<!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="Source to the Rust file `liballoc/macros.rs`."> <meta name="keywords" content="rust, rustlang, rust-lang"> <title>macros.rs.html -- source</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="../../main.css" id="themeStyle"> <script src="../../storage.js"></script> <link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"> </head> <body class="rustdoc source"> <!--[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='../../alloc/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> </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"> </div> </form> </nav> <section id='main' class="content"><pre class="line-numbers"><span id="1"> 1</span> <span id="2"> 2</span> <span id="3"> 3</span> <span id="4"> 4</span> <span id="5"> 5</span> <span id="6"> 6</span> <span id="7"> 7</span> <span id="8"> 8</span> <span id="9"> 9</span> <span id="10"> 10</span> <span id="11"> 11</span> <span id="12"> 12</span> <span id="13"> 13</span> <span id="14"> 14</span> <span id="15"> 15</span> <span id="16"> 16</span> <span id="17"> 17</span> <span id="18"> 18</span> <span id="19"> 19</span> <span id="20"> 20</span> <span id="21"> 21</span> <span id="22"> 22</span> <span id="23"> 23</span> <span id="24"> 24</span> <span id="25"> 25</span> <span id="26"> 26</span> <span id="27"> 27</span> <span id="28"> 28</span> <span id="29"> 29</span> <span id="30"> 30</span> <span id="31"> 31</span> <span id="32"> 32</span> <span id="33"> 33</span> <span id="34"> 34</span> <span id="35"> 35</span> <span id="36"> 36</span> <span id="37"> 37</span> <span id="38"> 38</span> <span id="39"> 39</span> <span id="40"> 40</span> <span id="41"> 41</span> <span id="42"> 42</span> <span id="43"> 43</span> <span id="44"> 44</span> <span id="45"> 45</span> <span id="46"> 46</span> <span id="47"> 47</span> <span id="48"> 48</span> <span id="49"> 49</span> <span id="50"> 50</span> <span id="51"> 51</span> <span id="52"> 52</span> <span id="53"> 53</span> <span id="54"> 54</span> <span id="55"> 55</span> <span id="56"> 56</span> <span id="57"> 57</span> <span id="58"> 58</span> <span id="59"> 59</span> <span id="60"> 60</span> <span id="61"> 61</span> <span id="62"> 62</span> <span id="63"> 63</span> <span id="64"> 64</span> <span id="65"> 65</span> <span id="66"> 66</span> <span id="67"> 67</span> <span id="68"> 68</span> <span id="69"> 69</span> <span id="70"> 70</span> <span id="71"> 71</span> <span id="72"> 72</span> <span id="73"> 73</span> <span id="74"> 74</span> <span id="75"> 75</span> <span id="76"> 76</span> <span id="77"> 77</span> <span id="78"> 78</span> <span id="79"> 79</span> <span id="80"> 80</span> <span id="81"> 81</span> <span id="82"> 82</span> <span id="83"> 83</span> <span id="84"> 84</span> <span id="85"> 85</span> <span id="86"> 86</span> <span id="87"> 87</span> <span id="88"> 88</span> <span id="89"> 89</span> <span id="90"> 90</span> <span id="91"> 91</span> <span id="92"> 92</span> <span id="93"> 93</span> <span id="94"> 94</span> <span id="95"> 95</span> <span id="96"> 96</span> <span id="97"> 97</span> <span id="98"> 98</span> <span id="99"> 99</span> <span id="100">100</span> <span id="101">101</span> <span id="102">102</span> <span id="103">103</span> <span id="104">104</span> <span id="105">105</span> <span id="106">106</span> <span id="107">107</span> </pre><pre class="rust "> <span class="comment">// Copyright 2013-2016 The Rust Project Developers. See the COPYRIGHT</span> <span class="comment">// file at the top-level directory of this distribution and at</span> <span class="comment">// http://rust-lang.org/COPYRIGHT.</span> <span class="comment">//</span> <span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span> <span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span> <span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span> <span class="comment">// option. This file may not be copied, modified, or distributed</span> <span class="comment">// except according to those terms.</span> <span class="doccomment">/// Creates a [`Vec`] containing the arguments.</span> <span class="doccomment">///</span> <span class="doccomment">/// `vec!` allows `Vec`s to be defined with the same syntax as array expressions.</span> <span class="doccomment">/// There are two forms of this macro:</span> <span class="doccomment">///</span> <span class="doccomment">/// - Create a [`Vec`] containing a given list of elements:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let v = vec![1, 2, 3];</span> <span class="doccomment">/// assert_eq!(v[0], 1);</span> <span class="doccomment">/// assert_eq!(v[1], 2);</span> <span class="doccomment">/// assert_eq!(v[2], 3);</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// - Create a [`Vec`] from a given element and size:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let v = vec![1; 3];</span> <span class="doccomment">/// assert_eq!(v, [1, 1, 1]);</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// Note that unlike array expressions this syntax supports all elements</span> <span class="doccomment">/// which implement [`Clone`] and the number of elements doesn't have to be</span> <span class="doccomment">/// a constant.</span> <span class="doccomment">///</span> <span class="doccomment">/// This will use `clone` to duplicate an expression, so one should be careful</span> <span class="doccomment">/// using this with types having a nonstandard `Clone` implementation. For</span> <span class="doccomment">/// example, `vec![Rc::new(1); 5]` will create a vector of five references</span> <span class="doccomment">/// to the same boxed integer value, not five references pointing to independently</span> <span class="doccomment">/// boxed integers.