#           class point :
  int ->
  object val mutable x : int method get_x : int method move : int -> unit end
#   val p : point = <obj>
#   - : int = 7
# - : unit = ()
# - : int = 10
#   val q : point = <obj>
#   - : int * int = (10, 17)
#           class color_point :
  int ->
  string ->
  object
    val c : string
    val mutable x : int
    method color : string
    method get_x : int
    method move : int -> unit
  end
#   val p' : color_point = <obj>
#   - : int * string = (5, "red")
#   val l : point list = [<obj>; <obj>]
#   val get_x : < get_x : 'a; .. > -> 'a = <fun>
# val set_x : < set_x : 'a; .. > -> 'a = <fun>
# - : int list = [10; 5]
#           # 
  class ref x_init = object
    val mutable x = x_init
    method get = x
    method set y = x <- y
  end;;
Error: Some type variables are unbound in this type:
         class ref :
           'a ->
           object
             val mutable x : 'a
             method get : 'a
             method set : 'a -> unit
           end
       The method get has type 'a where 'a is unbound
#           class ref :
  int ->
  object val mutable x : int method get : int method set : int -> unit end
#           class ['a] ref :
  'a -> object val mutable x : 'a method get : 'a method set : 'a -> unit end
#   - : int = 2
#             class ['a] circle :
  'a ->
  object
    constraint 'a = < move : int -> unit; .. >
    val mutable center : 'a
    method center : 'a
    method move : int -> unit
    method set_center : 'a -> unit
  end
#               class ['a] circle :
  'a ->
  object
    constraint 'a = #point
    val mutable center : 'a
    method center : 'a
    method move : int -> unit
    method set_center : 'a -> unit
  end
#   val c : point circle = <obj>
val c' : color_point circle = <obj>
#           class ['a] color_circle :
  'a ->
  object
    constraint 'a = #color_point
    val mutable center : 'a
    method center : 'a
    method color : string
    method move : int -> unit
    method set_center : 'a -> unit
  end
#   # 
  let c'' = new color_circle p;;
Error: This expression has type point but an expression was expected of type
         #color_point
       The first object type has no method color
# val c'' : color_point color_circle = <obj>
#   - : color_point circle = <obj>
# # (c'' :> point circle);;                 (* Echec *)
Error: Type
         color_point color_circle =
           < center : color_point; color : string; move : int -> unit;
             set_center : color_point -> unit >
       is not a subtype of
         point circle =
           < center : point; move : int -> unit; set_center : point -> unit > 
Type point = point is not a subtype of color_point = color_point 
# # fun x -> (x : color_point color_circle :> point circle);;
Error: Type
         color_point color_circle =
           < center : color_point; color : string; move : int -> unit;
             set_center : color_point -> unit >
       is not a subtype of
         point circle =
           < center : point; move : int -> unit; set_center : point -> unit > 
Type point = point is not a subtype of color_point = color_point 
#         class printable_point :
  int ->
  object
    val mutable x : int
    method get_x : int
    method move : int -> unit
    method print : unit
  end
#   val p : printable_point = <obj>
# 7- : unit = ()
#                     # 
  class printable_color_point y c = object (self)
    inherit color_point y c
    inherit printable_point y as super
    method print =
      print_string "(";
      super#print;
      print_string ", ";
      print_string (self#color);
      print_string ")"
  end;;
Warning 13: the following instance variables are overriden by the class printable_point :
  x
The behaviour changed in ocaml 3.10 (previous behaviour was hiding.)
class printable_color_point :
  int ->
  string ->
  object
    val c : string
    val mutable x : int
    method color : string
    method get_x : int
    method move : int -> unit
    method print : unit
  end
#   val p' : printable_color_point = <obj>
# (7, red)- : unit = ()
#           class functional_point :
  int ->
  object ('a) val x : int method get_x : int method move : int -> 'a end
#   val p : functional_point = <obj>
#   - : int = 7
# - : int = 10
# - : int = 7
#   - : #functional_point -> functional_point = <fun>
#                                                                       class virtual ['a] lst :
  unit ->
  object
    method virtual hd : 'a
    method iter : ('a -> unit) -> unit
    method map : ('a -> 'a) -> 'a lst
    method virtual null : bool
    method print : ('a -> unit) -> unit
    method virtual tl : 'a lst
  end
and ['a] nil :
  unit ->
  object
    method hd : 'a
    method iter : ('a -> unit) -> unit
    method map : ('a -> 'a) -> 'a lst
    method null : bool
    method print : ('a -> unit) -> unit
    method tl : 'a lst
  end
and ['a] cons :
  'a ->
  'a lst ->
  object
    val h : 'a
    val t : 'a lst
    method hd : 'a
    method iter : ('a -> unit) -> unit
    method map : ('a -> 'a) -> 'a lst
    method null : bool
    method print : ('a -> unit) -> unit
