C++ Math fpclassify()

The function returns the value of type int that matches one of the macro constants, depending on the value of x.

value	description
FP_INFINITE	Positive or negative infinity
FP_NAN	Not a Number
FP_ZERO	Value of zero.
FP_SUBNORMAL	Sub Normal value
FP_NORMAL	Normal value

Syntax

Suppose a number is x. Syntax would be:

int fpclassify(float x);
int fpclassify(double x);
int fpclassify(long double x);
int fpclassify(int x);

Parameter

x: The value which is to be matched with one of the macro constants.

Return value

It returns following integer values: FP_INFINITE, FP_NAN, FP_ZERO, FP_SUBNORMAL ,FP_NORMAL.

Example

Let's see the simple example.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
    double d=1.0/0.0;
    switch(fpclassify(d))
    {
    case FP_INFINITE:
    cout<<"1.0/0.0 is a infinite number ";  
    break;
    case FP_NAN:
    cout<<"1.0/0.0 is Not a Number";
    break;
    case FP_ZERO:
    cout<<"1.0/0.0 is zero.";
    break;
    case FP_SUBNORMAL:
    cout<<"1.0/0.0 is a subnormal value";
    break;
    case FP_NORMAL:
    cout<<"1.0/0.0 is a normal value";
    break;
    default:
    cout<<"wrong number";
    }
    return 0;
}

Output: