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<h1 id="firstHeading" class="firstHeading">operator==,!=<small>(std::function)</small></h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a>&lrm; | <a href="cpp-utility-functional.html">functional</a>&lrm; | <a href="cpp-utility-functional-function.html">function</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-functional.html">&lt;functional&gt;</a></code></div>
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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> R, <span class="kw1">class</span>... <span class="me1">ArgTypes</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-utility-functional-function.html"><span class="kw1059">std::<span class="me2">function</span></span></a><span class="sy1">&lt;</span>R<span class="br0">(</span>ArgTypes...<span class="br0">)</span><span class="sy1">&gt;</span><span class="sy3">&amp;</span> f,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="cpp-types-nullptr_t.html"><span class="kw102">std::<span class="me2">nullptr_t</span></span></a> <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
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<td>(1)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</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> R, <span class="kw1">class</span>... <span class="me1">ArgTypes</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span> <a href="cpp-types-nullptr_t.html"><span class="kw102">std::<span class="me2">nullptr_t</span></span></a>,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span class="kw4">const</span> <a href="cpp-utility-functional-function.html"><span class="kw1059">std::<span class="me2">function</span></span></a><span class="sy1">&lt;</span>R<span class="br0">(</span>ArgTypes...<span class="br0">)</span><span class="sy1">&gt;</span><span class="sy3">&amp;</span> f <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
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<td>(2)</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="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> R, <span class="kw1">class</span>... <span class="me1">ArgTypes</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">bool</span> operator<span class="sy3">!</span><span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-utility-functional-function.html"><span class="kw1059">std::<span class="me2">function</span></span></a><span class="sy1">&lt;</span>R<span class="br0">(</span>ArgTypes...<span class="br0">)</span><span class="sy1">&gt;</span><span class="sy3">&amp;</span> f,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="cpp-types-nullptr_t.html"><span class="kw102">std::<span class="me2">nullptr_t</span></span></a> <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
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<td>(3)</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="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> R, <span class="kw1">class</span>... <span class="me1">ArgTypes</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">bool</span> operator<span class="sy3">!</span><span class="sy1">=</span><span class="br0">(</span> <a href="cpp-types-nullptr_t.html"><span class="kw102">std::<span class="me2">nullptr_t</span></span></a>,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span class="kw4">const</span> <a href="cpp-utility-functional-function.html"><span class="kw1059">std::<span class="me2">function</span></span></a><span class="sy1">&lt;</span>R<span class="br0">(</span>ArgTypes...<span class="br0">)</span><span class="sy1">&gt;</span><span class="sy3">&amp;</span> f <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
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<td>(4)</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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<p>&#19982;&#31354;&#25351;&#38024;&#27604;&#36739; <code>std::function</code> &#12290;&#31354; function &#65288;&#21363;&#26080;&#21487;&#35843;&#29992;&#30446;&#26631;&#30340; function &#65289;&#27604;&#36739;&#30456;&#31561;&#65292;&#38750;&#31354; function &#27604;&#36739;&#19981;&#30456;&#31561;&#12290;</p>
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<p><code>!=</code> &#36816;&#31639;&#31526;&#20174; <code>operator==</code> <a href="cpp-language-operators.html#.E5.85.B3.E7.B3.BB.E8.BF.90.E7.AE.97.E7.AC.A6">&#21512;&#25104;</a>&#12290;</p>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>f</td>
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<td>&#35201;&#27604;&#36739;&#30340; <code>std::function</code></td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<div class="t-li1"><span class="t-li">1-2)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>f</span></span></div>
<div class="t-li1"><span class="t-li">3-4)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span><span class="kw4">bool</span><span class="br0">)</span> f</span></span></div>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;functional&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="kw1">using</span> SomeVoidFunc <span class="sy1">=</span> <a href="cpp-utility-functional-function.html"><span class="kw1059">std::<span class="me2">function</span></span></a><span class="sy1">&lt;</span><span class="kw4">void</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy1">&gt;</span><span class="sy4">;</span>
<span class="kw1">class</span> C <span class="br0">{</span>
<span class="kw1">public</span><span class="sy4">:</span>
C<span class="br0">(</span>SomeVoidFunc void_func <span class="sy1">=</span> nullptr<span class="br0">)</span> <span class="sy4">:</span>
void_func_<span class="br0">(</span>void_func<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">if</span> <span class="br0">(</span>void_func_ <span class="sy1">==</span> nullptr<span class="br0">)</span> <span class="br0">{</span> <span class="co1">// &#19982; nullptr &#30340;&#29305;&#21270;&#27604;&#36739;</span>
void_func_ <span class="sy1">=</span> <a href="cpp-utility-functional-bind.html"><span class="kw1052">std::<span class="me2">bind</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>C<span class="sy4">::</span><span class="me2">default_func</span>, this, std<span class="sy4">::</span><span class="me2">placeholders</span><span class="sy4">::</span>_1<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
void_func_<span class="br0">(</span><span class="nu0">7</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">void</span> default_func<span class="br0">(</span><span class="kw4">int</span> i<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> i <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><span class="sy4">;</span>
<span class="kw1">private</span><span class="sy4">:</span>
SomeVoidFunc void_func_<span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">void</span> user_func<span class="br0">(</span><span class="kw4">int</span> i<span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="br0">(</span>i <span class="sy2">+</span> <span class="nu0">1</span><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>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
C c1<span class="sy4">;</span>
C c2<span class="br0">(</span>user_func<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">7
8</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-utility-functional-move_only_function-operator==.html"><span class="t-lines"><span>operator==</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div>
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<td>&#27604;&#36739; <code>std::move_only_function</code> &#19982; <span class="t-c"><span class="mw-geshi cpp source-cpp">nullptr</span></span><br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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