310 lines
19 KiB
HTML
310 lines
19 KiB
HTML
<!DOCTYPE html>
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<title>std::basic_string<CharT,Traits,Allocator>::find_last_of</title>
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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>find_last_of</h1>
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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></td>
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<td rowspan="142">(1)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx11">
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<div><span class="mw-geshi cpp source-cpp">size_type find_last_of<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br />
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size_type pos <span class="sy1">=</span> npos <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-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">constexpr</span> size_type find_last_of<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br />
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size_type pos <span class="sy1">=</span> npos <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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</tbody>
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<tbody></tbody>
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<td></td>
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<td rowspan="142">(2)</td>
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<td>
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<div><span class="mw-geshi cpp source-cpp">size_type find_last_of<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s,<br />
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size_type pos, size_type count <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-cxx11">(C++11 前)</span></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> size_type find_last_of<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s,<br />
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size_type pos, size_type count <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-cxx11">(C++11 起)</span></td>
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<tbody></tbody>
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<td rowspan="142">(3)</td>
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<tr class="t-dcl t-until-cxx20">
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<div><span class="mw-geshi cpp source-cpp">size_type find_last_of<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s, size_type pos <span class="sy1">=</span> npos <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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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> size_type find_last_of<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s, size_type pos <span class="sy1">=</span> npos <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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<td rowspan="142">(4)</td>
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<div><span class="mw-geshi cpp source-cpp">size_type find_last_of<span class="br0">(</span> CharT ch, size_type pos <span class="sy1">=</span> npos <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-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">size_type find_last_of<span class="br0">(</span> CharT ch, size_type pos <span class="sy1">=</span> npos <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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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> size_type find_last_of<span class="br0">(</span> CharT ch,<br />
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size_type pos <span class="sy1">=</span> npos <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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</tbody>
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<tbody></tbody>
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<td></td>
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<td rowspan="142">(5)</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 /></span>
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<p>size_type<br />
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find_last_of<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t,<br /></p>
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size_type pos <span class="sy1">=</span> npos <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></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 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> size_type<br />
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find_last_of<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t,<br /></p>
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size_type pos <span class="sy1">=</span> npos <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></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>
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<tbody>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<p>寻找等于给定字符序列中字符之一的最后字符。不指定准确的搜索算法。搜索只考虑区间 <span class="texhtml" style="white-space: nowrap;">[0, pos]</span> 。若区间中不存在这种字符，则返回 <span class="t-lc"><a href="cpp-string-basic_string-npos.html">npos</a></span> 。</p>
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<div class="t-li1"><span class="t-li">1)</span> 寻找等于 <code>str</code> 中字符之一的最后字符。</div>
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<div class="t-li1"><span class="t-li">2)</span> 寻找等于范围 <code>[s, s+count)</code> 中字符之一的最后字符。此范围能包含空字符。</div>
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<div class="t-li1"><span class="t-li">3)</span> 寻找等于 <code>s</code> 所指向的字符串中字符之一的最后字符。用 <code>Traits::length(s)</code> ，由首个空字符确定字符串长度。</div>
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<div class="t-li1"><span class="t-li">4)</span> 寻找等于 <code>ch</code> 的最后字符。</div>
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<div class="t-li1"><span class="t-li">5)</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> ，然后寻找等于 <code>sv</code> 中字符之一的最后字符。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>
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<p>所有情况下，均调用 <a href="cpp-string-char_traits-cmp.html"><tt>Traits::eq</tt></a> 检查相等性。</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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<table class="t-par-begin">
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<tr class="t-par">
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<td>str</td>
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<td>-</td>
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<td>鉴别要搜索的字符的 string</td>
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</tr>
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<tr class="t-par">
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<td>pos</td>
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<td>-</td>
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<td>搜索结束的位置</td>
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</tr>
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<tr class="t-par">
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<td>count</td>
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<td>-</td>
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<td>鉴别要搜索的字符的字符串长度</td>
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</tr>
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<tr class="t-par">
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<td>s</td>
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<td>-</td>
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<td>指向鉴别要搜索的字符的字符串的指针</td>
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</tr>
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<tr class="t-par">
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<td>ch</td>
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<td>-</td>
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<td>要搜索的字符</td>
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</tr>
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<tr class="t-par">
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<td>t</td>
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<td>-</td>
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<td>鉴别要搜索的字符的对象（可转换为 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> ）</td>
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</tr>
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</table>
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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>找到的字符位置，或若找不到这种字符则为 <span class="t-lc"><a href="cpp-string-basic_string-npos.html">npos</a></span> 。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<div class="t-li1"><span class="t-li">5)</span>
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<div class="t-noexcept-full"><a href="cpp-language-noexcept_spec.html"><tt>noexcept</tt></a> 说明：
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<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>
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</div>
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</div>
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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 class="t-example-live-link"></div>
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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<string></span>
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<span class="co2">#include<iostream></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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<span class="kw4">const</span> <a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> path<span class="sy1">=</span><span class="st0">"/root/config"</span><span class="sy4">;</span>
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<span class="kw4">auto</span> <span class="kw4">const</span> pos<span class="sy1">=</span>path.<span class="me1">find_last_of</span><span class="br0">(</span><span class="st0">'/'</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> leaf<span class="sy1">=</span>path.<span class="me1">substr</span><span class="br0">(</span>pos<span class="sy2">+</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
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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> leaf <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></pre></div>
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</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">config</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
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<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>
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<table class="dsctable" style="font-size:0.8em">
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<tr>
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<th>DR</th>
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<th>应用于</th>
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<th>出版时的行为</th>
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<th>正确行为</th>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2064">LWG 2064</a></td>
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<td>C++11</td>
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<td>重载 <span class="t-v">(3)</span> 与 <span class="t-v">(4)</span> 为 noexcept</td>
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<td>移除</td>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2946">LWG 2946</a></td>
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<td>C++17</td>
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<td><code>string_view</code> 重载在某些情况下导致歧义</td>
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<td>通过使之为模板来避免</td>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://wg21.link/P1148R0">P1148R0</a></td>
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<td>C++11<br />
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C++17</td>
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<td>重载 <span class="t-v">(4)</span>/<span class="t-v">(5)</span> 的 noexcept 意外地被 LWG2064/LWG2946 丢弃</td>
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<td>恢复</td>
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</tr>
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</table>
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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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<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-string-basic_string-find.html"><span class="t-lines"><span>find</span></span></a></div>
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|
</div>
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|
</td>
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<td>于字符串中寻找字符<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string-rfind.html"><span class="t-lines"><span>rfind</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找子串的最后一次出现<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
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|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string-find_first_of.html"><span class="t-lines"><span>find_first_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找字符的首次出现<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-string-basic_string-find_first_not_of.html"><span class="t-lines"><span>find_first_not_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找字符的首次缺失<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-string-basic_string-find_last_not_of.html"><span class="t-lines"><span>find_last_not_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找字符的最后一次缺失<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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