On Thu, Jul 21, 2011 at 12:22 PM, Thomas
The analogy between OO-interfaces and typeclasses seems to be a bit misleading here, though. Because IIUC then in Haskell typeclasses are not a substitute for a type - a misconception that bit me here, while in (at least the OO-languages I use) interfaces can usually be used instead of types (except object creation & assignment).
I prefer to say that the only similarity between OO classes and typeclasses is the word "class". Trying to make comparisons always ends in tears.
For example: if n < 0 then (k :: X) else (BeginCont k (n-1) :: BeginCont X) does not type check in Haskell. The "equivalent" construct would type check in OO(*) - although I understand that this does not mean the same in OO as in Haskell.
It is possible to do the same in Haskell using existentials. But forget that I've said that and don't try to use it. Most of the time you don't need them and there are better solutions. Cheers, =) -- Felipe.