Lambda the Ultimate

Hi! Let's say it makes a lot of sense in my domain to define the types WriteReference and ReadOnlyReference. I wish to create a monad that manipulates references, so my first idea was to define


(>>=) :: WriteReference a -> (a -> WriteReference b) -> WriteReference b
(>>=) :: WriteReference a -> (a -> ReadOnlyReference b) -> ReadOnlyReference b
(>>=) :: ReadOnlyReference a -> (a -> ReadOnlyReference b) -> ReadOnlyReference b
(>>=) :: ReadOnlyReference a -> (a -> WriteReference b) -> WriteReference b

return :: a -> ReadOnlyReference a


It looks ugly but it does its job, even though I fear it won't play nice with Haskell syntactic sugar for monads.

Does it make more sense to define Reference as a class, and then to define WriteReference and ReadOnlyReference as instances of this class, so that we can write something like:


data WR a = WR a
data RR a = RR a

bind :: (Reference r1, Reference r2) => r1 a -> (a -> r2 b) -> r2 b
bind e k = let x = get e in k x


Can anyone help me understand why I should favor one approach over the other?

Thanks