[Haskell-beginners] Further constraining types

[Thomas]

> (==) (Natural a) (Natural b) | a == b = True
> | otherwise = False

Essentially the same, but I usually write this a little shorter as
(==) (Natural a) (Natural b) = a == b

> (Natural a) * (Natural b) | a < 0 || b < 0 = Indeterminate
> | otherwise = Natural ((Prelude.*) a b)

Why this? A 'Natural x' should already guarantee that 'x' is not 
negative (otherwise it would be 'Indeterminate').

> Thoughts?

It seems very reasonable to me.

Regards,
Thomas