Checking if a double (or float) is NaN in C++

Question

Is there an isnan() function?

PS.: I\'m in MinGW (if that makes a difference).

I had this solved by using isnan() from , which doe

Answer 1

You can use numeric_limits::quiet_NaN( ) defined in the limits standard library to test with. There's a separate constant defined for double.

#include 
#include 
#include 

using namespace std;

int main( )
{
   cout << "The quiet NaN for type float is:  "
        << numeric_limits::quiet_NaN( )
        << endl;

   float f_nan = numeric_limits::quiet_NaN();

   if( isnan(f_nan) )
   {
       cout << "Float was Not a Number: " << f_nan << endl;
   }

   return 0;
}

I don't know if this works on all platforms, as I only tested with g++ on Linux.