325 lines
21 KiB
HTML
325 lines
21 KiB
HTML
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<title>std::tuple</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_utility_tuple skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>tuple</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-utility.html">utility</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-tuple.html"><tuple></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">></span><br />
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<span class="kw1">class</span> tuple<span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<p>类模板 <code>std::tuple</code> 是固定大小的异类值汇集。它是 <span class="t-lc"><a href="cpp-utility-pair.html">std::pair</a></span> 的推广。</p>
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<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_destructible.html"><span class="kw564">std::<span class="me2">is_trivially_destructible</span></span></a><span class="sy1"><</span>Ti<span class="sy1">></span><span class="sy4">::</span><span class="me2">value</span></span></span> 对 <code>Types</code> 中的每个 <code>Ti</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，则 <code>tuple</code> 的析构函数为平凡。</p>
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<h3><span class="mw-headline" id=".E6.A8.A1.E6.9D.BF.E5.BD.A2.E5.8F.82">模板形参</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>Types...</td>
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<td>-</td>
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<td><code>tuple</code> 所存储的元素的类型。支持空列表。</td>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-utility-tuple-tuple.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造新的 <code>tuple</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</td>
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<td>赋值一个 <code>tuple</code> 的内容给另一个<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-swap.html"><span class="t-lines"><span>swap</span></span></a></div>
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</div>
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</td>
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<td>交换两个 <code>tuple</code> 的内容<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E9.9D.9E.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">非成员函数</span></h3>
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<table class="t-dsc-begin">
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<div><a href="cpp-utility-tuple-make_tuple.html"><span class="t-lines"><span>make_tuple</span></span></a></div>
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</div>
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</td>
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<td>创建一个 <code>tuple</code> 对象，其类型根据各实参类型定义<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-tie.html"><span class="t-lines"><span>tie</span></span></a></div>
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</div>
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</td>
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<td>创建左值引用的 <code>tuple</code>，或将 tuple 解包为独立对象<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-forward_as_tuple.html"><span class="t-lines"><span>forward_as_tuple</span></span></a></div>
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</div>
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</td>
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<td>创建<a href="cpp-language-reference.html#.E8.BD.AC.E5.8F.91.E5.BC.95.E7.94.A8">转发引用</a>的 <code>tuple</code><br />
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<span class="t-mark">(函数模板)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-tuple_cat.html"><span class="t-lines"><span>tuple_cat</span></span></a></div>
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</div>
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</td>
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<td>通过连接任意数量的元组来创建一个<code>tuple</code><br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-get.html"><span class="t-lines"><span>std::get<span class="t-dsc-small">(std::tuple)</span></span></span></a></div>
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</div>
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</td>
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<td>元组式访问指定的元素<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-operator_cmp.html"><span class="t-lines"><span>operator==</span><span>operator!=</span><span>operator<</span><span>operator<=</span><span>operator></span><span>operator>=</span><span>operator<=></span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>按字典顺序比较 tuple 中的值<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-swap2.html"><span class="t-lines"><span>std::swap<span class="t-dsc-small">(std::tuple)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>特化 <span class="t-lc"><a href="cpp-algorithm-swap.html">std::swap</a></span> 算法<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BE.85.E5.8A.A9.E7.B1.BB">辅助类</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-tuple_size.html"><span class="t-lines"><span>std::tuple_size<span class="t-dsc-small"><std::tuple></span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>在编译时获得 <code>tuple</code> 的大小<br />
