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web/cppreference-zh/chmhelp/cpp-numeric-fenv-fe_exceptions.html
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<!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>FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_fenv_FE_exceptions 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"><small>FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT</small></h1>
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<div id="bodyContent">
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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-fenv.html">fenv</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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<tbody>
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<tr class="t-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-cfenv.html"><cfenv></a></code></div>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define FE_DIVBYZERO /*implementation defined power of 2*/</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-cxx11">(C++11 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define FE_INEXACT /*implementation defined power of 2*/</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-cxx11">(C++11 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define FE_INVALID /*implementation defined power of 2*/</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-cxx11">(C++11 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define FE_OVERFLOW /*implementation defined power of 2*/</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-cxx11">(C++11 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define FE_UNDERFLOW /*implementation defined power of 2*/</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-cxx11">(C++11 起)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define FE_ALL_EXCEPT FE_DIVBYZERO | FE_INEXACT | \<br /></span></span>
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<p><span class="mw-geshi cpp source-cpp"> FE_INVALID | FE_OVERFLOW | \<br /></span></p>
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<span class="mw-geshi cpp source-cpp"> FE_UNDERFLOW</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-cxx11">(C++11 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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<p>所有这些宏常量（除了 <span class="t-lc"><strong class="selflink">FE_ALL_EXCEPT</strong></span> ）都展开成值为 2 的相异次幂整数常量表达式，唯一地鉴别所有受支持浮点异常。每个宏仅若受支持才得到定义。</p>
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<p>宏常量 <span class="t-lc"><strong class="selflink">FE_ALL_EXCEPT</strong></span> 展开成所有其他 <code>FE_*</code> 的逐位或，且始终有定义，若实现不支持浮点异常，则为零。</p>
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<table class="t-dsc-begin">
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<tr class="t-dsc-hitem">
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<td>常量</td>
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<td>定义</td>
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</tr>
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<tr class="t-dsc">
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<td><code>FE_DIVBYZERO</code></td>
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<td>出现于之前浮点运算的极点错误</td>
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</tr>
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<tr class="t-dsc">
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<td><code>FE_INEXACT</code></td>
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<td>不准确结果：必须舍入以存储之前浮点运算的结果</td>
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</tr>
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<tr class="t-dsc">
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<td><code>FE_INVALID</code></td>
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<td>出现于之前浮点运算的定义域错误</td>
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</tr>
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<tr class="t-dsc">
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<td><code>FE_OVERFLOW</code></td>
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<td>之前浮点运算的结果过大而无法表示</td>
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</tr>
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<tr class="t-dsc">
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<td><code>FE_UNDERFLOW</code></td>
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<td>之前浮点运算的结果为有精度损失的非正规值</td>
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</tr>
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<tr class="t-dsc">
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<td><code>FE_ALL_EXCEPT</code></td>
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<td>所有受支持浮点异常的逐位或</td>
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</tr>
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</table>
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<p>实现可于 <code><cfenv></code> 定义附加宏常量以鉴别附加浮点异常。所有这种常量都以 <code>FE_</code> 后随至少一个大写字母开始。</p>
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<p>进一步的细节见 <span class="t-lc"><a href="cpp-numeric-math-math_errhandling.html">math_errhandling</a></span> 。</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-template-editlink" style=""></div>
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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 <cfenv></span>
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<span class="co2">#include <cmath></span>
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<span class="co2">#pragma STDC FENV_ACCESS ON</span>
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<span class="kw4">volatile</span> <span class="kw4">double</span> zero <span class="sy1">=</span> <span class="nu16">0.0</span><span class="sy4">;</span> <span class="co1">// 支持 FENV_ACCESS 处不需要 volatile</span>
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<span class="kw4">volatile</span> <span class="kw4">double</span> one <span class="sy1">=</span> <span class="nu16">1.0</span><span class="sy4">;</span> <span class="co1">// 支持 FENV_ACCESS 处不需要 volatile</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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<a href="cpp-numeric-fenv-feclearexcept.html"><span class="kw1450">std::<span class="me2">feclearexcept</span></span></a><span class="br0">(</span>FE_ALL_EXCEPT<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"1.0/0.0 = "</span> <span class="sy1"><<</span> <span class="nu16">1.0</span> <span class="sy2">/</span> zero <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span><a href="cpp-numeric-fenv-fetestexcept.html"><span class="kw1451">std::<span class="me2">fetestexcept</span></span></a><span class="br0">(</span>FE_DIVBYZERO<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"division by zero reported<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"divsion by zero not reported<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<a href="cpp-numeric-fenv-feclearexcept.html"><span class="kw1450">std::<span class="me2">feclearexcept</span></span></a><span class="br0">(</span>FE_ALL_EXCEPT<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"1.0/10 = "</span> <span class="sy1"><<</span> one<span class="sy2">/</span><span class="nu0">10</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span><a href="cpp-numeric-fenv-fetestexcept.html"><span class="kw1451">std::<span class="me2">fetestexcept</span></span></a><span class="br0">(</span>FE_INEXACT<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"inexact result reported<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"inexact result not reported<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<a href="cpp-numeric-fenv-feclearexcept.html"><span class="kw1450">std::<span class="me2">feclearexcept</span></span></a><span class="br0">(</span>FE_ALL_EXCEPT<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"sqrt(-1) = "</span> <span class="sy1"><<</span> <a href="cpp-numeric-math-sqrt.html"><span class="kw1329">std::<span class="me2">sqrt</span></span></a><span class="br0">(</span><span class="sy2">-</span><span class="nu0">1</span><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="kw1">if</span><span class="br0">(</span><a href="cpp-numeric-fenv-fetestexcept.html"><span class="kw1451">std::<span class="me2">fetestexcept</span></span></a><span class="br0">(</span>FE_INVALID<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"invalid result reported<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1752">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"invalid result not reported<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</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">1.0/0.0 = inf
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division by zero reported
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1.0/10 = 0.1
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inexact result reported
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sqrt(-1) = -nan
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invalid result reported</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">
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<div><a href="cpp-numeric-math-math_errhandling.html"><span class="t-lines"><span>math_errhandling</span><span>MATH_ERRNO</span><span>MATH_ERREXCEPT</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>定义常用数学函数所用的错误处理机制<br />
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<span class="t-mark">(宏常量)</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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