Re: [Haskell-cafe] Haskell type system and the lambda cube

voigt@tcs.inf.tu-dresden.de wrote:

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2009/5/24 Petr Pudlak : If all Haskell had would be HM, it would be System F.

That cannot be quite right, can it? System F has more powerful polymorphism than HM.

As I recall HM is along the edge to \lambda^2. Haskell 98 is typically described in terms of System F_\omega. I've heard people say GADTs are a subset of (or equivalent to?) System F_c, though I'm not familiar with F_c myself. Like most interesting languages, Haskell as a whole doesn't belong on one of the vertices. I've yet to see a nice diagram that presents non-vertex languages like HM and what arcs can cause one to (often unexpectedly) degenerate into another. -- Live well, ~wren