79 lines
4.3 KiB
HTML
79 lines
4.3 KiB
HTML
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<title>std::same_as</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_concepts_same_as 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>same_as</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-concepts.html">concepts</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-concepts.html"><concepts></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> T, <span class="kw1">class</span> U <span class="sy1">></span><br />
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concept same_as <span class="sy1">=</span> <span class="coMULTI">/* see below */</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p>概念 <code>same_as<T, U></code> 若且唯若 <code>T</code> 与 <code>U</code> 代表同一类型才得到满足。</p>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">same_as</span><span class="sy1"><</span>T, U<span class="sy1">></span></span></span> 包含 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">same_as</span><span class="sy1"><</span>U, T<span class="sy1">></span></span></span> ，反之亦然。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="kw1">namespace</span> detail <span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T, <span class="kw1">class</span> U <span class="sy1">></span>
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concept SameHelper <span class="sy1">=</span> <a href="cpp-types-is_same.html"><span class="kw589">std::<span class="me2">is_same_v</span></span></a><span class="sy1"><</span>T, U<span class="sy1">></span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T, <span class="kw1">class</span> U <span class="sy1">></span>
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concept same_as <span class="sy1">=</span> detail<span class="sy4">::</span><span class="me2">SameHelper</span><span class="sy1"><</span>T, U<span class="sy1">></span> <span class="sy3">&&</span> detail<span class="sy4">::</span><span class="me2">SameHelper</span><span class="sy1"><</span>U, T<span class="sy1">></span><span class="sy4">;</span></pre></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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<div><a href="cpp-types-is_same.html"><span class="t-lines"><span>is_same</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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<td>检查两个类型是否相同<br />
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<span class="t-mark">(类模板)</span></td>
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