Is FPH implemented in GHC?

Simon Peyton-Jones simonpj at
Wed Sep 10 10:24:57 EDT 2008

Not yet.  But Dimitrios has just started a postdoc at MSR, so we will be working on fixing, once and for all, the impredicative story in GHC.

Meanwhile, why do you ask?  Making impredicative polymorphism work seems to be the Right Thing, but it's something of a "technology push", perhpas a solution in search of a problem.  Do you have an application that needs it?

This is a general question to GHC users.  (If you don't know what impredicative polymorphism is, think "can I have a type like (Maybe (forall a. [a] -> [a]))".)


| -----Original Message-----
| From: glasgow-haskell-users-bounces at [mailto:glasgow-haskell-users-
| bounces at] On Behalf Of Wolfgang Jeltsch
| Sent: 10 September 2008 15:21
| To: glasgow-haskell-users at
| Subject: Is FPH implemented in GHC?
| Hello,
| is FPH implemented in GHC?  If yes, will it be part of GHC 6.10.1?
| Best wishes,
| Wolfgang
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