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<title>std::basic_string&lt;CharT,Traits,Allocator&gt;::operator+=</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_string&lt;CharT,Traits,Allocator&gt;::</span>operator+=</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-string.html">string</a>&lrm; | <a href="cpp-string-basic_string.html">basic string</a></span></div>
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<td rowspan="142">(1)</td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&amp;</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&amp;</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<td rowspan="142">(2)</td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> CharT ch <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> CharT ch <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<tbody></tbody>
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<td rowspan="142">(3)</td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<td rowspan="142">(4)</td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <a href="cpp-utility-initializer_list.html"><span class="kw960">std::<span class="me2">initializer_list</span></span></a><span class="sy1">&lt;</span>CharT<span class="sy1">&gt;</span> ilist <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <a href="cpp-utility-initializer_list.html"><span class="kw960">std::<span class="me2">initializer_list</span></span></a><span class="sy1">&lt;</span>CharT<span class="sy1">&gt;</span> ilist <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<td rowspan="142">(5)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1">&lt;</span> <span class="kw1">class</span> T <span class="sy1">&gt;</span><br />
basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&amp;</span> t <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1">&lt;</span> <span class="kw1">class</span> T <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> basic_string<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&amp;</span> t <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<p>&#21518;&#38468;&#39069;&#22806;&#23383;&#31526;&#21040;&#23383;&#31526;&#20018;&#12290;</p>
<div class="t-li1"><span class="t-li">1)</span> &#21518;&#38468; string <code>str</code> &#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#21518;&#38468;&#23383;&#31526; <code>ch</code> &#12290;</div>
<div class="t-li1"><span class="t-li">3)</span> &#21518;&#38468; <code>s</code> &#25152;&#25351;&#21521;&#30340;&#31354;&#32456;&#27490;&#23383;&#31526;&#20018;&#12290;</div>
<div class="t-li1"><span class="t-li">4)</span> &#21518;&#38468; initializer_list <code>ilist</code> &#20013;&#30340;&#23383;&#31526;&#12290;</div>
<div class="t-li1"><span class="t-li">5)</span> &#22914;&#21516;&#29992; <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">&lt;</span>CharT, Traits<span class="sy1">&gt;</span> sv <span class="sy1">=</span> t<span class="sy4">;</span></span></span> &#38544;&#24335;&#36716;&#25442; <code>t</code> &#20026; string_view <code>sv</code> &#65292;&#28982;&#21518;&#21518;&#38468;&#23383;&#31526;&#20018;&#35270;&#22270; <code>sv</code> &#20013;&#30340;&#23383;&#31526;&#65292;&#22914;&#21516;&#29992; <span class="t-c"><span class="mw-geshi cpp source-cpp">append<span class="br0">(</span>sv<span class="br0">)</span></span></span> &#12290;&#27492;&#37325;&#36733;&#20165;&#33509; <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">&lt;</span><span class="kw4">const</span> T<span class="sy3">&amp;</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">&lt;</span>CharT, Traits<span class="sy1">&gt;&gt;</span></span></span> &#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#19988; <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">&lt;</span><span class="kw4">const</span> T<span class="sy3">&amp;</span>, <span class="kw4">const</span> CharT<span class="sy2">*</span><span class="sy1">&gt;</span></span></span> &#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> &#25165;&#21442;&#19982;&#37325;&#36733;&#20915;&#35758;&#12290;</div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td>str</td>
<td>-</td>
<td>&#35201;&#21518;&#38468;&#30340; string</td>
</tr>
<tr class="t-par">
<td>ch</td>
<td>-</td>
<td>&#35201;&#21518;&#38468;&#30340;&#23383;&#31526;&#20540;</td>
</tr>
<tr class="t-par">
<td>s</td>
<td>-</td>
<td>&#25351;&#21521;&#35201;&#21518;&#38468;&#30340;&#31354;&#32456;&#27490;&#23383;&#31526;&#20018;&#30340;&#25351;&#38024;</td>
</tr>
<tr class="t-par">
<td>ilist</td>
<td>-</td>
<td>&#25317;&#26377;&#35201;&#21518;&#38468;&#30340;&#23383;&#31526;&#30340; <span class="t-lc"><a href="cpp-utility-initializer_list.html">std::initializer_list</a></span></td>
</tr>
<tr class="t-par">
<td>t</td>
<td>-</td>
<td>&#25317;&#26377;&#35201;&#21518;&#38468;&#30340;&#23383;&#31526;&#30340;&#65288;&#21487;&#36716;&#25442;&#20026; <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> &#65289;&#30340;&#23545;&#35937;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span></p>
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">&#22797;&#26434;&#24230;</span></h3>
<p>&#26080;&#26631;&#20934;&#22797;&#26434;&#24230;&#20445;&#35777;&#65292;&#20856;&#22411;&#23454;&#29616;&#34920;&#29616;&#31867;&#20284; <a href="cpp-container-vector-insert.html"><tt>std::vector::insert</tt></a> &#12290;</p>
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">&#24322;&#24120;</span></h3>
