[Haskell-cafe] Re: Double -> CDouble, realToFrac doesn't work

[Robert Dockins]

>  >[...] Thus (a-b) is not the same as -(b-a) for IEEE floats!
> 
> Nor is x*0 equal to 0 for every x; nor does x == y imply f(x) == f(y) 
> for every x, y, f; nor is addition or multiplication associative. There 
> aren't many identities that do hold of floating point numbers.

Yes, but they DO hold for Rational (I believe).  The argument against 
NaN = 0 :% 0, Inf = 1 :% 0, etc. is that the otherwise valid identies 
for _Rational_ are disturbed.