MockMessenger`, which will start with an empty list of messages. +Then we create a new `LimitTracker` and give it a reference to the new +`MockMessenger` and a `max` value of 100. We call the `set_value` method on the +`LimitTracker` with a value of 80, which is more than 75 percent of 100. Then +we assert that the list of messages that the `MockMessenger` is keeping track +of should now have one message in it. + +However, there’s one problem with this test, as shown here: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-21/output.txt}} +``` + +We can’t modify the `MockMessenger` to keep track of the messages, because the +`send` method takes an immutable reference to `self`. We also can’t take the +suggestion from the error text to use `&mut self` instead, because then the +signature of `send` wouldn’t match the signature in the `Messenger` trait +definition (feel free to try and see what error message you get). + +This is a situation in which interior mutability can help! We’ll store the +`sent_messages` within a `RefCell`, and then the `send` method will be +able to modify `sent_messages` to store the messages we’ve seen. Listing 15-22 +shows what that looks like: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-22/src/lib.rs:here}} +``` + +Listing 15-22: Using `RefCell` to mutate an inner +value while the outer value is considered immutable + +The `sent_messages` field is now of type `RefCell>` instead of +`Vec`. In the `new` function, we create a new `RefCell>` +instance around the empty vector. + +For the implementation of the `send` method, the first parameter is still an +immutable borrow of `self`, which matches the trait definition. We call +`borrow_mut` on the `RefCell>` in `self.sent_messages` to get a +mutable reference to the value inside the `RefCell>`, which is +the vector. Then we can call `push` on the mutable reference to the vector to +keep track of the messages sent during the test. + +The last change we have to make is in the assertion: to see how many items are +in the inner vector, we call `borrow` on the `RefCell>` to get an +immutable reference to the vector. + +Now that you’ve seen how to use `RefCell`, let’s dig into how it works! + +#### Keeping Track of Borrows at Runtime with `RefCell` + +When creating immutable and mutable references, we use the `&` and `&mut` +syntax, respectively. With `RefCell`, we use the `borrow` and `borrow_mut` +methods, which are part of the safe API that belongs to `RefCell`. The +`borrow` method returns the smart pointer type `Ref`, and `borrow_mut` +returns the smart pointer type `RefMut`. Both types implement `Deref`, so we +can treat them like regular references. + +The `RefCell` keeps track of how many `Ref` and `RefMut` smart +pointers are currently active. Every time we call `borrow`, the `RefCell` +increases its count of how many immutable borrows are active. When a `Ref` +value goes out of scope, the count of immutable borrows goes down by one. Just +like the compile-time borrowing rules, `RefCell` lets us have many immutable +borrows or one mutable borrow at any point in time. + +If we try to violate these rules, rather than getting a compiler error as we +would with references, the implementation of `RefCell` will panic at +runtime. Listing 15-23 shows a modification of the implementation of `send` in +Listing 15-22. We’re deliberately trying to create two mutable borrows active +for the same scope to illustrate that `RefCell` prevents us from doing this +at runtime. + +Filename: src/lib.rs + +```rust,ignore,panics +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-23/src/lib.rs:here}} +``` + +Listing 15-23: Creating two mutable references in the +same scope to see that `RefCell` will panic + +We create a variable `one_borrow` for the `RefMut` smart pointer returned +from `borrow_mut`. Then we create another mutable borrow in the same way in the +variable `two_borrow`. This makes two mutable references in the same scope, +which isn’t allowed. When we run the tests for our library, the code in Listing +15-23 will compile without any errors, but the test will fail: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-23/output.txt}} +``` + +Notice that the code panicked with the message `already borrowed: +BorrowMutError`. This is how `RefCell` handles violations of the borrowing +rules at runtime. + +Catching borrowing errors at runtime rather than compile time means that you +would find a mistake in your code later in the development process and possibly +not until your code was deployed to production. Also, your code would incur a +small runtime performance penalty as a result of keeping track of the borrows +at runtime rather than compile time. However, using `RefCell` makes it +possible to write a mock object that can modify itself to keep track of the +messages it has seen while you’re using it in a context where only immutable +values are allowed. You can use `RefCell` despite its trade-offs to get more +functionality than regular references provide. + +### Having Multiple Owners of Mutable Data by Combining `Rc` and `RefCell` + +A common way to use `RefCell` is in combination with `Rc`. Recall that +`Rc` lets you have multiple owners of some data, but it only gives immutable +access to that data. If you have an `Rc` that holds a `RefCell`, you can +get a value that can have multiple owners *and* that you can mutate! + +For example, recall the cons list example in Listing 15-18 where we used +`Rc` to allow multiple lists to share ownership of another list. Because +`Rc` holds only immutable values, we can’t change any of the values in the +list once we’ve created them. Let’s add in `RefCell` to gain the ability to +change the values in the lists. Listing 15-24 shows that by using a +`RefCell` in the `Cons` definition, we can modify the value stored in all +the lists: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-24/src/main.rs}} +``` + +Listing 15-24: Using `Rc>` to create a +`List` that we can mutate + +We create a value that is an instance of `Rc>` and store it in a +variable named `value` so we can access it directly later. Then we create a +`List` in `a` with a `Cons` variant that holds `value`. We need to clone +`value` so both `a` and `value` have ownership of the inner `5` value rather +than transferring ownership from `value` to `a` or having `a` borrow from +`value`. + +We wrap the list `a` in an `Rc` so when we create lists `b` and `c`, they +can both refer to `a`, which is what we did in Listing 15-18. + +After we’ve created the lists in `a`, `b`, and `c`, we add 10 to the value in +`value`. We do this by calling `borrow_mut` on `value`, which uses the +automatic dereferencing feature we discussed in Chapter 5 (see the section +[“Where’s the `->` Operator?”][wheres-the---operator]) to +dereference the `Rc` to the inner `RefCell` value. The `borrow_mut` +method returns a `RefMut` smart pointer, and we use the dereference operator +on it and change the inner value. + +When we print `a`, `b`, and `c`, we can see that they all have the modified +value of 15 rather than 5: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-24/output.txt}} +``` + +This technique is pretty neat! By using `RefCell`, we have an outwardly +immutable `List` value. But we can use the methods on `RefCell` that provide +access to its interior mutability so we can modify our data when we need to. +The runtime checks of the borrowing rules protect us from data races, and it’s +sometimes worth trading a bit of speed for this flexibility in our data +structures. + +The standard library has other types that provide interior mutability, such as +`Cell`, which is similar except that instead of giving references to the +inner value, the value is copied in and out of the `Cell`. There’s also +`Mutex`, which offers interior mutability that’s safe to use across threads; +we’ll discuss its use in Chapter 16. Check out the standard library docs for +more details on the differences between these types. + +[wheres-the---operator]: ch05-03-method-syntax.html#wheres-the---operator diff --git a/src/ch15-06-reference-cycles.md b/src/ch15-06-reference-cycles.md new file mode 100644 index 0000000..7094c65 --- /dev/null +++ b/src/ch15-06-reference-cycles.md @@ -0,0 +1,318 @@ +## Reference Cycles Can Leak Memory + +Rust’s memory safety guarantees make it difficult, but not impossible, to +accidentally create memory that is never cleaned up (known as a *memory leak*). +Preventing memory leaks entirely is not one of Rust’s guarantees in the same +way that disallowing data races at compile time is, meaning memory leaks are +memory safe in Rust. We can see that Rust allows memory leaks by using `Rc` +and `RefCell`: it’s possible to create references where items refer to each +other in a cycle. This creates memory leaks because the reference count of each +item in the cycle will never reach 0, and the values will never be dropped. + +### Creating a Reference Cycle + +Let’s look at how a reference cycle might happen and how to prevent it, +starting with the definition of the `List` enum and a `tail` method in Listing +15-25: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-25/src/main.rs}} +``` + +Listing 15-25: A cons list definition that holds a +`RefCell` so we can modify what a `Cons` variant is referring to + +We’re using another variation of the `List` definition from Listing 15-5. The +second element in the `Cons` variant is now `RefCell>`, meaning that +instead of having the ability to modify the `i32` value as we did in Listing +15-24, we want to modify which `List` value a `Cons` variant is pointing to. +We’re also adding a `tail` method to make it convenient for us to access the +second item if we have a `Cons` variant. + +In Listing 15-26, we’re adding a `main` function that uses the definitions in +Listing 15-25. This code creates a list in `a` and a list in `b` that points to +the list in `a`. Then it modifies the list in `a` to point to `b`, creating a +reference cycle. There are `println!` statements along the way to show what the +reference counts are at various points in this process. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-26/src/main.rs:here}} +``` + +Listing 15-26: Creating a reference cycle of two `List` +values pointing to each other + +We create an `Rc` instance holding a `List` value in the variable `a` +with an initial list of `5, Nil`. We then create an `Rc` instance +holding another `List` value in the variable `b` that contains the value 10 and +points to the list in `a`. + +We modify `a` so it points to `b` instead of `Nil`, creating a cycle. We +do that by using the `tail` method to get a reference to the +`RefCell>` in `a`, which we put in the variable `link`. Then we use +the `borrow_mut` method on the `RefCell>` to change the value inside +from an `Rc` that holds a `Nil` value to the `Rc` in `b`. + +When we run this code, keeping the last `println!` commented out for the +moment, we’ll get this output: + +```console +{{#include ../listings/ch15-smart-pointers/listing-15-26/output.txt}} +``` + +The reference count of the `Rc` instances in both `a` and `b` are 2 after +we change the list in `a` to point to `b`. At the end of `main`, Rust drops the +variable `b`, which decreases the reference count of the `Rc` instance +from 2 to 1. The memory that `Rc` has on the heap won’t be dropped at +this point, because its reference count is 1, not 0. Then Rust drops `a`, which +decreases the reference count of the `a` `Rc` instance from 2 to 1 as +well. This instance's memory can’t be dropped either, because the other +`Rc` instance still refers to it. The memory allocated to the list will +remain uncollected forever. To visualize this reference cycle, we’ve created a +diagram in Figure 15-4. + +Reference cycle of lists + +Figure 15-4: A reference cycle of lists `a` and `b` +pointing to each other + +If you uncomment the last `println!