<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="generator" content="rustdoc"> <title>Patterns</title> <link rel="stylesheet" type="text/css" href="../rust.css"> <link rel="shortcut icon" href="https://www.rust-lang.org/favicon.ico"> </head> <body class="rustdoc"> <!--[if lte IE 8]> <div class="warning"> This old browser is unsupported and will most likely display funky things. </div> <![endif]--> <div id="versioninfo"> <img src="https://www.rust-lang.org/logos/rust-logo-32x32-blk.png" width="32" height="32" alt="Rust logo"><br> <span class="white-sticker"><a href="https://www.rust-lang.org">Rust</a> 1.27.1</span><br> <a href="https://github.com/rust-lang/rust/commit/" class="hash white-sticker"></a> </div> <h1 class="title">Patterns</h1> <p><small>There is a new edition of the book and this is an old link.</small></p> <blockquote> <p>Patterns are a special syntax within Rust for matching against the structure of our types, complex or simple. A pattern is made up of some combination of literals; destructured arrays, enums, structs, or tuples; variables, wildcards, and placeholders. These pieces describe the “shape” of the data we’re working with.</p> </blockquote> <pre class="rust rust-example-rendered"> <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">5</span>); <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="number">10</span>; <span class="kw">match</span> <span class="ident">x</span> { <span class="prelude-val">Some</span>(<span class="number">50</span>) <span class="op">=></span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Got 50"</span>), <span class="prelude-val">Some</span>(<span class="ident">y</span>) <span class="op">=></span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Matched, y = {:?}"</span>, <span class="ident">y</span>), <span class="kw">_</span> <span class="op">=></span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Default case, x = {:?}"</span>, <span class="ident">x</span>), }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(5)%3B%0Alet%20y%20%3D%2010%3B%0A%0Amatch%20x%20%7B%0A%20%20%20%20Some(50)%20%3D%3E%20println!(%22Got%2050%22)%2C%0A%20%20%20%20Some(y)%20%3D%3E%20println!(%22Matched%2C%20y%20%3D%20%7B%3A%3F%7D%22%2C%20y)%2C%0A%20%20%20%20_%20%3D%3E%20println!(%22Default%20case%2C%20x%20%3D%20%7B%3A%3F%7D%22%2C%20x)%2C%0A%7D%0A%7D">Run</a></pre> <hr /> <p>Here are the relevant sections in the new and old books:</p> <ul> <li><strong><a href="second-edition/ch18-00-patterns.html">In the second edition: Ch 18.03 — Patterns</a></strong></li> <li><a href="second-edition/ch06-02-match.html#patterns-that-bind-to-values">In the second edition: Ch 6.02 — Match</a></li> <li><small><a href="first-edition/patterns.html">In the first edition: Ch 3.15 — Patterns</a></small></li> </ul> <footer><p> Copyright © 2011 The Rust Project Developers. Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a> or the <a href="https://opensource.org/licenses/MIT">MIT license</a>, at your option. </p><p> This file may not be copied, modified, or distributed except according to those terms. </p></footer> </body> </html>