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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="An automatically-implemented extension trait on [`RngCore`] providing high-level generic methods for sampling values and other convenience methods."><meta name="keywords" content="rust, rustlang, rust-lang, Rng"><title>Rng in rand - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><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="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script src="../crates.js"></script><script defer src="../main.js"></script>
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</a><h2 class="location"><a href="#">Rng</a></h2><div class="sidebar-elems"><section><div class="block"><h3 class="sidebar-title"><a href="#provided-methods">Provided Methods</a></h3><ul><li><a href="#method.fill">fill</a></li><li><a href="#method.gen">gen</a></li><li><a href="#method.gen_bool">gen_bool</a></li><li><a href="#method.gen_range">gen_range</a></li><li><a href="#method.gen_ratio">gen_ratio</a></li><li><a href="#method.sample">sample</a></li><li><a href="#method.sample_iter">sample_iter</a></li><li><a href="#method.try_fill">try_fill</a></li></ul></div><div class="block"><h3 class="sidebar-title"><a href="#implementors">Implementors</a></h3></div></section><h2 class="location"><a href="index.html">In rand</a></h2><div id="sidebar-vars" data-name="Rng" data-ty="trait" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../rand/index.html">
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<h1 class="fqn"><span class="in-band">Trait <a href="index.html">rand</a>::<wbr><a class="trait" href="#">Rng</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span></h1><span class="out-of-band"><a class="srclink" href="../src/rand/rng.rs.html#55-303">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="docblock item-decl"><pre class="rust trait"><code>pub trait Rng: <a class="trait" href="trait.RngCore.html" title="trait rand::RngCore">RngCore</a> {
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fn <a href="#method.gen" class="fnname">gen</a><T>(&mut self) -> T<br> <span class="where">where<br> <a class="struct" href="distributions/struct.Standard.html" title="struct rand::distributions::Standard">Standard</a>: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T></span>,
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{ ... }
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<span class="item-spacer"></span> fn <a href="#method.gen_range" class="fnname">gen_range</a><T, R>(&mut self, range: R) -> T<br> <span class="where">where<br> T: <a class="trait" href="distributions/uniform/trait.SampleUniform.html" title="trait rand::distributions::uniform::SampleUniform">SampleUniform</a>,<br> R: <a class="trait" href="distributions/uniform/trait.SampleRange.html" title="trait rand::distributions::uniform::SampleRange">SampleRange</a><T></span>,
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{ ... }
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<span class="item-spacer"></span> fn <a href="#method.sample" class="fnname">sample</a><T, D: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>>(&mut self, distr: D) -> T { ... }
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<span class="item-spacer"></span> fn <a href="#method.sample_iter" class="fnname">sample_iter</a><T, D>(self, distr: D) -> <a class="struct" href="distributions/struct.DistIter.html" title="struct rand::distributions::DistIter">DistIter</a><D, Self, T><span class="notable-traits"><span class="notable-traits-tooltip">ⓘ<span class="notable-traits-tooltiptext"><span class="docblock"><span class="notable">Notable traits for <a class="struct" href="distributions/struct.DistIter.html" title="struct rand::distributions::DistIter">DistIter</a><D, R, T></span><code class="content"><span class="where fmt-newline">impl<D, R, T> <a class="trait" href="https://doc.rust-lang.org/1.62.1/core/iter/traits/iterator/trait.Iterator.html" title="trait core::iter::traits::iterator::Iterator">Iterator</a> for <a class="struct" href="distributions/struct.DistIter.html" title="struct rand::distributions::DistIter">DistIter</a><D, R, T> <span class="where fmt-newline">where<br> D: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>,<br> R: <a class="trait" href="trait.Rng.html" title="trait rand::Rng">Rng</a>, </span></span><span class="where fmt-newline"> type <a href="https://doc.rust-lang.org/1.62.1/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" class="associatedtype">Item</a> = T;</span></code></span></span></span></span><br> <span class="where">where<br> D: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>,<br> Self: <a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span>,
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{ ... }
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<span class="item-spacer"></span> fn <a href="#method.fill" class="fnname">fill</a><T: <a class="trait" href="trait.Fill.html" title="trait rand::Fill">Fill</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(&mut self, dest: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.reference.html">&mut </a>T) { ... }
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<span class="item-spacer"></span> fn <a href="#method.try_fill" class="fnname">try_fill</a><T: <a class="trait" href="trait.Fill.html" title="trait rand::Fill">Fill</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(&mut self, dest: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.reference.html">&mut </a>T) -> <a class="enum" href="https://doc.rust-lang.org/1.62.1/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.unit.html">()</a>, <a class="struct" href="struct.Error.html" title="struct rand::Error">Error</a>> { ... }
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<span class="item-spacer"></span> fn <a href="#method.gen_bool" class="fnname">gen_bool</a>(&mut self, p: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.f64.html">f64</a>) -> <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.bool.html">bool</a> { ... }
