Seeing this old thread[1], I hope something happened towards enabling this. Does anybody know the current status about using TH on GADTs? [1] http://www.haskell.org/pipermail/template-haskell/2006-August/000567.html On 14 April 2010 10:32, Ozgur Akgun wrote:

answering to myself: I guess this is related: http://hackage.haskell.org/trac/ghc/ticket/3497

On 14 April 2010 10:13, Ozgur Akgun wrote:

...

Cafe,

How can I provide a Data instance for a GADT? I am trying to TH on it, and Uniplate requires Data. I tried StandaloneDeriving, but it seems not to work.

Best,

-- Ozgur Akgun

-- Ozgur Akgun

-- Ozgur Akgun

There have been a couple of emails about Template Haskell support for · GADTs · View patterns · Reifying instances There’s a ticket for this already http://hackage.haskell.org/trac/ghc/ticket/3497 It’s mainly a library design question, in this case the design of the Template Haskell data types in Language.Haskell.TH.Syntax. It needs some motivated person to propose a design, get a consensus, and write some boilerplate code. Just use the standard libraries process An issue is the extent to which it’s ok to change the Template Haskell data types (and thereby break people’s code), but that’s something the interested parties can work out together. If you evolve a consensus design I’m more than happy to make it part of GHC. I just don’t want to drive the consensus building! Simon From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Ozgur Akgun Sent: 14 April 2010 10:53 To: Haskell cafe Subject: [Haskell-cafe] Re: Data instance for a GADT Seeing this old thread[1], I hope something happened towards enabling this. Does anybody know the current status about using TH on GADTs? [1] http://www.haskell.org/pipermail/template-haskell/2006-August/000567.html On 14 April 2010 10:32, Ozgur Akgun mailto:ozgurakgun@gmail.com> wrote: answering to myself: I guess this is related: http://hackage.haskell.org/trac/ghc/ticket/3497 On 14 April 2010 10:13, Ozgur Akgun mailto:ozgurakgun@gmail.com> wrote: Cafe, How can I provide a Data instance for a GADT? I am trying to TH on it, and Uniplate requires Data. I tried StandaloneDeriving, but it seems not to work.