On Thu, Feb 08, 2001 at 08:51:57PM +0000, Marcin 'Qrczak' Kowalczyk wrote:
... class (Show a, Read a, Eq a) => Comfortable a instance (Show a, Read a, Eq a) => Comfortable a ... The latter syntax is nice: obvious what it means, not legal today. This instance of course conflicts with any other instance of that class, so it can be recognized and treated specially as a "class synonym".
Why isn't it legal? I just tried it, and Hugs accepted it, with or without extensions. "where" clauses are optional, right?
.... Don't know if local instances or local classes can be defined to make sense, nor if they could be useful enough...
Well, let's see. Local classes already exist: just don't export them. Local instances would not be hard to add with special syntax, though really they should be part of a more general mechanism for dealing with instances explicitly. Agreed that they might not be useful enough. Best, Dylan Thurston