Re: [Haskell-cafe] Hello and help request

To put it another way, they're closer to Java interfaces - though type classes are a more general idea, as demonstrated by the multi-parameter type classes supported by ghc et al. You can think of them as a predicate - "this type has implementations for these overloaded functions".

Ok, very clear. This should mean that I must concentrate on data/newtype, right? So, if I've understood well, <data> adds parameters (with pattern matching?) and recursion to structure definition. Still right? Enrico