std::fpclassify
STD：：fpclass
| Defined in header | | |
|---|---|---|
| int fpclassify( float arg | (1) | (since C++11) |
| int fpclassify( double arg | (2) | (since C++11) |
| int fpclassify( long double arg | (3) | (since C++11) |
| int fpclassify( Integral arg | (4) | (since C++11) |
1-3%29对浮点数进行分类arg分为以下几类：零、次正规、正规、无限、NAN或实现定义范畴.
4%29一组重载或接受from任何论点积分型等效于%282%29%28的参数转换为double29%。
参数
| arg | - | floating point value |
|---|
返回值
其中之一FP_INFINITE，，，FP_NAN，，，FP_NORMAL，，，FP_SUBNORMAL，，，FP_ZERO或实现定义类型，指定arg...
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
| isfinite (C++11) | checks if the given number has finite value (function) |
|---|---|
| isinf (C++11) | checks if the given number is infinite (function) |
| isnan (C++11) | checks if the given number is NaN (function) |
| isnormal (C++11) | checks if the given number is normal (function) |
| numeric_limits | provides an interface to query properties of all fundamental numeric types. (class template) |
c fpclass的文档
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