20 Jul
2010
20 Jul
'10
2:47 p.m.
H98 and H2010 allow a context to be given for datatypes, e.g. the "Eq a" in
data Eq a => Foo a = Constr a
I have made a proposal to remove support for that context (ticket #139).
Although I would prefer that contexts of datatypes did the right and useful thing, in the absence of a proposal of that nature, I am quite happy to add my +1 to their removal instead. As Igloo notes, GADTs are a more viable way to achieve the storing of the dictionary within the constructor, e.g. data OrdTree a where Leaf :: a -> OrdTree a Branch :: Ord a => OrdTree a -> OrdTree a -> OrdTree a Regards, Malcolm