561 lines
49 KiB
HTML
561 lines
49 KiB
HTML
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<title>std::basic_string<CharT,Traits,Allocator>::compare</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_basic_string_compare 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::basic_string<CharT,Traits,Allocator>::</span>compare</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-string.html">string</a>‎ | <a href="cpp-string-basic_string.html">basic string</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<td rowspan="142">(1)</td>
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<tr class="t-dcl t-until-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td><span class="t-mark-rev t-until-cxx11">(C++11 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx11 t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<td rowspan="142">(2)</td>
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<tr class="t-dcl t-until-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(3)</td>
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<tr class="t-dcl t-until-cxx14">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br /></span>
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<p> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br /></p>
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size_type pos2, size_type count2 <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx14">(C++14 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx14 t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br /></span>
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<p> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br /></p>
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size_type pos2, size_type count2 <span class="sy1">=</span> npos <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br /></span>
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<p> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br /></p>
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size_type pos2, size_type count2 <span class="sy1">=</span> npos <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<tbody></tbody>
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<td rowspan="142">(4)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(5)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<td rowspan="142">(6)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> CharT<span class="sy2">*</span> s, size_type count2 <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> CharT<span class="sy2">*</span> s, size_type count2 <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(7)</td>
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<td></td>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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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> T <span class="sy1">></span><br />
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<span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t <span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="br0">(</span><span class="coMULTI">/* see below */</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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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> T <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t <span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="br0">(</span><span class="coMULTI">/* see below */</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(8)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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<td>
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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> T <span class="sy1">></span><br /></span>
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<p><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br /></p>
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<span class="kw4">const</span> T<span class="sy3">&</span> t <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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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> T <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br /></p>
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<span class="kw4">const</span> T<span class="sy3">&</span> t <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<tr class="t-dcl-rev-aux">
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<td rowspan="142">(9)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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<td>
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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> T <span class="sy1">></span><br /></span>
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<p><span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> T<span class="sy3">&</span> t,<br /></p>
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size_type pos2, size_type count2 <span class="sy1">=</span> npos<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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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> T <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">int</span> compare<span class="br0">(</span> size_type pos1, size_type count1,<br />