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<span class="t-mark">(类模板特化)</span></td>
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</tr>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-tuple_element.html"><span class="t-lines"><span>std::tuple_element<span class="t-dsc-small"><std::tuple></span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>获得指定元素的类型<br />
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<span class="t-mark">(类模板特化)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-uses_allocator.html"><span class="t-lines"><span>std::uses_allocator<span class="t-dsc-small"><std::tuple></span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>特化 <span class="t-lc"><a href="cpp-memory-uses_allocator.html">std::uses_allocator</a></span> 类型特征<br />
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<span class="t-mark">(类模板特化)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-tuple-ignore.html"><span class="t-lines"><span>ignore</span></span></a></div>
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</div>
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</td>
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<td>用 <a href="cpp-utility-tuple-tie.html"><tt>tie</tt></a> 解包 <code>tuple</code> 时用来跳过元素的占位符<br />
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<span class="t-mark">(常量)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.8E.A8.E5.AF.BC.E6.8C.87.E5.BC.95.28C.2B.2B17_.E8.B5.B7.29"><a href="cpp-utility-tuple-deduction_guides.html">推导指引</a><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></span></h3>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p><a rel="nofollow" class="external text" href="https://wg21.link/N4387">N4387</a> （作为对 C++11 的缺陷报告应用）前，函数不能用复制列表初始化返回 <code>tuple</code> ：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1">std<span class="sy4">::</span><span class="me2">tuple</span><span class="sy1"><</span><span class="kw4">int</span>, <span class="kw4">int</span><span class="sy1">></span> foo_tuple<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <span class="br0">{</span><span class="nu0">1</span>, <span class="sy2">-</span><span class="nu0">1</span><span class="br0">}</span><span class="sy4">;</span> <span class="co1">// N4387 前错误</span>
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<span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">tuple</span><span class="sy1"><</span><span class="kw4">int</span>, <span class="kw4">int</span><span class="sy1">></span><span class="br0">{</span><span class="nu0">1</span>, <span class="sy2">-</span><span class="nu0">1</span><span class="br0">}</span><span class="sy4">;</span> <span class="co1">// 始终有效</span>
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<span class="kw1">return</span> <a href="cpp-utility-tuple-make_tuple.html"><span class="kw1111">std::<span class="me2">make_tuple</span></span></a><span class="br0">(</span><span class="nu0">1</span>, <span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 始终有效</span>
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<span class="br0">}</span></pre></div>
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</div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <tuple></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <string></span>
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<span class="co2">#include <stdexcept></span>
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std<span class="sy4">::</span><span class="me2">tuple</span><span class="sy1"><</span><span class="kw4">double</span>, <span class="kw4">char</span>, <a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy1">></span> get_student<span class="br0">(</span><span class="kw4">int</span> id<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">if</span> <span class="br0">(</span>id <span class="sy1">==</span> <span class="nu0">0</span><span class="br0">)</span> <span class="kw1">return</span> <a href="cpp-utility-tuple-make_tuple.html"><span class="kw1111">std::<span class="me2">make_tuple</span></span></a><span class="br0">(</span><span class="nu16">3.8</span>, <span class="st0">'A'</span>, <span class="st0">"Lisa Simpson"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>id <span class="sy1">==</span> <span class="nu0">1</span><span class="br0">)</span> <span class="kw1">return</span> <a href="cpp-utility-tuple-make_tuple.html"><span class="kw1111">std::<span class="me2">make_tuple</span></span></a><span class="br0">(</span><span class="nu16">2.9</span>, <span class="st0">'C'</span>, <span class="st0">"Milhouse Van Houten"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>id <span class="sy1">==</span> <span class="nu0">2</span><span class="br0">)</span> <span class="kw1">return</span> <a href="cpp-utility-tuple-make_tuple.html"><span class="kw1111">std::<span class="me2">make_tuple</span></span></a><span class="br0">(</span><span class="nu16">1.7</span>, <span class="st0">'D'</span>, <span class="st0">"Ralph Wiggum"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">throw</span> <a href="cpp-error-invalid_argument.html"><span class="kw769">std::<span class="me2">invalid_argument</span></span></a><span class="br0">(</span><span class="st0">"id"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">auto</span> student0 <span class="sy1">=</span> get_student<span class="br0">(</span><span class="nu0">0</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"ID: 0, "</span>
