You have brought up prolog, unification, etc .. and knowing this is the Haskell board, just wondering what anyones thoughts on the hybrid haskell based language CURRY, for these kind of problems. It seems that it's development is stalled... and sorry ahead of time if I am wrong on that point.
In a previous life, I was a logic programming zealot, and looked at curry. As far as I was concerned, it shared a significant problem with most logic programming work: the designers had a bit of a slack attitude to semantics. The key problem was that it had non-deterministic functions so you could write (haskell syntax): main = do if f 42 /= f 42 then putStr "Look ma, no referential transparency\n" else return () and expect the putStr could get executed. For reference, it's not a problem in Prolog (if you overlook IO being done with side effects ;-)) because the variables are explicit, and not just a notational convenience as they are in lambda calculus: main :- f(42,X), f(42,Y), .... cheers, T. -- Dr Thomas Conway drtomc@gmail.com Silence is the perfectest herald of joy: I were but little happy, if I could say how much.