Hello,
On 10/16/07, apfelmus
Iavor Diatchki wrote:
apfelmus wrote:
fundeps are too tricky to get powerful and sound at the same time.
I am not aware of any soundness problems related to functional dependencies---could you give an example?
http://hackage.haskell.org/trac/haskell-prime/wiki/FunctionalDependencies#Lo...
But I should have said "sound, complete and decidable" instead :)
There is nothing about the system being unsound there. Furthermore, I am unclear about the problem described by the link... The two sets of predicates are logically equivalent (have the same set of ground instances), here is a full derivation: (B a b, C [a] c d) using the instance (B a b, C [a] c d, C [a] b Bool) using the FD rule (B a b, C [a] c d, C [a] b Bool, b = c) using b = c (B a b, C [a] c d, C [a] b Bool, b = c, C [a] b d) omitting unnecessary predicates and rearranging: (b = c, B a b, C [a] b d) The derivation in the other direction is much simpler: (b = c, B a b, C [a] b d) using b = c (b = c, B a b, C [a] b d, C [a] c d) omitting unnecessary predicates (B a b, C [a] c d) -- Iavor