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<span class="sy1"><<</span> <span class="st0">"GPA: "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1"><</span><span class="nu0">0</span><span class="sy1">></span><span class="br0">(</span>student0<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">", "</span>
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<span class="sy1"><<</span> <span class="st0">"grade: "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1"><</span><span class="nu0">1</span><span class="sy1">></span><span class="br0">(</span>student0<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">", "</span>
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<span class="sy1"><<</span> <span class="st0">"name: "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1"><</span><span class="nu0">2</span><span class="sy1">></span><span class="br0">(</span>student0<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="kw4">double</span> gpa1<span class="sy4">;</span>
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<span class="kw4">char</span> grade1<span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a> name1<span class="sy4">;</span>
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<a href="cpp-utility-tuple-tie.html"><span class="kw1112">std::<span class="me2">tie</span></span></a><span class="br0">(</span>gpa1, grade1, name1<span class="br0">)</span> <span class="sy1">=</span> get_student<span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"ID: 1, "</span>
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<span class="sy1"><<</span> <span class="st0">"GPA: "</span> <span class="sy1"><<</span> gpa1 <span class="sy1"><<</span> <span class="st0">", "</span>
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<span class="sy1"><<</span> <span class="st0">"grade: "</span> <span class="sy1"><<</span> grade1 <span class="sy1"><<</span> <span class="st0">", "</span>
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<span class="sy1"><<</span> <span class="st0">"name: "</span> <span class="sy1"><<</span> name1 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="co1">// C++17 结构化绑定：</span>
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<span class="kw4">auto</span> <span class="br0">[</span> gpa2, grade2, name2 <span class="br0">]</span> <span class="sy1">=</span> get_student<span class="br0">(</span><span class="nu0">2</span><span class="br0">)</span><span class="sy4">;</span>
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|
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"ID: 2, "</span>
|
|
<span class="sy1"><<</span> <span class="st0">"GPA: "</span> <span class="sy1"><<</span> gpa2 <span class="sy1"><<</span> <span class="st0">", "</span>
|
|
<span class="sy1"><<</span> <span class="st0">"grade: "</span> <span class="sy1"><<</span> grade2 <span class="sy1"><<</span> <span class="st0">", "</span>
|
|
<span class="sy1"><<</span> <span class="st0">"name: "</span> <span class="sy1"><<</span> name2 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
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</div>
|
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
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<div class="text source-text">
|
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<pre class="de1">ID: 0, GPA: 3.8, grade: A, name: Lisa Simpson
|
|
ID: 1, GPA: 2.9, grade: C, name: Milhouse Van Houten
|
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ID: 2, GPA: 1.7, grade: D, name: Ralph Wiggum</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
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|
<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
|
|
<table class="dsctable" style="font-size:0.8em">
|
|
<tr>
|
|
<th>DR</th>
|
|
<th>应用于</th>
|
|
<th>出版时的行为</th>
|
|
<th>正确行为</th>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2796">LWG 2796</a></td>
|
|
<td>C++11</td>
|
|
<td><code>tuple</code> 的析构函数的平凡性未指明</td>
|
|
<td>已指明</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
|
|
<div class="t-ref-std-c++20">
|
|
<ul>
|
|
<li>C++20 标准（ISO/IEC 14882:2020）：</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>20.5 Tuples [tuple]</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
<div class="t-ref-std-c++17">
|
|
<ul>
|
|
<li>C++17 标准（ISO/IEC 14882:2017）：</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>23.5 Tuples [tuple]</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
<div class="t-ref-std-c++14">
|
|
<ul>
|
|
<li>C++14 标准（ISO/IEC 14882:2014）：</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>20.4 Tuples [tuple]</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
<div class="t-ref-std-c++11">
|
|
<ul>
|
|
<li>C++11 标准（ISO/IEC 14882:2011）：</li>
|
|
</ul>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>20.4 Tuples [tuple]</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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