153 lines
12 KiB
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153 lines
12 KiB
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<title>std::tuple_cat</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_utility_tuple_tuple_cat 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_cat</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-utility.html">utility</a>‎ | <a href="cpp-utility-tuple.html">tuple</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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<td></td>
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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">Tuples</span> <span class="sy1">></span><br />
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<a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1"><</span>CTypes...<span class="sy1">></span> tuple_cat<span class="br0">(</span>Tuples<span class="sy3">&&</span>... <span class="me1">args</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx14">(C++14 前)</span></td>
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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">Tuples</span> <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1"><</span>CTypes...<span class="sy1">></span> tuple_cat<span class="br0">(</span>Tuples<span class="sy3">&&</span>... <span class="me1">args</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td>
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<p>构造所有 <code>args</code> 中的 tuple 所连接成 tuple 。</p>
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<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-decay.html"><span class="kw629">std::<span class="me2">decay_t</span></span></a><span class="sy1"><</span>Tuples<span class="sy1">></span>...</span></span> 中的任何类型不是 <span class="t-lc"><a href="cpp-utility-tuple.html">std::tuple</a></span> 的特化则行为未定义。然而，实现可以选择支持遵循仿 tuple 协议的类型（例如 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 与 <span class="t-lc"><a href="cpp-utility-pair.html">std::pair</a></span> ）。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<td>args</td>
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<td>-</td>
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<td>要连接的零或更多 tuple</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p><span class="t-lc"><a href="cpp-utility-tuple.html">std::tuple</a></span> 对象，由所有参数 tuple 的所有元素组成，对于每个独立元素构造自 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">get</span><span class="sy1"><</span>i<span class="sy1">></span><span class="br0">(</span><a href="cpp-utility-forward.html"><span class="kw1116">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Ti<span class="sy1">></span><span class="br0">(</span>arg<span class="br0">)</span><span class="br0">)</span></span></span> 。</p>
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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 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 <iostream></span>
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<span class="co2">#include <tuple></span>
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<span class="co2">#include <string></span>
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<span class="co1">// 打印任何大小 tuple 的帮助函数</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Tuple, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">></span>
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<span class="kw1">struct</span> TuplePrinter <span class="br0">{</span>
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<span class="kw4">static</span> <span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">const</span> Tuple<span class="sy3">&</span> t<span class="br0">)</span>
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<span class="br0">{</span>
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TuplePrinter<span class="sy1"><</span>Tuple, N<span class="sy2">-</span><span class="nu0">1</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">print</span><span class="br0">(</span>t<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">", "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1"><</span>N<span class="sy2">-</span><span class="nu0">1</span><span class="sy1">></span><span class="br0">(</span>t<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Tuple<span class="sy1">></span>
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<span class="kw1">struct</span> TuplePrinter<span class="sy1"><</span>Tuple, <span class="nu0">1</span><span class="sy1">></span> <span class="br0">{</span>
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<span class="kw4">static</span> <span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">const</span> Tuple<span class="sy3">&</span> t<span class="br0">)</span>
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<span class="br0">{</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> 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>t<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">></span>
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<span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">const</span> <a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1"><</span>Args...<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span>
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<span class="br0">{</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">"("</span><span class="sy4">;</span>
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TuplePrinter<span class="sy1"><</span>decltype<span class="br0">(</span>t<span class="br0">)</span>, sizeof...<span class="br0">(</span>Args<span class="br0">)</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">print</span><span class="br0">(</span>t<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">")<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="co1">// 结束帮助函数</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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<a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1"><</span><span class="kw4">int</span>, <a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a>, <span class="kw4">float</span><span class="sy1">></span> t1<span class="br0">(</span><span class="nu0">10</span>, <span class="st0">"Test"</span>, <span class="nu16">3.14</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">int</span> n <span class="sy1">=</span> <span class="nu0">7</span><span class="sy4">;</span>
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<span class="kw4">auto</span> t2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">tuple_cat</span><span class="br0">(</span>t1, <a href="cpp-utility-tuple-make_tuple.html"><span class="kw1112">std::<span class="me2">make_tuple</span></span></a><span class="br0">(</span><span class="st0">"Foo"</span>, <span class="st0">"bar"</span><span class="br0">)</span>, t1, <a href="cpp-utility-tuple-tie.html"><span class="kw1113">std::<span class="me2">tie</span></span></a><span class="br0">(</span>n<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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n <span class="sy1">=</span> <span class="nu0">10</span><span class="sy4">;</span>
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print<span class="br0">(</span>t2<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></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">(10, Test, 3.14, Foo, bar, 10, Test, 3.14, 10)</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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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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<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>
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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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</table>
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</div>
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<div class="visualClear"></div>
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