NaN, an acronym for Not a Number is an exception that usually occurs in the cases when an expression results in a number that is undefined or can’t be represented. It is used for floating-point operations. For example:
- The square root of negative numbers
- Division by zero
- Taking the log of zero or a negative number etc.
CPP
// C++ code to demonstrate NaN exception
#include <cmath>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
float a = 2, b = -2;
// Prints the number (1.41421)
cout << sqrt(a) << endl;
// Prints "nan" exception
// sqrt(-2) is complex number
cout << sqrt(b) << endl;
return 0;
}
Output
1.41421-nan
Time Complexity: O(1)
Space Complexity: O(1)
How to check for NaN in C++?
Method 1: Using compare (“==”) operator.
In this method, we check if a number is complex by comparing it with itself. If the result is true, then the number is not complex i.e., real. But if the result is false, then “nan” is returned, i.e. the number is complex.
CPP
// C++ code to check for NaN exception
// using "==" operator
#include <cmath>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
float a = sqrt(2);
float b = sqrt(-2);
// Returns true, a is real number
// prints "Its a real number"
a == a ? cout << "Its a real number" << endl
: cout << "Its NaN" << endl;
// Returns false, b is complex number
// prints "Its nan"
b == b ? cout << "Its a real number" << endl
: cout << "Its NaN" << endl;
return 0;
}
Output
Its a real numberIts NaN
Time Complexity: O(1)
Space Complexity: O(1)
Method 2: Using inbuilt function “isnan()”
Another way to check for NaN is by using “isnan()” function, this function returns true if a number is complex else it returns false. This C library function is present in <cmath> header file.
CPP
// C++ code to check for NaN exception
// using "isnan()"
#include <cmath>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
float a = sqrt(2);
float b = sqrt(-2);
// Returns false as a
// is real number
isnan(a) ? cout << "Its NaN" << endl
: cout << "Its a real number" << endl;
// Returns true as b is NaN
isnan(b) ? cout << "Its NaN" << endl
: cout << "Its a real number" << endl;
return 0;
}
Output
Its a real numberIts NaN
Time Complexity: O(1)
Space Complexity: O(1)
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Last Updated : 06 Feb, 2023
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