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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="Creates a parallel iterator that produces an element exactly once."><title>once in rayon::iter - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="rayon" data-themes="" data-resource-suffix="" data-rustdoc-version="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../../static.files/storage-e2aeef58.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-263c88ec.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><rustdoc-topbar><h2><a href="#">once</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../rayon/index.html">rayon</a><span class="version">1.11.0</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">once</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#examples" title="Examples">Examples</a></li></ul></section><div id="rustdoc-modnav"><h2><a href="index.html">In rayon::<wbr>iter</a></h2></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="../index.html">rayon</a>::<wbr><a href="index.html">iter</a></div><h1>Function <span class="fn">once</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../src/rayon/iter/once.rs.html#24-26">Source</a> </span></div><pre class="rust item-decl"><code>pub fn once<T: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a>>(item: T) -> <a class="struct" href="struct.Once.html" title="struct rayon::iter::Once">Once</a><T></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><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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<h2 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>rayon::prelude::<span class="kw-2">*</span>;
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<span class="kw">use </span>rayon::iter::once;
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<span class="kw">let </span>pi = (<span class="number">0</span>..<span class="number">1234</span>).into_par_iter()
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.chain(once(-<span class="number">1</span>))
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.chain(<span class="number">1234</span>..<span class="number">10_000</span>);
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<span class="macro">assert_eq!</span>(pi.clone().count(), <span class="number">10_001</span>);
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<span class="macro">assert_eq!</span>(pi.clone().filter(|<span class="kw-2">&</span>x| x < <span class="number">0</span>).count(), <span class="number">1</span>);
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<span class="macro">assert_eq!</span>(pi.position_any(|x| x < <span class="number">0</span>), <span class="prelude-val">Some</span>(<span class="number">1234</span>));</code></pre></div></div></details></section></div></main></body></html> |