| <!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="Extension trait on iterators, providing random sampling methods."><meta name="keywords" content="rust, rustlang, rust-lang, IteratorRandom"><title>IteratorRandom in rand::seq - 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">Trait IteratorRandom</h2><div class="sidebar-elems"><div class="block items"><h3 class="sidebar-title"><a href="#provided-methods">Provided Methods</a></h3><div class="sidebar-links"><a href="#method.choose">choose</a><a href="#method.choose_multiple">choose_multiple</a><a href="#method.choose_multiple_fill">choose_multiple_fill</a><a href="#method.choose_stable">choose_stable</a></div><h3 class="sidebar-title"><a href="#implementors">Implementors</a></h3></div><h2 class="location">Other items in<br><a href="../index.html">rand</a>::<wbr><a href="index.html">seq</a></h2><div id="sidebar-vars" data-name="IteratorRandom" 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"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></a><nav class="sub"><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><div> |
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| <h1 class="fqn"><span class="in-band">Trait <a href="../index.html">rand</a>::<wbr><a href="index.html">seq</a>::<wbr><a class="trait" href="#">IteratorRandom</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/seq/mod.rs.html#288-489" title="goto source code">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 IteratorRandom: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html" title="trait core::iter::traits::iterator::Iterator">Iterator</a> + <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> { |
| fn <a href="#method.choose" class="fnname">choose</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a><Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a>><br> <span class="where">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span>, |
| { ... } |
| <div class="item-spacer"></div> fn <a href="#method.choose_stable" class="fnname">choose_stable</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a><Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a>><br> <span class="where">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span>, |
| { ... } |
| <div class="item-spacer"></div> fn <a href="#method.choose_multiple_fill" class="fnname">choose_multiple_fill</a><R>(<br> self, <br> rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R, <br> buf: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&mut [</a>Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">]</a><br> ) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a><br> <span class="where">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span>, |
| { ... } |
| <div class="item-spacer"></div> fn <a href="#method.choose_multiple" class="fnname">choose_multiple</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R, amount: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>) -> <a class="struct" href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a><Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a>><br> <span class="where">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span>, |
| { ... } |
| }</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Extension trait on iterators, providing random sampling methods.</p> |
| <p>This trait is implemented on all iterators <code>I</code> where <code>I: Iterator + Sized</code> |
| and provides methods for |
| choosing one or more elements. You must <code>use</code> this trait:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">rand::seq::IteratorRandom</span>; |
| |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span> <span class="op">=</span> <span class="ident">rand::thread_rng</span>(); |
| |
| <span class="kw">let</span> <span class="ident">faces</span> <span class="op">=</span> <span class="string">"😀😎😐😕😠😢"</span>; |
| <span class="macro">println!</span>(<span class="string">"I am {}!"</span>, <span class="ident">faces</span>.<span class="ident">chars</span>().<span class="ident">choose</span>(<span class="kw-2">&mut</span> <span class="ident">rng</span>).<span class="ident">unwrap</span>());</code></pre></div> |
| <p>Example output (non-deterministic):</p> |
| <div class="example-wrap"><pre class="language-none"><code>I am 😀!</code></pre></div></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.choose" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/rand/seq/mod.rs.html#304-353" title="goto source code">source</a></div><h4 class="code-header">fn <a href="#method.choose" class="fnname">choose</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a><Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a>> <span class="where fmt-newline">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h4></div></summary><div class="docblock"><p>Choose one element at random from the iterator.</p> |
| <p>Returns <code>None</code> if and only if the iterator is empty.</p> |
| <p>This method uses <a href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#method.size_hint" title="Iterator::size_hint"><code>Iterator::size_hint</code></a> for optimisation. With an |
| accurate hint and where <a href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#method.nth" title="Iterator::nth"><code>Iterator::nth</code></a> is a constant-time operation |
| this method can offer <code>O(1)</code> performance. Where no size hint is |
| available, complexity is <code>O(n)</code> where <code>n</code> is the iterator length. |
| Partial hints (where <code>lower > 0</code>) also improve performance.</p> |
| <p>Note that the output values and the number of RNG samples used |
| depends on size hints. In particular, <code>Iterator</code> combinators that don’t |
| change the values yielded but change the size hints may result in |
| <code>choose</code> returning different elements. If you want consistent results |
| and RNG usage consider using <a href="trait.IteratorRandom.html#method.choose_stable" title="IteratorRandom::choose_stable"><code>IteratorRandom::choose_stable</code></a>.</p> |
