functional dependency syntax?

[Hal Daume III]

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
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