Fix prelude definitions of abs/signum for Floats/Doubles

[Daniel Fischer]

On Thursday 11 April 2013, 08:07:57, Levent Erkok wrote:
> On Thu, Apr 11, 2013 at 2:58 AM, Shachaf Ben-Kiki <shachaf at gmail.com> wrote:
> > Maybe it would be simpler to say:
> > 
> > signum x | x == 0    = x
> > 
> >          | isNaN x   = x
> >          | x > 0     = 1
> >          | otherwise = negate 1
> >     
> >     Shachaf
> 
> Thanks Shachaf. This version is equivalent to the one I proposed, and it
> saves one test; so it's definitely preferable. I'll put this one in the
> ticket that'll finally be created for GHC.

Also

    abs x
        | x < 0 = negate x
        | otherwise = x

keeps the number of tests at one.

Cheers,
Daniel