Dan,
If you want to enforce associativity just create your own Eq instance andmake it a pattern there.
Could you elaborate on that? It's still early here and I've had only one cup of of coffee yet.
Cheers, Stefan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe