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<title>std::tuple_size&lt;std::tuple&gt;</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>tuple_size<small>&lt;std::tuple&gt;</small></h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a>&lrm; | <a href="cpp-utility-tuple.html">tuple</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-tuple.html">&lt;tuple&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw1">struct</span> tuple_size<span class="sy1">&lt;</span> <a href="cpp-utility-tuple.html"><span class="kw1098">std::<span class="me2">tuple</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;</span> <span class="sy1">&gt;</span><br /></p>
&nbsp; &nbsp; <span class="sy4">:</span> <a href="cpp-types-integral_constant.html"><span class="kw647">std::<span class="me2">integral_constant</span></span></a><span class="sy1">&lt;</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a>, sizeof...<span class="br0">(</span>Types<span class="br0">)</span><span class="sy1">&gt;</span> <span class="br0">{</span> <span class="br0">}</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#25552;&#20379;&#23545; tuple &#20013;&#20803;&#32032;&#25968;&#37327;&#30340;&#35775;&#38382;&#65292;&#20316;&#20026;&#32534;&#35793;&#26102;&#24120;&#37327;&#34920;&#36798;&#24335;&#12290;</p>
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<h2><span class="mw-headline" id=".E7.BB.A7.E6.89.BF.E8.87.AA_std::integral_constant">&#32487;&#25215;&#33258; <a href="cpp-types-integral_constant.html"><span style="font-size:0.7em; line-height:130%">std::</span>integral_constant</a></span></h2>
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.B8.B8.E9.87.8F">&#25104;&#21592;&#24120;&#37327;</span></h3>
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<div><span class="t-lines"><span>value</span></span></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#38745;&#24577;]</span></span></span></div>
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<td><code>sizeof...(Types)</code><br />
<span class="t-mark">(&#20844;&#24320;&#38745;&#24577;&#25104;&#21592;&#24120;&#37327;)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">&#25104;&#21592;&#20989;&#25968;</span></h3>
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<div><span class="t-lines"><span>operator std::size_t</span></span></div>
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<td>&#36716;&#25442;&#23545;&#35937;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a></span></span> &#65292;&#36820;&#22238; <code>value</code><br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><span class="t-lines"><span>operator()</span></span></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
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<td>&#36820;&#22238; <code>value</code><br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">&#25104;&#21592;&#31867;&#22411;</span></h3>
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<td>&#31867;&#22411;</td>
<td>&#23450;&#20041;</td>
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<td><code>value_type</code></td>
<td><code>std::size_t</code></td>
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<td><code>type</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-integral_constant.html"><span class="kw647">std::<span class="me2">integral_constant</span></span></a><span class="sy1">&lt;</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a>, value<span class="sy1">&gt;</span></span></span></td>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;tuple&gt;</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T<span class="sy1">&gt;</span>
<span class="kw4">void</span> test<span class="br0">(</span>T value<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">int</span> a<span class="br0">[</span>std<span class="sy4">::</span><span class="me2">tuple_size_v</span><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="br0">]</span><span class="sy4">;</span> <span class="co1">// &#33021;&#29992;&#20110;&#32534;&#35793;&#26102;</span>
<a href="cpp-io-cout.html"><span class="kw1756">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">tuple_size</span><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="br0">{</span><span class="br0">}</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// &#25110;&#36816;&#34892;&#26102;</span>
<span class="sy1">&lt;&lt;</span> sizeof a <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> sizeof value <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
test<span class="br0">(</span><a href="cpp-utility-tuple-make_tuple.html"><span class="kw1110">std::<span class="me2">make_tuple</span></span></a><span class="br0">(</span><span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu16">3.14</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
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<pre class="de1">3 12 16</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<td><a href="cpp-language-structured_binding.html">&#32467;&#26500;&#21270;&#32465;&#23450;</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span></td>
<td>&#32465;&#23450;&#25351;&#23450;&#30340;&#21517;&#23383;&#21040;&#21021;&#22987;&#21270;&#22120;&#30340;&#23376;&#23545;&#35937;&#25110;&#20803;&#32452;&#20803;&#32032;</td>
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<div><a href="cpp-utility-tuple_size.html"><span class="t-lines"><span>tuple_size</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>&#33719;&#24471;&#20803;&#32452;&#24335;&#31867;&#22411;&#30340;&#20803;&#32032;&#25968;<br />
<span class="t-mark">(&#31867;&#27169;&#26495;)</span></td>
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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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<td>&#20803;&#32452;&#24335;&#35775;&#38382;&#25351;&#23450;&#30340;&#20803;&#32032;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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