75 lines
6.1 KiB
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75 lines
6.1 KiB
HTML
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<title>std::chrono::weekday::operator[]</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::weekday::</span>operator[]</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.html">weekday</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">weekday_indexed</span> operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">unsigned</span> index<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>(1)</td>
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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> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">weekday_last</span> operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">last_spec</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>(2)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 从 <code>*this</code> 和 <code>index</code> 构造 <code>weekday_indexed</code> 。结果表示在某个待指定月份中的第 <code>index</code> 个星期之日。若 <code>index</code> 不在范围 [1, 5] 中或若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>ok<span class="br0">(</span><span class="br0">)</span></span></span> ，则结果中保有的值未指定。</div>
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<div class="t-li1"><span class="t-li">2)</span> 从 <code>*this</code> 构造 <code>weekday_last</code> 。结果表示某个待指定月份中的最后一个星期之日。</div>
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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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<div class="t-li1"><span class="t-li">1)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">weekday_indexed</span><span class="br0">(</span><span class="sy2">*</span>this, index<span class="br0">)</span></span></span></div>
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<div class="t-li1"><span class="t-li">2)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">weekday_last</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span></span></span></div>
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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="co1">// 2019 年十月中的第二个星期二</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> Tuesday<span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span> <span class="sy2">/</span> October <span class="sy2">/</span> 2019y <span class="br0">}</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="co1">// 2019 年十月中的最后一个星期二</span>
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<span class="sy1"><<</span> year_month_day<span class="br0">{</span> Tuesday<span class="br0">[</span>last<span class="br0">]</span> <span class="sy2">/</span> October <span class="sy2">/</span> 2019y <span class="br0">}</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</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
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2019-10-29</pre></div>
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