fpclassify

Header: <math.h>

Categorizes floating-point value arg into the following categories: zero, subnormal, normal, infinite, NAN, or implementation-defined category. The macro returns an integral value.

# Declarations

#define fpclassify(arg) /* implementation defined */

(since C99)

# Parameters

# Return value

One of FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO or implementation-defined type, specifying the category of arg.

# Example

#include <float.h>
#include <math.h>
#include <stdio.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));
}

# See also