isnan()

Anonymous contributor's avatar
Anonymous contributor
Anonymous contributor's avatar
Anonymous contributor
Published Nov 15, 2022
Contribute to Docs

The isnan() function returns a number telling whether a given value is a NaN value.

Syntax

isnan(x)

The x parameter is a floating-point value that can be of type float, double, long double, or int. The return value is 1 if x is NaN. Otherwise, 0 is returned.

Note: Common cases of a NaN value include:

  • Taking the square root of a negative value
  • Dividing positive or negative zero by positive or negative zero (0/0)

Example

In the example below, the isnan() function checks whether or not the value of x is NaN:

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

This produces the following output:

value of isnan(x) is: 1

Codebyte Example

In the example below, each possible data type is applied to the isnan() function. The application of the int type involves the sqrt() function:

us
Visit us
code
Hide code
Code
Output
Hide output
Hide output
Loading...

All contributors

Looking to contribute?

Learn C++ on Codecademy