470 lines
33 KiB
HTML
470 lines
33 KiB
HTML
<!DOCTYPE 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::duration</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_duration skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>duration</h1>
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<div id="bodyContent">
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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 id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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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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<td></td>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><br /></span>
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<p> <span class="kw1">class</span> Rep,<br />
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<span class="kw1">class</span> Period <span class="sy1">=</span> <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">1</span><span class="sy1">></span><br /></p>
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<span class="sy1">></span> <span class="kw1">class</span> duration<span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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<p>类模板 <code>std::chrono::duration</code> 表示时间间隔。</p>
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<p>它由 <code>Rep</code> 类型的计次数和计次周期组成，其中计次周期是一个编译期有理数常量，表示从一个计次到下一个的秒数。</p>
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<p>存储于 <code>duration</code> 的数据仅有 <code>Rep</code> 类型的计次数。若 <code>Rep</code> 是浮点数，则 <code>duration</code> 能表示小数的计次数。 <code>Period</code> 被包含为时长类型的一部分，且只在不同时长间转换时使用。</p>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<table class="t-dsc-begin">
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<td>成员类型</td>
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<td>定义</td>
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<td><code>rep</code></td>
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<td><code>Rep</code> ，表示计次数的算术类型</td>
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<td><code>period</code></td>
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<td><span class="t-rev-inl t-until-cxx17"><span><code>Period</code></span> <span><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></span></span><span class="t-rev-inl t-since-cxx17"><span><code>typename Period::type</code></span> <span><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></span></span> ，表示计次周期的 <span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::ratio</a></span> （即每秒的次数）</td>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<table class="t-dsc-begin">
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-chrono-duration-duration.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造新 duration<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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</td>
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<td>赋值内容<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-count.html"><span class="t-lines"><span>count</span></span></a></div>
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</div>
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</td>
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<td>返回计次的计数<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-zero.html"><span class="t-lines"><span>zero</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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</div>
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</td>
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<td>返回特殊时长值零<br />
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<span class="t-mark">(公开静态成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-min.html"><span class="t-lines"><span>min</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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</div>
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</td>
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<td>返回特殊时长值最小值<br />
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<span class="t-mark">(公开静态成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-max.html"><span class="t-lines"><span>max</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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</div>
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</td>
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<td>返回特殊时长值最大值<br />
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<span class="t-mark">(公开静态成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator_arith.html"><span class="t-lines"><span>operator+</span><span>operator-</span></span></a></div>
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</div>
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</td>
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<td>实现一元 + 和一元 -<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator_arith2.html"><span class="t-lines"><span>operator++</span><span>operator++<span class="t-dsc-small">(int)</span></span><span>operator--</span><span>operator--<span class="t-dsc-small">(int)</span></span></span></a></div>
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</div>
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</td>
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<td>递增或递减滴答计数<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator_arith3.html"><span class="t-lines"><span>operator+=</span><span>operator-=</span><span>operator*=</span><span>operator/=</span><span>operator%=</span></span></a></div>
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</div>
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</td>
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<td>实现二个时长间的复合赋值<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E9.9D.9E.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">非成员函数</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator_arith4.html"><span class="t-lines"><span>operator+</span><span>operator-</span><span>operator*</span><span>operator/</span><span>operator%</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>实现以时长为实参的算术运算<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator_cmp.html"><span class="t-lines"><span>operator==</span><span>operator!=</span><span>operator<</span><span>operator<=</span><span>operator></span><span>operator>=</span><span>operator<=></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>比较两个时长<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-duration_cast.html"><span class="t-lines"><span>duration_cast</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>转换时长到另一个拥有不同嘀嗒间隔的时长<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-floor.html"><span class="t-lines"><span>floor<span class="t-dsc-small">(std::chrono::duration)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>以向下取整的方式，将一个时长转换为另一个时长<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-ceil.html"><span class="t-lines"><span>ceil<span class="t-dsc-small">(std::chrono::duration)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>以向上取整的方式，将一个时长转换为另一个时长<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-round.html"><span class="t-lines"><span>round<span class="t-dsc-small">(std::chrono::duration)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>转换时长到另一个时长，就近取整，偶数优先<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-abs.html"><span class="t-lines"><span>abs<span class="t-dsc-small">(std::chrono::duration)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>获取时长的绝对值<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-operator_ltlt.html"><span class="t-lines"><span>operator<<</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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</div>
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</td>
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<td>进行 <code>duration</code> 上的流输出<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-from_stream.html"><span class="t-lines"><span>from_stream</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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</div>
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</td>
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<td>按照提供的格式，从流分析 <code>duration</code><br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BE.85.E5.8A.A9.E7.B1.BB.E5.9E.8B">辅助类型</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc-hitem">
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<td>类型</td>
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<td>定义</td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::chrono::nanoseconds</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 64 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1519">std::<span class="me2">nano</span></span></a><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::chrono::microseconds</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 55 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1520">std::<span class="me2">micro</span></span></a><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::chrono::milliseconds</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 45 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1521">std::<span class="me2">milli</span></span></a><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::chrono::seconds</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 35 位的有符号整数类型*/</span><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::chrono::minutes</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 29 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">60</span><span class="sy1">>></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::chrono::hours</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 23 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">3600</span><span class="sy1">>></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc">std::chrono::days</span> <span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 25 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">86400</span><span class="sy1">>></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc">std::chrono::weeks</span> <span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 22 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">604800</span><span class="sy1">>></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc">std::chrono::months</span> <span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 20 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">2629746</span><span class="sy1">>></span></span></span></td>
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</tr>
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<tr class="t-dsc">
|
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<td><span class="t-lc">std::chrono::years</span> <span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">duration<span class="sy1"><</span><span class="coMULTI">/*至少 17 位的有符号整数类型*/</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">31556952</span><span class="sy1">>></span></span></span></td>
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</tr>
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</table>
|
|
<p>注意：到 <code>hours</code> 为止的每个预定义时长类型至少涵盖 ±292 年的范围。</p>
|
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<table class="t-rev-begin">
|
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<tr class="t-rev t-since-cxx20">
|
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<td>
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<p>每个预定义时长类型 <code>days</code> 、 <code>weeks</code> 、 <code>months</code> 和 <code>years</code> 至少涵盖 ±40000 年范围。 <code>years</code> 等于 365.2425 <code>days</code> （格里高利年的平均长度）。 <code>months</code> 等于 30.436875 <code>days</code> （ <code>years</code> 的准确的 1/12 ）。</p>
|
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</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</table>
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|
<h3><span class="mw-headline" id=".E8.BE.85.E5.8A.A9.E7.B1.BB">辅助类</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-common_type.html"><span class="t-lines"><span>std::common_type<span class="t-dsc-small"><std::chrono::duration></span></span></span></a></div>
|
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
|
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</div>
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</td>
|
|
<td>特化 <span class="t-lc"><a href="cpp-types-common_type.html">std::common_type</a></span> 特征<br />
|
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<span class="t-mark">(类模板特化)</span></td>
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</tr>
|
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-treat_as_floating_point.html"><span class="t-lines"><span>treat_as_floating_point</span></span></a></div>
|
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
|
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</td>
|
|
<td>指示时长可转换为拥有不同计次的时长<br />
|
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<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-duration_values.html"><span class="t-lines"><span>duration_values</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>构造给定类型计次的零、最小及最大值<br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-duration-formatter.html"><span class="t-lines"><span>std::formatter<span class="t-dsc-small"><std::chrono::duration></span></span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td><span class="t-lc">std::formatter</span> 的特化，按提供的格式格式化 <code>duration</code><br />