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<span class="item-spacer"></span> fn <a href="#method.gen_ratio" class="fnname">gen_ratio</a>(&mut self, numerator: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.u32.html">u32</a>, denominator: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.u32.html">u32</a>) -> <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.bool.html">bool</a> { ... }
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}</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>An automatically-implemented extension trait on <a href="trait.RngCore.html" title="RngCore"><code>RngCore</code></a> providing high-level
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generic methods for sampling values and other convenience methods.</p>
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<p>This is the primary trait to use when generating random values.</p>
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<h2 id="generic-usage"><a href="#generic-usage">Generic usage</a></h2>
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<p>The basic pattern is <code>fn foo<R: Rng + ?Sized>(rng: &mut R)</code>. Some
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things are worth noting here:</p>
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<ul>
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<li>Since <code>Rng: RngCore</code> and every <code>RngCore</code> implements <code>Rng</code>, it makes no
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difference whether we use <code>R: Rng</code> or <code>R: RngCore</code>.</li>
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<li>The <code>+ ?Sized</code> un-bounding allows functions to be called directly on
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type-erased references; i.e. <code>foo(r)</code> where <code>r: &mut dyn RngCore</code>. Without
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this it would be necessary to write <code>foo(&mut r)</code>.</li>
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</ul>
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<p>An alternative pattern is possible: <code>fn foo<R: Rng>(rng: R)</code>. This has some
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trade-offs. It allows the argument to be consumed directly without a <code>&mut</code>
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(which is how <code>from_rng(thread_rng())</code> works); also it still works directly
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on references (including type-erased references). Unfortunately within the
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function <code>foo</code> it is not known whether <code>rng</code> is a reference type or not,
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hence many uses of <code>rng</code> require an extra reference, either explicitly
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(<code>distr.sample(&mut rng)</code>) or implicitly (<code>rng.gen()</code>); one may hope the
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optimiser can remove redundant references later.</p>
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<p>Example:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand::Rng</span>;
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<span class="kw">fn</span> <span class="ident">foo</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Rng</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span>(<span class="ident">rng</span>: <span class="kw-2">&mut</span> <span class="ident">R</span>) -> <span class="ident">f32</span> {
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<span class="ident">rng</span>.<span class="ident">gen</span>()
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}
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</code></pre></div>
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</div></details><h2 id="provided-methods" class="small-section-header">Provided Methods<a href="#provided-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle" open><summary><div id="method.gen" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#93-96">source</a></div><h4 class="code-header">fn <a href="#method.gen" class="fnname">gen</a><T>(&mut self) -> T <span class="where fmt-newline">where<br> <a class="struct" href="distributions/struct.Standard.html" title="struct rand::distributions::Standard">Standard</a>: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>, </span></h4></div></summary><div class="docblock"><p>Return a random value supporting the <a href="distributions/struct.Standard.html"><code>Standard</code></a> distribution.</p>
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<h5 id="example"><a href="#example">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">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">thread_rng</span>();
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<span class="kw">let</span> <span class="ident">x</span>: <span class="ident">u32</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen</span>();
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<span class="macro">println!</span>(<span class="string">"{}"</span>, <span class="ident">x</span>);
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<span class="macro">println!</span>(<span class="string">"{:?}"</span>, <span class="ident">rng</span>.<span class="ident">gen</span>::<span class="op"><</span>(<span class="ident">f64</span>, <span class="ident">bool</span>)<span class="op">></span>());</code></pre></div>
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<h5 id="arrays-and-tuples"><a href="#arrays-and-tuples">Arrays and tuples</a></h5>
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<p>The <code>rng.gen()</code> method is able to generate arrays (up to 32 elements)
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and tuples (up to 12 elements), so long as all element types can be
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generated.
