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std:: fetestexcept

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fetestexcept
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定义于头文件 <cfenv>
int fetestexcept ( int excepts ) ;
(C++11 起)

确定当前设置了指定浮点异常子集中的哪些异常。参数 excepts 是 浮点异常宏 的按位或运算结果。

目录

参数

excepts - 列出待测试异常标志的位掩码

返回值

浮点异常宏的按位或运算结果，这些宏既包含在 excepts 中，又对应当前已设置的浮点异常。

示例

运行此代码 
#include <cfenv>
#include <cmath>
#include <iostream>
// #pragma STDC FENV_ACCESS ON
volatile double zero = 0.0; // volatile not needed where FENV_ACCESS is supported
volatile double one = 1.0;  // volatile not needed where FENV_ACCESS is supported
int main()
{
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout <<  "1.0/0.0 = " << 1.0 / zero << '\n';
    if (std::fetestexcept(FE_DIVBYZERO))
        std::cout << "division by zero reported\n";
    else
        std::cout << "division by zero not reported\n";
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "1.0/10 = " << one / 10 << '\n';
    if (std::fetestexcept(FE_INEXACT))
        std::cout << "inexact result reported\n";
    else
        std::cout << "inexact result not reported\n";
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "sqrt(-1) = " << std::sqrt(-1) << '\n';
    if (std::fetestexcept(FE_INVALID))
        std::cout << "invalid result reported\n";
    else
        std::cout << "invalid result not reported\n";
}

可能的输出： 

1.0/0.0 = inf
division by zero reported
1.0/10 = 0.1
inexact result reported
sqrt(-1) = -nan
invalid result reported

参见

(C++11)
清除指定的浮点状态标志
(函数)
C 文档 用于 fetestexcept