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<span class="kw4">const</span> T<span class="sy3">&</span> t,<br /></p>
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size_type pos2, size_type count2 <span class="sy1">=</span> npos<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody>
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<tr class="t-dcl-sep">
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<td></td>
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</table>
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<p>比较二个字符序列。</p>
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<div class="t-li1"><span class="t-li">1)</span> 比较此 string 与 <i>str</i> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 比较此 string 的 <code>[pos1, pos1+count1)</code> 子串与 <i>str</i> 。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">count1 <span class="sy1">></span> size<span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span> pos1</span></span> 则子串为 <code>[pos1, size())</code> 。</div>
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<div class="t-li1"><span class="t-li">3)</span> 比较此 string 的 <code>[pos1, pos1+count1)</code> 子串与 <i>str</i> 的子串 <code>[pos2, pos2+count2)</code> 。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">count1 <span class="sy1">></span> size<span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span> pos1</span></span> 则第一子串为 <code>[pos1, size())</code> 。类似地若 <span class="t-c"><span class="mw-geshi cpp source-cpp">count2 <span class="sy1">></span> str.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span> pos2</span></span> 则第二子串为 <code>[pos2, str.size())</code> 。</div>
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<div class="t-li1"><span class="t-li">4)</span> 比较此 string 与始于 <i>s</i> 所指向字符的长度为 <code>Traits::length(s)</code> 的空终止字符序列。</div>
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<div class="t-li1"><span class="t-li">5)</span> 比较此 string 的 <code>[pos1, pos1+count1)</code> 子串与始于 <i>s</i> 所指向字符的长度为 <code>Traits::length(s)</code> 的空终止字符序列。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">count1 <span class="sy1">></span> size<span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span> pos1</span></span> 则子串为 <code>[pos1, size())</code> 。</div>
|
|
<div class="t-li1"><span class="t-li">6)</span> 比较此 string 的 <code>[pos1, pos1+count1)</code> 子串与范围 <code>[s, s + count2)</code> 中的字符。（注意：范围 <code>[s, s + count2)</code> 中的字符可包含空字符。）</div>
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<div class="t-li1"><span class="t-li">7)</span> 如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> sv <span class="sy1">=</span> t<span class="sy4">;</span></span></span> 隐式转换 <code>t</code> 为 string_view <code>sv</code> ，然后比较此 string 与 <code>sv</code> 。此重载仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 且 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <span class="kw4">const</span> CharT<span class="sy2">*</span><span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 才参与重载决议。</div>
|
|
<div class="t-li1"><span class="t-li">8)</span> 如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> sv <span class="sy1">=</span> t<span class="sy4">;</span></span></span> 隐式转换 <code>t</code> 为 string_view <code>sv</code> ，然后比较此 string 的 <code>[pos1, pos1+count1)</code> 子串与 <code>sv</code> ，如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="br0">(</span>data<span class="br0">(</span><span class="br0">)</span>, size<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">substr</span><span class="br0">(</span>pos1, count1<span class="br0">)</span>.<span class="me1">compare</span><span class="br0">(</span>sv<span class="br0">)</span></span></span> 。此重载仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 且 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <span class="kw4">const</span> CharT<span class="sy2">*</span><span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 才参与重载决议。</div>
|
|
<div class="t-li1"><span class="t-li">9)</span> 如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> sv <span class="sy1">=</span> t<span class="sy4">;</span></span></span> 隐式转换 <code>t</code> 为 string_view <code>sv</code> ，然后比较此 string 的 <code>[pos1, pos1+count1)</code> 子串与 <code>sv</code> 的 <code>[pos2, pos2+count2)</code> 子串，如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="br0">(</span>data<span class="br0">(</span><span class="br0">)</span>, size<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">substr</span><span class="br0">(</span>pos1, count1<span class="br0">)</span>.<span class="me1">compare</span><span class="br0">(</span>sv.<span class="me1">substr</span><span class="br0">(</span>pos2, count2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></span></span> 。此重载仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 且 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <span class="kw4">const</span> CharT<span class="sy2">*</span><span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 才参与重载决议。</div>
|
|