    method tl : 'a lst
  end
#   val l1 : int lst = <obj>
#   (3::10::[])- : unit = ()
#   val l2 : int lst = <obj>
# (4::11::[])- : unit = ()
#       val map_list : ('a -> 'b) -> 'a lst -> 'b lst = <fun>
#   val p1 : printable_color_point lst = <obj>
# ((3, red)::(10, red)::[])- : unit = ()
#           class virtual comparable :
  unit -> object ('a) method virtual leq : 'a -> bool end
#             class int_comparable :
  int -> object ('a) val x : int method leq : 'a -> bool method x : int end
#           class int_comparable2 :
  int ->
  object ('a)
    val x : int
    val mutable x' : int
    method leq : 'a -> bool
    method set_x : int -> unit
    method x : int
  end
#                         class ['a] sorted_list :
  unit ->
  object
    constraint 'a = #comparable
    val mutable l : 'a list
    method add : 'a -> unit
    method hd : 'a
  end
#   val l : _#comparable sorted_list = <obj>
# val c : int_comparable = <obj>
# - : unit = ()
#   val c2 : int_comparable2 = <obj>
# # l#add (c2 :> int_comparable);;      (* Echec : 'a comp2 n'est un sous-type *)
Error: Type
         int_comparable2 =
           < leq : int_comparable2 -> bool; set_x : int -> unit; x : int >
       is not a subtype of
         int_comparable = < leq : int_comparable -> bool; x : int > 
Type int_comparable = < leq : int_comparable -> bool; x : int >
is not a subtype of
  int_comparable2 =
    < leq : int_comparable2 -> bool; set_x : int -> unit; x : int > 
# - : unit = ()
#             class int_comparable3 :
  int ->
  object
    val mutable x : int
    method leq : int_comparable -> bool
    method setx : int -> unit
    method x : int
  end
#   val c3 : int_comparable3 = <obj>
# - : unit = ()
# # (new sorted_list ())#add c3;;   (* Echec : leq n'est pas binaire *)
Error: This expression has type
         int_comparable3 =
           < leq : int_comparable -> bool; setx : int -> unit; x : int >
       but an expression was expected of type
         #comparable as 'a = < leq : 'a -> bool; .. >
       Type int_comparable = < leq : int_comparable -> bool; x : int >
       is not compatible with type
         int_comparable3 =
           < leq : int_comparable -> bool; setx : int -> unit; x : int > 
       The first object type has no method setx
#   val sort : (#comparable as 'a) list -> 'a list = <fun>
#     # let pr l =
    List.map (fun c -> print_int c#x; print_string " ") l;
    print_newline ();;
Warning 10: this expression should have type unit.
val pr : < x : int; .. > list -> unit = <fun>
#   val l : int_comparable list = [<obj>; <obj>; <obj>]
# 5 2 4 
- : unit = ()
# 2 4 5 
- : unit = ()
# val l : int_comparable2 list = [<obj>; <obj>]
# 2 0 
- : unit = ()
# 0 2 
- : unit = ()
#     val min : (#comparable as 'a) -> 'a -> 'a = <fun>
#   - : int = 7
# - : int = 3
#                                 class ['a] link :
  'a ->
  object ('b)
    val mutable next : 'b option
    val mutable x : 'a
    method append : 'b option -> unit
    method next : 'b option
    method set_next : 'b option -> unit
    method set_x : 'a -> unit
    method x : 'a
  end
#                   class ['a] double_link :
  'a ->
  object ('b)
    val mutable next : 'b option
    val mutable prev : 'b option
    val mutable x : 'a
    method append : 'b option -> unit
    method next : 'b option
    method prev : 'b option
    method set_next : 'b option -> unit
    method set_prev : 'b option -> unit
    method set_x : 'a -> unit
    method x : 'a
  end
#           val fold_right : ('a -> 'b -> 'b) -> 'a #link option -> 'b -> 'b = <fun>
#                                       class calculator :
  unit ->
  object ('a)
    val mutable acc : float
    val mutable arg : float
    val mutable equals : 'a -> float
    method acc : float
    method add : 'a
    method arg : float
    method enter : float -> 'a
    method equals : float
    method sub : 'a
  end
#   - : float = 5.
# - : float = 1.5
# - : float = 15.
#                       class calculator :
  unit ->
  object ('a)
    val mutable acc : float
    val mutable arg : float
    val mutable equals : 'a -> float
    method acc : float
    method add : 'a
    method arg : float
    method enter : float -> 'a
    method equals : float
    method sub : 'a
  end
#   - : float = 5.
# - : float = 1.5
# - : float = 15.
#                                 class calculator :
  float ->
  float ->
  object
    val acc : float
    val arg : float
    method add : calculator
    method enter : float -> calculator
    method equals : float
    method sub : calculator
  end
and calculator_add :
  float ->
  float ->
  object
    val acc : float
    val arg : float
    method add : calculator
    method enter : float -> calculator
    method equals : float
    method sub : calculator
  end
and calculator_sub :
  float ->
  float ->
  object
    val acc : float
    val arg : float
    method add : calculator
    method enter : float -> calculator
    method equals : float
    method sub : calculator
  end
#   val calculator : calculator = <obj>
#   - : float = 5.
# - : float = 1.5
# - : float = 15.
#