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When using <code>rustc</code> ≥ 1.51, enable the <code>min_const_gen</code> feature to support
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arrays larger than 32 elements.</p>
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<p>For arrays of integers, especially for those with small element types
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(< 64 bit), it will likely be faster to instead use <a href="trait.Rng.html#method.fill" title="Rng::fill"><code>Rng::fill</code></a>.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">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">thread_rng</span>();
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<span class="kw">let</span> <span class="ident">tuple</span>: (<span class="ident">u8</span>, <span class="ident">i32</span>, <span class="ident">char</span>) <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen</span>(); <span class="comment">// arbitrary tuple support</span>
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<span class="kw">let</span> <span class="ident">arr1</span>: [<span class="ident">f32</span>; <span class="number">32</span>] <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen</span>(); <span class="comment">// array construction</span>
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">arr2</span> <span class="op">=</span> [<span class="number">0u8</span>; <span class="number">128</span>];
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<span class="ident">rng</span>.<span class="ident">fill</span>(<span class="kw-2">&mut</span> <span class="ident">arr2</span>); <span class="comment">// array fill</span></code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.gen_range" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#129-136">source</a></div><h4 class="code-header">fn <a href="#method.gen_range" class="fnname">gen_range</a><T, R>(&mut self, range: R) -> T <span class="where fmt-newline">where<br> T: <a class="trait" href="distributions/uniform/trait.SampleUniform.html" title="trait rand::distributions::uniform::SampleUniform">SampleUniform</a>,<br> R: <a class="trait" href="distributions/uniform/trait.SampleRange.html" title="trait rand::distributions::uniform::SampleRange">SampleRange</a><T>, </span></h4></div></summary><div class="docblock"><p>Generate a random value in the given range.</p>
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<p>This function is optimised for the case that only a single sample is
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made from the given range. See also the <a href="distributions/struct.Uniform.html"><code>Uniform</code></a> distribution
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type which may be faster if sampling from the same range repeatedly.</p>
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<p>Only <code>gen_range(low..high)</code> and <code>gen_range(low..=high)</code> are supported.</p>
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<h5 id="panics"><a href="#panics">Panics</a></h5>
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<p>Panics if the range is empty.</p>
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<h5 id="example-1"><a href="#example-1">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">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">thread_rng</span>();
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<span class="comment">// Exclusive range</span>
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<span class="kw">let</span> <span class="ident">n</span>: <span class="ident">u32</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen_range</span>(<span class="number">0</span>..<span class="number">10</span>);
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<span class="macro">println!</span>(<span class="string">"{}"</span>, <span class="ident">n</span>);
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<span class="kw">let</span> <span class="ident">m</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen_range</span>(<span class="op">-</span><span class="number">40.0</span>..<span class="number">1.3e5</span>);
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<span class="macro">println!</span>(<span class="string">"{}"</span>, <span class="ident">m</span>);
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<span class="comment">// Inclusive range</span>
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<span class="kw">let</span> <span class="ident">n</span>: <span class="ident">u32</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen_range</span>(<span class="number">0</span>..<span class="op">=</span><span class="number">10</span>);
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<span class="macro">println!</span>(<span class="string">"{}"</span>, <span class="ident">n</span>);</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.sample" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#152-154">source</a></div><h4 class="code-header">fn <a href="#method.sample" class="fnname">sample</a><T, D: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>>(&mut self, distr: D) -> T</h4></div></summary><div class="docblock"><p>Sample a new value, using the given distribution.</p>
