FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN

来自cppreference.com
< c‎ | numeric‎ | math
 
 
 
常用数学函数
函数
基本运算
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指数函数
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幂函数
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三角及双曲函数
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误差及伽马函数
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临近整数的浮点运算
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浮点数操作函数
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分类
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宏常量
FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN
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定义于头文件 <math.h>
#define FP_NORMAL    /*implementation defined*/
(C99 起)
#define FP_SUBNORMAL /*implementation defined*/
(C99 起)
#define FP_ZERO      /*implementation defined*/
(C99 起)
#define FP_INFINITE  /*implementation defined*/
(C99 起)
#define FP_NAN       /*implementation defined*/
(C99 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 <stdio.h>
#include <math.h>
#include <float.h>
 
const char *show_classification(double x) {
    switch(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(void)
{
    printf("1.0/0.0 is %s\n", show_classification(1/0.0));
    printf("0.0/0.0 is %s\n", show_classification(0.0/0.0));
    printf("DBL_MIN/2 is %s\n", show_classification(DBL_MIN/2));
    printf("-0.0 is %s\n", show_classification(-0.0));
    printf(" 1.0 is %s\n", show_classification(1.0));
}

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] 引用

  • C11 standard (ISO/IEC 9899:2011):
  • 7.12/6 FP_NORMAL, ... (p: 232)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.12/6 FP_NORMAL, ... (p: 213)

[编辑] 参阅

对给定的浮点值分类
(函数) [编辑]
FP_categoriesC++ 文档