133 lines
10 KiB
HTML
133 lines
10 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::make_pair</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_utility_pair_make_pair skin-cppreference2 action-view cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>make_pair</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-utility.html">utility</a>‎ | <a href="cpp-utility-pair.html">pair</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dsc-header">
|
|
<td>
|
|
<div>定义于头文件 <code><a href="cpp-header-utility.html"><utility></a></code></div>
|
|
</td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
<tbody class="t-dcl-rev">
|
|
<tr class="t-dcl t-until-cxx11">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T1, <span class="kw1">class</span> T2 <span class="sy1">></span><br />
|
|
<a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>T1,T2<span class="sy1">></span> make_pair<span class="br0">(</span> T1 t, T2 u <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-until-cxx11">(C++11 前)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx11 t-until-cxx14">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T1, <span class="kw1">class</span> T2 <span class="sy1">></span><br />
|
|
<a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>V1,V2<span class="sy1">></span> make_pair<span class="br0">(</span> T1<span class="sy3">&&</span> t, T2<span class="sy3">&&</span> u <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
|
|
<span class="t-mark-rev t-until-cxx14">(C++14 前)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx14">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T1, <span class="kw1">class</span> T2 <span class="sy1">></span><br />
|
|
<span class="kw4">constexpr</span> <a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>V1,V2<span class="sy1">></span> make_pair<span class="br0">(</span> T1<span class="sy3">&&</span> t, T2<span class="sy3">&&</span> u <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td>
|
|
</tr>
|
|
</tbody>
|
|
<tbody>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>构造 <span class="t-lc"><a href="cpp-utility-pair.html">std::pair</a></span> 对象,从参数类型推导目标类型。</p>
|
|
<table class="t-rev-begin">
|
|
<tr class="t-rev t-since-cxx11">
|
|
<td>
|
|
<p>推导结果类型 <code>V1</code> 与 <code>V2</code> 是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-decay.html"><span class="kw628">std::<span class="me2">decay</span></span></a><span class="sy1"><</span>T1<span class="sy1">></span><span class="sy4">::</span><span class="me2">type</span></span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-decay.html"><span class="kw628">std::<span class="me2">decay</span></span></a><span class="sy1"><</span>T2<span class="sy1">></span><span class="sy4">::</span><span class="me2">type</span></span></span> (应用到按值传递的函数参数的通常类型变换),除非应用 <span class="t-lc"><a href="cpp-types-decay.html">std::decay</a></span> 到某类型 <code>X</code> 产生 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1"><</span>X<span class="sy1">></span></span></span> ,此情况下推导结果类型是 <code>X&</code> 。</p>
|
|
</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>t, u</td>
|
|
<td>-</td>
|
|
<td>构造 pair 所用的值</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p>含有指定值的 <span class="t-lc"><a href="cpp-utility-pair.html">std::pair</a></span> 对象。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <utility></span>
|
|
<span class="co2">#include <functional></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw4">int</span> n <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>
|
|
<span class="kw4">int</span> a<span class="br0">[</span><span class="nu0">5</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span><span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<span class="co1">// 从二个 int 建造 pair</span>
|
|
<span class="kw4">auto</span> p1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">make_pair</span><span class="br0">(</span>n, a<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"The value of p1 is "</span>
|
|
<span class="sy1"><<</span> <span class="st0">"("</span> <span class="sy1"><<</span> p1.<span class="me1">first</span> <span class="sy1"><<</span> <span class="st0">", "</span> <span class="sy1"><<</span> p1.<span class="me1">second</span> <span class="sy1"><<</span> <span class="st0">")<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
|
|
<span class="co1">// 从到 int 的引用和数组(退化成指针)建造 pair</span>
|
|
<span class="kw4">auto</span> p2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">make_pair</span><span class="br0">(</span><a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>n<span class="br0">)</span>, a<span class="br0">)</span><span class="sy4">;</span>
|
|
n <span class="sy1">=</span> <span class="nu0">7</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"The value of p2 is "</span>
|
|
<span class="sy1"><<</span> <span class="st0">"("</span> <span class="sy1"><<</span> p2.<span class="me1">first</span> <span class="sy1"><<</span> <span class="st0">", "</span> <span class="sy1"><<</span> <span class="sy2">*</span><span class="br0">(</span>p2.<span class="me1">second</span> <span class="sy2">+</span> <span class="nu0">2</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">")<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出:</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">The value of p1 is (1, 2)
|
|
The value of p2 is (7, 3)</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-utility-functional-unwrap_reference.html"><span class="t-lines"><span>unwrap_reference</span><span>unwrap_ref_decay</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>获取包装于 <span class="t-lc"><a href="cpp-utility-functional-reference_wrapper.html">std::reference_wrapper</a></span> 的引用类型<br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|