125 lines
17 KiB
HTML
125 lines
17 KiB
HTML
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<title>std::experimental::not_fn</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_experimental_not_fn 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::experimental::</span>not_fn</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-experimental.html">experimental</a></span></div>
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<div>定义于头文件 <code><a href="https://zh.cppreference.com/mwiki/index.php?title=cpp/header/experimental/functional&action=edit&redlink=1" class="new" title="cpp/header/experimental/functional（页面不存在）"><experimental/functional></a></code></div>
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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> F<span class="sy1">></span><br />
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<span class="coMULTI">/*unspecified*/</span> not_fn<span class="br0">(</span> F<span class="sy3">&&</span> f <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-libfund-ts-2 t-mark-ts">(库基础 TS v2)</span></td>
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<p>创建转发调用包装器，它返回其所保有的可调用对象的逻辑补。</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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<td>f</td>
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<td>-</td>
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<td>对象，从该对象构造包装器所保有的<a href="cpp-named_req-Callable.html"><span style="font-style:italic">可调用</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Callable)</span></a> 对象</td>
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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>令 <code>FD</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-decay.html"><span class="kw629">std::<span class="me2">decay_t</span></span></a><span class="sy1"><</span>F<span class="sy1">></span></span></span> ， <code>fd</code> 为从 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>F<span class="sy1">></span><span class="br0">(</span>f<span class="br0">)</span></span></span> 构造的 <code>FD</code> 类型左值。</p>
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<p>则 <code>not_fn</code> 返回未指定类型的转发调用包装器，使得 <span class="t-c"><span class="mw-geshi cpp source-cpp">fn<span class="br0">(</span>a1, a2, ..., aN<span class="br0">)</span></span></span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>INVOKE<span class="br0">(</span>fd, a1, ..., aN<span class="br0">)</span></span></span> ，其中 <code>INVOKE</code> 是 <a href="cpp-named_req-Callable.html"><span style="font-style:italic">可调用</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Callable)</span></a> 中描述的操作。</p>
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<p>返回的调用包装器始终为<a href="cpp-named_req-MoveConstructible.html"><span style="font-style:italic">可移动构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveConstructible)</span></a> ，而若 FD 为<a href="cpp-named_req-CopyConstructible.html"><span style="font-style:italic">可复制构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyConstructible)</span></a> 则它亦为<a href="cpp-named_req-CopyConstructible.html"><span style="font-style:italic">可复制构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyConstructible)</span></a> 。</p>
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<h3><span class="mw-headline" id=".E6.8F.90.E9.86.92">提醒</span></h3>
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<p>若 <code>fd</code> 非<a href="cpp-named_req-Callable.html"><span style="font-style:italic">可调用</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Callable)</span></a> ，或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_constructible.html"><span class="kw520">std::<span class="me2">is_constructible</span></span></a><span class="sy1"><</span>FD, F<span class="sy1">></span><span class="sy4">::</span><span class="me2">value</span></span></span> 非 <code>true</code> ，则行为未定义。</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>不抛异常，除非 <code>fd</code> 的构造抛出。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<pre class="de1"><span class="kw1">namespace</span> detail <span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> F<span class="sy1">></span>
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<span class="kw1">struct</span> not_fn_t <span class="br0">{</span>
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F f<span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">></span>
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<span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>Args<span class="sy3">&&</span>... <span class="me1">args</span><span class="br0">)</span>
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<span class="kw1">noexcept</span><span class="br0">(</span><span class="kw1">noexcept</span><span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="co1">// QoI 的 cv 限定重载</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">></span>
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<span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>Args<span class="sy3">&&</span>... <span class="me1">args</span><span class="br0">)</span> <span class="kw4">const</span>
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<span class="kw1">noexcept</span><span class="br0">(</span><span class="kw1">noexcept</span><span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">></span>
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<span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>Args<span class="sy3">&&</span>... <span class="me1">args</span><span class="br0">)</span> <span class="kw4">volatile</span>
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<span class="kw1">noexcept</span><span class="br0">(</span><span class="kw1">noexcept</span><span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">></span>
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<span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>Args<span class="sy3">&&</span>... <span class="me1">args</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw4">volatile</span>
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<span class="kw1">noexcept</span><span class="br0">(</span><span class="kw1">noexcept</span><span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>f, <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>Args<span class="sy1">></span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> F<span class="sy1">></span>
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detail<span class="sy4">::</span><span class="me2">not_fn_t</span><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>F<span class="sy1">>></span> not_fn<span class="br0">(</span>F<span class="sy3">&&</span> f<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="br0">{</span> <a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>F<span class="sy1">></span><span class="br0">(</span>f<span class="br0">)</span> <span class="br0">}</span><span class="sy4">;</span> <span class="br0">}</span></pre></div>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p><code>not_fn</code> 的用意是替换 C++03 时代的取反器 <span class="t-lc"><a href="cpp-utility-functional-not1.html">std::not1</a></span> 和 <span class="t-lc"><a href="cpp-utility-functional-not2.html">std::not2</a></span> 。</p>
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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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-functional-not_fn.html"><span class="t-lines"><span>not_fn</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>创建返回其保有的函数对象的结果之补的函数对象<br />
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<span class="t-mark">(函数模板)</span></td>
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