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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a>&lrm; | <a href="cpp-utility-variadic.html">variadic</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-cstdarg.html">&lt;cstdarg&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> va_copy<span class="br0">(</span> std<span class="sy4">::</span><span class="kw4">va_list</span> dest, std<span class="sy4">::</span><span class="kw4">va_list</span> src <span class="br0">)</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><code>va_copy</code> &#23439;&#22797;&#21046; <code>src</code> &#21040; <code>dest</code> &#12290;</p>
<p><span class="t-lc"><a href="cpp-utility-variadic-va_end.html">va_end</a></span> &#24212;&#24403;&#22312;&#20989;&#25968;&#36820;&#22238;&#21069;&#25110;&#20219;&#20309; <code>dest</code> &#30340;&#21518;&#32487;&#37325;&#21021;&#22987;&#21270;&#65288;&#36890;&#36807;&#23545; <span class="t-lc"><a href="cpp-utility-variadic-va_start.html">va_start</a></span> &#25110; <code>va_copy</code> &#30340;&#35843;&#29992;&#65289;&#21069;&#23545; <code>dest</code> &#35843;&#29992;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>dest</td>
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<td>&#35201;&#21021;&#22987;&#21270;&#30340; <span class="t-lc">std::va_list</span> &#31867;&#22411;&#23454;&#20363;</td>
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<td>src</td>
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<td>&#23558;&#29992;&#20110;&#21021;&#22987;&#21270; <code>dest</code> &#30340;&#28304; <span class="t-lc">std::va_list</span></td>
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<h3><span class="mw-headline" id=".E5.B1.95.E5.BC.80.E5.80.BC">&#23637;&#24320;&#20540;</span></h3>
<p>&#65288;&#26080;&#65289;</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;cstdarg&gt;</span>
<span class="co2">#include &lt;cmath&gt;</span>
<span class="kw4">double</span> sample_stddev<span class="br0">(</span><span class="kw4">int</span> count, ...<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">double</span> sum <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="kw4">va_list</span> args1<span class="sy4">;</span>
<a href="cpp-utility-variadic-va_start.html"><span class="kw961">va_start</span></a><span class="br0">(</span>args1, count<span class="br0">)</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="kw4">va_list</span> args2<span class="sy4">;</span>
va_copy<span class="br0">(</span>args2, args1<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> i <span class="sy1">&lt;</span> count<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
<span class="kw4">double</span> num <span class="sy1">=</span> <a href="cpp-utility-variadic-va_arg.html"><span class="kw962">va_arg</span></a><span class="br0">(</span>args1, <span class="kw4">double</span><span class="br0">)</span><span class="sy4">;</span>
sum <span class="sy2">+</span><span class="sy1">=</span> num<span class="sy4">;</span>
<span class="br0">}</span>
<a href="cpp-utility-variadic-va_end.html"><span class="kw963">va_end</span></a><span class="br0">(</span>args1<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">double</span> mean <span class="sy1">=</span> sum <span class="sy2">/</span> count<span class="sy4">;</span>
<span class="kw4">double</span> sum_sq_diff <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> i <span class="sy1">&lt;</span> count<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
<span class="kw4">double</span> num <span class="sy1">=</span> <a href="cpp-utility-variadic-va_arg.html"><span class="kw962">va_arg</span></a><span class="br0">(</span>args2, <span class="kw4">double</span><span class="br0">)</span><span class="sy4">;</span>
sum_sq_diff <span class="sy2">+</span><span class="sy1">=</span> <span class="br0">(</span>num<span class="sy2">-</span>mean<span class="br0">)</span> <span class="sy2">*</span> <span class="br0">(</span>num<span class="sy2">-</span>mean<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<a href="cpp-utility-variadic-va_end.html"><span class="kw963">va_end</span></a><span class="br0">(</span>args2<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">return</span> <a href="cpp-numeric-math-sqrt.html"><span class="kw1328">std::<span class="me2">sqrt</span></span></a><span class="br0">(</span>sum_sq_diff <span class="sy2">/</span> count<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> sample_stddev<span class="br0">(</span><span class="nu0">4</span>, <span class="nu16">25.0</span>, <span class="nu16">27.3</span>, <span class="nu16">26.9</span>, <span class="nu16">25.7</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></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">0.920258</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-utility-variadic-va_start.html"><span class="t-lines"><span>va_start</span></span></a></div>
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<td>&#21551;&#29992;&#23545;&#21487;&#21464;&#20989;&#25968;&#23454;&#21442;&#30340;&#35775;&#38382;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-utility-variadic-va_arg.html"><span class="t-lines"><span>va_arg</span></span></a></div>
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<td>&#35775;&#38382;&#19979;&#19968;&#20010;&#21487;&#21464;&#20989;&#25968;&#23454;&#21442;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div><a href="cpp-utility-variadic-va_end.html"><span class="t-lines"><span>va_end</span></span></a></div>
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<td>&#32467;&#26463;&#23545;&#21487;&#21464;&#20989;&#25968;&#23454;&#21442;&#30340;&#36941;&#21382;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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