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<h6 id="example-2"><a href="#example-2">Example</a></h6>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">Rng</span>};
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<span class="kw">use</span> <span class="ident">rand::distributions::Uniform</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">thread_rng</span>();
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<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">sample</span>(<span class="ident">Uniform::new</span>(<span class="number">10u32</span>, <span class="number">15</span>));
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<span class="comment">// Type annotation requires two types, the type and distribution; the</span>
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<span class="comment">// distribution can be inferred.</span>
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<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">sample</span>::<span class="op"><</span><span class="ident">u16</span>, <span class="kw">_</span><span class="op">></span>(<span class="ident">Uniform::new</span>(<span class="number">10</span>, <span class="number">15</span>));</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.sample_iter" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#192-198">source</a></div><h4 class="code-header">fn <a href="#method.sample_iter" class="fnname">sample_iter</a><T, D>(self, distr: D) -> <a class="struct" href="distributions/struct.DistIter.html" title="struct rand::distributions::DistIter">DistIter</a><D, Self, T><span class="notable-traits"><span class="notable-traits-tooltip">ⓘ<span class="notable-traits-tooltiptext"><span class="docblock"><span class="notable">Notable traits for <a class="struct" href="distributions/struct.DistIter.html" title="struct rand::distributions::DistIter">DistIter</a><D, R, T></span><code class="content"><span class="where fmt-newline">impl<D, R, T> <a class="trait" href="https://doc.rust-lang.org/1.62.1/core/iter/traits/iterator/trait.Iterator.html" title="trait core::iter::traits::iterator::Iterator">Iterator</a> for <a class="struct" href="distributions/struct.DistIter.html" title="struct rand::distributions::DistIter">DistIter</a><D, R, T> <span class="where fmt-newline">where<br> D: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>,<br> R: <a class="trait" href="trait.Rng.html" title="trait rand::Rng">Rng</a>, </span></span><span class="where fmt-newline"> type <a href="https://doc.rust-lang.org/1.62.1/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" class="associatedtype">Item</a> = T;</span></code></span></span></span></span> <span class="where fmt-newline">where<br> D: <a class="trait" href="distributions/trait.Distribution.html" title="trait rand::distributions::Distribution">Distribution</a><T>,<br> Self: <a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h4></div></summary><div class="docblock"><p>Create an iterator that generates values using the given distribution.</p>
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<p>Note that this function takes its arguments by value. This works since
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<code>(&mut R): Rng where R: Rng</code> and
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<code>(&D): Distribution where D: Distribution</code>,
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however borrowing is not automatic hence <code>rng.sample_iter(...)</code> may
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need to be replaced with <code>(&mut rng).sample_iter(...)</code>.</p>
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<h5 id="example-3"><a href="#example-3">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">Rng</span>};
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<span class="kw">use</span> <span class="ident">rand::distributions</span>::{<span class="ident">Alphanumeric</span>, <span class="ident">Uniform</span>, <span class="ident">Standard</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">thread_rng</span>();
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<span class="comment">// Vec of 16 x f32:</span>
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<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">f32</span><span class="op">></span> <span class="op">=</span> (<span class="kw-2">&mut</span> <span class="ident">rng</span>).<span class="ident">sample_iter</span>(<span class="ident">Standard</span>).<span class="ident">take</span>(<span class="number">16</span>).<span class="ident">collect</span>();
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<span class="comment">// String:</span>
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<span class="kw">let</span> <span class="ident">s</span>: <span class="ident">String</span> <span class="op">=</span> (<span class="kw-2">&mut</span> <span class="ident">rng</span>).<span class="ident">sample_iter</span>(<span class="ident">Alphanumeric</span>)