` and run the program, Rust will try to +print this cycle with `a` pointing to `b` pointing to `a` and so forth until it +overflows the stack. + +In this case, right after we create the reference cycle, the program ends. The +consequences of this cycle aren’t very dire. However, if a more complex program +allocated lots of memory in a cycle and held onto it for a long time, the +program would use more memory than it needed and might overwhelm the system, +causing it to run out of available memory. + +Creating reference cycles is not easily done, but it’s not impossible either. +If you have `RefCell` values that contain `Rc` values or similar nested +combinations of types with interior mutability and reference counting, you must +ensure that you don’t create cycles; you can’t rely on Rust to catch them. +Creating a reference cycle would be a logic bug in your program that you should +use automated tests, code reviews, and other software development practices to +minimize. + +Another solution for avoiding reference cycles is reorganizing your data +structures so that some references express ownership and some references don’t. +As a result, you can have cycles made up of some ownership relationships and +some non-ownership relationships, and only the ownership relationships affect +whether or not a value can be dropped. In Listing 15-25, we always want `Cons` +variants to own their list, so reorganizing the data structure isn’t possible. +Let’s look at an example using graphs made up of parent nodes and child nodes +to see when non-ownership relationships are an appropriate way to prevent +reference cycles. + +### Preventing Reference Cycles: Turning an `Rc` into a `Weak` + +So far, we’ve demonstrated that calling `Rc::clone` increases the +`strong_count` of an `Rc` instance, and an `Rc` instance is only cleaned +up if its `strong_count` is 0. You can also create a *weak reference* to the +value within an `Rc` instance by calling `Rc::downgrade` and passing a +reference to the `Rc`. When you call `Rc::downgrade`, you get a smart +pointer of type `Weak`. Instead of increasing the `strong_count` in the +`Rc` instance by 1, calling `Rc::downgrade` increases the `weak_count` by 1. +The `Rc` type uses `weak_count` to keep track of how many `Weak` +references exist, similar to `strong_count`. The difference is the `weak_count` +doesn’t need to be 0 for the `Rc` instance to be cleaned up. + +Strong references are how you can share ownership of an `Rc` instance. Weak +references don’t express an ownership relationship. They won’t cause a +reference cycle because any cycle involving some weak references will be broken +once the strong reference count of values involved is 0. + +Because the value that `Weak` references might have been dropped, to do +anything with the value that a `Weak` is pointing to, you must make sure the +value still exists. Do this by calling the `upgrade` method on a `Weak` +instance, which will return an `Option>`. You’ll get a result of `Some` +if the `Rc` value has not been dropped yet and a result of `None` if the +`Rc` value has been dropped. Because `upgrade` returns an `Option>`, +Rust will ensure that the `Some` case and the `None` case are handled, and +there won’t be an invalid pointer. + +As an example, rather than using a list whose items know only about the next +item, we’ll create a tree whose items know about their children items *and* +their parent items. + +#### Creating a Tree Data Structure: a `Node` with Child Nodes + +To start, we’ll build a tree with nodes that know about their child nodes. +We’ll create a struct named `Node` that holds its own `i32` value as well as +references to its children `Node` values: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-27/src/main.rs:here}} +``` + +We want a `Node` to own its children, and we want to share that ownership with +variables so we can access each `Node` in the tree directly. To do this, we +define the `Vec` items to be values of type `Rc`. We also want to +modify which nodes are children of another node, so we have a `RefCell` in +`children` around the `Vec>`. + +Next, we’ll use our struct definition and create one `Node` instance named +`leaf` with the value 3 and no children, and another instance named `branch` +with the value 5 and `leaf` as one of its children, as shown in Listing 15-27: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-27/src/main.rs:there}} +``` + +Listing 15-27: Creating a `leaf` node with no children +and a `branch` node with `leaf` as one of its children + +We clone the `Rc` in `leaf` and store that in `branch`, meaning the +`Node` in `leaf` now has two owners: `leaf` and `branch`. We can get from +`branch` to `leaf` through `branch.children`, but there’s no way to get from +`leaf` to `branch`. The reason is that `leaf` has no reference to `branch` and +doesn’t know they’re related. We want `leaf` to know that `branch` is its +parent. We’ll do that next. + +#### Adding a Reference from a Child to Its Parent + +To make the child node aware of its parent, we need to add a `parent` field to +our `Node` struct definition. The trouble is in deciding what the type of +`parent` should be. We know it can’t contain an `Rc`, because that would +create a reference cycle with `leaf.parent` pointing to `branch` and +`branch.children` pointing to `leaf`, which would cause their `strong_count` +values to never be 0. + +Thinking about the relationships another way, a parent node should own its +children: if a parent node is dropped, its child nodes should be dropped as +well. However, a child should not own its parent: if we drop a child node, the +parent should still exist. This is a case for weak references! + +So instead of `Rc`, we’ll make the type of `parent` use `Weak`, +specifically a `RefCell>`. Now our `Node` struct definition looks +like this: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-28/src/main.rs:here}} +``` + +A node will be able to refer to its parent node but doesn’t own its parent. +In Listing 15-28, we update `main` to use this new definition so the `leaf` +node will have a way to refer to its parent, `branch`: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-28/src/main.rs:there}} +``` + +Listing 15-28: A `leaf` node with a weak reference to its +parent node `branch` + +Creating the `leaf` node looks similar to how creating the `leaf` node looked +in Listing 15-27 with the exception of the `parent` field: `leaf` starts out +without a parent, so we create a new, empty `Weak` reference instance. + +At this point, when we try to get a reference to the parent of `leaf` by using +the `upgrade` method, we get a `None` value. We see this in the output from the +first `println!` statement: + +```text +leaf parent = None +``` + +When we create the `branch` node, it will also have a new `Weak` +reference in the `parent` field, because `branch` doesn’t have a parent node. +We still have `leaf` as one of the children of `branch`. Once we have the +`Node` instance in `branch`, we can modify `leaf` to give it a `Weak` +reference to its parent. We use the `borrow_mut` method on the +`RefCell>` in the `parent` field of `leaf`, and then we use the +`Rc::downgrade` function to create a `Weak` reference to `branch` from +the `Rc` in `branch.` + +When we print the parent of `leaf` again, this time we’ll get a `Some` variant +holding `branch`: now `leaf` can access its parent! When we print `leaf`, we +also avoid the cycle that eventually ended in a stack overflow like we had in +Listing 15-26; the `Weak` references are printed as `(Weak)`: + +```text +leaf parent = Some(Node { value: 5, parent: RefCell { value: (Weak) }, +children: RefCell { value: [Node { value: 3, parent: RefCell { value: (Weak) }, +children: RefCell { value: [] } }] } }) +``` + +The lack of infinite output indicates that this code didn’t create a reference +cycle. We can also tell this by looking at the values we get from calling +`Rc::strong_count` and `Rc::weak_count`. + +#### Visualizing Changes to `strong_count` and `weak_count` + +Let’s look at how the `strong_count` and `weak_count` values of the `Rc` +instances change by creating a new inner scope and moving the creation of +`branch` into that scope. By doing so, we can see what happens when `branch` is +created and then dropped when it goes out of scope. The modifications are shown +in Listing 15-29: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch15-smart-pointers/listing-15-29/src/main.rs:here}} +``` + +Listing 15-29: Creating `branch` in an inner scope and +examining strong and weak reference counts + +After `leaf` is created, its `Rc` has a strong count of 1 and a weak +count of 0. In the inner scope, we create `branch` and associate it with +`leaf`, at which point when we print the counts, the `Rc` in `branch` +will have a strong count of 1 and a weak count of 1 (for `leaf.parent` pointing +to `branch` with a `Weak`). When we print the counts in `leaf`, we’ll see +it will have a strong count of 2, because `branch` now has a clone of the +`Rc` of `leaf` stored in `branch.children`, but will still have a weak +count of 0. + +When the inner scope ends, `branch` goes out of scope and the strong count of +the `Rc` decreases to 0, so its `Node` is dropped. The weak count of 1 +from `leaf.parent` has no bearing on whether or not `Node` is dropped, so we +don’t get any memory leaks! + +If we try to access the parent of `leaf` after the end of the scope, we’ll get +`None` again. At the end of the program, the `Rc` in `leaf` has a strong +count of 1 and a weak count of 0, because the variable `leaf` is now the only +reference to the `Rc` again. + +All of the logic that manages the counts and value dropping is built into +`Rc` and `Weak` and their implementations of the `Drop` trait. By +specifying that the relationship from a child to its parent should be a +`Weak` reference in the definition of `Node`, you’re able to have parent +nodes point to child nodes and vice versa without creating a reference cycle +and memory leaks. + +## Summary + +This chapter covered how to use smart pointers to make different guarantees and +trade-offs from those Rust makes by default with regular references. The +`Box` type has a known size and points to data allocated on the heap. The +`Rc` type keeps track of the number of references to data on the heap so +that data can have multiple owners. The `RefCell` type with its interior +mutability gives us a type that we can use when we need an immutable type but +need to change an inner value of that type; it also enforces the borrowing +rules at runtime instead of at compile time. + +Also discussed were the `Deref` and `Drop` traits, which enable a lot of the +functionality of smart pointers. We explored reference cycles that can cause +memory leaks and how to prevent them using `Weak`. + +If this chapter has piqued your interest and you want to implement your own +smart pointers, check out [“The Rustonomicon”][nomicon] for more useful +information. + +Next, we’ll talk about concurrency in Rust. You’ll even learn about a few new +smart pointers. + +[nomicon]: ../nomicon/index.html diff --git a/src/ch16-00-concurrency.md b/src/ch16-00-concurrency.md index 9db08e0..410f3e4 100644 --- a/src/ch16-00-concurrency.md +++ b/src/ch16-00-concurrency.md @@ -1,395 +1,49 @@ # Fearless Concurrency -So, with Rust, it's more subtle than that. That is, while threading proper -isn't part of the language itself, Rust's type system is structured in such a -way as to make it possible to build those kinds of libraries. In other words, -Rust's focus on aliasability ends up solving these problems. - -This is a library abstraction. - -Shared mutable state is a problem. Both useful. Functional languages get rid of -mutability. - -Ownership rules (that tame the "shared" aspect) enable fearless concurrency: the -compiler is making sure you don't shoot yourself in your foot. - -## What are threads - - - -## Rust's concurrency tradeoffs - -Lots of different languages tackle this problem in different ways. We are not -going to talk about that: exercise for the reader is investigate other languages -and compare and contrast with Rust's approach. - -This is how Rust does it, what rust means by threads - -OS threads are exposed in the standard library bc a systems programming language -should integrate with your system. - -If you have a different threaded mechanism, you need a runtime, rust is trying -to not have a heavy runtime. - -These are the reasons Rust's concurrency model is this way as opposed to other -language's ways, which are optimizing for different things. - - -## Let's get a thread: `thread::spawn` - -Code examples - just print stuff, no data sharing - -## Communicating between threads - - -### Closures, Ownership, and Borrowing - -The property of being allowed to use variables from the surrounding scope is -also subject to all of the usual rules around ownership and borrowing. Since -closures attempt to infer the types of their parameters, they also infer how -those parameters are borrowed. Closures make that inference by looking at how -they are used. Consider the example in Listing 13-5 that has functions that -borrow immutably, borrow mutably, and move their parameters, then closures that -reference values from their environment and call each of the functions. We'll -see how this affects inference of when a value is borrowed: - -