|
|
<span class="t-mark">(类模板特化)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.AD.97.E9.9D.A2.E9.87.8F">字面量</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc-header">
|
|
<td colspan="2">
|
|
<div>定义于内联命名空间 <code>std::literals::chrono_literals</code></div>
|
|
</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-operator_22_22h.html"><span class="t-lines"><span>operator""h</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>表示小时的 <span class="t-lc"><strong class="selflink">std::chrono::duration</strong></span> 字面量<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-operator_22_22min.html"><span class="t-lines"><span>operator""min</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>表示分钟的 <span class="t-lc"><strong class="selflink">std::chrono::duration</strong></span> 字面量<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-operator_22_22s.html"><span class="t-lines"><span>operator""s</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>表示秒的 <span class="t-lc"><strong class="selflink">std::chrono::duration</strong></span> 字面量<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-operator_22_22ms.html"><span class="t-lines"><span>operator""ms</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>表示毫秒的 <span class="t-lc"><strong class="selflink">std::chrono::duration</strong></span> 字面量<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-operator_22_22us.html"><span class="t-lines"><span>operator""us</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>表示微秒的 <span class="t-lc"><strong class="selflink">std::chrono::duration</strong></span> 字面量<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-chrono-operator_22_22ns.html"><span class="t-lines"><span>operator""ns</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>表示纳秒的 <span class="t-lc"><strong class="selflink">std::chrono::duration</strong></span> 字面量<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
<table class="t-rev-begin">
|
|
<tr class="t-rev t-since-cxx20">
|
|
<td>
|
|
<p>注意：字面量后缀 <code>d</code> 和 <code>y</code> 不指代 <code>days</code> 和 <code>years</code> ，而是分别指代 <a href="cpp-chrono-day.html"><tt>day</tt></a> 和 <a href="cpp-chrono-year.html"><tt>year</tt></a> 。</p>
|
|
</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<p>此示例演示如何定义几种自定义时长类型及在类型间转换：</p>
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <chrono></span>
|
|
|
|
<span class="kw4">constexpr</span> <span class="kw4">auto</span> year <span class="sy1">=</span> 31556952ll<span class="sy4">;</span> <span class="co1">// 格里高利历年的平均秒数</span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">using</span> shakes <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span><span class="sy1"><</span><span class="kw4">int</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">1</span>, <span class="nu0">100000000</span><span class="sy1">>></span><span class="sy4">;</span>
|
|
<span class="kw1">using</span> jiffies <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span><span class="sy1"><</span><span class="kw4">int</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1522">std::<span class="me2">centi</span></span></a><span class="sy1">></span><span class="sy4">;</span>
|
|
<span class="kw1">using</span> microfortnights <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span><span class="sy1"><</span><span class="kw4">float</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">14</span><span class="sy2">*</span><span class="nu0">24</span><span class="sy2">*</span><span class="nu0">60</span><span class="sy2">*</span><span class="nu0">60</span>, <span class="nu0">1000000</span><span class="sy1">>></span><span class="sy4">;</span>
|
|
<span class="kw1">using</span> nanocenturies <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span><span class="sy1"><</span><span class="kw4">float</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1515">std::<span class="me2">ratio</span></span></a><span class="sy1"><</span><span class="nu0">100</span><span class="sy2">*</span>year, <span class="nu0">1000000000</span><span class="sy1">>></span><span class="sy4">;</span>
|
|
|
|
std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">seconds</span> sec<span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
<a href="cpp-io-cout.html"><span class="kw1751">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"1 second is:<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
|
|
<span class="co1">// 无精度损失的整数尺度转换：无转型</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1751">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">microseconds</span><span class="br0">(</span>sec<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" microseconds<span class="es1">\n</span>"</span>
|
|
<span class="sy1"><<</span> shakes<span class="br0">(</span>sec<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" shakes<span class="es1">\n</span>"</span>
|
|
<span class="sy1"><<</span> jiffies<span class="br0">(</span>sec<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" jiffies<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
|
|
<span class="co1">// 有精度损失的整数尺度转换：需要转型</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1751">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <a href="cpp-chrono-duration-duration_cast.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration_cast</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">minutes</span><span class="sy1">></span><span class="br0">(</span>sec<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span>
|
|
<span class="sy1"><<</span> <span class="st0">" minutes<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
|
|
<span class="co1">// 浮点尺度转换：无转型</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1751">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> microfortnights<span class="br0">(</span>sec<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" microfortnights<span class="es1">\n</span>"</span>
|
|
<span class="sy1"><<</span> nanocenturies<span class="br0">(</span>sec<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" nanocenturies<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">1 second is:
|
|
1000000 microseconds
|
|
100000000 shakes
|
|
100 jiffies
|
|
0 minutes
|
|
0.82672 microfortnights
|
|
0.316887 nanocenturies</pre></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="visualClear"></div>
|
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</div>
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</div>
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</div>
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</body>
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</html>
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