> PS to my earlier message. I am not at all certain that > the Odersky/Laufer thing would in fact solve Janis's problem. > You want not only a rank-3 type, but also higher-order unification, > since you want to instantiate 't' to > \c. forall d . (c->d) -> d -> d
Simon, You are correct to have doubts. Indeed our system would not handle this case, as type variables can only be instantiated to monomorophic types, not to type schemes. The closest you can get to it is to wrap the instance type in a type constructor. I.e. `t' could be instantiated to T (\c. forall d . (c->d) -> d -> d) where T was declared newtype T = T (\c. forall d . (c->d) -> d -> d) But I guess that does not solve Janis's problem. Cheers -- Martin _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell