Minor containers API changes

[Johan Tibell]

On Mon, Nov 28, 2011 at 5:29 PM, Kazu Yamamoto <kazu at iij.ad.jp> wrote:
> Hello,
>
> This is off-topic but I'm curious.
>
> Why the container package does not provide a type-class to unify APIs?
> Are there any technical/historical reasons?

Mostly technical I would say. I hope we should be able to do this
right now when we have constraint kinds [1] i.e. we can do something
like:

class Map m where
    type C :: Constraints
    insert :: C => k -> v -> Map k v -> Map k v

instance Map HashMap where
    type C = Ord
    insert = ...

1. http://blog.omega-prime.co.uk/?p=127

-- Johan