84 lines
5.5 KiB
HTML
84 lines
5.5 KiB
HTML
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<title>std::chrono::weekday_indexed::weekday_indexed</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_weekday_indexed_weekday_indexed 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::chrono::weekday_indexed::</span>weekday_indexed</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-chrono.html">chrono</a>‎ | <a href="cpp-chrono-weekday_indexed.html">weekday indexed</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">weekday_indexed<span class="br0">(</span><span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> weekday_indexed<span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">weekday</span><span class="sy3">&</span> wd, <span class="kw4">unsigned</span> index<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p>构造 <code>weekday_indexed</code> 。</p>
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<div class="t-li1"><span class="t-li">1)</span> 默认构造函数保留 <span class="t-lc">std::chrono::weekday</span> 和下标值未初始化。</div>
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<div class="t-li1"><span class="t-li">2)</span> 构造存储星期之日 <code>wd</code> 和下标 <code>index</code> 的 <code>weekday_indexed</code> 。若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>wd.<span class="me1">ok</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">||</span> index <span class="sy1">></span> <span class="nu0">7</span></span></span> 则保有的值未指定。</div>
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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>更方便的构造 <code>weekday_indexed</code> 的方式是用 <code>weekday</code> 的 <code>operator[]</code> ，即 <span class="t-c"><span class="mw-geshi cpp source-cpp">wd<span class="br0">[</span>index<span class="br0">]</span></span></span> 。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <chrono></span>
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<span class="co2">#include <iostream></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">;</span>
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<span class="kw4">auto</span> wdi <span class="sy1">=</span> Tuesday<span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span><span class="sy4">;</span> <span class="co1">// wdi 是表示第 2 个星期二的 weekday_indexed</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> year_month_day<span class="br0">{</span> wdi <span class="sy2">/</span> October <span class="sy2">/</span> 2019y <span class="br0">}</span> <span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div class="text source-text">
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<pre class="de1">2019-10-08</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div><a href="cpp-chrono-weekday-operator_at.html"><span class="t-lines"><span>operator[]</span></span></a></div>
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<td>从此 <code>weekday</code> 构造 <a href="cpp-chrono-weekday_indexed.html"><tt>weekday_indexed</tt></a> 或 <a href="cpp-chrono-weekday_last.html"><tt>weekday_last</tt></a> 的便利语法<br />
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<span class="t-mark">(<code>std::chrono::weekday</code> 的公开成员函数)</span></td>
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