-Filename: src/main.rs - -```rust -#[derive(Debug)] -struct Foo; - -fn borrows(f: &Foo) { - println!("Took {:?} by reference.", f); -} - -fn borrows_mut(f: &mut Foo) { - println!("Took {:?} by mutable reference.", f); -} - -fn moves(f: Foo) { - println!("Took ownership of {:?}.", f); -} - -fn main() { - let f1 = Foo; - let closure_that_borrows = |x| borrows(x); - closure_that_borrows(&f1); - - let mut f2 = Foo; - let closure_that_borrows_mut = |y| borrows_mut(y); - closure_that_borrows_mut(&mut f2); - - let f3 = Foo; - let closure_that_moves = |z| moves(z); - closure_that_moves(f3); -} -``` - -
- -Listing 16-something: Closures that borrow, borrow mutably, and take ownership -of their parameters, which is inferred from how the closure body uses the -parameters - -
-
- -Here, Rust is able to look at how we use the parameters of each closure inside -their bodies. If the closure passes its parameter it to a function that takes -`&Foo`, then the type of the parameter must be `&Foo`. If it passes the -parameter to a function that takes `&mut Foo`, then the type of parameter must -be `&mut Foo`, and so on. If we try to use `f3` after the call to -`closure_that_moves` in the last line of `main`, we'll get a compiler error -since ownership of `f3` was transferred to `closure_that_moves`, which -transferred ownership to the function `moves`. - -### Overriding Inferred Borrowing with the `move` Keyword - -Rust will allow you to override the borrowing inference by using the `move` -keyword. This will cause all of the closure's parameters to be taken by -ownership, instead of whatever they were inferred as. Consider this example: - -```rust -let mut num = 4; - -{ - let mut add_num = |x| num += x; - - add_num(6); -} - -assert_eq!(10, num); -``` - -In this case, the `add_num` closure took a mutable reference to `num`, then -when we called `add_num`, it mutated the underlying value. In the last line, -`num` contains 10, as we'd expect. We also needed to declare `add_num` itself -as `mut` too, because we're mutating its environment. - -If we change the definition of `add_num` to a `move` closure, the behavior is -different: - -```rust -let mut num = 4; - -{ - let mut add_num = move |x| num += x; - - add_num(6); -} - -assert_eq!(4, num); -``` - -In the last line, `num` now contains 4: `add_num` took ownership of a copy of -`num`, rather than mutably borrowing `num`. - -One of the most common places you'll see the `move` keyword used is with -threads, since it's important that one thread is no longer allowed to use a -value once the value has been transferred to another thread through a closure -in order to prevent data races. We'll talk more about that in Chapter XX. - -### Closures and Lifetimes - -Remember Listing 10-8 from the Lifetime Syntax section of Chapter 10? It looked -like this: - -```rust,ignore -{ - let r; - - { - let x = 5; - r = &x; - } - - println!("r: {}", r); -} -``` - -This example doesn't compile since `x` doesn't have a long enough lifetime. -Because closures may borrow variables from their enclosing scope, we can -construct a similar example with a closure that borrows `x` and tries to return -that borrowed value. The code in Listing 13-6 also won't compile: - -
- -```rust,ignore -{ - let closure; - - { - let x = 4; - - closure = || x ; // A closure that takes no arguments and returns x. - } -} -``` - -
- -Listing 16-something: A closure that tries to return a borrowed value that does -not live long enough - -
-
- -We get an error because `x` does not live long enough: - -```text -error: `x` does not live long enough - --> - | -8 | closure = || x ; // A closure that takes no arguments and returns x. - | -- ^ does not live long enough - | | - | capture occurs here -9 | } - | - borrowed value only lives until here -10 | } - | - borrowed value needs to live until here -``` - -To fix the error in the code in Listing 13-6, we can use the `move` keyword -from the last section to make the closure take ownership of `x`. Because `x` is -a number, it is a `Copy` type and therefore will be copied into the closure. -The code in Listing 13-7 will compile: - -
- -```rust -{ - let closure; - - { - let mut x = 4; - - closure = move || x ; // A closure that takes no arguments and returns x. - - x = 5; - - assert_eq!(closure(), 4); - } -} -``` - -
- -Listing 16-something: Moving a value into the closure to fix the lifetime error - -
-
- -Even though we modified `x` between the closure definition and `assert_eq!`, -since `closure` now has its own version, the changes to `x` won't change the -version of `x` that's in the closure. - -Rust doesn't provide a way to say that some values a closure uses should be -borrowed and some should be moved; it's either all by inference or all moved by -adding the `move` keyword. However, we can accomplish the goal of borrowing -some values and taking ownership of others by combining `move` with some extra -bindings. Consider this example where we want to borrow `s1` but take ownership -of `s2`: - -```rust -let s1 = String::from("hello"); -let s2 = String::from("goodbye"); - -let r = &s1; - -let calculation = move || { - r; - s2; -}; - -println!("Can still use s1 here but not s2: {}", s1); -``` - -We've declared `calculation` to `move` all the values it references. Before -defining `calculation`, we declare a new variable `r` that borrows `s1`. Then -in the body of the `calculation` closure, we use `r` instead of using `s1` -directly. The closure takes ownership of `r`, but `r` is a reference, so the -closure hasn't taken ownership of `s1` even though `calculation` uses `move`. - -### `Channels` - -Look up examples of cases where channels are useful - -Can match modeling of certain problems - -#### `Send` - -Send is a trait that means i'm allowed to transfer ownership to another thread -down a channel - -What things can be send and what can't? - -## Sharing data between threads - -Try to share data and get an error about which trait it doesn't implement - -### `Sync` - -It's ok to access a thing from multiple threads at once - -Immutable things can be sync easily. - -### `Arc` - -Atomic Reference Counting. Inner data still has to be immutable. - -Steve knows the motivating code that goes here. - -### `Mutex` - -For mutable data. - -`lock` method, you get a Mutex guard. Change, then unlock, which usually happens -automatically when the Mutex guard goes out of scope. If you do this wrong, your -code will hang. - -Deadlocks are safe, you have to manage that yourself. Deadlock bugs usually -happen bc you forget to unlock, but drop unlocks automatically. - - -## Maybe make the I/O project concurrent? - -Might be a lot of boilerplate without scoped threads, maybe just allude. - - - -This is a really rough sketch of some ideas that this chapter might cover. - -From a comment of steveklabnik's on [the definitely not orange website]. "that paper" refers to [Boehm 2004]. - -[the definitely not orange website]: https://news.ycombinator.com/item?id=13078384 -[Boehm 2004]: http://www.hpl.hp.com/techreports/2004/HPL-2004-209.pdf - - -So for example, in that paper, 4.1 is about the problem of concurrent -modifiability. And indeed, it says - -> Indeed, under the implementation strategy we outlined above, in which the -> compiler is unaware of threads, it is allowed to transform code subject only -> to sequential correctness constraints and hence could generate the code -> containing a race. - -However, in Rust, this re-ordering can't happen: Rust won't let you alias x and -y between two threads without some sort of synchronization primitive. But this -isn't because Rust knows about concurrency, it's because Rust knows about -aliasing. In a sense, Rust-the-language makes this program _impossible to -write_, but a library re-enables you to write this program. You need unsafe to -do this, but it's all wrapped up inside of the implementation of, for example, -Mutex. - -From the last part of this section: - -> Resolving it essential requires a programming-language-defined and -> compiler-respected memory model, simply to ensure that the user and compiler -> can agree on when there is a data race. - -We're in agreement here, but the model is built around aliasing, not -concurrency. - -4.2 is about speculatively executing store instructions. I know less about -this, but again, it's built on the idea of two threads accessing data at the -same time, unsynchronized. This can't happen in Rust due to the aliasing rules. - -4.3 is about register promotion. This cannot happen in Rust, because you don't -call a function to acquire the lock, then do whatever you want. Mutex hides -the value it's locking inside of itself, unable to be accessed from the -outside, and the call to acquire the lock returns a mutable reference to the -inner data. The call to acquire the lock is the only way to get said reference, -and Rust's aliasing rules will forbid any other kind of access through the -returned reference. So this kind of transformation can't happen in Rust either. - -Section 5 is about performance. It's true that synchronization primitives are -expensive. Rust can again use unsafe code in a disciplined way to provide safe -concurrent modification, while ruling out data races entirely. For example, -consider a simple map operation. We take an array of integers, and for each -element, add one to it. This is an embarrassingly parallel operation, yet, as -the paper mentions, with a pthreads-style approach to making it safe, one would -need either a single lock around the whole array, which destroys the -concurrency entirely, or some set of more fine-grained locks, which introduce -cost, as well as limiting the amount of concurrency to some degree. - -But with a [small utility function][fn], which performs a small (ie, non-atomic) -check at runtime, we can safety split up our array into as many disjoint chunks -as we'd like, and then pass each one off to its own thread, which is free to do -the modification with no more synchronization needed. In fact, libraries like -Rayon can even determine roughly the correct amount for you, if you don't want -to think about it, and it will near-transparently just handle this for you (you -change a call from iter() to par_iter() and you're done). - -[fn]: https://github.com/rust-lang/rust/blob/f8614c397313db00e4b4626d1ba77ae00dbf7549/src/libcore/slice.rs#L344-L355 - -So yeah. I'm in agreement with the paper that the language needs to do _some_ -kind of reasoning, but since aliasing and concurrency are so tightly related, I -would argue that the language could understand only aliasing, not concurrency, -and then library abstractions are sufficient. - -## Arc - -Check out [this awesome explanation of `Arc`](http://stackoverflow.com/a/40985661/51683). +Handling concurrent programming safely and efficiently is another of Rust’s +major goals. *Concurrent programming*, where different parts of a program +execute independently, and *parallel programming*, where different parts of a +program execute at the same time, are becoming increasingly important as more +computers take advantage of their multiple processors. Historically, +programming in these contexts has been difficult and error prone: Rust hopes to +change that. + +Initially, the Rust team thought that ensuring memory safety and preventing +concurrency problems were two separate challenges to be solved with different +methods. Over time, the team discovered that the ownership and type systems are +a powerful set of tools to help manage memory safety *and* concurrency +problems! By leveraging ownership and type checking, many concurrency errors +are compile-time errors in Rust rather than runtime errors. Therefore, rather +than making you spend lots of time trying to reproduce the exact circumstances +under which a runtime concurrency bug occurs, incorrect code will refuse to +compile and present an error explaining the problem. As a result, you can fix +your code while you’re working on it rather than potentially after it has been +shipped to production. We’ve nicknamed this aspect of Rust *fearless* +*concurrency*. Fearless concurrency allows you to write code that is free of +subtle bugs and is easy to refactor without introducing new bugs. + +> Note: For simplicity’s sake, we’ll refer to many of the problems as +> *concurrent* rather than being more precise by saying *concurrent and/or +> parallel*. If this book were about concurrency and/or parallelism, we’d be +> more specific. For this chapter, please mentally substitute *concurrent +> and/or parallel* whenever we use *concurrent*. + +Many languages are dogmatic about the solutions they offer for handling +concurrent problems. For example, Erlang has elegant functionality for +message-passing concurrency but has only obscure ways to share state between +threads. Supporting only a subset of possible solutions is a reasonable +strategy for higher-level languages, because a higher-level language promises +benefits from giving up some control to gain abstractions. However, lower-level +languages are expected to provide the solution with the best performance in any +given situation and have fewer abstractions over the hardware. Therefore, Rust +offers a variety of tools for modeling problems in whatever way is appropriate +for your situation and requirements. + +Here are the topics we’ll cover in this chapter: + +* How to create threads to run multiple pieces of code at the same time +* *Message-passing* concurrency, where channels send messages between threads +* *Shared-state* concurrency, where multiple threads have access to some piece + of data +* The `Sync` and `Send` traits, which extend Rust’s concurrency guarantees to + user-defined types as well as types provided by the standard library diff --git a/src/ch16-01-threads.md b/src/ch16-01-threads.md new file mode 100644 index 0000000..378a562 --- /dev/null +++ b/src/ch16-01-threads.md @@ -0,0 +1,310 @@ +## Using Threads to Run Code Simultaneously + +In most current operating systems, an executed program’s code is run in a +*process*, and the operating system manages multiple processes at once. Within +your program, you can also have independent parts that run simultaneously. The +features that run these independent parts are called *threads*. + +Splitting the computation in your program into multiple threads can improve +performance because the program does multiple tasks at the same time, but it +also adds complexity. Because threads can run simultaneously, there’s no +inherent guarantee about the order in which parts of your code on different +threads will run. This can lead to problems, such as: + +* Race conditions, where threads are accessing data or resources in an + inconsistent order +* Deadlocks, where two threads are waiting for each other to finish using a + resource the other thread has, preventing both threads from continuing +* Bugs that happen only in certain situations and are hard to reproduce and fix + reliably + +Rust attempts to mitigate the negative effects of using threads, but +programming in a multithreaded context still takes careful thought and requires +a code structure that is different from that in programs running in a single +thread. + +Programming languages implement threads in a few different ways. Many operating +systems provide an API for creating new threads. This model where a language +calls the operating system APIs to create threads is sometimes called *1:1*, +meaning one operating system thread per one language thread. + +Many programming languages provide their own special implementation of threads. +Programming language-provided threads are known as *green* threads, and +languages that use these green threads will execute them in the context of a +different number of operating system threads. For this reason, the +green-threaded model is called the *M:N* model: there are `M` green threads per +`N` operating system threads, where `M` and `N` are not necessarily the same +number. + +Each model has its own advantages and trade-offs, and the trade-off most +important to Rust is runtime support. *Runtime* is a confusing term and can +have different meanings in different contexts. + +In this context, by *runtime* we mean code that is included by the language in +every binary. This code can be large or small depending on the language, but +every non-assembly language will have some amount of runtime code. For that +reason, colloquially when people say a language has “no runtime,” they often +mean “small runtime.” Smaller runtimes have fewer features but have the +advantage of resulting in smaller binaries, which make it easier to combine the +language with other languages in more contexts. Although many languages are +okay with increasing the runtime size in exchange for more features, Rust needs +to have nearly no runtime and cannot compromise on being able to call into C to +maintain performance. + +The green-threading M:N model requires a larger language runtime to manage +threads. As such, the Rust standard library only provides an implementation of +1:1 threading. Because Rust is such a low-level language, there are crates that +implement M:N threading if you would rather trade overhead for aspects such as +more control over which threads run when and lower costs of context switching, +for example. + +Now that we’ve defined threads in Rust, let’s explore how to use the +thread-related API provided by the standard library. + +### Creating a New Thread with `spawn` + +To create a new thread, we call the `thread::spawn` function and pass it a +closure (we talked about closures in Chapter 13) containing the code we want to +run in the new thread. The example in Listing 16-1 prints some text from a main +thread and other text from a new thread: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-01/src/main.rs}} +``` + +Listing 16-1: Creating a new thread to print one thing +while the main thread prints something else + +Note that with this function, the new thread will be stopped when the main +thread ends, whether or not it has finished running. The output from this +program might be a little different every time, but it will look similar to the +following: + + + +```text +hi number 1 from the main thread! +hi number 1 from the spawned thread! +hi number 2 from the main thread! +hi number 2 from the spawned thread! +hi number 3 from the main thread! +hi number 3 from the spawned thread! +hi number 4 from the main thread! +hi number 4 from the spawned thread! +hi number 5 from the spawned thread! +``` + +The calls to `thread::sleep` force a thread to stop its execution for a short +duration, allowing a different thread to run. The threads will probably take +turns, but that isn’t guaranteed: it depends on how your operating system +schedules the threads. In this run, the main thread printed first, even though +the print statement from the spawned thread appears first in the code. And even +though we told the spawned thread to print until `i` is 9, it only got to 5 +before the main thread shut down. + +If you run this code and only see output from the main thread, or don’t see any +overlap, try increasing the numbers in the ranges to create more opportunities +for the operating system to switch between the threads. + +### Waiting for All Threads to Finish Using `join` Handles + +The code in Listing 16-1 not only stops the spawned thread prematurely most of +the time due to the main thread ending, but also can’t guarantee that the +spawned thread will get to run at all. The reason is that there is no guarantee +on the order in which threads run! + +We can fix the problem of the spawned thread not getting to run, or not getting +to run completely, by saving the return value of `thread::spawn` in a variable. +The return type of `thread::spawn` is `JoinHandle`. A `JoinHandle` is an owned +value that, when we call the `join` method on it, will wait for its thread to +finish. Listing 16-2 shows how to use the `JoinHandle` of the thread we created +in Listing 16-1 and call `join` to make sure the spawned thread finishes before +`main` exits: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-02/src/main.rs}} +``` + +Listing 16-2: Saving a `JoinHandle` from `thread::spawn` +to guarantee the thread is run to completion + +Calling `join` on the handle blocks the thread currently running until the +thread represented by the handle terminates. *Blocking* a thread means that +thread is prevented from performing work or exiting. Because we’ve put the call +to `join` after the main thread’s `for` loop, running Listing 16-2 should +produce output similar to this: + + + +```text +hi number 1 from the main thread! +hi number 2 from the main thread! +hi number 1 from the spawned thread! +hi number 3 from the main thread! +hi number 2 from the spawned thread! +hi number 4 from the main thread! +hi number 3 from the spawned thread! +hi number 4 from the spawned thread! +hi number 5 from the spawned thread! +hi number 6 from the spawned thread! +hi number 7 from the spawned thread! +hi number 8 from the spawned thread! +hi number 9 from the spawned thread! +``` + +The two threads continue alternating, but the main thread waits because of the +call to `handle.join()` and does not end until the spawned thread is finished. + +But let’s see what happens when we instead move `handle.join()` before the +`for` loop in `main`, like this: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/no-listing-01-join-too-early/src/main.rs}} +``` + +The main thread will wait for the spawned thread to finish and then run its +`for` loop, so the output won’t be interleaved anymore, as shown here: + + + +```text +hi number 1 from the spawned thread! +hi number 2 from the spawned thread! +hi number 3 from the spawned thread! +hi number 4 from the spawned thread! +hi number 5 from the spawned thread! +hi number 6 from the spawned thread! +hi number 7 from the spawned thread! +hi number 8 from the spawned thread! +hi number 9 from the spawned thread! +hi number 1 from the main thread! +hi number 2 from the main thread! +hi number 3 from the main thread! +hi number 4 from the main thread! +``` + +Small details, such as where `join` is called, can affect whether or not your +threads run at the same time. + +### Using `move` Closures with Threads + +The `move` closure is often used alongside `thread::spawn` because it allows +you to use data from one thread in another thread. + +In Chapter 13, we mentioned we can use the `move` keyword before the parameter +list of a closure to force the closure to take ownership of the values it uses +in the environment. This technique is especially useful when creating new +threads in order to transfer ownership of values from one thread to another. + +Notice in Listing 16-1 that the closure we pass to `thread::spawn` takes no +arguments: we’re not using any data from the main thread in the spawned +thread’s code. To use data from the main thread in the spawned thread, the +spawned thread’s closure must capture the values it needs. Listing 16-3 shows +an attempt to create a vector in the main thread and use it in the spawned +thread. However, this won’t yet work, as you’ll see in a moment. