[Haskell-cafe] Re: Typeclass question

Stefan O'Rear wrote:

[...] Unfortunately, it turns out that allowing foralls inside function arguments makes typechecking much harder, in general impossible.

Just a tiny correction: AFAIK, it is type /inference/ which becomes undecidable in the presence of higher rank types -- checking works just fine (it could be true that it's harder, though). Cheers Ben