226 lines
18 KiB
HTML
226 lines
18 KiB
HTML
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<title>std::filesystem::path::concat, std::filesystem::path::operator+=</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_filesystem_path_concat 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::filesystem::path::</span>concat, <span style="font-size:0.7em; line-height:130%">std::filesystem::path::</span>operator+=</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-filesystem.html">filesystem</a>‎ | <a href="cpp-filesystem-path.html">path</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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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dcl t-since-cxx17">
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<td>
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<div><span class="mw-geshi cpp source-cpp">path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> path<span class="sy3">&</span> p <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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<td>
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<div><span class="mw-geshi cpp source-cpp">path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> string_type<span class="sy3">&</span> str <span class="br0">)</span><span class="sy4">;</span><br />
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path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</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>value_type<span class="sy1">></span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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<td>
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<div><span class="mw-geshi cpp source-cpp">path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> value_type<span class="sy2">*</span> ptr <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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<td>
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<div><span class="mw-geshi cpp source-cpp">path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> value_type x <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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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> CharT <span class="sy1">></span><br />
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path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> CharT x <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(5)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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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> Source <span class="sy1">></span><br />
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path<span class="sy3">&</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> Source<span class="sy3">&</span> source <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(6)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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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> Source <span class="sy1">></span><br />
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path<span class="sy3">&</span> concat<span class="br0">(</span> <span class="kw4">const</span> Source<span class="sy3">&</span> source <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(7)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17">
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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> InputIt <span class="sy1">></span><br />
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path<span class="sy3">&</span> concat<span class="br0">(</span> InputIterator first, InputIterator last <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(8)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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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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<td></td>
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</tr>
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</tbody>
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</table>
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<p>连接当前路径与参数。</p>
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<div class="t-li1"><span class="t-li">1-3,6-7)</span> 后附 <span class="t-c"><span class="mw-geshi cpp source-cpp">path<span class="br0">(</span>other<span class="br0">)</span>.<span class="me1">native</span><span class="br0">(</span><span class="br0">)</span></span></span> 到以原生格式存储于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 的路径名。这会直接操纵 <span class="t-c"><span class="mw-geshi cpp source-cpp">native<span class="br0">(</span><span class="br0">)</span></span></span> 的值，并且可能无法在操作系统间移植。</div>
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<div class="t-li1"><span class="t-li">4-5)</span> 同 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> <span class="sy2">*</span>this <span class="sy2">+</span><span class="sy1">=</span> <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="br0">(</span><span class="sy3">&</span>x, <span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span></span></span></div>
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<div class="t-li1"><span class="t-li">8)</span> 同 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> <span class="sy2">*</span>this <span class="sy2">+</span><span class="sy1">=</span> path<span class="br0">(</span>first, last<span class="br0">)</span><span class="sy4">;</span></span></span></div>
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<p><span class="t-v">(6)</span> 与 <span class="t-v">(7)</span> 仅若 <code>Source</code> 与 <code>path</code> 不是同一类型，而且：</p>
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<ul>
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<li><code>Source</code> 是 <span class="t-lc"><a href="cpp-string-basic_string.html">std::basic_string</a></span> 或 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> 的特化，或</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_traits.html"><span class="kw651">std::<span class="me2">iterator_traits</span></span></a><span class="sy1"><</span><a href="cpp-types-decay.html"><span class="kw629">std::<span class="me2">decay_t</span></span></a><span class="sy1"><</span>Source</span><span class="mw-geshi cpp source-cpp"><span class="sy1">>></span><span class="sy4">::</span><span class="me2">value_type</span></span></span> 合法并代表可能有 const 限定的编码字符类型（ <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 、 <span class="t-rev-inl t-since-cxx20"><span><span class="t-c"><span class="mw-geshi cpp source-cpp">char8_t</span></span> 、</span> <span><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></span><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char16_t</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char32_t</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> ）</li>
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</ul>
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<p>才参与重载决议</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>p</td>
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<td>-</td>
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<td>要附加的路径</td>
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</tr>
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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>要附加的字符串或字符串视图</td>
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</tr>
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<tr class="t-par">
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<td>ptr</td>
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<td>-</td>
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<td>指向要附加的空终止字符串起始的指针</td>
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</tr>
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<tr class="t-par">
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<td>x</td>
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<td>-</td>
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<td>要附加的单个字符</td>
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</tr>
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<tr class="t-par">
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<td>source</td>
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<td>-</td>
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<td><span class="t-lc"><a href="cpp-string-basic_string.html">std::basic_string</a></span> 、 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> 、空终止多字符字符串或指向空终止多字符序列的输入迭代器，它表示路径名（以可执行或原生格式）</td>
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</tr>
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<tr class="t-par">
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<td>first, last</td>
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<td>-</td>
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<td>一对指定代表路径名的字符序列的<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a></td>
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</tr>
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<tr class="t-par-hitem">
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<td colspan="3">类型要求</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>InputIt</code> 必须满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> 的要求。</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>InputIt</code> 的 value_type 必须是编码字符类型（<span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char16_t</span></span></span> 及 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char32_t</span></span></span>）之一</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>CharT</code> 必须是编码字符类型（<span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char16_t</span></span></span> 及 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char32_t</span></span></span>）之一</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><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></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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<p>若内存分配失败则可能抛出 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-memory-new-bad_alloc.html"><span class="kw693">std::<span class="me2">bad_alloc</span></span></a></span></span> 。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>不同于 <span class="t-lc"><a href="cpp-filesystem-path-append.html">append()</a></span> 或 <span class="t-lc"><a href="cpp-filesystem-path-append.html">operator/=</a></span> ，决不放入附加的分隔符。</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 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 <iostream></span>
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<span class="co2">#include <filesystem></span>
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<span class="kw1">namespace</span> fs <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">filesystem</span><span class="sy4">;</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
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fs<span class="sy4">::</span><span class="me2">path</span> p1<span class="sy4">;</span> <span class="co1">// 空路径</span>
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p1 <span class="sy2">+</span><span class="sy1">=</span> <span class="st0">"var"</span><span class="sy4">;</span> <span class="co1">// 不插入分隔符</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> <span class="st0">"<span class="es1">\"</span><span class="es1">\"</span> + <span class="es1">\"</span>var<span class="es1">\"</span> == "</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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p1 <span class="sy2">+</span><span class="sy1">=</span> <span class="st0">"lib"</span><span class="sy4">;</span> <span class="co1">// does not insert a separator</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> <span class="st0">"<span class="es1">\"</span><span class="es1">\"</span> + <span class="es1">\"</span>var<span class="es1">\"</span> + <span class="es1">\"</span>lib<span class="es1">\"</span> == "</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></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">"" + "var" == "var"
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"" + "var" + "lib" == "varlib"</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/issue3055">LWG 3055</a></td>
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<td>C++17</td>
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<td>连接单个字符的规定为谬构</td>
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<td>使之为良构</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/issue3244">LWG 3244</a></td>
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<td>C++17</td>
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<td>缺失 <code>Source</code> 不能为 <code>path</code> 的制约</td>
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<td>已添加</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-filesystem-path-append.html"><span class="t-lines"><span>append</span><span>operator/=</span></span></a></div>
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</div>
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</td>
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<td>添加元素到带目录分隔符的路径<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<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-filesystem-path-operator_slash.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>用目录分隔符连接二个路径<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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</div>
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<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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