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-03/src/main.rs}} +``` + +Listing 16-3: Attempting to use a vector created by the +main thread in another thread + +The closure uses `v`, so it will capture `v` and make it part of the closure’s +environment. Because `thread::spawn` runs this closure in a new thread, we +should be able to access `v` inside that new thread. But when we compile this +example, we get the following error: + +```console +{{#include ../listings/ch16-fearless-concurrency/listing-16-03/output.txt}} +``` + +Rust *infers* how to capture `v`, and because `println!` only needs a reference +to `v`, the closure tries to borrow `v`. However, there’s a problem: Rust can’t +tell how long the spawned thread will run, so it doesn’t know if the reference +to `v` will always be valid. + +Listing 16-4 provides a scenario that’s more likely to have a reference to `v` +that won’t be valid: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-04/src/main.rs}} +``` + +Listing 16-4: A thread with a closure that attempts to +capture a reference to `v` from a main thread that drops `v` + +If we were allowed to run this code, there’s a possibility the spawned thread +would be immediately put in the background without running at all. The spawned +thread has a reference to `v` inside, but the main thread immediately drops +`v`, using the `drop` function we discussed in Chapter 15. Then, when the +spawned thread starts to execute, `v` is no longer valid, so a reference to it +is also invalid. Oh no! + +To fix the compiler error in Listing 16-3, we can use the error message’s +advice: + + + +```text +help: to force the closure to take ownership of `v` (and any other referenced variables), use the `move` keyword + | +6 | let handle = thread::spawn(move || { + | ^^^^^^^ +``` + +By adding the `move` keyword before the closure, we force the closure to take +ownership of the values it’s using rather than allowing Rust to infer that it +should borrow the values. The modification to Listing 16-3 shown in Listing +16-5 will compile and run as we intend: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-05/src/main.rs}} +``` + +Listing 16-5: Using the `move` keyword to force a closure +to take ownership of the values it uses + +What would happen to the code in Listing 16-4 where the main thread called +`drop` if we use a `move` closure? Would `move` fix that case? Unfortunately, +no; we would get a different error because what Listing 16-4 is trying to do +isn’t allowed for a different reason. If we added `move` to the closure, we +would move `v` into the closure’s environment, and we could no longer call +`drop` on it in the main thread. We would get this compiler error instead: + +```console +{{#include ../listings/ch16-fearless-concurrency/output-only-01-move-drop/output.txt}} +``` + +Rust’s ownership rules have saved us again! We got an error from the code in +Listing 16-3 because Rust was being conservative and only borrowing `v` for the +thread, which meant the main thread could theoretically invalidate the spawned +thread’s reference. By telling Rust to move ownership of `v` to the spawned +thread, we’re guaranteeing Rust that the main thread won’t use `v` anymore. If +we change Listing 16-4 in the same way, we’re then violating the ownership +rules when we try to use `v` in the main thread. The `move` keyword overrides +Rust’s conservative default of borrowing; it doesn’t let us violate the +ownership rules. + +With a basic understanding of threads and the thread API, let’s look at what we +can *do* with threads. diff --git a/src/ch16-02-message-passing.md b/src/ch16-02-message-passing.md new file mode 100644 index 0000000..c087ce2 --- /dev/null +++ b/src/ch16-02-message-passing.md @@ -0,0 +1,258 @@ +## Using Message Passing to Transfer Data Between Threads + +One increasingly popular approach to ensuring safe concurrency is *message +passing*, where threads or actors communicate by sending each other messages +containing data. Here’s the idea in a slogan from [the Go language +documentation](https://golang.org/doc/effective_go.html#concurrency): +“Do not communicate by sharing memory; instead, share memory by communicating.” + +One major tool Rust has for accomplishing message-sending concurrency is the +*channel*, a programming concept that Rust’s standard library provides an +implementation of. You can imagine a channel in programming as being like a +channel of water, such as a stream or a river. If you put something like a +rubber duck or boat into a stream, it will travel downstream to the end of the +waterway. + +A channel in programming has two halves: a transmitter and a receiver. The +transmitter half is the upstream location where you put rubber ducks into the +river, and the receiver half is where the rubber duck ends up downstream. One +part of your code calls methods on the transmitter with the data you want to +send, and another part checks the receiving end for arriving messages. A +channel is said to be *closed* if either the transmitter or receiver half is +dropped. + +Here, we’ll work up to a program that has one thread to generate values and +send them down a channel, and another thread that will receive the values and +print them out. We’ll be sending simple values between threads using a channel +to illustrate the feature. Once you’re familiar with the technique, you could +use channels to implement a chat system or a system where many threads perform +parts of a calculation and send the parts to one thread that aggregates the +results. + +First, in Listing 16-6, we’ll create a channel but not do anything with it. +Note that this won’t compile yet because Rust can’t tell what type of values we +want to send over the channel. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-06/src/main.rs}} +``` + +Listing 16-6: Creating a channel and assigning the two +halves to `tx` and `rx` + +We create a new channel using the `mpsc::channel` function; `mpsc` stands for +*multiple producer, single consumer*. In short, the way Rust’s standard library +implements channels means a channel can have multiple *sending* ends that +produce values but only one *receiving* end that consumes those values. Imagine +multiple streams flowing together into one big river: everything sent down any +of the streams will end up in one river at the end. We’ll start with a single +producer for now, but we’ll add multiple producers when we get this example +working. + +The `mpsc::channel` function returns a tuple, the first element of which is the +sending end and the second element is the receiving end. The abbreviations `tx` +and `rx` are traditionally used in many fields for *transmitter* and *receiver* +respectively, so we name our variables as such to indicate each end. We’re +using a `let` statement with a pattern that destructures the tuples; we’ll +discuss the use of patterns in `let` statements and destructuring in Chapter +18. Using a `let` statement this way is a convenient approach to extract the +pieces of the tuple returned by `mpsc::channel`. + +Let’s move the transmitting end into a spawned thread and have it send one +string so the spawned thread is communicating with the main thread, as shown in +Listing 16-7. This is like putting a rubber duck in the river upstream or +sending a chat message from one thread to another. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-07/src/main.rs}} +``` + +Listing 16-7: Moving `tx` to a spawned thread and sending +“hi” + +Again, we’re using `thread::spawn` to create a new thread and then using `move` +to move `tx` into the closure so the spawned thread owns `tx`. The spawned +thread needs to own the transmitting end of the channel to be able to send +messages through the channel. + +The transmitting end has a `send` method that takes the value we want to send. +The `send` method returns a `Result` type, so if the receiving end has +already been dropped and there’s nowhere to send a value, the send operation +will return an error. In this example, we’re calling `unwrap` to panic in case +of an error. But in a real application, we would handle it properly: return to +Chapter 9 to review strategies for proper error handling. + +In Listing 16-8, we’ll get the value from the receiving end of the channel in +the main thread. This is like retrieving the rubber duck from the water at the +end of the river or like getting a chat message. + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-08/src/main.rs}} +``` + +Listing 16-8: Receiving the value “hi” in the main thread +and printing it + +The receiving end of a channel has two useful methods: `recv` and `try_recv`. +We’re using `recv`, short for *receive*, which will block the main thread’s +execution and wait until a value is sent down the channel. Once a value is +sent, `recv` will return it in a `Result`. When the sending end of the +channel closes, `recv` will return an error to signal that no more values will +be coming. + +The `try_recv` method doesn’t block, but will instead return a `Result` +immediately: an `Ok` value holding a message if one is available and an `Err` +value if there aren’t any messages this time. Using `try_recv` is useful if +this thread has other work to do while waiting for messages: we could write a +loop that calls `try_recv` every so often, handles a message if one is +available, and otherwise does other work for a little while until checking +again. + +We’ve used `recv` in this example for simplicity; we don’t have any other work +for the main thread to do other than wait for messages, so blocking the main +thread is appropriate. + +When we run the code in Listing 16-8, we’ll see the value printed from the main +thread: + + + +```text +Got: hi +``` + +Perfect! + +### Channels and Ownership Transference + +The ownership rules play a vital role in message sending because they help you +write safe, concurrent code. Preventing errors in concurrent programming is the +advantage of thinking about ownership throughout your Rust programs. Let’s do +an experiment to show how channels and ownership work together to prevent +problems: we’ll try to use a `val` value in the spawned thread *after* we’ve +sent it down the channel. Try compiling the code in Listing 16-9 to see why +this code isn’t allowed: + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-09/src/main.rs}} +``` + +Listing 16-9: Attempting to use `val` after we’ve sent it +down the channel + +Here, we try to print `val` after we’ve sent it down the channel via `tx.send`. +Allowing this would be a bad idea: once the value has been sent to another +thread, that thread could modify or drop it before we try to use the value +again. Potentially, the other thread’s modifications could cause errors or +unexpected results due to inconsistent or nonexistent data. However, Rust gives +us an error if we try to compile the code in Listing 16-9: + +```console +{{#include ../listings/ch16-fearless-concurrency/listing-16-09/output.txt}} +``` + +Our concurrency mistake has caused a compile time error. The `send` function +takes ownership of its parameter, and when the value is moved, the receiver +takes ownership of it. This stops us from accidentally using the value again +after sending it; the ownership system checks that everything is okay. + +### Sending Multiple Values and Seeing the Receiver Waiting + +The code in Listing 16-8 compiled and ran, but it didn’t clearly show us that +two separate threads were talking to each other over the channel. In Listing +16-10 we’ve made some modifications that will prove the code in Listing 16-8 is +running concurrently: the spawned thread will now send multiple messages and +pause for a second between each message. + +Filename: src/main.