On Tue, Mar 16, 2010 at 08:54:15AM -0500, Louis Wasserman wrote:
A couple potentially contentious design decisions:
* There is no distinction between keys and priority values. A utility type Prio p a with the instance Ord p => Ord (Prio p a) is exported to allow usage of distinct keys and priority values.
I disagree with this one. It requires an Ord instance that isn't really an ordering, and makes a Functor instance impossible. I would prefer an interface separating keys and values like that of Data.Map (which would also increase consistency within the package). Other comments: The Foldable instance breaks the abstraction. I think it should process elements in order. How does this implementation compare with using Map/Set as a priority queue? The documentation for union should mention that it's not stable. That's a pity, but may be justified if there's a big performance difference with the representations that support stable union. I think the containers package should offer general extractor functions with a parameter of type (a -> Maybe (b, a)), so we wouldn't need special cases like these ones.