<!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>Casting between types</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> 1.27.0</span><br> <a href="https://github.com/rust-lang/rust/commit/" class="hash white-sticker"></a> </div> <h1 class="title">Casting between types</h1> <p><small>There is a new edition of the book and this is an old link.</small></p> <blockquote> <p>A type cast expression is denoted with the binary operator <code>as</code>. Executing an <code>as</code> expression casts the value on the left-hand side to the type on the right-hand side.</p> </blockquote> <pre class="rust rust-example-rendered"> <span class="kw">fn</span> <span class="ident">average</span>(<span class="ident">values</span>: <span class="kw-2">&</span>[<span class="ident">f64</span>]) <span class="op">-></span> <span class="ident">f64</span> { <span class="kw">let</span> <span class="ident">sum</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="ident">sum</span>(<span class="ident">values</span>); <span class="kw">let</span> <span class="ident">size</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="ident">len</span>(<span class="ident">values</span>) <span class="kw">as</span> <span class="ident">f64</span>; <span class="ident">sum</span> <span class="op">/</span> <span class="ident">size</span> }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20sum(values%3A%20%26%5Bf64%5D)%20-%3E%20f64%20%7B%200.0%20%7D%0Afn%20len(values%3A%20%26%5Bf64%5D)%20-%3E%20i32%20%7B%200%20%7D%0A%0Afn%20average(values%3A%20%26%5Bf64%5D)%20-%3E%20f64%20%7B%0A%20%20%20%20let%20sum%3A%20f64%20%3D%20sum(values)%3B%0A%20%20%20%20let%20size%3A%20f64%20%3D%20len(values)%20as%20f64%3B%0A%20%20%20%20sum%20%2F%20size%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/appendix-01-keywords.html">In the second edition: Appendix A — Keywords</a></strong></li> <li><a href="../reference/expressions/operator-expr.html#type-cast-expressions">In the Rust Reference: Type Cast Expressions</a></li> <li><a href="../std/mem/fn.transmute.html">In the Rust documentation: <code>mem::transmute</code></a></li> <li><small><a href="first-edition/casting-between-types.html">In the first edition: Ch 3.29 — Casting between types</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>