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.<span class="ident">take</span>(<span class="number">7</span>)
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.<span class="ident">map</span>(<span class="ident">char::from</span>)
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.<span class="ident">collect</span>();
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<span class="comment">// Combined values</span>
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<span class="macro">println!</span>(<span class="string">"{:?}"</span>, (<span class="kw-2">&mut</span> <span class="ident">rng</span>).<span class="ident">sample_iter</span>(<span class="ident">Standard</span>).<span class="ident">take</span>(<span class="number">5</span>)
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.<span class="ident">collect</span>::<span class="op"><</span><span class="ident">Vec</span><span class="op"><</span>(<span class="ident">f64</span>, <span class="ident">bool</span>)<span class="op">></span><span class="op">></span>());
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<span class="comment">// Dice-rolling:</span>
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<span class="kw">let</span> <span class="ident">die_range</span> <span class="op">=</span> <span class="ident">Uniform::new_inclusive</span>(<span class="number">1</span>, <span class="number">6</span>);
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">roll_die</span> <span class="op">=</span> (<span class="kw-2">&mut</span> <span class="ident">rng</span>).<span class="ident">sample_iter</span>(<span class="ident">die_range</span>);
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<span class="kw">while</span> <span class="ident">roll_die</span>.<span class="ident">next</span>().<span class="ident">unwrap</span>() <span class="op">!</span><span class="op">=</span> <span class="number">6</span> {
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<span class="macro">println!</span>(<span class="string">"Not a 6; rolling again!"</span>);
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}</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.fill" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#218-220">source</a></div><h4 class="code-header">fn <a href="#method.fill" class="fnname">fill</a><T: <a class="trait" href="trait.Fill.html" title="trait rand::Fill">Fill</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(&mut self, dest: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.reference.html">&mut </a>T)</h4></div></summary><div class="docblock"><p>Fill any type implementing <a href="trait.Fill.html" title="Fill"><code>Fill</code></a> with random data</p>
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<p>The distribution is expected to be uniform with portable results, but
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this cannot be guaranteed for third-party implementations.</p>
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<p>This is identical to <a href="trait.Rng.html#method.try_fill"><code>try_fill</code></a> except that it panics on error.</p>
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<h5 id="example-4"><a href="#example-4">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">Rng</span>};
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">arr</span> <span class="op">=</span> [<span class="number">0i8</span>; <span class="number">20</span>];
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<span class="ident">thread_rng</span>().<span class="ident">fill</span>(<span class="kw-2">&mut</span> <span class="ident">arr</span>[..]);</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.try_fill" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#246-248">source</a></div><h4 class="code-header">fn <a href="#method.try_fill" class="fnname">try_fill</a><T: <a class="trait" href="trait.Fill.html" title="trait rand::Fill">Fill</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(&mut self, dest: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.reference.html">&mut </a>T) -> <a class="enum" href="https://doc.rust-lang.org/1.62.1/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.unit.html">()</a>, <a class="struct" href="struct.Error.html" title="struct rand::Error">Error</a>></h4></div></summary><div class="docblock"><p>Fill any type implementing <a href="trait.Rng.html#method.fill"><code>Fill</code></a> with random data</p>
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<p>The distribution is expected to be uniform with portable results, but
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this cannot be guaranteed for third-party implementations.</p>
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<p>This is identical to <a href="trait.Rng.html#method.fill"><code>fill</code></a> except that it forwards errors.</p>
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<h5 id="example-5"><a href="#example-5">Example</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">Rng</span>};
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">arr</span> <span class="op">=</span> [<span class="number">0u64</span>; <span class="number">4</span>];
