Extensible Records

Simon Peyton-Jones simonpj at microsoft.com
Mon Nov 12 04:20:33 EST 2007

|  There seems to be widespread agreement that the current situation wrt
|  records is unacceptable, but the official GHC policy is that there are too
|  many good ideas to choose from - so nothing gets done! I hence humbly
|  propose that [http://www.cs.uu.nl/~daan/download/papers/scopedlabels.pdf]
|  be adapted to GHC. In my naivete, I assume that porting an existing
|  implementation would be much easier than starting from scratch.


| I think this would be a BIG mistake. Whatever system GHC settles on
| is almost certain to become part of the Haskell standard, and this
| particular system has some deep limitations which could not be got
| round without ripping it all out and starting again.

That this thread has attracted so much traffic in such a short time illustrates both its importance and why we have done nothing about it in GHC for ages!  It's a swamp with many use-cases, many design choices, and many local optima.  (It's less clear whether there is a global optimum, but I hope there is.)

I'm happy to see a Wiki page to summarise and contrast different approaches; that seems like a constructive thing to do.  (Email discussions tend to evaporate and then be repeated.)   A useful thing to do would be to give a series of use-cases, or examples, showing the kinds of thing one would like to be able to do.  Then you can classify the approaches by what examples they can handle.


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