I don't understand the implementation of System.Double

Take a close look at the implementation of System.Double (use Reflector or any other dissassembler).

Look, for example, at the following excerpt:

public const double PositiveInfinity = (double)1.0 / (double)0.0;
public const double NaN = (double)1.0 / (double)0.0;

 

Huh?!?! What ?!!? Why ?!?!

Of course, I had to run and check:

double myNaN = double.NaN;
bool isInf = (double.IsPositiveInfinity(myNaN));
// isInf is set to FALSE

double myInf = double.PositiveInfinity;
bool isNaN = (double.IsNaN(myInf));
// isNaN is set to FALSE

 

It doesn't end there. Look at the implementation of IsNaN:

public static bool IsNaN(double d)
{
    return (d != d);
}

 

All'n'all, I must confess I can't make any sense of all this!

I promise to publish if/when I do.