]> From: Richard Jones <rich@annexia.org> > Thanks for your answer David. In response to the above, I'd say that > I've found OCaml objects to generally be OK, but sometimes they can be > really infuriating! Examples: > > * Type inference doesn't work sometimes, so you need to add 'just the > right' type declaration to an expression to get it to compile. Yes, that's most unfortunate. There are two such difficulties with classes * use of polymorphic or labelled methods (you need to know the type of the objects) * escaping type variables in class definitions For the first one, there is little to be done: whenever you call such a method, you must make sure the type of the object is known. For the second one, there is maybe some room for improvement. > * Upcasting - sometimes it works, sometimes it requires an explicit > :> to upcast. Once or twice I've had a really strange error where > I've needed to do some sort of double upcast-and-type-declaration, > IIRC it was (obj :> superclass : superclass) It should be (obj : current :> superclass). This is the only "guaranteed" cast. Otherwise, you are trying your luck. Still, simple cast should work for all non-recursive classes. > * Polymorphic methods have a really odd & unintuitive syntax. Sorry. My idea was that they would only be used in very special cases, particularly considering the typing problem described above. > * It seems like you need to use a separate MLI file to be able to > define completely private (as opposed to just protected) methods, > which isn't really documented well. Not quite: you can also define a class type by hand and constrain your definition with it. class c : ct = object ... end This may be surprising when coming from Java, but this is more coherent with the rest of the language. Overall, I would not characterize ocaml objects as weak, but rather nonintuitive. Jacques Garrigue ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners