<!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>Closures</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">Closures</h1> <p><small>There is a new edition of the book and this is an old link.</small></p> <blockquote> <p>Anonymous functions you can save in a variable or pass as arguments to other functions.</p> </blockquote> <pre class="rust rust-example-rendered"> <span class="kw">let</span> <span class="ident">expensive_closure</span> <span class="op">=</span> <span class="op">|</span><span class="ident">num</span><span class="op">|</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"calculating slowly..."</span>); <span class="ident">thread</span>::<span class="ident">sleep</span>(<span class="ident">Duration</span>::<span class="ident">from_secs</span>(<span class="number">2</span>)); <span class="ident">num</span> };<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Athread%3B%0Ause%20std%3A%3Atime%3A%3ADuration%3B%0A%0Alet%20expensive_closure%20%3D%20%7Cnum%7C%20%7B%0A%20%20%20%20println!(%22calculating%20slowly...%22)%3B%0A%20%20%20%20thread%3A%3Asleep(Duration%3A%3Afrom_secs(2))%3B%0A%20%20%20%20num%0A%7D%3B%0Aexpensive_closure(5)%3B%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/ch13-01-closures.html">In the second edition: Ch 13.01 — Closures</a></strong></li> <li><small><a href="first-edition/closures.html">In the first edition: Ch 3.23 — Closures</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>