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