<p>按下列方式比较始于 <code>data1</code> 的 <code>count1</code> 个字符组成的字符序列与始于 <code>data2</code> 的 <code>count2</code> 个字符组成的字符序列。首先，如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp">size_type rlen <span class="sy1">=</span> <a href="cpp-algorithm-min.html"><span class="kw1642">std::<span class="me2">min</span></span></a><span class="br0">(</span>count1, count2<span class="br0">)</span></span></span> 计算要比较的字符数。然后调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">compare</span><span class="br0">(</span>data1, data2, rlen<span class="br0">)</span></span></span> 比较序列。对于标准字符特性，此函数进行逐字符字典序比较。若结果为零（到此为止的字符序列相等），则按下列方式比较其大小：</p>
|
|
<table class="wikitable" style="text-align:center;">
|
|
<tr>
|
|
<th colspan="2">条件</th>
|
|
<th>结果</th>
|
|
<th>返回值</th>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2" style="text-align:left;"><code>Traits::compare(<span class="t-spar">data1</span>, <span class="t-spar">data2</span>, <span class="t-spar">rlen</span>) < 0</code></td>
|
|
<td><span class="t-spar">data1</span> <i>小于</i> <span class="t-spar">data2</span></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1"><</span><span class="nu0">0</span></span></span></td>
|
|
</tr>
|
|
<tr>
|
|
<td rowspan="3"><code>Traits::compare(<span class="t-spar">data1</span>, <span class="t-spar">data2</span>, <span class="t-spar">rlen</span>) == 0</code></td>
|
|
<td><span class="t-spar">size1</span> < <span class="t-spar">size2</span></td>
|
|
<td><span class="t-spar">data1</span> <i>小于</i> <span class="t-spar">data2</span></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1"><</span><span class="nu0">0</span></span></span></td>
|
|
</tr>
|
|
<tr>
|
|
<td><span class="t-spar">size1</span> == <span class="t-spar">size2</span></td>
|
|
<td><span class="t-spar">data1</span> <i>等于</i> <span class="t-spar">data2</span></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span></td>
|
|
</tr>
|
|
<tr>
|
|
<td><span class="t-spar">size1</span> > <span class="t-spar">size2</span></td>
|
|
<td><span class="t-spar">data1</span> <i>大于</i> <span class="t-spar">data2</span></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1">></span><span class="nu0">0</span></span></span></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2" style="text-align:left;"><code>Traits::compare(<span class="t-spar">data1</span>, <span class="t-spar">data2</span>, <span class="t-spar">rlen</span>) > 0</code></td>
|
|
<td><span class="t-spar">data1</span> <i>大于</i> <span class="t-spar">data2</span></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1">></span><span class="nu0">0</span></span></span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>str</td>
|
|
<td>-</td>
|
|
<td>要比较的另一 string</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>s</td>
|
|
<td>-</td>
|
|
<td>指向要比较的字符串的指针</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>count1</td>
|
|
<td>-</td>
|
|
<td>此 string 要比较的字符数</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>pos1</td>
|
|
<td>-</td>
|
|
<td>此 string 中要比较的首字符的位置</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>count2</td>
|
|
<td>-</td>
|
|
<td>给定字符串要比较的字符数</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>pos2</td>
|
|
<td>-</td>
|
|
<td>给定字符串的要比较的首字符位置</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>t</td>
|
|
<td>-</td>
|
|
<td>要比较的对象（可转换为 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> ）</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 在字典序中先出现于参数所指定的字符序列，则为负值。</p>
|
|
<p>若两个序列比较等价则为零。</p>
|
|
<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 在字典序中后出现于参数所指定的字符序列，则为正值。</p>
|
|
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
|
|
<p>接收名为 <code>pos1</code> 或 <code>pos2</code> 的参数的重载若参数在范围外则抛出 <span class="t-lc"><a href="cpp-error-out_of_range.html">std::out_of_range</a></span> 。</p>
|
|
<div class="t-li1"><span class="t-li">7)</span>
|
|
<div class="t-noexcept-full"><a href="cpp-language-noexcept_spec.html"><tt>noexcept</tt></a> 说明：
|
|
<div class="t-noexcept-box"><span class="t-cc"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">is_nothrow_convertible_v</span><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span><span class="br0">)</span></span></span></div>
|
|
</div>
|
|
</div>
|
|
<div class="t-li1"><span class="t-li">8-9)</span> 抛出任何到 <code>basic_string_view</code> 的转换所抛的异常。</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
|
|
<table class="eq-fun-cpp-table">
|
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<tr>
|
|
<td>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> CharT, <span class="kw1">class</span> Traits, <span class="kw1">class</span> Alloc<span class="sy1">></span>
|
|
<span class="kw4">int</span> basic_string<span class="sy1"><</span>CharT, Traits, Alloc<span class="sy1">></span><span class="sy4">::</span><span class="me2">compare</span><span class="br0">(</span><span class="kw4">const</span> <a href="cpp-string-basic_string.html"><span class="kw1228">std::<span class="me2">basic_string</span></span></a><span class="sy3">&</span> s<span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span>
|
|
<span class="br0">{</span>
|
|
size_type lhs_sz <span class="sy1">=</span> size<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
size_type rhs_sz <span class="sy1">=</span> s.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span><span class="kw4">int</span> result <span class="sy1">=</span> traits_type<span class="sy4">::</span><span class="me2">compare</span><span class="br0">(</span>data<span class="br0">(</span><span class="br0">)</span>, s.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span>, <a href="cpp-algorithm-min.html"><span class="kw1642">std::<span class="me2">min</span></span></a><span class="br0">(</span>lhs_sz, rhs_sz<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
|
|
<span class="kw1">return</span> result<span class="sy4">;</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span>lhs_sz <span class="sy1"><</span> rhs_sz<span class="br0">)</span>
|
|
<span class="kw1">return</span> <span class="sy2">-</span><span class="nu0">1</span><span class="sy4">;</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span>lhs_sz <span class="sy1">></span> rhs_sz<span class="br0">)</span>
|
|
<span class="kw1">return</span> <span class="nu0">1</span><span class="sy4">;</span>
|
|
<span class="kw1">return</span> <span class="nu0">0</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p>对于不要求三路比较的情形， <span class="t-lc"><a href="cpp-string-basic_string.html">std::basic_string</a></span> 提供通常<a href="cpp-string-basic_string-operator_cmp.html">关系运算符</a>（ <code><</code> 、 <code><=</code> 、 <code>==</code> 、 <code>></code> 等）。</p>
|
|
<p>此函数默认（以默认 <span class="t-lc"><a href="cpp-string-char_traits.html">std::char_traits</a></span> ）不会考虑本地环境。具本地环境的三路比较见 <span class="t-lc"><a href="cpp-locale-collate-compare.html">std::collate::compare</a></span> 。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <cassert></span>
|
|
<span class="co2">#include <string></span>
|
|
<span class="co2">#include <iostream></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="co1">// 1) 与另一 string 比较</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw4">int</span> compare_value<span class="br0">{</span>
|
|
<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Batman"</span><span class="br0">}</span>.<span class="me1">compare</span><span class="br0">(</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Superman"</span><span class="br0">}</span><span class="br0">)</span>
|
|
<span class="br0">}</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="br0">(</span>
|
|
compare_value <span class="sy1"><</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Batman comes before Superman<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
compare_value <span class="sy1">></span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Superman comes before Batman<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
<span class="st0">"Superman and Batman are the same.<span class="es1">\n</span>"</span>
|
|
<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="co1">// 2) 与另一 string 比较子串</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw4">int</span> compare_value<span class="br0">{</span>
|
|
<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Batman"</span><span class="br0">}</span>.<span class="me1">compare</span><span class="br0">(</span><span class="nu0">3</span>, <span class="nu0">3</span>, <a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Superman"</span><span class="br0">}</span><span class="br0">)</span>
|
|
<span class="br0">}</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="br0">(</span>
|
|
compare_value <span class="sy1"><</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"man comes before Superman<span class="es1">\n</span>"</span> <span class="sy4">:</span>
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|
compare_value <span class="sy1">></span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Superman comes before man<span class="es1">\n</span>"</span> <span class="sy4">:</span>
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|
<span class="st0">"man and Superman are the same.<span class="es1">\n</span>"</span>
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<span class="br0">)</span><span class="sy4">;</span>
|
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<span class="br0">}</span>
|
|
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<span class="co1">// 3) 与另一子串比较子串</span>
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<span class="br0">{</span>
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<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> a<span class="br0">{</span><span class="st0">"Batman"</span><span class="br0">}</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> b<span class="br0">{</span><span class="st0">"Superman"</span><span class="br0">}</span><span class="sy4">;</span>
|
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<span class="kw4">int</span> compare_value<span class="br0">{</span>a.<span class="me1">compare</span><span class="br0">(</span><span class="nu0">3</span>, <span class="nu0">3</span>, b, <span class="nu0">5</span>, <span class="nu0">3</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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|
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="br0">(</span>
|
|
compare_value <span class="sy1"><</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"man comes before man<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
compare_value <span class="sy1">></span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"man comes before man<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
