Re: Records in Haskell

On Wed, Dec 28, 2011 at 2:12 PM, Donn Cave wrote:

Quoth Greg Weber , ...

...

Many of the built-in record proposals seem more ambitious (create a new record from an existing one, generalize in some other direction). More power or generalization could be very useful, but it can wait for later - Haskell's records are glaringly bad because they lack name-spacing.

I think one of the problems being faced with improving records is a false choice between a quick but hacky library desugaring or a major "Extensible" records built into the compiler. What I am proposing is that (unless someone proposes a great desugaring solution) we make it the immediate goal to have records built into the compiler, but done in the simplest (perhaps least "Extensible") way that just accomplishes name-spacing.

It's sure easy to imagine something like that happening, in principle, but ... are you saying that extensibility specifically has been a major issue? Could be, I haven't been paying so much attention.

Yes, I believe it is common knowledge and stated in many places that the community cannot decide on the best *extensible* record system. http://www.haskell.org/haskellwiki/GHC:FAQ#Extensible_Records

Wouldn't extensibility more or less come along with row polymorphism? I mean, my understanding of the term is that an expression that instantiates a particular record field, can incorporate a record lacking that field, which seems to me to be implicit in row polymorphism anyway. I would think row polymorphism is a must-have.

Perhaps if you want *extensible* records. If you would like to make some progress with records in the near future rather than keeping records in limbo, I think we really need to give up for the moment on any higher form of abstraction than straight-forward name-spacing.

If you're interested in looking at old, Haskell-related record systems, also see O'Haskell.

I am interested in any potential solution. You could link to it on the ExtensibleRecords wiki page and explain it a bit for future reference. O'Haskell seems to be very much concerned with being as extensible as possible - to the point of trying to do OO in Haskell. Greg Weber

Donn

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