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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>ratio_subtract</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-numeric.html">numeric</a>&lrm; | <a href="cpp-numeric-ratio.html">ratio</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-ratio.html">&lt;ratio&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> R1, <span class="kw1">class</span> R2 <span class="sy1">&gt;</span><br />
<span class="kw1">using</span> ratio_subtract <span class="sy1">=</span> <span class="coMULTI">/* see below */</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#21035;&#21517;&#27169;&#26495; <code>std::ratio_subtract</code> &#25351;&#20195;&#20108;&#20010; <span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::ratio</a></span> &#29305;&#21270; <code>R1</code> &#21644; <code>R2</code> &#25152;&#34920;&#31034;&#30340;&#20934;&#30830;&#26377;&#29702;&#20998;&#25968;&#30456;&#20943;&#30340;&#32467;&#26524;&#12290;</p>
<p>&#32467;&#26524;&#26159;&#19968;&#20010; <span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::ratio</a></span> &#29305;&#21270; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-ratio-ratio.html"><span class="kw1522">std::<span class="me2">ratio</span></span></a><span class="sy1">&lt;</span>U, V<span class="sy1">&gt;</span></span></span> &#65292;&#32473;&#23450; <span class="t-c"><span class="mw-geshi cpp source-cpp">Num <span class="sy1">==</span> R1<span class="sy4">::</span><span class="me2">num</span> <span class="sy2">*</span> R2<span class="sy4">::</span><span class="me2">den</span> <span class="sy2">-</span> R2<span class="sy4">::</span><span class="me2">num</span> <span class="sy2">*</span> R1<span class="sy4">::</span><span class="me2">den</span></span></span> &#21644; <span class="t-c"><span class="mw-geshi cpp source-cpp">Denom <span class="sy1">==</span> R1<span class="sy4">::</span><span class="me2">den</span> <span class="sy2">*</span> R2<span class="sy4">::</span><span class="me2">den</span></span></span> &#65288;&#35745;&#31639;&#26080;&#31639;&#26415;&#28322;&#20986;&#65289;&#65292; <code>U</code> &#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-ratio-ratio.html"><span class="kw1522">std::<span class="me2">ratio</span></span></a><span class="sy1">&lt;</span>Num, Denom<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">num</span></span></span> &#32780; <code>V</code> &#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-ratio-ratio.html"><span class="kw1522">std::<span class="me2">ratio</span></span></a><span class="sy1">&lt;</span>Num, Denom<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">den</span></span></span> &#12290;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">&#27880;&#24847;</span></h3>
<p>&#33509; <code>U</code> &#25110; <code>V</code> &#19981;&#33021;&#20197; <code>std::intmax_t</code> &#34920;&#31034;&#65292;&#21017;&#31243;&#24207;&#20026;&#30149;&#24335;&#12290;&#33509; <code>Num</code> &#25110; <code>Denom</code> &#19981;&#33021;&#20197; <code>std::intmax_t</code> &#34920;&#31034;&#65292;&#21017;&#31243;&#24207;&#20026;&#30149;&#24335;&#65292;&#38500;&#38750;&#23454;&#29616;&#29983;&#25104;&#20102; <code>U</code> &#21644; <code>V</code> &#30340;&#27491;&#30830;&#20540;&#12290;</p>
<p>&#19978;&#36848;&#23450;&#20041;&#35201;&#27714; <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">ratio_subtract</span><span class="sy1">&lt;</span>R1, R2<span class="sy1">&gt;</span></span></span> &#30340;&#32467;&#26524;&#24050;&#32463;&#34987;&#32422;&#20998;&#21040;&#26368;&#31616;&#65307;&#20363;&#22914; <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">ratio_subtract</span><span class="sy1">&lt;</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">2</span><span class="sy1">&gt;</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">6</span><span class="sy1">&gt;&gt;</span></span></span> &#19982; <span class="t-c"><span class="mw-geshi cpp source-cpp"><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">3</span><span class="sy1">&gt;</span></span></span> &#26159;&#21516;&#19968;&#31867;&#22411;&#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;iostream&gt;</span>
<span class="co2">#include &lt;ratio&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> two_third <span class="sy1">=</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">2</span>, <span class="nu0">3</span><span class="sy1">&gt;</span><span class="sy4">;</span>
<span class="kw1">using</span> one_sixth <span class="sy1">=</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">6</span><span class="sy1">&gt;</span><span class="sy4">;</span>
<span class="kw1">using</span> diff <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ratio_subtract</span><span class="sy1">&lt;</span>two_third, one_sixth<span class="sy1">&gt;</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;2/3 - 1/6 = &quot;</span> <span class="sy1">&lt;&lt;</span> diff<span class="sy4">::</span><span class="me2">num</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;/&#39;</span> <span class="sy1">&lt;&lt;</span> diff<span class="sy4">::</span><span class="me2">den</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></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">2/3 - 1/6 = 1/2</pre></div>
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