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<title>std::chrono::duration&lt;Rep,Period&gt;::duration</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::duration&lt;Rep,Period&gt;::</span>duration</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-chrono.html">chrono</a>&lrm; | <a href="cpp-chrono-duration.html">duration</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> duration<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>(1)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp">duration<span class="br0">(</span> <span class="kw4">const</span> duration<span class="sy3">&amp;</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>(2)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> Rep2 <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <span class="kw1">explicit</span> duration<span class="br0">(</span> <span class="kw4">const</span> Rep2<span class="sy3">&amp;</span> r <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> Rep2, <span class="kw1">class</span> Period2 <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> duration<span class="br0">(</span> <span class="kw4">const</span> duration<span class="sy1">&lt;</span>Rep2,Period2<span class="sy1">&gt;</span><span class="sy3">&amp;</span> d <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(4)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#20174;&#25968;&#20010;&#21487;&#36873;&#25968;&#25454;&#28304;&#20043;&#19968;&#26500;&#36896;&#26032;&#30340; <code>duration</code> &#12290;</p>
<div class="t-li1"><span class="t-li">1)</span> &#40664;&#35748;&#26500;&#36896;&#20989;&#25968;&#35774;&#20026;&#40664;&#35748;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#22797;&#21046;&#26500;&#36896;&#20989;&#25968;&#35774;&#20026;&#40664;&#35748;&#65288;&#36827;&#34892;&#35745;&#27425;&#25968;&#30340;&#36880;&#20301;&#22797;&#21046;&#65289;&#12290;</div>
<div class="t-li1"><span class="t-li">3)</span> &#26500;&#36896;&#25317;&#26377;&#35745;&#27425; <code>r</code> &#30340;&#26102;&#38271;&#12290;&#27880;&#24847;&#27492;&#26500;&#36896;&#20989;&#25968;&#20165;&#33509; <code>const Rep2&amp;</code> &#65288;&#21442;&#25968;&#31867;&#22411;&#65289;&#33021;&#38544;&#24335;&#36716;&#25442;&#20026; <code>rep</code> &#65288;&#26102;&#38271;&#30340;&#35745;&#27425;&#31867;&#22411;&#65289;&#19988;&#28385;&#36275;&#19979;&#21015;&#26465;&#20214;&#25165;&#21442;&#19982;&#37325;&#36733;&#20915;&#35758;</div>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-treat_as_floating_point.html"><span class="kw1001">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">treat_as_floating_point</span></span></a><span class="sy1">&lt;</span>rep<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span></span></span> &#20026; true &#65292;&#25110;</li>
<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-treat_as_floating_point.html"><span class="kw1001">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">treat_as_floating_point</span></span></a><span class="sy1">&lt;</span>Rep2<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span></span></span> &#20026; false &#12290;</li>
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<div class="t-li1"><span class="t-li"></span> &#65288;&#21363;&#65292;&#25317;&#26377;&#25972;&#25968;&#35745;&#27425;&#30340;&#26102;&#38271;&#19981;&#33021;&#20174;&#28014;&#28857;&#20540;&#26500;&#36896;&#65292;&#20294;&#25317;&#26377;&#28014;&#28857;&#35745;&#27425;&#30340;&#26102;&#38271;&#33021;&#20174;&#25972;&#25968;&#20540;&#26500;&#36896;&#65289;</div>
<div class="t-li1"><span class="t-li">4)</span> &#36890;&#36807;&#36716;&#25442; <code>d</code> &#21040;&#30830;&#20999;&#30340;&#21608;&#26399;&#21644;&#35745;&#27425;&#26500;&#36896;&#26102;&#38271;&#65292;&#22914;&#21516;&#29992; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-duration-duration_cast.html"><span class="kw1000">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration_cast</span></span></a><span class="sy1">&lt;</span>duration<span class="sy1">&gt;</span><span class="br0">(</span>d<span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span></span></span> &#12290;&#20026;&#36991;&#20813;&#36716;&#25442;&#26102;&#25130;&#26029;&#65292;&#27492;&#26500;&#36896;&#20989;&#25968;&#21442;&#19982;&#37325;&#36733;&#20915;&#35758;&#65292;&#20165;&#33509;&#36716;&#25442;&#22240;&#25968;&#30340;&#35745;&#31639;&#65288;&#29992; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-ratio-ratio_divide.html"><span class="kw1544">std::<span class="me2">ratio_divide</span></span></a><span class="sy1">&lt;</span>Period2, Period<span class="sy1">&gt;</span></span></span> &#65289;&#19981;&#28322;&#20986;&#19988;&#65306;</div>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-treat_as_floating_point.html"><span class="kw1001">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">treat_as_floating_point</span></span></a><span class="sy1">&lt;</span>rep<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span> <span class="sy1">==</span> <span class="kw2">true</span></span></span></li>