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<span class="ident">thread_rng</span>().<span class="ident">try_fill</span>(<span class="kw-2">&mut</span> <span class="ident">arr</span>[..])<span class="question-mark">?</span>;
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</code></pre></div>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.gen_bool" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#270-273">source</a></div><h4 class="code-header">fn <a href="#method.gen_bool" class="fnname">gen_bool</a>(&mut self, p: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.f64.html">f64</a>) -> <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.bool.html">bool</a></h4></div></summary><div class="docblock"><p>Return a bool with a probability <code>p</code> of being true.</p>
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<p>See also the <a href="distributions/struct.Bernoulli.html"><code>Bernoulli</code></a> distribution, which may be faster if
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sampling from the same probability repeatedly.</p>
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<h5 id="example-6"><a href="#example-6">Example</a></h5>
|
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|
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">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">thread_rng</span>();
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<span class="macro">println!</span>(<span class="string">"{}"</span>, <span class="ident">rng</span>.<span class="ident">gen_bool</span>(<span class="number">1.0</span> <span class="op">/</span> <span class="number">3.0</span>));</code></pre></div>
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<h5 id="panics-1"><a href="#panics-1">Panics</a></h5>
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<p>If <code>p < 0</code> or <code>p > 1</code>.</p>
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</div></details><details class="rustdoc-toggle" open><summary><div id="method.gen_ratio" class="method has-srclink"><div class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#299-302">source</a></div><h4 class="code-header">fn <a href="#method.gen_ratio" class="fnname">gen_ratio</a>(&mut self, numerator: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.u32.html">u32</a>, denominator: <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.u32.html">u32</a>) -> <a class="primitive" href="https://doc.rust-lang.org/1.62.1/std/primitive.bool.html">bool</a></h4></div></summary><div class="docblock"><p>Return a bool with a probability of <code>numerator/denominator</code> of being
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true. I.e. <code>gen_ratio(2, 3)</code> has chance of 2 in 3, or about 67%, of
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returning true. If <code>numerator == denominator</code>, then the returned value
|
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|
is guaranteed to be <code>true</code>. If <code>numerator == 0</code>, then the returned
|
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|
value is guaranteed to be <code>false</code>.</p>
|
|
|
<p>See also the <a href="distributions/struct.Bernoulli.html"><code>Bernoulli</code></a> distribution, which may be faster if
|
|
|
sampling from the same <code>numerator</code> and <code>denominator</code> repeatedly.</p>
|
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|
<h5 id="panics-2"><a href="#panics-2">Panics</a></h5>
|
|
|
<p>If <code>denominator == 0</code> or <code>numerator > denominator</code>.</p>
|
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|
<h5 id="example-7"><a href="#example-7">Example</a></h5>
|
|
|
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">thread_rng</span>, <span class="ident">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">thread_rng</span>();
|
|
|
<span class="macro">println!</span>(<span class="string">"{}"</span>, <span class="ident">rng</span>.<span class="ident">gen_ratio</span>(<span class="number">2</span>, <span class="number">3</span>));</code></pre></div>
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</div></details></div><h2 id="implementors" class="small-section-header">Implementors<a href="#implementors" class="anchor"></a></h2><div class="item-list" id="implementors-list"><section id="impl-Rng" class="impl has-srclink"><span class="rightside"><a class="srclink" href="../src/rand/rng.rs.html#305">source</a></span><a href="#impl-Rng" class="anchor"></a><h3 class="code-header in-band">impl<R: <a class="trait" href="trait.RngCore.html" title="trait rand::RngCore">RngCore</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.62.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> <a class="trait" href="trait.Rng.html" title="trait rand::Rng">Rng</a> for R</h3></section></div><script type="text/javascript" src="../implementors/rand/rng/trait.Rng.js" data-ignore-extern-crates="" async></script></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="rand" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.62.1 (e092d0b6b 2022-07-16)" ></div>
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