[Haskell-cafe] Re: Data instance for a GADT

José Pedro Magalhães jpm at cs.uu.nl
Mon Apr 19 03:35:49 EDT 2010


Hi Ozgur,

At least template-haskell-2.4.0.0 (which comes with GHC 6.12) has syntax for
type equality constraints [1], so I'm guessing it should support GADTs (I
haven't actually tested it). It also has syntax for type families.


Cheers,
Pedro

[1]
http://hackage.haskell.org/packages/archive/template-haskell/2.4.0.0/doc/html/Language-Haskell-TH-Syntax.html#t%3ACxt

On Wed, Apr 14, 2010 at 11:53, Ozgur Akgun <ozgurakgun at gmail.com> wrote:

> 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 <ozgurakgun at 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 <ozgurakgun at 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.
>>>
>>> Best,
>>>
>>> --
>>> Ozgur Akgun
>>>
>>
>>
>>
>> --
>> Ozgur Akgun
>>
>
>
>
> --
> Ozgur Akgun
>
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