138 lines
7.0 KiB
HTML
138 lines
7.0 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>imaginary</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_numeric_complex_imaginary skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading">imaginary</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-numeric.html">numeric</a>‎ | <a href="c-numeric-complex.html">complex</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<div>定义于头文件 <code><complex.h></code></div>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-c99">
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<td>
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<div><span class="mw-geshi c source-c"><span class="co2">#define imaginary _Imaginary</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tbody>
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</table>
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<p>此宏展开成关键词 <a href="c-keyword-_Imaginary.html">_Imaginary</a> 。</p>
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<p>这是一个便利宏，使你能用 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">float</span> imaginary</span></span> 、 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">double</span> imaginary</span></span> 及 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">long</span> <span class="kw4">double</span> imaginary</span></span> 作为书写三种纯虚数 C 类型 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">float</span> _Imaginary</span></span> 、 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">double</span> _Imaginary</span></span> 以及 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">long</span> <span class="kw4">double</span> _Imaginary</span></span> 的替用方式。</p>
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<p>同 C 中的任意纯虚数支持，仅若支持虚数才定义此宏。</p>
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<table class="t-rev-begin">
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<tr class="t-rev t-since-c99 t-until-c11">
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<td>推荐编译器定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_IEC_559_COMPLEX__</span></span> ，但并不强制要求其支持虚数。 POSIX 推荐检查是否定义宏 <span class="t-c"><span class="mw-geshi c source-c"><a href="c-numeric-complex-Imaginary_I.html"><span class="kw745">_Imaginary_I</span></a></span></span> 以鉴别是否支持虚数。</td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span><br />
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<span class="t-mark-rev t-until-c11">(C11 前)</span></td>
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<tr class="t-rev t-since-c11">
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<td>
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<p>若定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_IEC_559_COMPLEX__</span></span> ，则支持虚数。</p>
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</td>
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<td><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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</tr>
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</table>
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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>允许程序取消定义，而且可在之后重定义 <span class="t-c"><span class="mw-geshi c source-c">imaginary</span></span> 宏。</p>
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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="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <complex.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">double</span> imaginary i <span class="sy1">=</span> <span class="nu16">2.0</span><span class="sy2">*</span>I<span class="sy4">;</span> <span class="co1">// 纯虚数</span>
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<span class="kw4">double</span> f <span class="sy1">=</span> <span class="nu16">1.0</span><span class="sy4">;</span> <span class="co1">// 纯实数</span>
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<span class="kw4">double</span> <a href="c-numeric-complex-complex.html"><span class="kw743">complex</span></a> z <span class="sy1">=</span> f <span class="sy2">+</span> i<span class="sy4">;</span> <span class="co1">// 复数</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"z = %.1f%+.1fi<span class="es1">\n</span>"</span>, <a href="c-numeric-complex-creal.html"><span class="kw753">creal</span></a><span class="br0">(</span>z<span class="br0">)</span>, <a href="c-numeric-complex-cimag.html"><span class="kw750">cimag</span></a><span class="br0">(</span>z<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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<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">z = 1.0+2.0i</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.3.1/5 imaginary (p: 188)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>G.6/1 imaginary (p: 537)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.3.1/3 imaginary (p: 170)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>G.6/1 imaginary (p: 472)</li>
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</ul>
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</dd>
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</dl>
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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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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-numeric-complex-complex.html"><span class="t-lines"><span>complex</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>复数类型宏<br />
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<span class="t-mark">(关键词宏)</span></td>
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</tr>
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</table>
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</div>
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</div>
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<div class="visualClear"></div>
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</div>
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</body>
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