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<title>rand::random - Rust</title>
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<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>
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<h1 class='fqn'><span class='in-band'>Function <a href='index.html'>rand</a>::<wbr><a class="fn" href=''>random</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/rand/lib.rs.html#955-957' title='goto source code'>[src]</a></span></h1>
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<pre class='rust fn'>pub fn random<T>() -> T <span class="where fmt-newline">where<br> T: <a class="trait" href="../rand/trait.Rand.html" title="trait rand::Rand">Rand</a>, </span></pre><div class='docblock'><p>Generates a random value using the thread-local random number generator.</p>
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<p><code>random()</code> can generate various types of random things, and so may require
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type hinting to generate the specific type you want.</p>
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<p>This function uses the thread local random number generator. This means
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that if you're calling <code>random()</code> in a loop, caching the generator can
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increase performance. An example is shown below.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<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>
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<p>Caching the thread local random number generator:</p>
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<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>
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