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<title>std::move_only_function&lt;R(Args...) cv ref noexcept(noex)&gt;::operator bool</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::move_only_function&lt;R(Args...) <i>cv</i> <i>ref</i> noexcept(<i>noex</i>)&gt;::</span>operator bool</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-move_only_function.html">move only function</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">explicit</span> operator <span class="kw4">bool</span><span class="br0">(</span><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><span class="t-mark-rev t-since-cxx23">(C++23 &#36215;)</span></td>
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<p>&#26816;&#26597; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#26159;&#21542;&#23384;&#20648;&#21487;&#35843;&#29992;&#30446;&#26631;&#65292;&#21363;&#38750;&#31354;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<p>(none)</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#33509; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#23384;&#20648;&#21487;&#35843;&#29992;&#30446;&#26631;&#21017;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#65292;&#21542;&#21017;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> &#12290;</p>
<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="kw4">void</span> sampleFunction<span class="br0">(</span><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="st0">&quot;This is the sample function!<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">void</span> checkFunc<span class="br0">(</span> std<span class="sy4">::</span><span class="me2">move_only_function</span><span class="sy1">&lt;</span><span class="kw4">void</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy1">&gt;</span> <span class="kw4">const</span> <span class="sy3">&amp;</span>func <span class="br0">)</span>
<span class="br0">{</span>
<span class="co1">// Use operator bool to determine if callable target is available.</span>
<span class="kw1">if</span><span class="br0">(</span> func <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="st0">&quot;Function is not empty! Calling function.<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
func<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">else</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="st0">&quot;Function is empty. Nothing to do.<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
std<span class="sy4">::</span><span class="me2">move_only_function</span><span class="sy1">&lt;</span><span class="kw4">void</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy1">&gt;</span> f1<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">move_only_function</span><span class="sy1">&lt;</span><span class="kw4">void</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy1">&gt;</span> f2<span class="br0">{</span> sampleFunction <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> <span class="st0">&quot;f1: &quot;</span><span class="sy4">;</span>
checkFunc<span class="br0">(</span>f1<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> <span class="st0">&quot;f2: &quot;</span><span class="sy4">;</span>
checkFunc<span class="br0">(</span>f2<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">f1: Function is empty. Nothing to do.
f2: Function is not empty! Calling function.
This is the sample function!</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-function-operator_bool.html"><span class="t-lines"><span>operator bool</span></span></a></div>
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<td>&#26816;&#26597;&#26159;&#21542;&#21253;&#21547;&#20102;&#26377;&#25928;&#30340;&#30446;&#26631;<br />
<span class="t-mark">(<code>std::function&lt;R(Args...)&gt;</code> &#30340;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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