69 lines
6.6 KiB
HTML
69 lines
6.6 KiB
HTML
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::experimental::ranges::</span>Iterator</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="sy1">></span><br /></span>
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<p>concept <span class="kw4">bool</span> Iterator <span class="sy1">=</span><br />
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requires<span class="br0">(</span>I i<span class="br0">)</span> <span class="br0">{</span><br />
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<span class="br0">{</span> <span class="sy2">*</span>i <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">></span> <span class="kw4">auto</span><span class="sy3">&&</span><span class="sy4">;</span> <span class="co1">// 要求： i 可解引用</span><br />
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<span class="br0">}</span> <span class="sy3">&&</span><br /></p>
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<a href="cpp-experimental-ranges-iterator-WeaklyIncrementable.html"><span class="kw2564">ranges::<span class="me2">WeaklyIncrementable</span></span></a><span class="sy1"><</span>I<span class="sy1">></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>Iterator</code> 概念组成迭代器分类学的基础；每个迭代器都满足 <code>Iterator</code> 要求。</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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<p>除非另外提醒，每个用于 <i>requires 表达式</i>中的表达式都要求保持相等性且稳定，而表达式的求值必须只修改其非常运算数。必须不修改常运算数。</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><code>Iterator</code> 自身仅指定解引用和自增迭代器的操作。大多数算法将要求额外操作：</p>
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<li>比较迭代器与哨位（见 <a href="cpp-experimental-ranges-iterator-Sentinel.html"><code>Sentinel</code></a> ）；</li>
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<li>从迭代器读取值（见 <a href="cpp-experimental-ranges-iterator-Readable.html"><code>Readable</code></a> 及 <a href="cpp-experimental-ranges-iterator-InputIterator.html"><code>InputIterator</code></a> ）；</li>
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<li>写入值到迭代器（见 <a href="cpp-experimental-ranges-iterator-Writable.html"><code>Writable</code></a> 及 <a href="cpp-experimental-ranges-iterator-OutputIterator.html"><code>OutputIterator</code></a> ）</li>
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<li>更丰富的迭代器动作集合（见 <a href="cpp-experimental-ranges-iterator-ForwardIterator.html"><code>ForwardIterator</code></a> 、 <a href="cpp-experimental-ranges-iterator-BidirectionalIterator.html"><code>BidirectionalIterator</code></a> 、 <a href="cpp-experimental-ranges-iterator-RandomAccessIterator.html"><code>RandomAccessIterator</code></a> ）</li>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">-</span><span class="sy1">></span> <span class="kw4">auto</span><span class="sy3">&&</span></span></span> 制约解引用的结果类型不能为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> 。</p>
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