Hello, On 10/16/07, apfelmus <[EMAIL PROTECTED]> wrote: > 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#Lossofconfluence > > 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 _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
