64 lines
4.3 KiB
HTML
64 lines
4.3 KiB
HTML
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<title>std::array 的推导指引</title>
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<h1 id="firstHeading" class="firstHeading"><code>std::array</code> 的推导指引</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-container.html">container</a>‎ | <a href="cpp-container-array.html">array</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-array.html"><array></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>... <span class="me1">U</span><span class="sy1">></span><br />
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array<span class="br0">(</span>T, U...<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">></span> array<span class="sy1"><</span>T, <span class="nu0">1</span> <span class="sy2">+</span> sizeof...<span class="br0">(</span>U<span class="br0">)</span><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<p>为 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 提供一个<a href="cpp-language-class_template_argument_deduction.html">推导指引</a>，以提供 <span class="t-lc"><a href="cpp-experimental-make_array.html">std::experimental::make_array</a></span> 对于从变长参数包构造 std::array 的等价物。</p>
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<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</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="sy3">&&</span> ...<span class="br0">)</span></span></span> 非 true 则程序为谬构。注意它在 <span class="t-c"><span class="mw-geshi cpp source-cpp">sizeof...<span class="br0">(</span>U<span class="br0">)</span></span></span> 为零时为 true 。</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="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <array></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">int</span> <span class="kw4">const</span> x <span class="sy1">=</span> <span class="nu0">10</span><span class="sy4">;</span>
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<a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a> a<span class="br0">{</span><span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">5</span>, x<span class="br0">}</span><span class="sy4">;</span> <span class="co1">// OK 创建 std::array<int, 5></span>
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<span class="co1">// std::array b{1, 2u}; // 错误，所有参数必须拥有相同类型</span>
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<span class="br0">}</span></pre></div>
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