I just wasted about 2 hours tracking down a bug that ended up being due to (set? '()) now evaluating to #t. I have no problems with set-union, intersection, etc. being defined for lists, but to treat lists as sets always is perverse to me. The contracts for set operations should use set-like? for (or/c set? list?) and keep the two constructions separate.
This conflation is almost as bad as treating empty list as false. -Ian _________________________ Racket Developers list: http://lists.racket-lang.org/dev
