On Sun, May 29, 2011 at 7:59 PM, David Mazieres <dm-list-haskell-pr...@scs.stanford.edu> wrote: > One of the more disgusting but also powerful implications of > FunctionalDependencies is that, in conjunction with > OverlappingInstances and UndecidableInstances, you can do recursive > programming at the type level. This has been (ab)used to do some cool > things (e.g., HList, HaskellDB, OOHaskell). >
It would seem very strange to me if haskell-prime made the choice of fundeps/type families based on the behaviour with OverlappingInstances. I'm under the impression that Overlapping is generally considered one of the more controversial extensions, and on the LanguageQualities wiki page [1] it's explicitly given as an example of something which violates them. So not only is Overlapping not in the language, but I imagine there are many people (myself included) who would like to ensure it stays out. My personal opinion is that if Haskell wants a more complete facility for type-level programming, that should be addressed directly, instead of via creative abuse of the class system and related machinery. Ben [1]: http://hackage.haskell.org/trac/haskell-prime/wiki/LanguageQualities _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
