[Haskell-cafe] 0/0 > 1 == False

[Don Stewart]

cristi:
> On Thu, 10 Jan 2008 10:22:03 +0200, Mitar <mmitar at gmail.com> wrote:
> 
> >Hi!
> >
> >Why is 0/0 (which is NaN) > 1 == False and at the same time 0/0 < 1 ==
> >False. This means that 0/0 == 1? No, because also 0/0 == 1 == False.
> >
> >I understand that proper mathematical behavior would be that as 0/0 is
> >mathematically undefined that 0/0 cannot be even compared to 1.
> >
> >There is probably an implementation reason behind it, but do we really
> >want such "hidden" behavior? Would not it be better to throw some kind
> >of an error?
> 
> NaN is not 'undefined'
> 
> (0/0) /= (0/0) is True
> (0/0) == (0/0) is False
> 
> You can use these to test for NaN.

You can also use isNaN :)

    Prelude> isNaN (1/0)
    False
    Prelude> isNaN (0/0)
    True

-- Don