Is FPH implemented in GHC?

[Sittampalam, Ganesh]

> | A possibly related question is whether you would expect to make
record 
> | selectors and updaters work for all record types at the same time? 
> | That would definitely be very useful.

> I'm not sure what you mean by this.  Would you care to elaborate?

The most important thing for me is supporting record update for
existentially
quantified data records, as in the error below.

In general I also find working with code that involves existential type
variables quite hard work - for example I can't use foo as a record
selector
either, even if I immediately do something that seals the existential
type back
up again.

I don't understand this stuff well enough to be sure whether it's an
impredicativity issue or not, though.

Cheers,

Ganesh

Foo.hs:11:8:
    Record update for the non-Haskell-98 data type `Foo' is not (yet)
supported
    Use pattern-matching instead
    In the expression: rec {foo = id}
    In the definition of `f': f rec = rec {foo = id}

{-# LANGUAGE Rank2Types #-}

module Foo where

data Foo = forall a . Foo { foo :: a -> a, bar :: Int }

x :: Foo
x = Foo { foo = id, bar = 3 }

f :: Foo -> Foo
f rec = rec { foo = id }

g :: Foo -> Foo
g rec = rec { bar = 3 }

==============================================================================
Please access the attached hyperlink for an important electronic communications disclaimer: 

http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html
==============================================================================