]> Hi everybody, First of all, where can I find some documentation about the CVS versino of O'Caml? Is the documentation kept in CVS too? Anyway, on to the problem at hand: I have a class like this: class type ['a] node_type = object method as_variant : 'a constraint 'a = [> `Node of 'a node_type] end;; class ['a] node : ['a] node_type = object (self) method as_variant : 'a = `Node (self :> 'a node_type) end;; That works fine in O'Caml 3.04. But, I want to use the new polymorphic method feature in O'Caml 3.04+15. So I tried: # class type node_type = object method as_variant : [> `Node of node_type] end;; class type node_type = object method as_variant : [> `Node of node_type] end # class node : node_type = object (self) method as_variant = `Node (self :> node_type) end;; ^^^^ This expression cannot be coerced to type node_type = < as_variant : 'a. [> `Node of node_type] as 'a >; it has type < as_variant : 'c; .. > as 'b but is here used with type 'b # class node : node_type = object (self) method as_variant : 'a. [> `Node of node_type] as 'a = `Node (self :> node_type) end;; The class type object method as_variant : [> `Node of node_type] end is not matched by the class type node_type The class type object method as_variant : [> `Node of node_type] end is not matched by the class type object method as_variant : [> `Node of node_type] end The method as_variant has type 'a. [> `Node of node_type] as 'a but is expected to have type 'b. [> `Node of node_type] as 'b The universal variable 'b would escape its scope I have no idea what the error message means. To me, it is saying that class "node" doesn't match class type "node_type" even though everything has exactly the same type. Could somebody please explain it to me? What is the correct way of doing the above? Thanks, Brian ------------------- 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