<span class="st0">"man and man are the same.<span class="es1">\n</span>"</span>
|
|
<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="co1">// 与另一子串比较子串</span>
|
|
<span class="co1">// 默认到为另一 string 的末尾</span>
|
|
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>compare_value <span class="sy1">==</span> a.<span class="me1">compare</span><span class="br0">(</span><span class="nu0">3</span>, <span class="nu0">3</span>, b, <span class="nu0">5</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="co1">// 4) 与另一 char 指针比较</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw4">int</span> compare_value<span class="br0">{</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Batman"</span><span class="br0">}</span>.<span class="me1">compare</span><span class="br0">(</span><span class="st0">"Superman"</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="br0">(</span>
|
|
compare_value <span class="sy1"><</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Batman comes before Superman<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
compare_value <span class="sy1">></span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Superman comes before Batman<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
<span class="st0">"Superman and Batman are the same.<span class="es1">\n</span>"</span>
|
|
<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="co1">// 5) 与另一 char 指针比较子串</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw4">int</span> compare_value<span class="br0">{</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Batman"</span><span class="br0">}</span>.<span class="me1">compare</span><span class="br0">(</span><span class="nu0">3</span>, <span class="nu0">3</span>, <span class="st0">"Superman"</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="br0">(</span>
|
|
compare_value <span class="sy1"><</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"man comes before Superman<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
compare_value <span class="sy1">></span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Superman comes before man<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
<span class="st0">"man and Superman are the same.<span class="es1">\n</span>"</span>
|
|
<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="co1">// 6) 与另一 char 指针子串比较子串</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw4">int</span> compare_value<span class="br0">{</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">{</span><span class="st0">"Batman"</span><span class="br0">}</span>.<span class="me1">compare</span><span class="br0">(</span><span class="nu0">0</span>, <span class="nu0">3</span>, <span class="st0">"Superman"</span>, <span class="nu0">5</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="br0">(</span>
|
|
compare_value <span class="sy1"><</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Bat comes before Super<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
compare_value <span class="sy1">></span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"Super comes before Bat<span class="es1">\n</span>"</span> <span class="sy4">:</span>
|
|
<span class="st0">"Super and Bat are the same.<span class="es1">\n</span>"</span>
|
|
<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">Batman comes before Superman
|
|
Superman comes before man
|
|
man and man are the same.
|
|
Batman comes before Superman
|
|
Superman comes before man
|
|
Bat comes before Super</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
|
|
<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
|
|
<table class="dsctable" style="font-size:0.8em">
|
|
<tr>
|
|
<th>DR</th>
|
|
<th>应用于</th>
|
|
<th>出版时的行为</th>
|
|
<th>正确行为</th>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2946">LWG 2946</a></td>
|
|
<td>C++17</td>
|
|
<td><code>string_view</code> 重载在某些情况下导致歧义</td>
|
|
<td>通过使之为模板来避免</td>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://wg21.link/P1148R0">P1148R0</a></td>
|
|
<td>C++17</td>
|
|
<td>重载 <span class="t-v">(7)</span> 的 noexcept 被 LWG2946 意外丢弃</td>
|
|
<td>恢复</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string-operator_cmp.html"><span class="t-lines"><span>operator==</span><span>operator!=</span><span>operator<</span><span>operator></span><span>operator<=</span><span>operator>=</span><span>operator<=></span></span></a></div>
|
|
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>以字典序比较两个字符串<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string-substr.html"><span class="t-lines"><span>substr</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>返回子串<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-locale-collate.html"><span class="t-lines"><span>collate</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>定义字典序比较和字符串的散列<br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-byte-strcoll.html"><span class="t-lines"><span>strcoll</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>按照当前本地环境比较两个字符串<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-lexicographical_compare.html"><span class="t-lines"><span>lexicographical_compare</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>当一个范围按字典顺序小于另一个范围时，返回 true<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|