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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>floor<small>(std::chrono::duration)</small></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>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-chrono.html">&lt;chrono&gt;</a></code></div>
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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> ToDuration, <span class="kw1">class</span> Rep, <span class="kw1">class</span> Period<span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> ToDuration floor<span class="br0">(</span><span class="kw4">const</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>Rep, Period<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><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p>&#36820;&#22238;&#21487;&#34920;&#31034;&#20026; <code>ToDuration</code> &#30340;&#23567;&#20110;&#25110;&#31561;&#20110; <code>d</code> &#30340;&#26368;&#22823;&#26102;&#38271; <code>t</code> &#12290;</p>
<p>&#20989;&#25968;&#19981;&#21442;&#19982;&#37325;&#36733;&#20915;&#35758;&#65292;&#38500;&#38750; <code>ToDuration</code> &#26159; <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> &#30340;&#29305;&#21270;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>d</td>
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<td>&#35201;&#36716;&#25442;&#30340;&#26102;&#38271;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#21521;&#19979;&#21462;&#25972;&#21040; <code>ToDuration</code> &#31867;&#22411;&#26102;&#38271;&#30340; <code>d</code> &#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">&#21487;&#33021;&#30340;&#23454;&#29616;</span></h3>
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<pre class="de1"><span class="kw1">namespace</span> detail <span class="br0">{</span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span><span class="sy1">&gt;</span> <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_duration_v <span class="sy1">=</span> <span class="kw2">false</span><span class="sy4">;</span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> Rep, <span class="kw1">class</span> Period<span class="sy1">&gt;</span> <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_duration_v<span class="sy1">&lt;</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>Rep, Period<span class="sy1">&gt;&gt;</span> <span class="sy1">=</span> <span class="kw2">true</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> To, <span class="kw1">class</span> Rep, <span class="kw1">class</span> Period,
<span class="kw1">class</span> <span class="sy1">=</span> <a href="cpp-types-enable_if.html"><span class="kw631">std::<span class="me2">enable_if_t</span></span></a><span class="sy1">&lt;</span>detail<span class="sy4">::</span><span class="me2">is_duration_v</span><span class="sy1">&lt;</span>To<span class="sy1">&gt;&gt;&gt;</span>
<span class="kw4">constexpr</span> To floor<span class="br0">(</span><span class="kw4">const</span> duration<span class="sy1">&lt;</span>Rep, Period<span class="sy1">&gt;</span><span class="sy3">&amp;</span> d<span class="br0">)</span>
<span class="br0">{</span>
To t <span class="sy1">=</span> <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>To<span class="sy1">&gt;</span><span class="br0">(</span>d<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>t <span class="sy1">&gt;</span> d<span class="br0">)</span>
<span class="kw1">return</span> t <span class="sy2">-</span> To<span class="br0">{</span><span class="nu0">1</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">return</span> t<span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;iomanip&gt;</span>
<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>
<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>
<span class="kw1">using</span> Sec <span class="sy1">=</span> <a href="cpp-chrono-duration.html"><span class="kw997">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">seconds</span></span></a><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;Duration<span class="es1">\t</span>Floor<span class="es1">\t</span>Round<span class="es1">\t</span>Ceil<span class="es1">\n</span>&quot;</span>
<span class="st0">&quot;(ms)<span class="es1">\t</span><span class="es1">\t</span>(sec)<span class="es1">\t</span>(sec)<span class="es1">\t</span>(sec)<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="kw4">auto</span> <span class="kw4">const</span> d<span class="sy4">:</span> <span class="br0">{</span>
<span class="sy2">+</span>4999ms, <span class="sy2">+</span>5000ms, <span class="sy2">+</span>5001ms, <span class="sy2">+</span>5499ms, <span class="sy2">+</span>5500ms, <span class="sy2">+</span>5999ms,
<span class="sy2">-</span>4999ms, <span class="sy2">-</span>5000ms, <span class="sy2">-</span>5001ms, <span class="sy2">-</span>5499ms, <span class="sy2">-</span>5500ms, <span class="sy2">-</span>5999ms, <span class="br0">}</span><span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-showpos.html"><span class="kw1770">std::<span class="me2">showpos</span></span></a> <span class="sy1">&lt;&lt;</span> d.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;<span class="es1">\t</span><span class="es1">\t</span>&quot;</span>
<span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">floor</span><span class="sy1">&lt;</span>Sec<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 class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\t</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">round</span><span class="sy1">&lt;</span>Sec<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 class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\t</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">ceil</span> <span class="sy1">&lt;</span>Sec<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 class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">Duration Floor Round Ceil
(ms) (sec) (sec) (sec)
+4999 +4 +5 +5
+5000 +5 +5 +5
+5001 +5 +5 +6
+5499 +5 +5 +6
+5500 +5 +6 +6
+5999 +5 +6 +6
-4999 -5 -5 -4
-5000 -5 -5 -5
-5001 -6 -5 -5
-5499 -6 -5 -5
-5500 -6 -6 -5
-5999 -6 -6 -5</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-chrono-duration-duration_cast.html"><span class="t-lines"><span>duration_cast</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>&#36716;&#25442;&#26102;&#38271;&#21040;&#21478;&#19968;&#20010;&#25317;&#26377;&#19981;&#21516;&#22016;&#21970;&#38388;&#38548;&#30340;&#26102;&#38271;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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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>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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<td>&#20197;&#21521;&#19978;&#21462;&#25972;&#30340;&#26041;&#24335;&#65292;&#23558;&#19968;&#20010;&#26102;&#38271;&#36716;&#25442;&#20026;&#21478;&#19968;&#20010;&#26102;&#38271;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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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>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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<td>&#36716;&#25442;&#26102;&#38271;&#21040;&#21478;&#19968;&#20010;&#26102;&#38271;&#65292;&#23601;&#36817;&#21462;&#25972;&#65292;&#20598;&#25968;&#20248;&#20808;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-chrono-time_point-floor.html"><span class="t-lines"><span>floor<span class="t-dsc-small">(std::chrono::time_point)</span></span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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<td>&#36716;&#25442; time_point &#21040;&#21478;&#19968;&#20010;&#65292;&#21521;&#19979;&#21462;&#25972;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-numeric-math-floor.html"><span class="t-lines"><span>floor</span><span>floorf</span><span>floorl</span></span></a></div>
<div><span class="t-lines"><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></div>
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<td>&#19981;&#22823;&#20110;&#32473;&#23450;&#20540;&#30340;&#26368;&#25509;&#36817;&#25972;&#25968;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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