106 lines
7.0 KiB
HTML
106 lines
7.0 KiB
HTML
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ranges::subrange<I,S,K>::</span>prev</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-ranges.html">ranges</a>‎ | <a href="cpp-ranges-subrange.html">subrange</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="br0">[</span><span class="br0">[</span>nodiscard<span class="br0">]</span><span class="br0">]</span> <span class="kw4">constexpr</span> subrange prev<span class="br0">(</span> std<span class="sy4">::</span><span class="me2">iter_difference_t</span><span class="sy1"><</span>I<span class="sy1">></span> n <span class="sy1">=</span> <span class="nu0">1</span> <span class="br0">)</span> <span class="kw4">const</span><br />
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requires std<span class="sy4">::</span><span class="me2">bidirectional_iterator</span><span class="sy1"><</span>I<span class="sy1">></span><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>获得在 <code>n >= 0</code> 或 <code>n < 0</code> 时分别为迭代器相对于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 的自减 <code>n</code> 次或自增 <code>min(-n, <a href="cpp-ranges-subrange-size.html">size()</a>)</code> 次的 <code>subrange</code> 。</p>
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<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">auto</span> tmp <span class="sy1">=</span> <span class="sy2">*</span>this<span class="sy4">;</span> tmp.<span class="me1">advance</span><span class="br0">(</span><span class="sy2">-</span>n<span class="br0">)</span><span class="sy4">;</span> <span class="kw1">return</span> tmp<span class="sy4">;</span></span></span> 。若迭代器在成为不可自减值后被自减则行为未定义。</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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<td>n</td>
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<td>-</td>
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<td>迭代器的最小自减次数</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>在 <code>n >= 0</code> 或 <code>n < 0</code> 时分别为迭代器相对于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 的自减 <code>n</code> 次或自增 <code>min(-n, <a href="cpp-ranges-subrange-size.html">size()</a>)</code> 次的 <code>subrange</code> 。</p>
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<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
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<p>通常在 <code>n >= 0</code> 为 <code>n < 0</code> 或时分别为迭代器上的 <code>n</code> 次自减或 <code>min(-n, <a href="cpp-ranges-subrange-size.html">size()</a>)</code> 次自增。</p>
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<p>若 <code>I</code> 实现 <a href="cpp-iterator-random_access_iterator.html"><code>random_access_iterator</code></a> ，且 <code>n >= 0</code> 或者 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">sized_sentinel_for</span><span class="sy1"><</span>S, I<span class="sy1">></span></span></span> 得到实现则为常数。</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-subrange-next.html"><span class="t-lines"><span>next</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>以给定距离前进迭代器并返回原 <code>subrange</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div><a href="cpp-ranges-subrange-advance.html"><span class="t-lines"><span>advance</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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</div>
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</td>
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<td>以给定距离前进迭代器<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<div class="t-dsc-member-div">
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<div><a href="cpp-iterator-prev.html"><span class="t-lines"><span>prev</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</td>
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<td>令迭代器自减<br />
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<span class="t-mark">(函数模板)</span></td>
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<div><a href="cpp-iterator-ranges-prev.html"><span class="t-lines"><span>ranges::prev</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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</div>
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</td>
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<td>自减迭代器给定的距离或到边界<br />
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<span class="t-mark">(niebloid)</span></td>
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