Hello all, There has been very recently a thread discussing the design decisions involved in creating a sequence abstraction. This was naturally of interest to me as the current Edison maintainer, and generated a fair bit of interesting discussion. I'd like to kick off a new thread here to talk about future directions for the Edison API in particular. 1) Regarding Sequence, I have become convinced by the discussion that the Edison Sequence class should be broken down into smaller classes. Furthermore, it would be very nice to make these smaller classes shared across the various families of data structure abstractions in Edison (Sequences, Collections and Associative Collections). The formulation of Sequence of kind * -> * may need to be sacrificed to this end. I am not convinced that losing the maps and zips would be a major blow; however there are a couple of strategies for retaining them in some form. 2) The associated collection API is in a similar situation, except there are no zips. 3) I am reluctant to undertake a major overhaul of the Edison API while the future of type classes in Haskell' is so hazy. I haven't heard any news from the Haskell' type classes focus group in quite some time, and last I was aware, discussion was somewhat stalled. I there any hope for a coherent story here in the nearish future? 4) I am on the verge of deciding that nobody wants non-observable collections (ie, collections in which the element values are not available for inspection). Currently Edison has no implementations which are non-observable, and I am not aware of anyone else creating a datastructure implementation in Haskell which is non-observable. Therefore, I am considering removing this feature of the Edison typeclass hierarchy to reduce complexity. Shout if you think this would be a terrible mistake. 5) OTOH, something people DO seem to want is collection "views", or the ability to treat a datastructure as though it were something else. For example, it would be nice to transparently treat the keys of a finite map as a set, or to treat a nested sequence as a single flattened sequence. Such uses require the separation of operations which can create datastructures from those which merely inspect them (or some fancy bidirectional stuff I don't think I want to get into). 6) Edison 1.2 has now been out for a couple of months. If you've used or looked at the new Edison, I'd love to hear what you think. I think the next development cycle will involve pretty substantial changes, and if you want to get your gripes addressed, now is a good time to voice them. Alternately, if you think there are some aspects that are very important to keep, that's also good information. 7) Finally, I somehow feel like there should be a nice categorical formulation of these datastructure abstractions which would help to drive a refactoring of the API typeclasses in a principled way, rather than on an ad-hoc I-sort-of-think-these-go-together sort of way. Unfortunately, my category-fu is quite weak, so all I have is this vague intuition that I can't substantiate. I'm sort of familiar with initial algebras, but I think they may be too concrete. I'm looking for some way to classify algebras that have, eg, the property of having folds, or of being set-like, etc. If anybody can point me in the right direction wrt this, that would be great. Rob Dockins Speak softly and drive a Sherman tank. Laugh hard; it's a long way to the bank. -- TMBG