25 Jan
2010
25 Jan
'10
2:46 p.m.
type family F a b :: * -> * -- F's arity is 2, -- although its overall kind is * -> * -> * -> *
I believe what you're missing is that with the definition F a b :: * -> *, F needs three arguments (of kind *) in order to become kind *. If F a b :: * -> * as stated, then F a :: * -> * -> * and F :: * -> * -> * -> *, just like reported. Cheers, /Niklas