182 lines
18 KiB
HTML
182 lines
18 KiB
HTML
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<title>std::literals::complex_literals::operator""i, operator""if, operator""il</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_complex_operator_i skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::literals::complex_literals::</span>operator""i, operator""if, operator""il</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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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> complex<span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>i<span class="br0">(</span><span class="kw4">long</span> <span class="kw4">double</span> arg<span class="br0">)</span><span class="sy4">;</span><br />
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<span class="kw4">constexpr</span> complex<span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>i<span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> arg<span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td>
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<tr class="t-dcl t-since-cxx14">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> complex<span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span> operator<span class="st0">""</span><span class="kw1">if</span><span class="br0">(</span><span class="kw4">long</span> <span class="kw4">double</span> arg<span class="br0">)</span><span class="sy4">;</span><br />
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<span class="kw4">constexpr</span> complex<span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span> operator<span class="st0">""</span><span class="kw1">if</span><span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> arg<span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td>
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<tr class="t-dcl t-since-cxx14">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> complex<span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>il<span class="br0">(</span><span class="kw4">long</span> <span class="kw4">double</span> arg<span class="br0">)</span><span class="sy4">;</span><br />
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<span class="kw4">constexpr</span> complex<span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>il<span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> arg<span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td>
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<p>构成表示虚数的 <span class="t-lc"><a href="cpp-numeric-complex.html">std::complex</a></span> 字面量。</p>
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<div class="t-li1"><span class="t-li">1)</span> 构成实部为零而虚部为 <code>arg</code> 的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span></span></span> 字面量</div>
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<div class="t-li1"><span class="t-li">2)</span> 构成实部为零而虚部为 <code>arg</code> 的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span></span></span> 字面量</div>
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<div class="t-li1"><span class="t-li">3)</span> 构成实部为零而虚部为 <code>arg</code> 的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span></span></span> 字面量</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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<table class="t-par-begin">
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<td>arg</td>
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<td>-</td>
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<td>虚数的值</td>
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</table>
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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>实部为零而虚部为 <code>arg</code> 的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a></span></span> 字面量</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>这些运算符声明于命名空间 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">::</span><span class="me2">complex_literals</span></span></span> ，其中 <code>literals</code> 和 <code>complex_literals</code> 都是内联命名空间。可以由 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">complex_literals</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">::</span><span class="me2">complex_literals</span></span></span> 获取对这些运算符的访问。</p>
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<p>尽管 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">if</span></span></span> 在 C++ 中是<a href="cpp-keywords-if.html" class="mw-redirect">关键词</a>，它亦为 <span class="t-c"><span class="mw-geshi cpp source-cpp">operator <span class="st0">""</span><span class="kw1">if</span></span></span> 形式的<a href="cpp-language-user_literal.html">字面量运算符</a> 的 <span class="t-spar">ud-suffix</span> ，并在如 <span class="t-c"><span class="mw-geshi cpp source-cpp">1if</span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp">1.0if</span></span> 的字面量表达式中，因为它不被空白符分隔而且它不是独立记号。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<table class="eq-fun-cpp-table">
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<th>版本一</th>
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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="kw4">constexpr</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>i<span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> d<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">{</span><span class="nu16">0.0</span>, <span class="kw1">static_cast</span><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">(</span>d<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">constexpr</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>i<span class="br0">(</span><span class="kw4">long</span> <span class="kw4">double</span> d<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">{</span><span class="nu16">0.0</span>, <span class="kw1">static_cast</span><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span><span class="br0">(</span>d<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<tr>
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<th>版本二</th>
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</tr>
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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="kw4">constexpr</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span> operator<span class="st0">""</span><span class="kw1">if</span><span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> d<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span><span class="br0">{</span><span class="nu17">0.0f</span>, <span class="kw1">static_cast</span><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span><span class="br0">(</span>d<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">constexpr</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span> operator<span class="st0">""</span><span class="kw1">if</span><span class="br0">(</span><span class="kw4">long</span> <span class="kw4">double</span> d<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span><span class="br0">{</span><span class="nu17">0.0f</span>, <span class="kw1">static_cast</span><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span><span class="br0">(</span>d<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<tr>
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<th>版本三</th>
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</tr>
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<tr>
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<td>
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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="kw4">constexpr</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>il<span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span> d<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span><span class="br0">{</span>0.0L, <span class="kw1">static_cast</span><span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span><span class="br0">(</span>d<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">constexpr</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span> operator<span class="st0">""</span>il<span class="br0">(</span><span class="kw4">long</span> <span class="kw4">double</span> d<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">></span><span class="br0">{</span>0.0L, d<span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</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 class="t-example-live-link"></div>
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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 <iostream></span>
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<span class="co2">#include <complex></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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<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">complex_literals</span><span class="sy4">;</span>
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<a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">double</span><span class="sy1">></span> c <span class="sy1">=</span> <span class="nu16">1.0</span> <span class="sy2">+</span> 1i<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">"abs"</span> <span class="sy1"><<</span> c <span class="sy1"><<</span> <span class="st0">" = "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">abs</span><span class="br0">(</span>c<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-numeric-complex.html"><span class="kw1472">std::<span class="me2">complex</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span> z <span class="sy1">=</span> <span class="nu17">3.0f</span> <span class="sy2">+</span> 4.0if<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">"abs"</span> <span class="sy1"><<</span> z <span class="sy1"><<</span> <span class="st0">" = "</span> <span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">abs</span><span class="br0">(</span>z<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<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">abs(1,1) = 1.41421
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abs(3,4) = 5</pre></div>
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</div>
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</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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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-numeric-complex-complex.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造一个复数<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-complex-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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</td>
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<td>赋值内容<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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