[Haskell-cafe] Pointfree rank-2 typed function

Martijn van Steenbergen martijn at van.steenbergen.nl
Tue Nov 24 15:58:23 EST 2009

Simon Peyton-Jones wrote:
> It used to be, because GHC used to implement so-called "deep skolemisation".  See Section 4.6.2 of
> http://research.microsoft.com/en-us/um/people/simonpj/papers/higher-rank/putting.pdf
> Deep skolemisation was an unfortunate casualty of the push to add impredicative polymoprhism.  However, as I mentioned in an earlier email, I'm currently planning to take impredicative polymorphism *out*, which means that deep skolemisation might come back *in*. 

Are there workarounds for uses of impredicative types, or do we lose the 
ability to express certain programs as a result?



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