</span> <span class="doccomment">///</span> <span class="doccomment">/// [`Vec`]: ../std/vec/struct.Vec.html</span> <span class="doccomment">/// [`Clone`]: ../std/clone/trait.Clone.html</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span> <span class="attribute">#[<span class="ident">macro_export</span>]</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="attribute">#[<span class="ident">allow_internal_unstable</span>]</span> <span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">vec</span> { (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">elem</span>:<span class="ident">expr</span>; <span class="macro-nonterminal">$</span><span class="macro-nonterminal">n</span>:<span class="ident">expr</span>) <span class="op">=></span> ( <span class="macro-nonterminal">$</span><span class="kw">crate</span>::<span class="macro-nonterminal">vec</span>::<span class="ident">from_elem</span>(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">elem</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">n</span>) ); ($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>:<span class="ident">expr</span>),<span class="kw-2">*</span>) <span class="op">=></span> ( <span class="op"><</span>[_]<span class="op">></span>::<span class="ident">into_vec</span>(<span class="kw">box</span> [$(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>),<span class="kw-2">*</span>]) ); ($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>:<span class="ident">expr</span>,)<span class="kw-2">*</span>) <span class="op">=></span> (<span class="macro">vec</span><span class="macro">!</span>[$(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>),<span class="kw-2">*</span>]) } <span class="comment">// HACK(japaric): with cfg(test) the inherent `[T]::into_vec` method, which is</span> <span class="comment">// required for this macro definition, is not available. Instead use the</span> <span class="comment">// `slice::into_vec` function which is only available with cfg(test)</span> <span class="comment">// NB see the slice::hack module in slice.rs for more information</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span> <span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">vec</span> { (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">elem</span>:<span class="ident">expr</span>; <span class="macro-nonterminal">$</span><span class="macro-nonterminal">n</span>:<span class="ident">expr</span>) <span class="op">=></span> ( <span class="macro-nonterminal">$</span><span class="kw">crate</span>::<span class="macro-nonterminal">vec</span>::<span class="ident">from_elem</span>(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">elem</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">n</span>) ); ($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>:<span class="ident">expr</span>),<span class="kw-2">*</span>) <span class="op">=></span> ( <span class="macro-nonterminal">$</span><span class="kw">crate</span>::<span class="macro-nonterminal">slice</span>::<span class="ident">into_vec</span>(<span class="kw">box</span> [$(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>),<span class="kw-2">*</span>]) ); ($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>:<span class="ident">expr</span>,)<span class="kw-2">*</span>) <span class="op">=></span> (<span class="macro">vec</span><span class="macro">!</span>[$(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>),<span class="kw-2">*</span>]) } <span class="doccomment">/// Creates a `String` using interpolation of runtime expressions.</span> <span class="doccomment">///</span> <span class="doccomment">/// The first argument `format!` receives is a format string. This must be a string</span> <span class="doccomment">/// literal. The power of the formatting string is in the `{}`s contained.</span> <span class="doccomment">///</span> <span class="doccomment">/// Additional parameters passed to `format!` replace the `{}`s within the</span> <span class="doccomment">/// formatting string in the order given unless named or positional parameters</span> <span class="doccomment">/// are used, see [`std::fmt`][fmt] for more information.</span> <span class="doccomment">///</span> <span class="doccomment">/// A common use for `format!` is concatenation and interpolation of strings.</span> <span class="doccomment">/// The same convention is used with [`print!`] and [`write!`] macros,</span> <span class="doccomment">/// depending on the intended destination of the string.</span> <span class="doccomment">///</span> <span class="doccomment">/// [fmt]: ../std/fmt/index.html</span> <span class="doccomment">/// [`print!`]: ../std/macro.print.html</span> <span class="doccomment">/// [`write!`]: ../std/macro.write.html</span> <span class="doccomment">///</span> <span class="doccomment">/// # Panics</span> <span class="doccomment">///</span> <span class="doccomment">/// `format!` panics if a formatting trait implementation returns an error.</span> <span class="doccomment">/// This indicates an incorrect implementation</span> <span class="doccomment">/// since `fmt::Write for String` never returns an error itself.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// format!("test");</span> <span class="doccomment">/// format!("hello {}", "world!");</span> <span class="doccomment">/// format!("x = {}, y = {y}", 10, y = 30);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">macro_export</span>]</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">format</span> { ($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">arg</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=></span> (<span class="macro-nonterminal">$</span><span class="kw">crate</span>::<span class="macro-nonterminal">fmt</span>::<span class="ident">format</span>(<span class="macro">format_args</span><span class="macro">!</span>($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">arg</span>)<span class="kw-2">*</span>))) } </pre> </section> <section id='search' class="content hidden"></section> <section class="footer"></section> <aside id="help" class="hidden"> <div> <h1 class="hidden">Help</h1> <div class="shortcuts"> <h2>Keyboard Shortcuts</h2> <dl> <dt><kbd>?</kbd></dt> <dd>Show this help dialog</dd> <dt><kbd>S</kbd></dt> <dd>Focus the search field</dd> <dt><kbd>↑</kbd></dt> <dd>Move up in search results</dd> <dt><kbd>↓</kbd></dt> <dd>Move down in search results</dd> <dt><kbd>↹</kbd></dt> <dd>Switch tab</dd> <dt><kbd>⏎</kbd></dt> <dd>Go to active search result</dd> <dt><kbd>+</kbd></dt> <dd>Expand all sections</dd> <dt><kbd>-</kbd></dt> <dd>Collapse all sections</dd> </dl> </div> <div class="infos"> <h2>Search Tricks</h2> <p> Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type. </p> <p> Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>. </p> <p> Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>) </p> </div> </div> </aside> <script> window.rootPath = "../../"; window.currentCrate = "alloc"; </script> <script src="../../main.js"></script> <script defer src="../../search-index.js"></script> </body> </html>