deriving instances for "hidden" types

[John Meacham]

DrIFT can do this:
http://repetae.net/john/computer/haskell/DrIFT/

it is nearing its 2.0 release, if anyone finds any bugs/obvious
misfeatures let me know soon.
	John

> ----- Original Message -----
> From: "Simon Peyton-Jones" <simonpj@microsoft.com>
> To: "Hal Daume III" <hdaume@ISI.EDU>; "Haskell Mailing List"
> <haskell@haskell.org>
> Sent: Monday, July 29, 2002 11:26 AM
> Subject: RE: deriving instances for "hidden" types
> 
> 
> > | I've often felt a tinge of disappointment not being able to
> > | derive classes over data structures that are defined in the
> > | libraries (DeepSeq FiniteMap, for instance).  I was wondering
> > | if any of the tools (drift, etc.) or GHCs built-in meta
> > | programming would allow you to say something like:
> > |
> > | derive (DeepSeq a, DeepSeq b) => DeepSeq (FiniteMap a b)
> >
> > I think Hal was only suggesting doing this in case where
> > the representation of the data structure was visible to the library
> > client.  (As others have said, it's not a good idea if the rep is
> > abstract.)
> >
> > Template Haskell will be able to do this.  Heart transplant operation
> > is in progress.  Blood on floor, but patient still alive.
> >
> > Simon
-- 
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John Meacham - California Institute of Technology, Alum. - john@foo.net
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