[Haskell-cafe] Finally tagless and abstract relational Algebra

Jacques Carette carette at mcmaster.ca
Mon Dec 28 11:49:42 EST 2009

Günther Schmidt wrote:
> I do know that I could express my algorithms via list-comprehension or
> in a List Monad, all using tuples. And that would be concrete and
> grossly inefficient.
You should probably tell us what these algorithms accomplish, rather
than how one implementation goes.  From a higher-level view of what
you're trying to do [but not as high as saying 'implement abstract
relational algebra'], it will be easier to give concrete advice.

> So how would it be possible to express selecting /field/ b from
> /record/ x and field c from record y, creating record z, while making
> sure that record x does have field b and record y does have field c? I
> mean design a syntax for it?
Perhaps you should tell us why you think you need records at all, and
record sub-typing to boot.  You might well be right, but the
higher-level requirements will have a much bigger influence on the
design than anything else.


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