101 lines
5.7 KiB
HTML
101 lines
5.7 KiB
HTML
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<title>std::ranges::dangling</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_ranges_dangling 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::ranges::</span>dangling</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-ranges.html">ranges</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-ranges.html"><ranges></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">struct</span> dangling<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><code>dangling</code> 是占位类型兼空类类型，与模板别名 <a href="cpp-ranges-borrowed_iterator_t.html"><tt>ranges::borrowed_iterator_t</tt></a> 及 <a href="cpp-ranges-borrowed_iterator_t.html"><tt>ranges::borrowed_subrange_t</tt></a> 一同使用。</p>
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<p>某些通常返回 <a href="cpp-ranges-range.html"><code>range</code></a> 的迭代器或子范围的<a href="cpp-algorithm-ranges.html">有制约算法</a>，在接收不实现 <a href="cpp-ranges-borrowed_range.html"><code>borrowed_range</code></a> 的特定的右值 <code>range</code> 参数时，将取而代之地返回 <code>dangling</code> 以避免潜在返回悬垂的结果。</p>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<h2><span class="mw-headline" id="std::ranges::dangling::dangling"><span style="font-size:0.7em; line-height:130%">std::ranges::dangling::</span>dangling</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> dangling<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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<td>(1)</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">Args</span><span class="sy1">></span><br />
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<span class="kw4">constexpr</span> dangling<span class="br0">(</span>Args<span class="sy3">&&</span>...<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="br0">}</span></span></div>
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<td>(2)</td>
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<div class="t-li1"><span class="t-li">1)</span> <code>dangling</code> 可平凡默认构造。</div>
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<div class="t-li1"><span class="t-li">2)</span> <code>dangling</code> 能从任意数量及任意非 void 类型的参数构造。构造自身无任何副作用。
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<p>换言之，在良构的非聚合初始化中以 <code>dangling</code> 替换类型（例如迭代器类型）后，所得的初始化亦为良构。</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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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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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-ranges-borrowed_iterator_t.html"><span class="t-lines"><span>ranges::borrowed_iterator_t</span><span>ranges::borrowed_subrange_t</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>获得塑造 <a href="cpp-ranges-borrowed_range.html"><code>borrowed_range</code></a> 的迭代器类型或子范围类型<br />
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<span class="t-mark">(别名模板)</span></td>
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