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<title>std::chrono::day::operator+=, std::chrono::day::operator-=</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::day::</span>operator+=, <span style="font-size:0.7em; line-height:130%">std::chrono::day::</span>operator-=</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-day.html">day</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> day<span class="sy3">&amp;</span> operator<span class="sy2">+</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">days</span><span class="sy3">&amp;</span> d<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> day<span class="sy3">&amp;</span> operator<span class="sy2">-</span><span class="sy1">=</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">days</span><span class="sy3">&amp;</span> d<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<p>&#20174;&#26085;&#26399;&#20540;&#21152;&#25110;&#20943; <span class="t-c"><span class="mw-geshi cpp source-cpp">d.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span></span></span> &#26085;&#12290;</p>
<div class="t-li1"><span class="t-li">1)</span> &#31561;&#20215;&#20110; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this <span class="sy1">=</span> <span class="sy2">*</span>this <span class="sy2">+</span> d<span class="sy4">;</span></span></span></div>
<div class="t-li1"><span class="t-li">2)</span> &#31561;&#20215;&#20110; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this <span class="sy1">=</span> <span class="sy2">*</span>this <span class="sy2">-</span> d<span class="sy4">;</span></span></span></div>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#21040;&#20462;&#25913;&#21518;&#30340;&#27492; <code>day</code> &#30340;&#24341;&#29992;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">&#27880;&#24847;</span></h3>
<p>&#33509;&#32467;&#26524;&#20250;&#22312;&#33539;&#22260; [0, 255] &#22806;&#65292;&#21017;&#23454;&#38469;&#23384;&#20648;&#20540;&#26410;&#25351;&#23450;&#12290;</p>
<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;cassert&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>
std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">day</span> d <span class="br0">{</span><span class="nu0">15</span><span class="br0">}</span><span class="sy4">;</span>
d <span class="sy2">+</span><span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">days</span><span class="br0">(</span><span class="nu0">2</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>d <span class="sy1">==</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">day</span><span class="br0">(</span><span class="nu0">17</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
d <span class="sy2">-</span><span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">days</span><span class="br0">{</span><span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>d <span class="sy1">==</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">day</span><span class="br0">(</span><span class="nu0">14</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></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-day-operator_inc_dec.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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<td>&#33258;&#22686;&#25110;&#33258;&#20943; day<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><a href="cpp-chrono-day-operator_arith_2.html"><span class="t-lines"><span>operator+</span><span>operator-</span></span></a></div>
<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>&#21152;&#25110;&#20943;&#26085;&#25968;&#21644; <code>day</code> &#65292;&#25110;&#27714;&#20108;&#20010; <code>day</code> &#38388;&#30340;&#24046;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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