63 lines
6.4 KiB
HTML
63 lines
6.4 KiB
HTML
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<title>std::experimental::ranges::OutputIterator</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_experimental_ranges_iterator_OutputIterator 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::ranges::</span>OutputIterator</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-experimental.html">experimental</a>‎ | <a href="cpp-experimental-ranges.html">ranges</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-experimental-ranges-iterator.html"><experimental/ranges/iterator></a></code></div>
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<tr class="t-dcl t-since-ranges">
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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> I, <span class="kw1">class</span> T<span class="sy1">></span><br /></span>
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<p>concept <span class="kw4">bool</span> OutputIterator <span class="sy1">=</span><br />
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<a href="cpp-experimental-ranges-iterator-Iterator.html"><span class="kw2566">ranges::<span class="me2">Iterator</span></span></a><span class="sy1"><</span>I<span class="sy1">></span> <span class="sy3">&&</span> <a href="cpp-experimental-ranges-iterator-Writable.html"><span class="kw2563">ranges::<span class="me2">Writable</span></span></a><span class="sy1"><</span>I, T<span class="sy1">></span> <span class="sy3">&&</span><br />
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requires<span class="br0">(</span>I i, T<span class="sy3">&&</span> t<span class="br0">)</span> <span class="br0">{</span><br />
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<span class="sy2">*</span>i<span class="sy2">++</span> <span class="sy1">=</span> <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="br0">(</span>t<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 不要求保持相等性</span><br /></p>
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<span class="br0">}</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-ranges-ts t-mark-ts">(范围 TS)</span></td>
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<p><code>OutputIterator</code> 概念是 <a href="cpp-experimental-ranges-iterator-Iterator.html"><code>Iterator</code></a> 的细化，添加了能用于写入值类型和值类别为 <code>T</code> 所编码的值的要求（经由 <a href="cpp-experimental-ranges-iterator-Writable.html"><code>Writable</code></a> ）。不要求 <a href="cpp-experimental-ranges-concepts-EqualityComparable.html"><code>EqualityComparable</code></a> 。</p>
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<p>令 <code>E</code> 为满足 <span class="t-c"><span class="mw-geshi cpp source-cpp">decltype<span class="br0">(</span><span class="br0">(</span>E<span class="br0">)</span><span class="br0">)</span></span></span> 为 <code>T</code> 的表达式，而 <code>i</code> 为 <code>I</code> 类型的可解引用对象。 <code>OutputIterator<I, T></code> 仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>i<span class="sy2">++</span> <span class="sy1">=</span> E<span class="sy4">;</span></span></span> 拥有等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>i <span class="sy1">=</span> E<span class="sy4">;</span> <span class="sy2">++</span>i<span class="sy4">;</span></span></span> 的效果才得到满足</p>
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<h3><span class="mw-headline" id=".E7.9B.B8.E7.AD.89.E6.80.A7.E4.BF.9D.E6.8C.81">相等性保持</span></h3>
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<p>若表达式对给定的相等输入产生相等输出，则它<i>保持相等性</i>。</p>
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<ul>
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<li>表达式的输入由其运算数组成。</li>
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<li>表达式的输出由其结果和表达式所修改的所有运算数（若存在）组成。</li>
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</ul>
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<p>进一步要求每个要求保持相等性的表达式都<i>稳定</i>：这种表达式带相同输入对象的二次求值必须拥有相等的输出，而无任何对这些输入对象的显式中间修改。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>不同于 C++ 标准中的输出迭代器要求，范围 TS 中的 <code>OutputIterator</code> 不要求定义迭代器类别标签。</p>
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<p>输出迭代器上的算法应该为单趟。</p>
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