107 lines
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107 lines
11 KiB
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>clock_cast</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-chrono.html">chrono</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-chrono.html"><chrono></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Dest, <span class="kw1">class</span> Source, <span class="kw1">class</span> Duration<span class="sy1">></span><br />
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<span class="kw4">auto</span> clock_cast<span class="br0">(</span><span class="kw4">const</span> <a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Source, Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</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>转换时钟 <code>Source</code> 的时间点 <code>t</code> 为时钟 <code>Dest</code> 的等价时间点，必要时以 <span class="t-lc"><a href="cpp-chrono-system_clock.html">std::chrono::system_clock</a></span> 和/或 <span class="t-lc">std::chrono::utc_clock</span> 作为中介。</p>
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<ul>
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<li>若表达式 <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">clock_time_conversion</span><span class="sy1"><</span>Dest, Source<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 为良构，则返回该表达式的结果。</li>
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<li>否则，若下列二个表达式至少有一个为良构，则</li>
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</ul>
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<dd>
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<ul>
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<li>若二个表达式均为良构，则转换有歧义，而程序为谬构。</li>
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<li>否则，二个表达式恰有一个为良构；返回该表达式的结果。</li>
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</ul>
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</dd>
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</dl>
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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">clock_time_conversion</span><span class="sy1"><</span>Dest, <a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span><br />
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std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">clock_time_conversion</span><span class="sy1"><</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a>, Source<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span>t<span class="br0">)</span><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">clock_time_conversion</span><span class="sy1"><</span>Dest, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span><br />
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std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">clock_time_conversion</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span>, Source<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span></span></span></div>
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<ul>
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<li>否则，若下列二个表达式至少有一个为良构，则</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>若两个表达式均为良构，则转换有歧义，而程序为谬构。</li>
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<li>否则，二个表达式恰有一个为良构；返回该表达式的结果。</li>
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</ul>
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</dd>
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</dl>
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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">clock_time_conversion</span><span class="sy1"><</span>Dest, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span><br /></span></span>
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<p> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">clock_time_conversion</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span>, <a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span><br /></p>
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std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">clock_time_conversion</span><span class="sy1"><</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a>, Source<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span><span class="br0">)</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">clock_time_conversion</span><span class="sy1"><</span>Dest, <a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span><br /></span></span>
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<p> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">clock_time_conversion</span><span class="sy1"><</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a>, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span><br /></p>
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std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">clock_time_conversion</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span>, Source<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span></div>
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<li>否则，此函数不参与重载决议。</li>
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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>上面确定的转换结果。</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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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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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-clock_time_conversion.html"><span class="t-lines"><span>clock_time_conversion</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>定义如何转换一个时钟的时间点为另一个的特性类<br />
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<span class="t-mark">(类模板)</span></td>
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