77 lines
5.6 KiB
HTML
77 lines
5.6 KiB
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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<title>std::chrono::year::is_leap</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_year_is_leap 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::year::</span>is_leap</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-year.html">year</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">bool</span> is_leap<span class="br0">(</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><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p>确定 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 是否表示外推格里高利历中的闰年。</p>
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<p>若存储的年份值满足下列条件则 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 表示闰年</p>
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<ul>
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<li>被 4 整除且不被 100 整除；或</li>
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<li>被 400 整除。</li>
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</ul>
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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>若 <code>*this</code> 表示闰年则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，否则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</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 dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <chrono></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_literals</span><span class="sy4">;</span>
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<span class="kw1">for</span> <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">year</span> y <span class="sy4">:</span> <span class="br0">{</span>2020y, 2021y, 2000y, 3000y<span class="br0">}</span><span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">if</span> <span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> iy<span class="br0">{</span> <span class="kw1">static_cast</span><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span><span class="br0">(</span>y<span class="br0">)</span> <span class="br0">}</span><span class="sy4">;</span> y.<span class="me1">is_leap</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="br0">{</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> iy <span class="sy1"><<</span> <span class="st0">" is a leap year because it is divisible by "</span>
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<span class="sy1"><<</span> <span class="br0">(</span>iy <span class="sy2">%</span> <span class="nu0">400</span> <span class="sy1">==</span> <span class="nu0">0</span> <span class="sy4">?</span> <span class="st0">"400<span class="es1">\n</span>"</span> <span class="sy4">:</span> <span class="st0">"4 and not divisible by 100<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</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> iy <span class="sy1"><<</span> <span class="st0">" is not a leap year<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">2020 is a leap year because it is divisible by 4 and not divisible by 100
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2021 is not a leap year
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2000 is a leap year because it is divisible by 400
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3000 is not a leap year</pre></div>
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