FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN

来自cppreference.com
< cpp‎ | numeric‎ | math
 
 
 
常用数学函数
函数
基本运算
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
指数函数
(C++11)
(C++11)
(C++11)
(C++11)
幂函数
(C++11)
(C++11)
三角与双曲函数
(C++11)
(C++11)
(C++11)
误差与伽马函数
(C++11)
(C++11)
(C++11)
(C++11)
临近整数的浮点运算
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
浮点操作函数
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
分类/比较
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
宏常量
FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
 
定义于头文件 <cmath>
#define FP_NORMAL    /*implementation defined*/
(C++11 起)
#define FP_SUBNORMAL /*implementation defined*/
(C++11 起)
#define FP_ZERO      /*implementation defined*/
(C++11 起)
#define FP_INFINITE  /*implementation defined*/
(C++11 起)
#define FP_NAN       /*implementation defined*/
(C++11 起)

FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN 宏各代表一个独自的浮点数类别。它们都展开成整数常量表达式。

常量 解释
FP_NORMAL 指示值为正规,即不是无穷大、非正规、非数或零
FP_SUBNORMAL 指示值为非正规
FP_ZERO 指示值为正或负零
FP_INFINITE 指示值无法以底层类型表示(正或负无穷大)
FP_NAN 指示值是非数( NaN )

[编辑] 示例

#include <iostream>
#include <cmath>
#include <cfloat>
 
const char* show_classification(double x) {
    switch(std::fpclassify(x)) {
        case FP_INFINITE:  return "Inf";
        case FP_NAN:       return "NaN";
        case FP_NORMAL:    return "normal";
        case FP_SUBNORMAL: return "subnormal";
        case FP_ZERO:      return "zero";
        default:           return "unknown";
    }
}
int main()
{
    std::cout << "1.0/0.0 is " << show_classification(1/0.0) << '\n'
              << "0.0/0.0 is " << show_classification(0.0/0.0) << '\n'
              << "DBL_MIN/2 is " << show_classification(DBL_MIN/2) << '\n'
              << "-0.0 is " << show_classification(-0.0) << '\n'
              << "1.0 is " << show_classification(1.0) << '\n';
}

输出:

1.0/0.0 is Inf
0.0/0.0 is NaN
DBL_MIN/2 is subnormal
-0.0 is zero
1.0 is normal

[编辑] 参阅

归类给定的浮点值
(函数) [编辑]
FP_categoriesC 文档