164 lines
16 KiB
HTML
164 lines
16 KiB
HTML
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<title>std::collate<CharT>::compare, std::collate<CharT>::do_compare</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::collate<CharT>::</span>compare, <span style="font-size:0.7em; line-height:130%">std::collate<CharT>::</span>do_compare</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-locale.html">locale</a>‎ | <a href="cpp-locale-collate.html">collate</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-locale.html"><locale></a></code></div>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">public</span><span class="sy4">:</span><br /></span>
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<p><span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> low1, <span class="kw4">const</span> CharT<span class="sy2">*</span> high1,<br /></p>
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<span class="kw4">const</span> CharT<span class="sy2">*</span> low2, <span class="kw4">const</span> CharT<span class="sy2">*</span> high2 <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">protected</span><span class="sy4">:</span><br /></span>
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<p><span class="kw1">virtual</span> <span class="kw4">int</span> do_compare<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> low1, <span class="kw4">const</span> CharT<span class="sy2">*</span> high1,<br /></p>
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<span class="kw4">const</span> CharT<span class="sy2">*</span> low2, <span class="kw4">const</span> CharT<span class="sy2">*</span> high2 <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<div class="t-li1"><span class="t-li">1)</span> 公开成员函数，调用最终导出类的受保护虚成员函数 <code>do_compare</code> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 以此本地环境的对照规则，比较字符序列 <code>[low1, high1)</code> 与字符序列 <code>[low2, high2)</code> ，而若第一字符串后随第二个则返回 1 ，若第一字符串前趋第二个则返回 -1 ，若二个字符串等价则返回零。</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<td>low1</td>
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<td>-</td>
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<td>指向第一字符串首字符的指针</td>
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</tr>
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<tr class="t-par">
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<td>high1</td>
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<td>-</td>
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<td>第一字符串的尾后一位置指针</td>
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</tr>
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<tr class="t-par">
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<td>low2</td>
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<td>-</td>
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<td>指向第二字符串首字符的指针</td>
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</tr>
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<td>high2</td>
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<td>-</td>
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<td>第二字符串的尾后一位置指针</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>若第一字符串大于第二个（即以对照顺序后随第二个）则为 1 ，若第一字符串小于第二个（以对照顺序前趋第二个）则为 -1 ，若二个字符串等价则为零。</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>不要求三路比较时（例如在提供 <code>Compare</code> 参数给如 <span class="t-lc"><a href="cpp-algorithm-sort.html">std::sort</a></span> 的标准算法时）， <a href="cpp-locale-locale-operator().html"><tt>std::locale::operator()</tt></a> 可能更适合。</p>
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<p>对照顺序为字典顺序：国家字母表（其<i>等价类</i>）中字母的位置拥有高于其大小写或变体的优先级。在等价类内，小写字符先于其大写等价物对照，而且本地环境限定的顺序可能应用到有发音符号的字符。一些本地环境中，字符组作为单个<i>对照单元</i>比较。例如， <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"ch"</span></span></span> 在捷克语中后随 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"h"</span></span></span> 而前趋 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"i"</span></span></span> ， <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"dzs"</span></span></span> 在匈牙利语中后随 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"dz"</span></span></span> 而前趋 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"g"</span></span></span> 。</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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<div class="t-example">
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <string></span>
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<span class="co2">#include <locale></span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">typename</span> CharT<span class="sy1">></span>
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<span class="kw4">void</span> try_compare<span class="br0">(</span><span class="kw4">const</span> <a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="sy3">&</span> l, <span class="kw4">const</span> CharT<span class="sy2">*</span> p1, <span class="kw4">const</span> CharT<span class="sy2">*</span> p2<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">auto</span><span class="sy3">&</span> f <span class="sy1">=</span> <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>l<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1228">std::<span class="me2">basic_string</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span> s1<span class="br0">(</span>p1<span class="br0">)</span>, s2<span class="br0">(</span>p2<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>f.<span class="me1">compare</span><span class="br0">(</span><span class="sy3">&</span>s1<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, <span class="sy3">&</span>s1<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span> <span class="sy2">+</span> s1.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span>,
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<span class="sy3">&</span>s2<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, <span class="sy3">&</span>s2<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span> <span class="sy2">+</span> s2.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">)</span> <span class="sy1"><</span> <span class="nu0">0</span><span class="br0">)</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> p1 <span class="sy1"><<</span> <span class="st0">" before "</span> <span class="sy1"><<</span> p2 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="kw1">else</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> p2 <span class="sy1"><<</span> <span class="st0">" before "</span> <span class="sy1"><<</span> p1 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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std<span class="sy4">::</span><span class="me2">locale</span><span class="sy4">::</span><span class="me2">global</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"en_US.utf8"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a>.<span class="me1">imbue</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"In the American locale: "</span><span class="sy4">;</span>
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try_compare<span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span>, <span class="st0">"hrnec"</span>, <span class="st0">"chrt"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"In the Czech locale: "</span><span class="sy4">;</span>
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try_compare<span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"cs_CZ.utf8"</span><span class="br0">)</span>, <span class="st0">"hrnec"</span>, <span class="st0">"chrt"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"In the American locale: "</span><span class="sy4">;</span>
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try_compare<span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span>, L<span class="st0">"år"</span>, L<span class="st0">"ängel"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"In the Swedish locale: "</span><span class="sy4">;</span>
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try_compare<span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"sv_SE.utf8"</span><span class="br0">)</span>, L<span class="st0">"år"</span>, L<span class="st0">"ängel"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">In the American locale: chrt before hrnec
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In the Czech locale: hrnec before chrt
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In the American locale: ängel before år
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In the Swedish locale: år before ängel</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-byte-strcoll.html"><span class="t-lines"><span>strcoll</span></span></a></div>
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</div>
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</td>
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<td>按照当前本地环境比较两个字符串<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-wide-wcscoll.html"><span class="t-lines"><span>wcscoll</span></span></a></div>
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</div>
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</td>
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<td>按照当前本地环境比较两个宽字符串<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-locale-locale-operator().html"><span class="t-lines"><span>operator()</span></span></a></div>
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</div>
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</td>
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<td>用此 locale 的 collate 刻面以字典序比较两个字符串<br />
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<span class="t-mark">(<code>std::locale</code> 的公开成员函数)</span></td>
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<div class="visualClear"></div>
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