Enum on Float/Double

[George Russell]

Ketil Z Malde wrote:
> 
> George Russell <ger@tzi.de> writes:
> 
> > The situation with Enum on Ratio is pretty bad but at least
> > it's not hopeless, since rational numbers are at least exact.  But
> > for Float/Double it seems to be a total disaster area.
> 
> My vote would be to scrap it.  Enum sounds like it defines an ordering
> of elements, and that's IMHO not what the actual implementation looks
> like.  But I suppose it will have to wait.
> 
> > My preference would be for succ (+-0) to return the smallest positive
> > real, since then you could define succ x to be the unique y with
> > x < y and forall z . z < y => not (x < z), where such a y exists, and
> > I'm not sure if the Haskell standard knows about signed zeros.
> 
> Is this really useful?  Why would you need this number?  Peano
> artithmetic on reals? :-)
succ +- 0 is not very important, but having succ/pred return the
next representable real is occasionally useful.