| </div></details><details class="rustdoc-toggle" open><summary><div id="method.choose_stable" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/rand/seq/mod.rs.html#373-411" title="goto source code">source</a></div><h4 class="code-header">fn <a href="#method.choose_stable" class="fnname">choose_stable</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a><Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a>> <span class="where fmt-newline">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h4></div></summary><div class="docblock"><p>Choose one element at random from the iterator.</p> |
| <p>Returns <code>None</code> if and only if the iterator is empty.</p> |
| <p>This method is very similar to <a href="trait.IteratorRandom.html#method.choose"><code>choose</code></a> except that the result |
| only depends on the length of the iterator and the values produced by |
| <code>rng</code>. Notably for any iterator of a given length this will make the |
| same requests to <code>rng</code> and if the same sequence of values are produced |
| the same index will be selected from <code>self</code>. This may be useful if you |
| need consistent results no matter what type of iterator you are working |
| with. If you do not need this stability prefer <a href="trait.IteratorRandom.html#method.choose"><code>choose</code></a>.</p> |
| <p>Note that this method still uses <a href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#method.size_hint" title="Iterator::size_hint"><code>Iterator::size_hint</code></a> to skip |
| constructing elements where possible, however the selection and <code>rng</code> |
| calls are the same in the face of this optimization. If you want to |
| force every element to be created regardless call <code>.inspect(|e| ())</code>.</p> |
| </div></details><details class="rustdoc-toggle" open><summary><div id="method.choose_multiple_fill" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/rand/seq/mod.rs.html#426-448" title="goto source code">source</a></div><h4 class="code-header">fn <a href="#method.choose_multiple_fill" class="fnname">choose_multiple_fill</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R, buf: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&mut [</a>Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">]</a>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a> <span class="where fmt-newline">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h4></div></summary><div class="docblock"><p>Collects values at random from the iterator into a supplied buffer |
| until that buffer is filled.</p> |
| <p>Although the elements are selected randomly, the order of elements in |
| the buffer is neither stable nor fully random. If random ordering is |
| desired, shuffle the result.</p> |
| <p>Returns the number of elements added to the buffer. This equals the length |
| of the buffer unless the iterator contains insufficient elements, in which |
| case this equals the number of elements available.</p> |
| <p>Complexity is <code>O(n)</code> where <code>n</code> is the length of the iterator. |
| For slices, prefer <a href="trait.SliceRandom.html#tymethod.choose_multiple" title="SliceRandom::choose_multiple"><code>SliceRandom::choose_multiple</code></a>.</p> |
| </div></details><details class="rustdoc-toggle" open><summary><div id="method.choose_multiple" class="method has-srclink"><div class="rightside"><a class="srclink" href="../../src/rand/seq/mod.rs.html#466-488" title="goto source code">source</a></div><h4 class="code-header">fn <a href="#method.choose_multiple" class="fnname">choose_multiple</a><R>(self, rng: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&mut </a>R, amount: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>) -> <a class="struct" href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a><Self::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::traits::iterator::Iterator::Item">Item</a>> <span class="where fmt-newline">where<br> R: <a class="trait" href="../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h4></div></summary><div class="item-info"><div class="stab portability">This is supported on <strong>crate feature <code>alloc</code></strong> only.</div></div><div class="docblock"><p>Collects <code>amount</code> values at random from the iterator into a vector.</p> |
| <p>This is equivalent to <code>choose_multiple_fill</code> except for the result type.</p> |
| <p>Although the elements are selected randomly, the order of elements in |
| the buffer is neither stable nor fully random. If random ordering is |
| desired, shuffle the result.</p> |
| <p>The length of the returned vector equals <code>amount</code> unless the iterator |
| contains insufficient elements, in which case it equals the number of |
| elements available.</p> |
| <p>Complexity is <code>O(n)</code> where <code>n</code> is the length of the iterator. |
| For slices, prefer <a href="trait.SliceRandom.html#tymethod.choose_multiple" title="SliceRandom::choose_multiple"><code>SliceRandom::choose_multiple</code></a>.</p> |
| </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"><div id="impl-IteratorRandom" class="impl has-srclink"><div class="rightside"><a class="srclink" href="../../src/rand/seq/mod.rs.html#615" title="goto source code">source</a></div><a href="#impl-IteratorRandom" class="anchor"></a><h3 class="code-header in-band">impl<I> <a class="trait" href="trait.IteratorRandom.html" title="trait rand::seq::IteratorRandom">IteratorRandom</a> for I <span class="where fmt-newline">where<br> I: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html" title="trait core::iter::traits::iterator::Iterator">Iterator</a> + <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></h3></div></div><script type="text/javascript" src="../../implementors/rand/seq/trait.IteratorRandom.js" async></script></section><section id="search" class="content hidden"></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="1.60.0-nightly (1bd4fdc94 2022-01-12)" ></div> |
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