You don't need the parentheses. So, you want something like: class Foo a b c d e | a b -> c d, a -> d e where... which means from the paper: class Foo a b c d e | (a,b) -> (c,d), a -> (d,e) HTH - Hal -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume On Mon, 11 Nov 2002, Malcolm Wallace wrote:
I'm trying out MPTC with functional dependencies for the first time in GHC. However, I'm not sure of the syntax. MPJ's ESOP 2000 paper gives the following example:
class FiniteMap i e fm | fm -> (i,e) where emptyFM :: fm lookupFM :: i -> fm -> Maybe e extendFM :: i -> e -> fm -> fm
but ghc (5.02.2 and 5.04.1) complain
$ ghc-5.04.1 -fglasgow-exts -c -o FunDep.o FunDep.hs FunDep.hs:10: parse error on input `('
where the indicated line is that of the class declaration. What should the syntax be if it is not the above?
Regards, Malcolm _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users