2010/5/23 Günther Schmidt<gue.schm...@web.de>:
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.


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