NaN in C++ – What is it and how to check for it?
What is NaN ?
NaN, acronym for “Not a Number” is an exception which usually occurs in the cases when an expression results in a number that can’t be represented. For example square root of negative numbers.
// C++ code to demonstrate NaN exception#include<iostream>#include<cmath> // for sqrt()using namespace std;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
How to check for NaN ?
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 result is false, then “nan” is returned, i.e the number is complex.
// C++ code to check for NaN exception// using "==" operator#include<iostream>#include<cmath> // for sqrt()using namespace std;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 number Its NaN
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.
// C++ code to check for NaN exception// using "isnan()" #include<iostream>#include<cmath> // for sqrt() and isnan()using namespace std;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 number Its NaN
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