Basically, I have a bunch of instances that have a common functionality but I'd like to be able to group those instances and give each group a different default implementation of that functionality. It's so easy to do this in Java, for example, but I have no idea how to do it in Haskell. The above example will not compile, btw.
Before going into language extensions, is there anything wrong with: class C a where foo :: a -> Double fooA a = 5.0 --default A fooB a = 7.0 -- default B data Blah = Blah data Bar = Bar instance C Blah where foo = fooA instance C Bar where foo = fooB blah = Blah bar = Bar main = do print $ foo blah -- should print out 5 print $ foo bar -- should print out 7 It seems to match your spec. Claus _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
