FP_NAN
FP[医]正常的，FP[医]亚正常的，fp[医]零，FP[医]无限的，FP[医]南
| Defined in header | | |
|---|---|---|
| #define FP_NORMAL /*implementation defined*/ | | (since C++11) |
| #define FP_SUBNORMAL /*implementation defined*/ | | (since C++11) |
| #define FP_ZERO /*implementation defined*/ | | (since C++11) |
| #define FP_INFINITE /*implementation defined*/ | | (since C++11) |
| #define FP_NAN /*implementation defined*/ | | (since C++11) |
大FP_NORMAL，，，FP_SUBNORMAL，，，FP_ZERO，，，FP_INFINITE，，，FP_NAN宏分别代表一个不同类别的浮点数.。它们都展开为整数常量表达式。
| Constant | Explanation |
|---|---|
| FP_NORMAL | indicates that the value is normal, i.e. not an infinity, subnormal, not-a-number or zero |
| FP_SUBNORMAL | indicates that the value is subnormal |
| FP_ZERO | indicates that the value is positive or negative zero |
| FP_INFINITE | indicates that the value is not representable by the underlying type (positive or negative infinity) |
| FP_NAN | indicates that the value is not-a-number (NaN) |
例
二次
#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';
}
二次
产出：
二次
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
二次
另见
| fpclassify (C++11) | categorizes the given floating point value (function) |
|---|
c FP文件[医]类别
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