| <!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="Chain zero or more iterators together into one sequence."><meta name="keywords" content="rust, rustlang, rust-lang, chain"><title>chain in itertools - 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" href="../normalize.css"><link rel="stylesheet" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../ayu.css" disabled><link rel="stylesheet" href="../dark.css" disabled><link rel="stylesheet" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script defer src="sidebar-items.js"></script><script defer src="../main.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../itertools/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../itertools/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In itertools</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Macro <a href="index.html">itertools</a>::<wbr><a class="macro" href="#">chain</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></h1><span class="out-of-band"><a class="srclink" href="../src/itertools/lib.rs.html#400-416">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><div class="example-wrap"><pre class="rust macro"><code><span class="macro">macro_rules! </span>chain { |
| () => { ... }; |
| (<span class="macro-nonterminal">$first</span>:expr $(, <span class="macro-nonterminal">$rest</span>:expr )* $(,)<span class="question-mark">?</span>) => { ... }; |
| }</code></pre></div> |
| </div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p><a href="Iterator::chain">Chain</a> zero or more iterators together into one sequence.</p> |
| <p>The comma-separated arguments must implement [<code>IntoIterator</code>]. |
| The final argument may be followed by a trailing comma.</p> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <p>Empty invocations of <code>chain!</code> expand to an invocation of [<code>std::iter::empty</code>]:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::iter; |
| <span class="kw">use </span>itertools::chain; |
| |
| <span class="kw">let _</span>: iter::Empty<()> = <span class="macro">chain!</span>(); |
| <span class="kw">let _</span>: iter::Empty<i8> = <span class="macro">chain!</span>();</code></pre></div> |
| <p>Invocations of <code>chain!</code> with one argument expand to <a href="IntoIterator"><code>arg.into_iter()</code></a>:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::{ops::Range, slice}; |
| <span class="kw">use </span>itertools::chain; |
| <span class="kw">let _</span>: <Range<<span class="kw">_</span>> <span class="kw">as </span>IntoIterator>::IntoIter = <span class="macro">chain!</span>((<span class="number">2</span>..<span class="number">6</span>),); <span class="comment">// trailing comma optional! |
| </span><span class="kw">let _</span>: <<span class="kw-2">&</span>[<span class="kw">_</span>] <span class="kw">as </span>IntoIterator>::IntoIter = <span class="macro">chain!</span>(<span class="kw-2">&</span>[<span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>]);</code></pre></div> |
| <p>Invocations of <code>chain!</code> with multiple arguments <a href="IntoIterator"><code>.into_iter()</code></a> each |
| argument, and then <a href="Iterator::chain"><code>chain</code></a> them together:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::{iter::<span class="kw-2">*</span>, ops::Range, slice}; |
| <span class="kw">use </span>itertools::{assert_equal, chain}; |
| |
| <span class="comment">// e.g., this: |
| </span><span class="kw">let </span>with_macro: Chain<Chain<Once<<span class="kw">_</span>>, Take<Repeat<<span class="kw">_</span>>>>, slice::Iter<<span class="kw">_</span>>> = |
| <span class="macro">chain!</span>[once(<span class="kw-2">&</span><span class="number">0</span>), repeat(<span class="kw-2">&</span><span class="number">1</span>).take(<span class="number">2</span>), <span class="kw-2">&</span>[<span class="number">2</span>, <span class="number">3</span>, <span class="number">5</span>],]; |
| |
| <span class="comment">// ...is equivalent to this: |
| </span><span class="kw">let </span>with_method: Chain<Chain<Once<<span class="kw">_</span>>, Take<Repeat<<span class="kw">_</span>>>>, slice::Iter<<span class="kw">_</span>>> = |
| once(<span class="kw-2">&</span><span class="number">0</span>) |
| .chain(repeat(<span class="kw-2">&</span><span class="number">1</span>).take(<span class="number">2</span>)) |
| .chain(<span class="kw-2">&</span>[<span class="number">2</span>, <span class="number">3</span>, <span class="number">5</span>]); |
| |
| assert_equal(with_macro, with_method);</code></pre></div> |
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