<!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 `vec` macro in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, vec"><title>std::vec - 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><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc macro"><!--[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='../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><div class="sidebar-elems"><p class='location'><a href='index.html'>std</a></p><script>window.sidebarCurrent = {name: 'vec', ty: 'macro', 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"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><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='in-band'>Macro <a href='index.html'>std</a>::<wbr><a class="macro" href=''>vec</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><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/alloc/macros.rs.html#48-56' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">vec</span> {
( $ <span class="ident">elem</span> : <span class="ident">expr</span> ; $ <span class="ident">n</span> : <span class="ident">expr</span> ) <span class="op">=></span> { ... };
( $ ( $ <span class="ident">x</span> : <span class="ident">expr</span> ) , <span class="op">*</span> ) <span class="op">=></span> { ... };
( $ ( $ <span class="ident">x</span> : <span class="ident">expr</span> , ) <span class="op">*</span> ) <span class="op">=></span> { ... };
}</pre>
</div><div class='docblock'><p>Creates a <a href="../std/vec/struct.Vec.html"><code>Vec</code></a> containing the arguments.</p>
<p><code>vec!</code> allows <code>Vec</code>s to be defined with the same syntax as array expressions.
There are two forms of this macro:</p>
<ul>
<li>Create a <a href="../std/vec/struct.Vec.html"><code>Vec</code></a> containing a given list of elements:</li>
</ul>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>[<span class="number">0</span>], <span class="number">1</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>[<span class="number">1</span>], <span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>[<span class="number">2</span>], <span class="number">3</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20v%20%3D%20vec!%5B1%2C%202%2C%203%5D%3B%0Aassert_eq!(v%5B0%5D%2C%201)%3B%0Aassert_eq!(v%5B1%5D%2C%202)%3B%0Aassert_eq!(v%5B2%5D%2C%203)%3B%0A%7D">Run</a></pre>
<ul>
<li>Create a <a href="../std/vec/struct.Vec.html"><code>Vec</code></a> from a given element and size:</li>
</ul>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>; <span class="number">3</span>];
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>, [<span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>]);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20v%20%3D%20vec!%5B1%3B%203%5D%3B%0Aassert_eq!(v%2C%20%5B1%2C%201%2C%201%5D)%3B%0A%7D">Run</a></pre>
<p>Note that unlike array expressions this syntax supports all elements
which implement <a href="../std/clone/trait.Clone.html"><code>Clone</code></a> and the number of elements doesn't have to be
a constant.</p>
<p>This will use <code>clone</code> to duplicate an expression, so one should be careful
using this with types having a nonstandard <code>Clone</code> implementation. For
example, <code>vec![Rc::new(1); 5]</code> will create a vector of five references
to the same boxed integer value, not five references pointing to independently
boxed integers.</p>
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