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-10/src/main.rs}} +``` + +Listing 16-10: Sending multiple messages and pausing +between each + +This time, the spawned thread has a vector of strings that we want to send to +the main thread. We iterate over them, sending each individually, and pause +between each by calling the `thread::sleep` function with a `Duration` value of +1 second. + +In the main thread, we’re not calling the `recv` function explicitly anymore: +instead, we’re treating `rx` as an iterator. For each value received, we’re +printing it. When the channel is closed, iteration will end. + +When running the code in Listing 16-10, you should see the following output +with a 1-second pause in between each line: + + + +```text +Got: hi +Got: from +Got: the +Got: thread +``` + +Because we don’t have any code that pauses or delays in the `for` loop in the +main thread, we can tell that the main thread is waiting to receive values from +the spawned thread. + +### Creating Multiple Producers by Cloning the Transmitter + +Earlier we mentioned that `mpsc` was an acronym for *multiple producer, +single consumer*. Let’s put `mpsc` to use and expand the code in Listing 16-10 +to create multiple threads that all send values to the same receiver. We can do +so by cloning the transmitting half of the channel, as shown in Listing 16-11: + +Filename: src/main.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-11/src/main.rs:here}} +``` + +Listing 16-11: Sending multiple messages from multiple +producers + +This time, before we create the first spawned thread, we call `clone` on the +sending end of the channel. This will give us a new sending handle we can pass +to the first spawned thread. We pass the original sending end of the channel to +a second spawned thread. This gives us two threads, each sending different +messages to the receiving end of the channel. + +When you run the code, your output should look something like this: + + + +```text +Got: hi +Got: more +Got: from +Got: messages +Got: for +Got: the +Got: thread +Got: you +``` + +You might see the values in another order; it depends on your system. This is +what makes concurrency interesting as well as difficult. If you experiment with +`thread::sleep`, giving it various values in the different threads, each run +will be more nondeterministic and create different output each time. + +Now that we’ve looked at how channels work, let’s look at a different method of +concurrency. diff --git a/src/ch16-03-shared-state.md b/src/ch16-03-shared-state.md new file mode 100644 index 0000000..8704423 --- /dev/null +++ b/src/ch16-03-shared-state.md @@ -0,0 +1,241 @@ +## Shared-State Concurrency + +Message passing is a fine way of handling concurrency, but it’s not the only +one. Consider this part of the slogan from the Go language documentation again: +“do not communicate by sharing memory.” + +What would communicating by sharing memory look like? In addition, why would +message-passing enthusiasts not use it and do the opposite instead? + +In a way, channels in any programming language are similar to single ownership, +because once you transfer a value down a channel, you should no longer use that +value. Shared memory concurrency is like multiple ownership: multiple threads +can access the same memory location at the same time. As you saw in Chapter 15, +where smart pointers made multiple ownership possible, multiple ownership can +add complexity because these different owners need managing. Rust’s type system +and ownership rules greatly assist in getting this management correct. For an +example, let’s look at mutexes, one of the more common concurrency primitives +for shared memory. + +### Using Mutexes to Allow Access to Data from One Thread at a Time + +*Mutex* is an abbreviation for *mutual exclusion*, as in, a mutex allows only +one thread to access some data at any given time. To access the data in a +mutex, a thread must first signal that it wants access by asking to acquire the +mutex’s *lock*. The lock is a data structure that is part of the mutex that +keeps track of who currently has exclusive access to the data. Therefore, the +mutex is described as *guarding* the data it holds via the locking system. + +Mutexes have a reputation for being difficult to use because you have to +remember two rules: + +* You must attempt to acquire the lock before using the data. +* When you’re done with the data that the mutex guards, you must unlock the + data so other threads can acquire the lock. + +For a real-world metaphor for a mutex, imagine a panel discussion at a +conference with only one microphone. Before a panelist can speak, they have to +ask or signal that they want to use the microphone. When they get the +microphone, they can talk for as long as they want to and then hand the +microphone to the next panelist who requests to speak. If a panelist forgets to +hand the microphone off when they’re finished with it, no one else is able to +speak. If management of the shared microphone goes wrong, the panel won’t work +as planned! + +Management of mutexes can be incredibly tricky to get right, which is why so +many people are enthusiastic about channels. However, thanks to Rust’s type +system and ownership rules, you can’t get locking and unlocking wrong. + +#### The API of `Mutex` + +As an example of how to use a mutex, let’s start by using a mutex in a +single-threaded context, as shown in Listing 16-12: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-12/src/main.rs}} +``` + +Listing 16-12: Exploring the API of `Mutex` in a +single-threaded context for simplicity + +As with many types, we create a `Mutex` using the associated function `new`. +To access the data inside the mutex, we use the `lock` method to acquire the +lock. This call will block the current thread so it can’t do any work until +it’s our turn to have the lock. + +The call to `lock` would fail if another thread holding the lock panicked. In +that case, no one would ever be able to get the lock, so we’ve chosen to +`unwrap` and have this thread panic if we’re in that situation. + +After we’ve acquired the lock, we can treat the return value, named `num` in +this case, as a mutable reference to the data inside. The type system ensures +that we acquire a lock before using the value in `m`: `Mutex` is not an +`i32`, so we *must* acquire the lock to be able to use the `i32` value. We +can’t forget; the type system won’t let us access the inner `i32` otherwise. + +As you might suspect, `Mutex` is a smart pointer. More accurately, the call +to `lock` *returns* a smart pointer called `MutexGuard`, wrapped in a +`LockResult` that we handled with the call to `unwrap`. The `MutexGuard` smart +pointer implements `Deref` to point at our inner data; the smart pointer also +has a `Drop` implementation that releases the lock automatically when a +`MutexGuard` goes out of scope, which happens at the end of the inner scope in +Listing 16-12. As a result, we don’t risk forgetting to release the lock and +blocking the mutex from being used by other threads because the lock release +happens automatically. + +After dropping the lock, we can print the mutex value and see that we were able +to change the inner `i32` to 6. + +#### Sharing a `Mutex` Between Multiple Threads + +Now, let’s try to share a value between multiple threads using `Mutex`. +We’ll spin up 10 threads and have them each increment a counter value by 1, so +the counter goes from 0 to 10. The next example in Listing 16-13 will have +a compiler error, and we’ll use that error to learn more about using +`Mutex` and how Rust helps us use it correctly. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-13/src/main.rs}} +``` + +Listing 16-13: Ten threads each increment a counter +guarded by a `Mutex` + +We create a `counter` variable to hold an `i32` inside a `Mutex`, as we +did in Listing 16-12. Next, we create 10 threads by iterating over a range +of numbers. We use `thread::spawn` and give all the threads the same closure, +one that moves the counter into the thread, acquires a lock on the `Mutex` +by calling the `lock` method, and then adds 1 to the value in the mutex. When a +thread finishes running its closure, `num` will go out of scope and release the +lock so another thread can acquire it. + +In the main thread, we collect all the join handles. Then, as we did in Listing +16-2, we call `join` on each handle to make sure all the threads finish. At +that point, the main thread will acquire the lock and print the result of this +program. + +We hinted that this example wouldn’t compile. Now let’s find out why! + +```console +{{#include ../listings/ch16-fearless-concurrency/listing-16-13/output.txt}} +``` + +The error message states that the `counter` value was moved in the previous +iteration of the loop. So Rust is telling us that we can’t move the ownership +of lock `counter` into multiple threads. Let’s fix the compiler error with a +multiple-ownership method we discussed in Chapter 15. + +#### Multiple Ownership with Multiple Threads + +In Chapter 15, we gave a value multiple owners by using the smart pointer +`Rc` to create a reference counted value. Let’s do the same here and see +what happens. We’ll wrap the `Mutex` in `Rc` in Listing 16-14 and clone +the `Rc` before moving ownership to the thread. + +Filename: src/main.rs + +```rust,ignore,does_not_compile +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-14/src/main.rs}} +``` + +Listing 16-14: Attempting to use `Rc` to allow +multiple threads to own the `Mutex` + +Once again, we compile and get... different errors! The compiler is teaching us +a lot. + +```console +{{#include ../listings/ch16-fearless-concurrency/listing-16-14/output.txt}} +``` + +Wow, that error message is very wordy! Here’s the important part to focus +on: `` `Rc>` cannot be sent between threads safely ``. The compiler +is also telling us the reason why: ``the trait `Send` is not implemented for +`Rc>` ``. We’ll talk about `Send` in the next section: it’s one of +the traits that ensures the types we use with threads are meant for use in +concurrent situations. + +Unfortunately, `Rc` is not safe to share across threads. When `Rc` +manages the reference count, it adds to the count for each call to `clone` and +subtracts from the count when each clone is dropped. But it doesn’t use any +concurrency primitives to make sure that changes to the count can’t be +interrupted by another thread. This could lead to wrong counts—subtle bugs that +could in turn lead to memory leaks or a value being dropped before we’re done +with it. What we need is a type exactly like `Rc` but one that makes changes +to the reference count in a thread-safe way. + +#### Atomic Reference Counting with `Arc` + +Fortunately, `Arc` *is* a type like `Rc` that is safe to use in +concurrent situations. The *a* stands for *atomic*, meaning it’s an *atomically +reference counted* type. Atomics are an additional kind of concurrency +primitive that we won’t cover in detail here: see the standard library +documentation for [`std::sync::atomic`] for more details. At this point, you just +need to know that atomics work like primitive types but are safe to share +across threads. + +[`std::sync::atomic`]: ../std/sync/atomic/index.html + +You might then wonder why all primitive types aren’t atomic and why standard +library types aren’t implemented to use `Arc` by default. The reason is that +thread safety comes with a performance penalty that you only want to pay when +you really need to. If you’re just performing operations on values within a +single thread, your code can run faster if it doesn’t have to enforce the +guarantees atomics provide. + +Let’s return to our example: `Arc` and `Rc` have the same API, so we fix +our program by changing the `use` line, the call to `new`, and the call to +`clone`. The code in Listing 16-15 will finally compile and run: + +Filename: src/main.rs + +```rust +{{#rustdoc_include ../listings/ch16-fearless-concurrency/listing-16-15/src/main.rs}} +``` + +Listing 16-15: Using an `Arc` to wrap the `Mutex` +to be able to share ownership across multiple threads + +This code will print the following: + + + +```text +Result: 10 +``` + +We did it! We counted from 0 to 10, which may not seem very impressive, but it +did teach us a lot about `Mutex` and thread safety. You could also use this +program’s structure to do more complicated operations than just incrementing a +counter. Using this strategy, you can