[m-dev.] Constructor classes / Functional dependencies

[Michael Day]

Two years ago there was a discussion regarding collections in the future
standard library in which it was pointed out that extending the type class
system to include constructor classes and functional dependencies in
multiparameter type classes would be necessary to deliver the most useful
collection abstractions.

Of course, we still don't have these features, and lately I've been
regularly bitten by trying to abstract concepts that turn out to be
basically equivalent to collections and thus suffer the same problems:
images containing pixels, streams and strings containing characters,
meshes containing vertices and so on. Very frustrating.

Has anyone made any progress in extending the type class system? Does
anyone have any half finished code, design notes or idle musings lying
around? Although I feel grossly incapable of implementing such features
myself, I wouldn't mind to try and submit some horrendously incorrect
patches to get some discussion going on the issue :)

Michael

--------------------------------------------------------------------------
mercury-developers mailing list
Post messages to:       mercury-developers at cs.mu.oz.au
Administrative Queries: owner-mercury-developers at cs.mu.oz.au
Subscriptions:          mercury-developers-request at cs.mu.oz.au
--------------------------------------------------------------------------