impredicative polymorphism: seen on HCAR

Isaac Dupree isaacdupree at
Mon Jun 2 10:42:41 EDT 2008

I wrote:
> A side-effect is for those of us who want to have any concern for future 
> compatibility with non-GHC type systems (or the long future of GHC's, 
> even), whether one of the proposals would be likely to be easier for 
> someone else to implement in a different compiler.

actually, just as important is the ability of the GHC implementation to 
turn on and off (-XImpredicativeTypes?) so that we can use GHC to make 
sure our programs don't go beyond, e.g., Rank2Types if we don't want 
them to.


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