Tuesday, October 16, 2007

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.

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