58 lines
3.7 KiB
HTML
58 lines
3.7 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::strict_weak_order</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_concepts_strict_weak_order skin-cppreference2 action-view cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>strict_weak_order</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-concepts.html">concepts</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dsc-header">
|
|
<td>
|
|
<div>定义于头文件 <code><a href="cpp-header-concepts.html"><concepts></a></code></div>
|
|
</td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx20">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span> <span class="kw1">class</span> R, <span class="kw1">class</span> T, <span class="kw1">class</span> U <span class="sy1">></span><br />
|
|
concept strict_weak_order <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">relation</span><span class="sy1"><</span>R, T, U<span class="sy1">></span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>概念 <code>strict_weak_order<R, T, U></code> 指定 <a href="cpp-concepts-relation.html"><code>relation</code></a> <code>R</code> 在其参数上施加严格弱序。</p>
|
|
<h3><span class="mw-headline" id=".E8.AF.AD.E4.B9.89.E8.A6.81.E6.B1.82">语义要求</span></h3>
|
|
<p>若符合下列条件，则关系 <code>r</code> 是严格弱序：</p>
|
|
<ul>
|
|
<li>它非自反：对所有 <code>x</code> ， <code>r(x, x)</code> 为 <code>false</code> ；</li>
|
|
<li>它为传递：对所有 <code>a</code> 、 <code>b</code> 和 <code>c</code> ，若 <code>r(a, b)</code> 与 <code>r(b, c)</code> 均为 <code>true</code> ，则 <code>r(a, c)</code> 为 <code>true</code> ；</li>
|
|
<li>令 <code>e(a, b)</code> 为 <code>!r(a, b) && !r(b, a)</code> ，则 <code>e</code> 为传递： <code>e(a, b) && e(b, c)</code> 蕴含 <code>e(a, c)</code> 。</li>
|
|
</ul>
|
|
<p>在这些条件下，能证明 <code>e</code> 是等价关系，而 <code>r</code> 在 <code>e</code> 所确定的等价类上引入严格全序。</p>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p><a href="cpp-concepts-relation.html"><code>relation</code></a> 与 <code>strict_weak_order</code> 间的区别是纯语义的。</p>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|