129 lines
7.8 KiB
HTML
129 lines
7.8 KiB
HTML
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<title>std::chrono::duration<Rep,Period>::operator+(unary), std::chrono::duration<Rep,Period>::operator-(unary)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::duration<Rep,Period>::</span>operator+<span class="t-dsc-small">(unary)</span>, <span style="font-size:0.7em; line-height:130%">std::chrono::duration<Rep,Period>::</span>operator-<span class="t-dsc-small">(unary)</span></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-duration.html">duration</a></span></div>
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<td rowspan="142">(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> duration operator<span class="sy2">+</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <a href="cpp-types-common_type.html"><span class="kw636">std::<span class="me2">common_type_t</span></span></a><span class="sy1"><</span>duration<span class="sy1">></span> operator<span class="sy2">+</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<td rowspan="142">(2)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> duration operator<span class="sy2">-</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <a href="cpp-types-common_type.html"><span class="kw636">std::<span class="me2">common_type_t</span></span></a><span class="sy1"><</span>duration<span class="sy1">></span> operator<span class="sy2">-</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<p>实现 duration 的一元加和一元减。</p>
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<p>若 <code>rep_</code> 为 duration 对象中保有计次数的成员变量,而 <code>D</code> 是返回类型,则</p>
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<div class="t-li1"><span class="t-li">1)</span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> D<span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span><span class="sy4">;</span></span></span></div>
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<div class="t-li1"><span class="t-li">2)</span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> D<span class="br0">(</span><span class="sy2">-</span>rep_<span class="br0">)</span><span class="sy4">;</span></span></span></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<p>(无)</p>
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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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<div class="t-li1"><span class="t-li">1)</span> 此 duration 对象的副本</div>
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<div class="t-li1"><span class="t-li">2)</span> 此 duration 对象的副本,对其计次数取反</div>
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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 class="t-example">
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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 <chrono></span>
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<span class="co2">#include <iostream></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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<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> s1<span class="br0">(</span><span class="nu0">10</span><span class="br0">)</span><span class="sy4">;</span>
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<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> s2 <span class="sy1">=</span> <span class="sy2">-</span>s1<span class="sy4">;</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> <span class="st0">"negated 10 seconds are "</span> <span class="sy1"><<</span> s2.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" seconds<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</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">negated 10 seconds are -10 seconds</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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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 class="t-dsc">
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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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</table>
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