FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN
来自 cppreference.cn
| 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_NORMAL、FP_SUBNORMAL、FP_ZERO、FP_INFINITE、FP_NAN 宏各自表示一种不同的浮点数类别。它们都扩展为一个整数常量表达式。
| 常量 | 解释 |
FP_NORMAL
|
表示该值为 正常，即非无穷大、非次正常数、非非数值或非零 |
FP_SUBNORMAL
|
表示该值为 次正常数 |
FP_ZERO
|
表示该值为正零或负零 |
FP_INFINITE
|
表示该值无法用底层类型表示（正无穷大或负无穷大） |
FP_NAN
|
表示该值为非数值（NaN） |
[编辑] 示例
运行此代码
#include <cfloat> #include <cmath> #include <iostream> auto 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
| (C++11) |
对给定浮点值进行分类 (function) |
| FP_categories 的 C 文档
| |
