53 lines
4.0 KiB
HTML
53 lines
4.0 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>C++ 具名要求：函数对象 (FunctionObject)</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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</head>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_named_req_FunctionObject skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">C++ 具名要求：</span><span style="font-style:italic">函数对象</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(FunctionObject)</span></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-named_req.html">named req</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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<p><strong class="selflink"><span style="font-style:italic">函数对象</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(FunctionObject)</span></strong> 类型是可用在函数调用运算符左侧的对象的类型。</p>
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<h3><span class="mw-headline" id=".E8.A6.81.E6.B1.82">要求</span></h3>
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<p>若满足下列条件，则类型 <code>T</code> 满足 <span style="font-style:italic">函数对象</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(FunctionObject)</span></p>
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<ul>
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<li>类型 <code>T</code> 满足 <span class="t-lc"><a href="cpp-types-is_object.html">std::is_object</a></span>，且</li>
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</ul>
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<p>给定</p>
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<ul>
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<li><code>T</code> 或 <code>const T</code> 类型的值 <code>f</code></li>
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<li><code>args</code>，为适合的实参列表，可以为空</li>
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</ul>
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<p>则下列表达式必须合法：</p>
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<table class="wikitable">
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<tr>
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<th>表达式</th>
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<th>要求</th>
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</tr>
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<tr>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">f<span class="br0">(</span>args<span class="br0">)</span></span></span></td>
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<td>进行函数调用</td>
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</tr>
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</table>
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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>函数和到函数的引用不是函数对象类型，但因为函数到指针<a href="cpp-language-implicit_conversion.html">隐式转换</a>，它们能用在期待函数对象类型的地方。</p>
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<h3><span class="mw-headline" id=".E6.A0.87.E5.87.86.E5.BA.93">标准库</span></h3>
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<ul>
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<li>所有<a href="cpp-language-pointer.html#.E5.87.BD.E6.95.B0.E6.8C.87.E9.92.88">函数指针</a>都满足此要求。</li>
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<li>所有定义于 <a href="cpp-header-functional.html"><tt><functional></tt></a> 的函数对象。</li>
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<li>某些 <a href="cpp-header-functional.html"><tt><functional></tt></a> 的函数的返回类型。</li>
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</ul>
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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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