divide a calculation into independent +parts, split those parts across threads, and then use a `Mutex` to have each +thread update the final result with its part. + +### Similarities Between `RefCell`/`Rc` and `Mutex`/`Arc` + +You might have noticed that `counter` is immutable but we could get a mutable +reference to the value inside it; this means `Mutex` provides interior +mutability, as the `Cell` family does. In the same way we used `RefCell` in +Chapter 15 to allow us to mutate contents inside an `Rc`, we use `Mutex` +to mutate contents inside an `Arc`. + +Another detail to note is that Rust can’t protect you from all kinds of logic +errors when you use `Mutex`. Recall in Chapter 15 that using `Rc` came +with the risk of creating reference cycles, where two `Rc` values refer to +each other, causing memory leaks. Similarly, `Mutex` comes with the risk of +creating *deadlocks*. These occur when an operation needs to lock two resources +and two threads have each acquired one of the locks, causing them to wait for +each other forever. If you’re interested in deadlocks, try creating a Rust +program that has a deadlock; then research deadlock mitigation strategies for +mutexes in any language and have a go at implementing them in Rust. The +standard library API documentation for `Mutex` and `MutexGuard` offers +useful information. + +We’ll round out this chapter by talking about the `Send` and `Sync` traits and +how we can use them with custom types. diff --git a/src/ch16-04-extensible-concurrency-sync-and-send.md b/src/ch16-04-extensible-concurrency-sync-and-send.md new file mode 100644 index 0000000..4104e83 --- /dev/null +++ b/src/ch16-04-extensible-concurrency-sync-and-send.md @@ -0,0 +1,89 @@ +## Extensible Concurrency with the `Sync` and `Send` Traits + +Interestingly, the Rust language has *very* few concurrency features. Almost +every concurrency feature we’ve talked about so far in this chapter has been +part of the standard library, not the language. Your options for handling +concurrency are not limited to the language or the standard library; you can +write your own concurrency features or use those written by others. + +However, two concurrency concepts are embedded in the language: the +`std::marker` traits `Sync` and `Send`. + +### Allowing Transference of Ownership Between Threads with `Send` + +The `Send` marker trait indicates that ownership of values of the type implementing +`Send` can be transferred between threads. Almost every Rust type is `Send`, +but there are some exceptions, including `Rc`: this cannot be `Send` because +if you cloned an `Rc` value and tried to transfer ownership of the clone to +another thread, both threads might update the reference count at the same time. +For this reason, `Rc` is implemented for use in single-threaded situations +where you don’t want to pay the thread-safe performance penalty. + +Therefore, Rust’s type system and trait bounds ensure that you can never +accidentally send an `Rc` value across threads unsafely. When we tried to do +this in Listing 16-14, we got the error `the trait Send is not implemented for +Rc>`. When we switched to `Arc`, which is `Send`, the code +compiled. + +Any type composed entirely of `Send` types is automatically marked as `Send` as +well. Almost all primitive types are `Send`, aside from raw pointers, which +we’ll discuss in Chapter 19. + +### Allowing Access from Multiple Threads with `Sync` + +The `Sync` marker trait indicates that it is safe for the type implementing +`Sync` to be referenced from multiple threads. In other words, any type `T` is +`Sync` if `&T` (an immutable reference to `T`) is `Send`, meaning the reference +can be sent safely to another thread. Similar to `Send`, primitive types are +`Sync`, and types composed entirely of types that are `Sync` are also `Sync`. + +The smart pointer `Rc` is also not `Sync` for the same reasons that it’s not +`Send`. The `RefCell` type (which we talked about in Chapter 15) and the +family of related `Cell` types are not `Sync`. The implementation of borrow +checking that `RefCell` does at runtime is not thread-safe. The smart +pointer `Mutex` is `Sync` and can be used to share access with multiple +threads as you saw in the [“Sharing a `Mutex` Between Multiple +Threads”][sharing-a-mutext-between-multiple-threads] section. + +### Implementing `Send` and `Sync` Manually Is Unsafe + +Because types that are made up of `Send` and `Sync` traits are automatically +also `Send` and `Sync`, we don’t have to implement those traits manually. As +marker traits, they don’t even have any methods to implement. They’re just +useful for enforcing invariants related to concurrency. + +Manually implementing these traits involves implementing unsafe Rust code. +We’ll talk about using unsafe Rust code in Chapter 19; for now, the important +information is that building new concurrent types not made up of `Send` and +`Sync` parts requires careful thought to uphold the safety guarantees. [“The +Rustonomicon”][nomicon] has more information about these guarantees and how to +uphold them. + +## Summary + +This isn’t the last you’ll see of concurrency in this book: the project in +Chapter 20 will use the concepts in this chapter in a more realistic situation +than the smaller examples discussed here. + +As mentioned earlier, because very little of how Rust handles concurrency is +part of the language, many concurrency solutions are implemented as crates. +These evolve more quickly than the standard library, so be sure to search +online for the current, state-of-the-art crates to use in multithreaded +situations. + +The Rust standard library provides channels for message passing and smart +pointer types, such as `Mutex` and `Arc`, that are safe to use in +concurrent contexts. The type system and the borrow checker ensure that the +code using these solutions won’t end up with data races or invalid references. +Once you get your code to compile, you can rest assured that it will happily +run on multiple threads without the kinds of hard-to-track-down bugs common in +other languages. Concurrent programming is no longer a concept to be afraid of: +go forth and make your programs concurrent, fearlessly! + +Next, we’ll talk about idiomatic ways to model problems and structure solutions +as your Rust programs get bigger. In addition, we’ll discuss how Rust’s idioms +relate to those you might be familiar with from object-oriented programming. + +[sharing-a-mutext-between-multiple-threads]: +ch16-03-shared-state.html#sharing-a-mutext-between-multiple-threads +[nomicon]: ../nomicon/index.html diff --git a/src/ch17-00-oop.md b/src/ch17-00-oop.md index 4c71a8e..8661791 100644 --- a/src/ch17-00-oop.md +++ b/src/ch17-00-oop.md @@ -1,73 +1,13 @@ -# Is Rust OOP? +# Object Oriented Programming Features of Rust -Aphorism: DRY - -So how do you share code? - -I'm used to doing things to solve problems, what do i do instead? -Why do i need to do different things in Rust? Let's look at an example -with the Command pattern. - -## Command pattern - -Look up official def - -Want caller to be able to customize what gets done - -Method takes command object, calls a run fn - -How do we say "we want a thing that has a run function"? Answer: Traits! - -where T: Run - -This is the definition of the Fn trait! So we wouldn't implement this, we'd just -pass closures in - -## Supertraits - -Trait constraints that use other traits - -Copy requires Clone because Copy is a subset of Clone's behavior, since if you -have one, you can trivially implement the other. - -Traits that need behavior of another trait in a default method or something. - -## Trait objects - -Runtime decisions about deciding what shared code we use - -Give example code - -With traits, libraries are extensible. This is why trait objects are different -than having an enum and a match statement that has to be exhaustive at compile -time and we have to know all the things at compile time and no one can add -new things to the set of possible things - -T: trait is a compile time decision, monomorphization == static dispatch - -when you implement this trait, you get this other shared behavior - -dynamic dispatch (C++) - -### Implementation details - -- Like how other languages implement oo. - -### How to use it - -- Statically checked duck typing - -## Builder pattern - -When you don't know how many arguments you're going to have - -## Delegation - -Deref - be mad - -Deref is a way to delegate everything, if you don't want that, then write -boilerplate. Sending messages to your components. - -## How do you share data? - -Answer: get and set methods, this is awkward and might get better someday. +Object-oriented programming (OOP) is a way of modeling programs. Objects came +from Simula in the 1960s. Those objects influenced Alan Kay’s programming +architecture in which objects pass messages to each other. He coined the term +*object-oriented programming* in 1967 to describe this architecture. Many +competing definitions describe what OOP is; some definitions would classify +Rust as object oriented, but other definitions would not. In this chapter, +we’ll explore certain characteristics that are commonly considered object +oriented and how those characteristics translate to idiomatic Rust. We’ll then +show you how to implement an object-oriented design pattern in Rust and discuss +the trade-offs of doing so versus implementing a solution using some of Rust’s +strengths instead. diff --git a/src/ch17-01-what-is-oo.md b/src/ch17-01-what-is-oo.md new file mode 100644 index 0000000..86bf467 --- /dev/null +++ b/src/ch17-01-what-is-oo.md @@ -0,0 +1,149 @@ +## Characteristics of Object-Oriented Languages + +There is no consensus in the programming community about what features a +language must have to be considered object oriented. Rust is influenced by many +programming paradigms, including OOP; for example, we explored the features +that came from functional programming in Chapter 13. Arguably, OOP languages +share certain common characteristics, namely objects, encapsulation, and +inheritance. Let’s look at what each of those characteristics means and whether +Rust supports it. + +### Objects Contain Data and Behavior + +The book *Design Patterns: Elements of Reusable Object-Oriented Software* by +Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides (Addison-Wesley +Professional, 1994) colloquially referred to as *The Gang of Four* book, is a +catalog of object-oriented design patterns. It defines OOP this way: + +> Object-oriented programs are made up of objects. An *object* packages both +> data and the procedures that operate on that data. The procedures are +> typically called *methods* or *operations*. + +Using this definition, Rust is object oriented: structs and enums have data, +and `impl` blocks provide methods on structs and enums. Even though structs and +enums with methods aren’t *called* objects, they provide the same +functionality, according to the Gang of Four’s definition of objects. + +### Encapsulation that Hides Implementation Details + +Another aspect commonly associated with OOP is the idea of *encapsulation*, +which means that the implementation details of an object aren’t accessible to +code using that object. Therefore, the only way to interact with an object is +through its public API; code using the object shouldn’t be able to reach into +the object’s internals and change data or behavior directly. This enables the +programmer to change and refactor an object’s internals without needing to +change the code that uses the object. + +We discussed how to control encapsulation in Chapter 7: we can use the `pub` +keyword to decide which modules, types, functions, and methods in our code +should be public, and by default everything else is private. For example, we +can define a struct `AveragedCollection` that has a field containing a vector +of `i32` values. The struct can also have a field that contains the average of +the values in the vector, meaning the average doesn’t have to be computed +on demand whenever anyone needs it. In other words, `AveragedCollection` will +cache the calculated average for us. Listing 17-1 has the definition of the +`AveragedCollection` struct: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch17-oop/listing-17-01/src/lib.rs}} +``` + +Listing 17-1: An `AveragedCollection` struct that +maintains a list of integers and the average of the items in the +collection + +The struct is marked `pub` so that other code can use it, but the fields within +the struct remain private. This is important in this case because we want to +ensure that whenever a value is added or removed from the list, the average is +also updated. We do this by implementing `add`, `remove`, and `average` methods +on the struct, as shown in Listing 17-2: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch17-oop/listing-17-02/src/lib.rs:here}} +``` + +Listing 17-2: Implementations of the public methods +`add`, `remove`, and `average` on `AveragedCollection` + +The public methods `add`, `remove`, and `average` are the only ways to access +or modify data in an instance of `AveragedCollection`. When an item is added +to `list` using the `add` method or removed using the `remove` method, the +implementations of each call the private `update_average` method that handles +updating the `average` field as well. + +We leave the `list` and `average` fields private so there is no way for +external code to add or remove items to the `list` field directly; otherwise, +the `average` field might become out of sync when the `list` changes. The +`average` method returns the value in the `average` field, allowing external +code to read the `average` but not modify it. + +Because we’ve encapsulated the implementation details of the struct +`AveragedCollection`, we can easily change aspects, such as the data structure, +in the future. For instance, we could use a `HashSet` instead of a +`Vec` for the `list` field. As long as the signatures of the `add`, +`remove`, and `average` public methods stay the same, code using +`AveragedCollection` wouldn’t need to change. If we made `list` public instead, +this wouldn’t necessarily be the case: `HashSet` and `Vec` have +different methods for adding and removing items, so the external code would +likely have to change if it were modifying `list` directly. + +If encapsulation is a required aspect for a language to be considered object +oriented, then Rust meets that requirement. The option to use `pub` or not for +different parts of code enables encapsulation of implementation details. + +### Inheritance as a Type System and as Code Sharing + +*Inheritance* is a mechanism whereby an object can inherit from another +object’s definition, thus gaining the parent object’s data and behavior without +you having to define them again. + +If a language must have inheritance to be an object-oriented language, then +Rust is not one. There is no way to define a struct that inherits the parent +struct’s fields and method implementations. However, if you’re used to having +inheritance in your programming toolbox, you can use other solutions in Rust, +depending on your reason for reaching for inheritance in the first place. + +You choose inheritance for two main reasons. One is for reuse of code: you can +implement particular behavior for one type, and inheritance enables you to +reuse that implementation for a different type. You can share Rust code using +default trait method implementations instead, which you saw in Listing 10-14 +when we added a default implementation of the `summarize` method on the +`Summary` trait. Any type implementing the `Summary` trait would have the +`summarize` method available on it without any further code. This is similar to +a parent class having an implementation of a method and an inheriting child +class also having the implementation of the method. We can also override the +default implementation of the `summarize` method when we implement the +`Summary` trait, which is similar to a child class overriding the +implementation of a method inherited from a parent class. + +The other reason to use inheritance relates to the type system: to enable a +child type to be used in the same places as the parent type. This is also +called *polymorphism*, which means that you can substitute multiple objects for +each other at runtime if they share certain characteristics. + +> ### Polymorphism +> +> To many people, polymorphism is synonymous with inheritance. But it’s +> actually a more general concept that refers to code that can work with data +> of multiple types. For inheritance, those types are generally subclasses. +> +> Rust instead uses generics to abstract over different possible types and +> trait bounds to impose constraints on what those types must provide. This is +> sometimes called *bounded parametric polymorphism*. + +Inheritance has recently fallen out of favor as a programming design solution +in many programming languages because it’s often at risk of sharing more code +than necessary. Subclasses shouldn’t always share all characteristics of their +parent class but will do so with inheritance. This can make a program’s design +less flexible. It also introduces the possibility of calling methods on +subclasses that don’t make sense or that cause errors because the methods don’t +apply to the subclass. In addition, some languages will only allow a subclass +to inherit from one class, further restricting the flexibility of a program’s +design. + +For these reasons, Rust takes a different approach, using trait objects instead +of inheritance. Let’s look at how trait objects enable polymorphism in Rust. diff --git a/src/ch17-02-trait-objects.md b/src/ch17-02-trait-objects.md new file mode 100644 index 0000000..90535dd --- /dev/null +++ b/src/ch17-02-trait-objects.md @@ -0,0 +1,314 @@ +## Using Trait Objects That Allow for Values of Different Types + +In Chapter 8, we mentioned that one limitation of vectors is that they can +store elements of only one type. We created a workaround in Listing 8-10 where +we defined a `SpreadsheetCell` enum that had variants to hold integers, floats, +and text. This meant we could store different types of data in each cell and +still have a vector that represented a row of cells. This is a perfectly good +solution when our interchangeable items are a fixed set of types that we know +when our code is compiled. + +However, sometimes we want our library user to be able to extend the set of +types that are valid in a particular situation. To show how we might achieve +this, we’ll create an example graphical user interface (GUI) tool that iterates +through a list of items, calling a `draw` method on each one to draw it to the +screen—a common technique for GUI tools. We’ll create a library crate called +`gui` that contains the structure of a GUI library. This crate might include +some types for people to use, such as `Button` or `TextField`. In addition, +`gui` users will want to create their own types that can be drawn: for +instance, one programmer might add an `Image` and another might add a +`SelectBox`. + +We won’t implement a fully fledged GUI library for this example but will show +how the pieces would fit together. At the time of writing the library, we can’t +know and define all the types other programmers might want to create. But we do +know that `gui` needs to keep track of many values of different types, and it +needs to call a `draw` method on each of these differently typed values. It +doesn’t need to know exactly what will happen when we call the `draw` method, +just that the value will have that method available for us to call. + +To do this in a language with inheritance, we might define a class named +`Component` that has a method named `draw` on it. The other classes, such as +`Button`, `Image`, and `SelectBox`, would inherit from `Component` and thus +inherit the `draw` method. They could each override the `draw` method to define +their custom behavior, but the framework could treat all of the types as if +they were `Component` instances and call `draw` on them. But because Rust +doesn’t have inheritance, we need another way to structure the `gui` library to +allow users to extend it with new types. + +### Defining a Trait for Common Behavior + +To implement the behavior we want `gui` to have, we’ll define a trait named +`Draw` that will have one method named `draw`. Then we can define a vector that +takes a *trait object*. A trait object points to both an instance of a type +implementing our specified trait as well as a table used to look up trait +methods on that type at runtime. We create a trait object by specifying some +sort of pointer, such as a `&` reference or a `Box` smart pointer, then the +`dyn` keyword, and then specifying the relevant trait. (We’ll talk about the +reason trait objects must use a pointer in Chapter 19 in the section +[“Dynamically Sized Types and the `Sized` Trait.”][dynamically-sized]) We can use trait objects in place of a generic or concrete type. +Wherever we use a trait object, Rust’s type system will ensure at compile time +that any value used in that context will implement the trait object’s trait. +Consequently, we don’t need to know all the possible types at compile time. + +We’ve mentioned that in Rust, we refrain from calling structs and enums +“objects” to distinguish them from other languages’ objects. In a struct or +enum, the data in the struct fields and the behavior in `impl` blocks are +separated, whereas in other languages, the data and behavior combined into one +concept is often labeled an object. However, trait objects *are* more like +objects in other languages in the sense that they combine data and behavior. +But trait objects differ from traditional objects in that we can’t add data to +a trait object. Trait objects aren’t as generally useful as objects in other +languages: their specific purpose is to allow abstraction across common +behavior. + +Listing 17-3 shows how to define a trait named `Draw` with one method named +`draw`: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch17-oop/listing-17-03/src/lib.rs}} +``` + +Listing 17-3: Definition of the `Draw` trait + +This syntax should look familiar from our discussions on how to define traits +in Chapter 10. Next comes some new syntax: Listing 17-4 defines a struct named +`Screen` that holds a vector named `components`. This vector is of type +`Box`, which is a trait object; it’s a stand-in for any type inside +a `Box` that implements the `Draw` trait. + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch17-oop/listing-17-04/src/lib.rs:here}} +``` + +Listing 17-4: Definition of the `Screen` struct with a +`components` field holding a vector of trait objects that implement the `Draw` +trait + +On the `Screen` struct, we’ll define a method named `run` that will call the +`draw` method on each of its `components`, as shown in Listing 17-5: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch17-oop/listing-17-05/src/lib.rs:here}} +``` + +Listing 17-5: A `run` method on `Screen` that calls the +`draw` method on each component + +This works differently from defining a struct that uses a generic type +parameter with trait bounds. A generic type parameter can only be substituted +with one concrete type at a time, whereas trait objects allow for multiple +concrete types to fill in for the trait object at runtime. For example, we +could have defined the `Screen` struct using a generic type and a trait bound +as in Listing 17-6: + +Filename: src/lib.rs + +```rust,noplayground +{{#rustdoc_include ../listings/ch17-oop/listing-17-06/src/lib.rs:here}} +``` + +Listing 17-6: An alternate implementation of the `Screen` +struct and its `run` method using generics and trait bounds + +This restricts us to a `Screen` instance that has a list of components all of +type `Button` or all of type `TextField`. If you’ll only ever have homogeneous +collections, using generics and trait bounds is preferable because the +definitions will be monomorphized at compile time to use the concrete types. + +On the other hand, with the method using trait objects, one `Screen` instance +can hold a `Vec` that contains a `Box