124 lines
9.9 KiB
HTML
124 lines
9.9 KiB
HTML
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<title>std::experimental::to_array</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_experimental_to_array 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::experimental::</span>to_array</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-experimental.html">experimental</a></span></div>
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<div>定义于头文件 <code><a href="https://zh.cppreference.com/mwiki/index.php?title=cpp/header/experimental/array&action=edit&redlink=1" class="new" title="cpp/header/experimental/array（页面不存在）"><experimental/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, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1"><</span><a href="cpp-types-remove_cv.html"><span class="kw597">std::<span class="me2">remove_cv_t</span></span></a><span class="sy1"><</span>T<span class="sy1">></span>, N<span class="sy1">></span> to_array<span class="br0">(</span>T <span class="br0">(</span><span class="sy3">&</span>a<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-libfund-ts-2 t-mark-ts">(库基础 TS v2)</span></td>
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<p>从内建数组 <code>a</code> 创建 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 。 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 的元素从 <code>a</code> 的对应元素复制初始化。</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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<tr class="t-par">
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<td>a</td>
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<td>-</td>
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<td>用于初始化 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 的内建数组</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>从 <code>a</code> 的元素复制初始化对应元素的 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 对象。</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, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a>... <span class="me1">I</span><span class="sy1">></span>
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<span class="kw4">constexpr</span> <a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1"><</span><a href="cpp-types-remove_cv.html"><span class="kw597">std::<span class="me2">remove_cv_t</span></span></a><span class="sy1"><</span>T<span class="sy1">></span>, N<span class="sy1">></span>
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to_array_impl<span class="br0">(</span>T <span class="br0">(</span><span class="sy3">&</span>a<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span>, <a href="cpp-utility-integer_sequence.html"><span class="kw1108">std::<span class="me2">index_sequence</span></span></a><span class="sy1"><</span>I...<span class="sy1">></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="br0">{</span>a<span class="br0">[</span>I<span class="br0">]</span>...<span class="br0">}</span> <span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</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, <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="kw4">constexpr</span> <a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1"><</span><a href="cpp-types-remove_cv.html"><span class="kw597">std::<span class="me2">remove_cv_t</span></span></a><span class="sy1"><</span>T<span class="sy1">></span>, N<span class="sy1">></span> to_array<span class="br0">(</span>T <span class="br0">(</span><span class="sy3">&</span>a<span class="br0">)</span><span class="br0">[</span>N<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> detail<span class="sy4">::</span><span class="me2">to_array_impl</span><span class="br0">(</span>a, <a href="cpp-utility-integer_sequence.html"><span class="kw1110">std::<span class="me2">make_index_sequence</span></span></a><span class="sy1"><</span>N<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></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 class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <cstdlib></span>
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<span class="co2">#include <cassert></span>
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<span class="co2">#include <experimental/array></span>
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<span class="co2">#include <unistd.h></span>
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<span class="co1">// mkstemp(3) 可工作</span>
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<span class="kw1">template</span> <span class="sy1"><</span><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="kw4">int</span> tempfd<span class="br0">(</span><span class="kw4">char</span> <span class="kw4">const</span> <span class="br0">(</span><span class="sy3">&</span>tmpl<span class="br0">)</span><span class="br0">[</span>N<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> s <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">experimental</span><span class="sy4">::</span><span class="me2">to_array</span><span class="br0">(</span>tmpl<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">int</span> fd <span class="sy1">=</span> mkstemp<span class="br0">(</span>s.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>fd <span class="sy3">!</span><span class="sy1">=</span> <span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span>
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unlink<span class="br0">(</span>s.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">return</span> fd<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">int</span> fd <span class="sy1">=</span> tempfd<span class="br0">(</span><span class="st0">"/tmp/test.XXXXXX"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">int</span> rt <span class="sy1">=</span> close<span class="br0">(</span>fd<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>rt <span class="sy1">==</span> <span class="nu0">0</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</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 class="t-dsc-member-div">
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<div><a href="cpp-experimental-make_array.html"><span class="t-lines"><span>make_array</span></span></a></div>
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</div>
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<td>创建 <span class="t-lc"><a href="cpp-container-array.html">std::array</a></span> 对象，从参数推导出其大小和可选的元素类型<br />
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<span class="t-mark">(函数模板)</span></td>
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</div>
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<div class="visualClear"></div>
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