On 06/09/13 17:45, Gabor Greif wrote:

On 9/5/13, Adam Gundry wrote:

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I have been working on a new extension, OverloadedRecordFields, and it is now essentially feature-complete. Unfortunately, I doubt it will make it into 7.8, as the changes are quite extensive, but I hope to get it in HEAD soon thereafter.

That would be great, it appears to be a great example of -XConstraintKinds, too!

It relies quite heavily on type-level strings (-XDataKinds), if that's what you mean?

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I would really appreciate comments on the design [1], for which there is

How would such a feature interact with http://hackage.haskell.org/package/vinyl ?

The short answer is that it shouldn't. Vinyl (which I wasn't aware of before now, thanks for the pointer!) basically replaces the Haskell records system wholesale, making records entirely separate from data declarations, and turning fields into first-class objects. This should peaceably coexist with -XOverloadedRecordFields but I don't see a way to integrate the two. Adam

Gabor

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a prototype implementation [2] that works in GHC 7.6.3. If you'd like to review the code, you can check out the overloaded-record-fields branch from the Github repositories [3, 4], and there are notes on the implementation on the wiki [5].

Thanks!

Adam

[1] http://ghc.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields/Plan [2] https://github.com/adamgundry/records-prototype [3] https://github.com/adamgundry/ghc [4] https://github.com/adamgundry/packages-base [5] http://ghc.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields/Implemen...

On 09/09/13 16:53, Gabor Greif wrote:

On 9/9/13, Adam Gundry wrote:

...

On 06/09/13 17:45, Gabor Greif wrote:

...

On 9/5/13, Adam Gundry wrote:

...

I have been working on a new extension, OverloadedRecordFields, and it is now essentially feature-complete. Unfortunately, I doubt it will make it into 7.8, as the changes are quite extensive, but I hope to get it in HEAD soon thereafter.

That would be great, it appears to be a great example of -XConstraintKinds, too!

It relies quite heavily on type-level strings (-XDataKinds), if that's what you mean?

No, I mean ConstraintKinds, I assume all the Has* constraints have kind 'Constraint' ? (I strongly assume so).

Ah, I see your point. Yes, the kind of `Has` is * -> Symbol -> * -> Constraint although it is actually implemented as a typeclass in the base library, so in this respect it's not particularly special. (Instances of the typeclass are automatically generated and cannot be given in the normal way, however.) Cheers, Adam

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