[Haskell-cafe] Re: Polymorphic (typeclass) values in a list?

2007-10-21 Thread Peter Hercek
Brandon S. Allbery KF8NH wrote: On Oct 19, 2007, at 12:11 , Sebastian Sylvan wrote: On 19/10/2007, Kalman Noel [EMAIL PROTECTED] wrote: data ExistsNumber = forall a. Num a = Number a I'm without a Haskell compiler, but shouldn't that be exists a.? The problem is that exists is not

Re: [Haskell-cafe] Re: Polymorphic (typeclass) values in a list?

2007-10-21 Thread Kalman Noel
Peter Hercek wrote: When 'exists' is not a keyword, why 'forall' is needed at all? Isn't everything 'forall' qualified by default? “forall” isn't a keyword in Haskell 98. As an extension to the language, however, it makes certain types expressible that can not be written in H98, for example

Re: [Haskell-cafe] Re: Polymorphic (typeclass) values in a list?

2007-10-21 Thread Brandon S. Allbery KF8NH
On Oct 21, 2007, at 6:41 , Peter Hercek wrote: Brandon S. Allbery KF8NH wrote: On Oct 19, 2007, at 12:11 , Sebastian Sylvan wrote: On 19/10/2007, Kalman Noel [EMAIL PROTECTED] wrote: data ExistsNumber = forall a. Num a = Number a I'm without a Haskell compiler, but shouldn't that be