[Haskell-cafe] Re: Haskell, Queries and Monad Comprehension

2010/5/23 Günther Schmidt:

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is there anybody currently using Haskell to construct or implement a query language?

I've a half-baked, type-indexed (in HList style) implementation of relational algebra lying around somewhere, if that counts as a "query language". I was experimenting with using it as a sort of abstract collection interface, which actually worked rather nicely I think, but I didn't have time to flesh it out completely. In particular, only very simple queries and limited kinds of relation composition were supported. Definitely just toy code, though, and dreadfully inefficient; if you're looking for an "actual implementation" meaning "usable interface to an external persistence layer" then disregard this.

Well you're on the radar now :) BTW: I'm working on alternative, non-type-indexed version of extensible records (Which I have gathered to be an essential ingredient when you want to roll a Relational Algebra lib). There will be no first-class labels, but there also will be no need for singleton-types either (which is what you need with type-indexed solutions). And a bit less overhead all-around so it's kind making up for not having 1st class labels.