145 lines
8.5 KiB
HTML
145 lines
8.5 KiB
HTML
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<title>std::norm(std::complex)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>norm<span style="font-size:0.7em; line-height:130%">(std::complex)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-numeric.html">numeric</a>‎ | <a href="cpp-numeric-complex.html">complex</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-complex.html"><complex></a></code></div>
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<td rowspan="142">(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T <span class="sy1">></span><br />
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T norm<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span> z <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> T norm<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span> z <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 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">float</span> norm<span class="br0">(</span> <span class="kw4">float</span> z <span class="br0">)</span><span class="sy4">;</span><br /></span>
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<p><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> DoubleOrInteger <span class="sy1">></span><br />
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<span class="kw4">double</span> norm<span class="br0">(</span> DoubleOrInteger z <span class="br0">)</span><span class="sy4">;</span><br /></p>
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<span class="kw4">long</span> <span class="kw4">double</span> norm<span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> z <span class="br0">)</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">float</span> norm<span class="br0">(</span> <span class="kw4">float</span> z <span class="br0">)</span><span class="sy4">;</span><br /></span>
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<p><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> DoubleOrInteger <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <span class="kw4">double</span> norm<span class="br0">(</span> DoubleOrInteger z <span class="br0">)</span><span class="sy4">;</span><br /></p>
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<span class="kw4">constexpr</span> <span class="kw4">long</span> <span class="kw4">double</span> norm<span class="br0">(</span> <span class="kw4">long</span> <span class="kw4">double</span> z <span class="br0">)</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 返回复数 <code>z</code> 模的平方。</div>
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<div class="t-li1"><span class="t-li">2)</span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span></span></span> 和所有整数类型提供附加重载，把参数当做拥有零虚部的复数。</div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<td>z</td>
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<td>-</td>
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<td>复数值</td>
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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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<p><code>z</code> 的模的平方。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>此函数所计算的范数亦被称为<a href="https://en.wikipedia.org/wiki/Field_norm" class="extiw" title="enwiki:Field norm">域范数</a>或<a rel="nofollow" class="external text" href="http://mathworld.wolfram.com/AbsoluteSquare.html">绝对平方</a>。</p>
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<p><a href="cpp-numeric-complex-abs.html"><tt>std::abs</tt></a> 提供复数的<i>欧几里得范数</i>，其计算成本更高。某些情形中，可用 <code>std::norm</code> 替换它，例如若 <span class="t-c"><span class="mw-geshi cpp source-cpp">abs<span class="br0">(</span>z1<span class="br0">)</span> <span class="sy1">></span> abs<span class="br0">(</span>z2<span class="br0">)</span></span></span> 则 <span class="t-c"><span class="mw-geshi cpp source-cpp">norm<span class="br0">(</span>z1<span class="br0">)</span> <span class="sy1">></span> norm<span class="br0">(</span>z2<span class="br0">)</span></span></span> 。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div><a href="cpp-numeric-complex-abs.html"><span class="t-lines"><span>abs<span class="t-dsc-small">(std::complex)</span></span></span></a></div>
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<td>返回复数的模<br />
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<span class="t-mark">(函数模板)</span></td>
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<div><a href="cpp-numeric-complex-conj.html"><span class="t-lines"><span>conj</span></span></a></div>
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<td>返回复共轭<br />
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<span class="t-mark">(函数模板)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-complex-polar.html"><span class="t-lines"><span>polar</span></span></a></div>
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<td>从模和辐角构造复数<br />
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<span class="t-mark">(函数模板)</span></td>
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