C++ Math isnan

The function checks whether the number is a Not a Number or not. If the number is NaN, it returns 1 otherwise 0.

Note: The NaN is a non-representable value for floating point elements such as square root of negative number or the result of 0/0.

Syntax

Suppose a number is 'x'. Syntax would be:

bool isnan(float x);
bool isnan(double x);
bool isnan(long double x);
bool isnan(integral x);

Parameter

x : It is a floating point value.

Return value

It returns 1, if x is NAN otherwise 0.

Example 1

Let's see the simple example when the value of x is 0.0/0.0.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
    float x=0.0/0.0;
    cout<<"value of x is : "<<x<<'\n';
    cout<<"isnan(x) : "<<isnan(x);
    return 0;
}

Output:

value of x is : -nan
isnan(x) : 1

In this example, isnan(x) determines that the value of x is nan. Therefore, it returns 1.

Example 2

Let's see the simple example when the value of x is 4.3.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
    float x=4.3;
    cout<<"value of x is : "<<x<<'\n';
    cout<<"isnan(x) : "<<isnan(x);
    return 0;
}

Output:

value of x is : 4.3
isnan(x) : 0

In this example, isnan(x) function determines that the value of x is not 'nan'. Therefore, it returns 0 value.