#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)The FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN macros each represent a distinct category of floating-point numbers. They all expand to an integer constant expression.
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) [edit] Example
#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';
}
Output:
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[edit] See also
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