<p><span class="t-rev-inl t-since-cxx11"><span>&#33509;&#22240;&#20219;&#20309;&#21407;&#22240;&#25243;&#20986;&#24322;&#24120;&#65292;&#21017;&#27492;&#20989;&#25968;&#26080;&#25928;&#26524;&#65288;&#24378;&#24322;&#24120;&#20445;&#35777;&#65289;&#12290;</span> <span><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></span></span></p>
<p>&#33509;&#25805;&#20316;&#20250;&#23548;&#33268; <code>size() &gt; max_size()</code> &#65292;&#21017;&#25243;&#20986; <span class="t-lc"><a href="cpp-error-length_error.html">std::length_error</a></span> &#12290;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#37325;&#36733; <span class="t-v">(2)</span> &#33021;&#25509;&#21463;&#20219;&#20309;&#21487;&#38544;&#24335;&#36716;&#25442;&#20026; <code>CharT</code> &#30340;&#31867;&#22411;&#12290;&#23545;&#20110; <code>CharT</code> &#20026; <code>char</code> &#30340; <code>std::string</code> &#65292;&#21487;&#25509;&#21463;&#31867;&#22411;&#30340;&#38598;&#21512;&#21253;&#21547;&#20219;&#20309;&#31639;&#26415;&#31867;&#22411;&#12290;&#36825;&#21487;&#33021;&#25317;&#26377;&#38750;&#24847;&#22270;&#30340;&#25928;&#26524;&#12290;</p>
<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">&#32570;&#38519;&#25253;&#21578;</span></h3>
<p>&#19979;&#21015;&#26356;&#25913;&#34892;&#20026;&#30340;&#32570;&#38519;&#25253;&#21578;&#36861;&#28335;&#22320;&#24212;&#29992;&#20110;&#20197;&#21069;&#20986;&#29256;&#30340; C++ &#26631;&#20934;&#12290;</p>
<table class="dsctable" style="font-size:0.8em">
<tr>
<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</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> &#37325;&#36733;&#22312;&#26576;&#20123;&#24773;&#20917;&#19979;&#23548;&#33268;&#27495;&#20041;</td>
<td>&#36890;&#36807;&#20351;&#20043;&#20026;&#27169;&#26495;&#26469;&#36991;&#20813;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</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 &lt;iostream&gt;</span>
<span class="co2">#include &lt;iomanip&gt;</span>
<span class="co2">#include &lt;string&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> str<span class="sy4">;</span>
str.<span class="me1">reserve</span><span class="br0">(</span><span class="nu0">50</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// &#39044;&#30041;&#36275;&#22815;&#30340;&#23384;&#20648;&#31354;&#38388;&#20197;&#36991;&#20813;&#20869;&#23384;&#20998;&#37197;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-quoted.html"><span class="kw1802">std::<span class="me2">quoted</span></span></a><span class="br0">(</span>str<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span> <span class="co1">// &#31354;&#23383;&#31526;&#20018;</span>
str <span class="sy2">+</span><span class="sy1">=</span> <span class="st0">&quot;This&quot;</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">&lt;&lt;</span> <a href="cpp-io-manip-quoted.html"><span class="kw1802">std::<span class="me2">quoted</span></span></a><span class="br0">(</span>str<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
str <span class="sy2">+</span><span class="sy1">=</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">&quot; is &quot;</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">&lt;&lt;</span> <a href="cpp-io-manip-quoted.html"><span class="kw1802">std::<span class="me2">quoted</span></span></a><span class="br0">(</span>str<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
str <span class="sy2">+</span><span class="sy1">=</span> <span class="st0">&#39;a&#39;</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">&lt;&lt;</span> <a href="cpp-io-manip-quoted.html"><span class="kw1802">std::<span class="me2">quoted</span></span></a><span class="br0">(</span>str<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
str <span class="sy2">+</span><span class="sy1">=</span> <span class="br0">{</span><span class="st0">&#39; &#39;</span>,<span class="st0">&#39;s&#39;</span>,<span class="st0">&#39;t&#39;</span>,<span class="st0">&#39;r&#39;</span>,<span class="st0">&#39;i&#39;</span>,<span class="st0">&#39;n&#39;</span>,<span class="st0">&#39;g&#39;</span>,<span class="st0">&#39;.&#39;</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">&lt;&lt;</span> <a href="cpp-io-manip-quoted.html"><span class="kw1802">std::<span class="me2">quoted</span></span></a><span class="br0">(</span>str<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
str <span class="sy2">+</span><span class="sy1">=</span> <span class="nu16">76.85</span><span class="sy4">;</span> <span class="co1">// &#31561;&#20215;&#20110; str += static_cast&lt;char&gt;(76.85) &#65292;&#21487;&#33021;&#19981;&#21512;&#24847;&#22270;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-quoted.html"><span class="kw1802">std::<span class="me2">quoted</span></span></a><span class="br0">(</span>str<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">&quot;&quot;
&quot;This&quot;
&quot;This is &quot;
&quot;This is a&quot;
&quot;This is a string.&quot;
&quot;This is a string.L&quot;</pre></div>
</div>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</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-append.html"><span class="t-lines"><span>append</span></span></a></div>
</div>
</td>
<td>&#21518;&#38468;&#23383;&#31526;&#21040;&#32467;&#23614;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
</table>
</div>
<div class="visualClear"></div>
</div>
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