| I don't think that the rank-N system is any more expressive then the | rank-2 one. The reason is that by placing a polymorphic value in a | datatype we can decrese its rank. In this way we can reduce a program
Hmm. To be consistent, then, you'd have to argue for rank-2 data constructors only, since rank-2 functions can be simulated in the way you describe. | This is good to know because it narrows our choices! On the other | hand, it is a bit unfortunate that we do not have a current | implementation that implements the proposed rank-N extension. I have | been using GHC 6.4.2 as an example of the non-boxy version of the | rank-N proposal, is this reasonable? Yes, I think so. | I am not convinced. It seems to me that the higher rank polymorphism | extension is still under active research---after only 1 major version | of existsince, GHC has already changed the way it implements it, and | MLF seems to have some interesting ideas too. Well GHC changed *only* to reach for impredicativity, which is, as I say, a bridge too far for Haskell'. Otherwise it was just fine. MLF is also not relevant here, because its goal too is impredicativity, and it is a *much* more sophisticated type system with substantial implications for type inference. I could say more, but let's see what others think. Simon _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
