Am Donnerstag, 24. April 2008 21:27 schrieb John Meacham: > On Thu, Apr 24, 2008 at 08:48:15PM +0200, Wolfgang Jeltsch wrote: > […]
> > I also have some remark: Why not write > > > > > class Eq a => Num a = (Additive a, Multiplicative a) > > > > instead of > > > > > class Num a = Eq a => (Additive a, Multiplicative a) > > Well, because you can think of 'Num a' as an alias for 'Eq a => > (Additive a, Multiplicative a)', not that Eq is a superclass of Num > which the class declaration syntax implies. Hmm, in what way is Num a an alias for Eq a => (Additive a, Multiplicative a)? You cannot write this: > square :: (Eq a => (Additive a, Multiplicative a)) => a -> a I would say: “Under the condition that Eq a holds, Num a is an alias for (Additive a, Multiplicative a). And this seems to be perfectly expressed by my above proposal. Best wishes, Wolfgang _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime