Magnus Carlsson wrote: > > You can use overloading for the definition of theValue instead: > > class TheValue a where theValue :: a -> Maybe Int > > instance TheValue Base where theValue _ = Nothing > instance TheValue Derived where theValue x = Just (x.value) > ... or rather, you will be able to use overloading when the new version of O'Hugs is released in a few days :-) -- Johan