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<!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"><meta name="description" content="API documentation for the Rust `random` fn in crate `rand`."><meta name="keywords" content="rust, rustlang, rust-lang, random"><title>rand::random - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="https://www.rust-lang.org/favicon.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../rand/index.html'><div class='logo-container'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>rand</a></p><script>window.sidebarCurrent = {name: 'random', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../src/rand/lib.rs.html#652-654' title='goto source code'>[src]</a></span><span class='in-band'>Function <a href='index.html'>rand</a>::<wbr><a class="fn" href=''>random</a></span></h1><pre class='rust fn'>pub fn random<T>() -> T <span class="where fmt-newline">where<br> <a class="struct" href="../rand/distributions/struct.Standard.html" title="struct rand::distributions::Standard">Standard</a>: <a class="trait" href="../rand/distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>, </span></pre><div class='docblock'><p>Generates a random value using the thread-local random number generator.</p>
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<p>This is simply a shortcut for <code>thread_rng().gen()</code>. See [<code>thread_rng</code>] for
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documentation of the entropy source and <a href="distributions::Standard"><code>Standard</code></a> for documentation of
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distributions and type-specific generation.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">rand</span>::<span class="ident">random</span>::<span class="op"><</span><span class="ident">u8</span><span class="op">></span>();
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"{}"</span>, <span class="ident">x</span>);
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<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">rand</span>::<span class="ident">random</span>::<span class="op"><</span><span class="ident">f64</span><span class="op">></span>();
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"{}"</span>, <span class="ident">y</span>);
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<span class="kw">if</span> <span class="ident">rand</span>::<span class="ident">random</span>() { <span class="comment">// generates a boolean</span>
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"Better lucky than good!"</span>);
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}</pre></div>
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<p>If you're calling <code>random()</code> in a loop, caching the generator as in the
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following example can increase performance.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">rand</span>::<span class="ident">Rng</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];
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<span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="ident">v</span>.<span class="ident">iter_mut</span>() {
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<span class="kw-2">*</span><span class="ident">x</span> <span class="op">=</span> <span class="ident">rand</span>::<span class="ident">random</span>()
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}
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<span class="comment">// can be made faster by caching thread_rng</span>
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span> <span class="op">=</span> <span class="ident">rand</span>::<span class="ident">thread_rng</span>();
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<span class="kw">for</span> <span class="ident">x</span> <span class="kw">in</span> <span class="ident">v</span>.<span class="ident">iter_mut</span>() {
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<span class="kw-2">*</span><span class="ident">x</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen</span>();
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}</pre></div>
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