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<div class="t-li1"><span class="t-li"></span> &#25110;&#65306;</div>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-ratio-ratio_divide.html"><span class="kw1544">std::<span class="me2">ratio_divide</span></span></a><span class="sy1">&lt;</span>Period2, period<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">den</span> <span class="sy1">==</span> <span class="nu0">1</span></span></span> &#65292;&#19988;</li>
<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-treat_as_floating_point.html"><span class="kw1001">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">treat_as_floating_point</span></span></a><span class="sy1">&lt;</span>Rep2<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span> <span class="sy1">==</span> <span class="kw2">false</span></span></span> &#12290;</li>
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<div class="t-li1"><span class="t-li"></span> &#65288;&#21363;&#35201;&#20040;&#26102;&#38271;&#20351;&#29992;&#28014;&#28857;&#35745;&#27425;&#65292;&#35201;&#20040; <code>Period2</code> &#33021;&#20026;period&#25972;&#38500;&#65289;</div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>r</td>
<td>-</td>
<td>&#35745;&#27425;&#25968;</td>
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<td>d</td>
<td>-</td>
<td>&#20174;&#20043;&#22797;&#21046;&#30340;&#26102;&#38271;</td>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<p>&#19979;&#21015;&#20195;&#30721;&#23637;&#31034;&#25968;&#20010;&#22914;&#20309;&#26500;&#36896;&#26102;&#38271;&#30340;&#31034;&#20363;&#65288;&#21512;&#27861;&#32773;&#19982;&#38750;&#27861;&#32773;&#65289;&#65306;</p>
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<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;chrono&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-chrono-duration.html"><span class="kw999">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">hours</span></span></a> h<span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// &#19968;&#23567;&#26102;</span>
<a href="cpp-chrono-duration.html"><span class="kw996">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">milliseconds</span></span></a> ms<span class="br0">{</span><span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span> <span class="co1">// 3 &#27627;&#31186;</span>
<a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1533">std::<span class="me2">kilo</span></span></a><span class="sy1">&gt;</span> ks<span class="br0">(</span><span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 3000 &#31186;</span>
<span class="co1">// &#38169;&#35823;&#65306; treat_as_floating_point&lt;int&gt;::value == false,</span>
<span class="co1">// &#27492;&#26102;&#38271;&#21482;&#20801;&#35768;&#25972;&#25968;&#35745;&#27425;</span>
<span class="co1">// std::chrono::duration&lt;int, std::kilo&gt; d3(3.5);</span>
<span class="co1">// &#20351;&#29992;&#23567;&#25968;&#35745;&#27425;&#30340; 30Hz &#38047;</span>
<a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1">&lt;</span><span class="kw4">double</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1522">std::<span class="me2">ratio</span></span></a><span class="sy1">&lt;</span><span class="nu0">1</span>, <span class="nu0">30</span><span class="sy1">&gt;&gt;</span> hz30<span class="br0">(</span><span class="nu16">3.5</span><span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// &#20174; 3 &#27627;&#31186;&#26500;&#36896; 3000 &#24494;&#31186;</span>
<a href="cpp-chrono-duration.html"><span class="kw995">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">microseconds</span></span></a> us <span class="sy1">=</span> ms<span class="sy4">;</span>
<span class="co1">// error: 1/1000000 is not divisible by 1/1000</span>
<span class="co1">// std::chrono::milliseconds ms2 = us</span>
<a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1">&lt;</span><span class="kw4">double</span>, <a href="cpp-numeric-ratio-ratio.html"><span class="kw1528">std::<span class="me2">milli</span></span></a><span class="sy1">&gt;</span> ms2 <span class="sy1">=</span> us<span class="sy4">;</span> <span class="co1">// 3.0 &#27627;&#31186;</span>
<span class="br0">}</span></pre></div>
</div>
</div>
<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">&#32570;&#38519;&#25253;&#21578;</span></h3>
<p>&#19979;&#21015;&#26356;&#25913;&#34892;&#20026;&#30340;&#32570;&#38519;&#25253;&#21578;&#36861;&#28335;&#22320;&#24212;&#29992;&#20110;&#20197;&#21069;&#20986;&#29256;&#30340; C++ &#26631;&#20934;&#12290;</p>
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<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</th>
</tr>
<tr>
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue3050">LWG 3050</a></td>
<td>C++11</td>
<td>&#21487;&#36716;&#25442;&#24615;&#21046;&#32422;&#20351;&#29992;&#38750; const &#20129;&#20540;</td>
<td>&#26367;&#32780;&#20351;&#29992; const &#24038;&#20540;</td>
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</table>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div class="t-dsc-member-div">
<div><a href="cpp-chrono-duration-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
</div>
</td>
<td>&#36171;&#20540;&#20869;&#23481;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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