defining (-> Bool) as a set

I'd like to be able to define something like instance Eq a => Coll (-> Bool) a where empty = \_ -> False single x = \y -> if x == y then True else False union a b = \x -> a x || b x insert s x = \y -> x == y || s y and the like However, this seems to be impossible. Is this the type lambda restriction that's been discussed recently on the mailing list? - Hal -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume