[Haskell-cafe] Type vs TypeClass duality
tjay.dreaming at gmail.com
Tue Oct 23 23:00:14 EDT 2007
Very cool. I don't understand some (a lot of) parts though:
> instance Show a => Reify (ShowConstraint a) where
> reify = ShowC
ShowC has type "(Show a) => ShowConstraint a", whereas reify is
supposed to have type "ShowConstraint a".
> data SingleList (a :: * -> *) where
> Cons :: (a b) -> b -> SingleList a -> SingleList a
> Nil :: SingleList a
Cons has a type variable "b" in its signature, but no forall. I
suppose it comes from the * -> * in SingleList's type?
That's all I can come up with for now. A great deal of high level
coding flying around above my head now.
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