[Haskell-cafe] Generics for constructing Rows

[Sean Leather]

> That seems to be GP problem, as your solution doesn't scale well when I
> wan't to add/remove/change fields in the `Row` record.


Ah yes, this is a good use case. I wasn't paying close enough attention
before, and I didn't see an immediate implementation of your function at the
time.


> The perfect way
> as I see it, would be just editing `Row` data declaration, nothing else.
> Studying few papers about GP in Haskell, I reckon this could be
> represented as generic traversal, using my `Row` declaration with
> `Either`.  I don't see really good way to write a generic producer from
> `[String]` to version of `Row` without `Either`.  But SYB doesn't
> provide a way for passing type-class-parametric functions to gmapT, and
> SYB-with-class has large overhead of its usage.  I don't have enough
> time to find out how this can be written in SYB-with-class, if it really
> can be
> written.  The restriction of EMGM was described in my initial message.
>

I would suggest looking at Multirec. There's a draft of the paper to be
published at ICFP, and the library is on Hackage.

http://www.cs.uu.nl/wiki/GenericProgramming/Multirec
http://hackage.haskell.org/package/multirec

If you don't have anything generically useful by next week, I'll look at it
again when I have more time.

Regards,
Sean
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20090820/da3480ee/attachment.html