69 lines
6.6 KiB
HTML
69 lines
6.6 KiB
HTML
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<title>std::regex_traits<CharT>::transform</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_regex_regex_traits_transform 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::regex_traits<CharT>::</span>transform</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-regex.html">regex</a>‎ | <a href="cpp-regex-regex_traits.html">regex traits</a></span></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> ForwardIt <span class="sy1">></span><br />
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string_type transform<span class="br0">(</span> ForwardIt first, ForwardIt last<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<p>获得字符序列 <code>[first, last)</code> 的排序关键，满足若排序关键以 <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="sy1"><</span></span></span> 小于另一排序关键，则在当前感染的 locale 的对照顺序中，产生第一排序关键的字符序列优先于产生第二排序关键的字符序列。</p>
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<p>例如，在设置 regex 标志 <span class="t-lc"><a href="cpp-regex-syntax_option_type.html">std::regex_constants::collate</a></span> 时，若 <span class="t-c"><span class="mw-geshi cpp source-cpp">traits.<span class="me1">transform</span><span class="br0">(</span><span class="st0">"a"</span><span class="br0">)</span> <span class="sy1"><=</span> traits.<span class="me1">transform</span><span class="br0">(</span>c1<span class="br0">)</span> <span class="sy1"><=</span> traits.<span class="me1">transform</span><span class="br0">(</span><span class="st0">"b"</span><span class="br0">)</span></span></span> 则序列 <code>[a-b]</code> 会匹配某字符 <code>c1</code> 。注意此函数接收字符序列为参数，以适应定义为如 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span></span></span><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span>.<span class="me1">ae</span>.<span class="br0">]</span><span class="sy2">-</span>d<span class="br0">]</span></span></span> 的范围。</p>
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<p><span class="t-lc"><a href="cpp-regex-regex_traits.html">std::regex_traits</a></span> 的标准库特化返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-collate.html"><span class="kw1943">std::<span class="me2">collate</span></span></a><span class="sy1"><</span>CharT<span class="sy1">>></span><span class="br0">(</span>getloc<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">transform</span><span class="br0">(</span>str.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span>, str.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">+</span> str.<span class="me1">length</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span></span></span> ，对于某个构造为 <span class="t-c"><span class="mw-geshi cpp source-cpp">string_type str<span class="br0">(</span>first, last<span class="br0">)</span></span></span> 的临时字符串 <code>str</code> 。</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>first, last</td>
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<td>-</td>
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<td>一对<a href="cpp-named_req-ForwardIterator.html"><span style="font-style:italic">老式向前迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyForwardIterator)</span></a> ，确定要比较的字符序列</td>
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<td colspan="3">类型要求</td>
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<td colspan="3">-
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<code>ForwardIt</code> 必须满足<a href="cpp-named_req-ForwardIterator.html"><span style="font-style:italic">老式向前迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyForwardIterator)</span></a> 的要求。</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>当前感染的 locale 中字符序列 <code>[first, last)</code> 的对照关键。</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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