]> Hello, I would like to create two mutually recursive classes, parents (a) and children (b) Furthermore, I'd like to define them incrementally parents and children, parents and children with hands parents and children with hands and feet ... let's have a try : class type ['b] a0 = object ('a) method coerce: 'a method b: 'b constraint 'b = 'a #b0 (* ... *) end and ['a] b0 = object ('b) method coerce: 'b method a: 'a constraint 'a = 'b #a0 (* ... *) end class type ['b] a1 = object ('a) inherit ['b] a0 constraint 'b = 'a #b1 (* ... *) end and ['a] b1 = object ('b) inherit ['a] b0 constraint 'a = 'b #a1 (* ... *) end ... Unfortunately, this does not work : > constraint 'b = 'a #b0 > ^^ >This type < b : 'b; coerce : 'a; .. > as 'a should be an instance of >type 'c >Self type cannot escape its class which is odd from my mind, since the following code is well typed : class type ['c] c = object method c: 'c end class type ['b] a = object ('a) method b: 'b constraint 'b = 'a #c end I can get something better, using two type parameters : class type ['a, 'b] a0 = object method coerce: 'b method b: 'b constraint 'a = ('a, 'b) #a0 constraint 'b = ('a, 'b) #b0 end and ['a, 'b] b0 = object method coerce: 'b method a: 'a constraint 'a = ('a, 'b) #a0 constraint 'b = ('a, 'b) #b0 end but then the "self type" is no longer correlated to 'a/'b so that I can't implement the method coerce, so, I need to "virtualize" it, and to implement it only at the end of the class hierarchy, where I need to close it, saying 'a = 'self / 'b = 'self I don't want this, because I'd like be able to use these classes at any level (yes, a parent without feet does make sense...) Does this case of "Self type cannot escape its class" restriction really make sense ? Do you know how to work-around this ? thanks, damien ------------------- 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