#           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]
#           Characters 7-96:
  ......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
#   Characters 28-29:
  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>
# Characters 0-21:
  (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 is not a subtype of color_point 
# Characters 9-55:
  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 is not a subtype of 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 = ()
#                     Characters 85-102:
    inherit printable_point y as super
            ^^^^^^^^^^^^^^^^^
Warning 13: the following instance variables are overridden 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 cmp : 'a -> int end
#             class int_comparable :
  int -> object ('a) val x : int method cmp : 'a -> int method x : int end
#           class int_comparable2 :
  int ->
  object ('a)
    val x : int
    val mutable x' : int
    method cmp : 'a -> int
    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>
# Characters 6-28:
  l#add (c2 :> int_comparable);;      (* Echec : 'a comp2 n'est un sous-type *)
        ^^^^^^^^^^^^^^^^^^^^^^
Error: Type
         int_comparable2 =
           < cmp : int_comparable2 -> int; set_x : int -> unit; x : int >
       is not a subtype of
         int_comparable = < cmp : int_comparable -> int; x : int > 
       Type int_comparable = < cmp : int_comparable -> int; x : int >
       is not a subtype of
         int_comparable2 =
           < cmp : int_comparable2 -> int; set_x : int -> unit; x : int > 
# - : unit = ()
#             class int_comparable3 :
  int ->
  object
    val mutable x : int
    method cmp : int_comparable -> int
    method setx : int -> unit
    method x : int
  end
#   val c3 : int_comparable3 = <obj>
# - : unit = ()
# Characters 25-27:
  (new sorted_list ())#add c3;;   (* Error; strange message with -principal *)
                           ^^
Error: This expression has type
         int_comparable3 =
           < cmp : int_comparable -> int; setx : int -> unit; x : int >
       but an expression was expected of type
         #comparable as 'a = < cmp : 'a -> int; .. >
       Type int_comparable = < cmp : int_comparable -> int; x : int >
       is not compatible with type
         int_comparable3 =
           < cmp : int_comparable -> int; setx : int -> unit; x : int > 
       The first object type has no method setx
#   val sort : (#comparable as 'a) list -> 'a list = <fun>
#     Characters 13-66:
    List.map (fun c -> print_int c#x; print_string " ") l;
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.
#