Extensible records in Haskell

Simon Peyton-Jones simonpj@microsoft.com
Wed, 6 Nov 2002 09:44:31 -0000

The TRex record system is probably the main type-system extension that
GHC does not currently implement.  The trouble is that it's quite a bit
of work.  If it were just the type inference part it would be ok, but it
requires new primitive operations to insert fields in records, and I
think that interacts with GHC's current data structure representations.

So it's feasible but it's Real Work.  So far, to my surprise, no one has
asked for it.  You are nearly the first!   Another reason for holding
back is that Mark and I worked out a design, in the light of TRex (see
our paper at the Haskell workshop '99), but it'd be a pity to have Hugs
and GHC differing.... and I'm not sure that anyone would have enough
energy to change Hugs.

So for a variety of reasons, I'm inclined to leave it as a Good Reason
To Use Hugs, but I could probably be persuaded otherwise. =20


| -----Original Message-----
| From: Nicolas Oury [mailto:Nicolas.Oury@ens-lyon.fr]
| Sent: 06 November 2002 08:38
| To: glasgow-haskell-users@haskell.org
| Subject: Re : Extensible records in Haskell
|  >   > Hello, is there something like extensible records in ghc?
|  >Are you wanting something like Hugs' T-Rex or did you have something
|  >else in mind?
| Hello,
| For what I understand of T-Rex it is what I wait.
| I need something that can allow to use records without declaring their
| type first and that can be extended by creating a new records with the
| same contents plus one or less one.
| Best regards,
| Nicolas
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