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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 `once` fn in crate `rayon`."><meta name="keywords" content="rust, rustlang, rust-lang, once"><title>rayon::iter::once - 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="../../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='../../rayon/index.html'><div class='logo-container'><img src='../../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='../index.html'>rayon</a>::<wbr><a href='index.html'>iter</a></p><script>window.sidebarCurrent = {name: 'once', 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/rayon/iter/once.rs.html#24-26' title='goto source code'>[src]</a></span><span class='in-band'>Function <a href='../index.html'>rayon</a>::<wbr><a href='index.html'>iter</a>::<wbr><a class="fn" href=''>once</a></span></h1><pre class='rust fn'>pub fn once<T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a>>(item: T) -> <a class="struct" href="../../rayon/iter/struct.Once.html" title="struct rayon::iter::Once">Once</a><T></pre><div class='docblock'><p>Creates a parallel iterator that produces an element exactly once.</p>
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<p>This admits no parallelism on its own, but it could be chained to existing
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parallel iterators to extend their contents, or otherwise used for any code
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that deals with generic parallel iterators.</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">use</span> <span class="ident">rayon</span>::<span class="ident">prelude</span>::<span class="kw-2">*</span>;
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<span class="kw">use</span> <span class="ident">rayon</span>::<span class="ident">iter</span>::<span class="ident">once</span>;
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<span class="kw">let</span> <span class="ident">pi</span> <span class="op">=</span> (<span class="number">0</span>..<span class="number">1234</span>).<span class="ident">into_par_iter</span>()
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.<span class="ident">chain</span>(<span class="ident">once</span>(<span class="op">-</span><span class="number">1</span>))
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.<span class="ident">chain</span>(<span class="number">1234</span>..<span class="number">10_000</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">pi</span>.<span class="ident">clone</span>().<span class="ident">count</span>(), <span class="number">10_001</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">pi</span>.<span class="ident">clone</span>().<span class="ident">filter</span>(<span class="op">|</span><span class="kw-2">&</span><span class="ident">x</span><span class="op">|</span> <span class="ident">x</span> <span class="op"><</span> <span class="number">0</span>).<span class="ident">count</span>(), <span class="number">1</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">pi</span>.<span class="ident">position_any</span>(<span class="op">|</span><span class="ident">x</span><span class="op">|</span> <span class="ident">x</span> <span class="op"><</span> <span class="number">0</span>), <span class="prelude-val">Some</span>(<span class="number">1234</span>));</pre></div>
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