The Objective Caml system release 3.06 - The Caml language - Inria

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The evaluation of the body of a class only takes place at object creation time. Therefore, in the
following example, the instance variable x is initialized to different values for two different objects.
# let x0 = ref 0;;
val x0 : int ref = {contents = 0}
# class point =
# object
# val mutable x = incr x0; !x0
# method get_x = x
# method move d = x unit end
# new point#get_x;;
- : int = 1
# new point#get_x;;
- : int = 2
The class point can also be abstracted over the initial values of the x coordinate.
# class point = fun x_init ->
# object
# val mutable x = x_init
# method get_x = x
# method move d = x
object val mutable x : int method get_x : int method move : int -> unit end
Like in function definitions, the definition above can be abbreviated as:
# class point x_init =
# object
# val mutable x = x_init
# method get_x = x
# method move d = x
object val mutable x : int method get_x : int method move : int -> unit end
An instance of the class point is now a function that expects an initial parameter to create a point
object:
# new point;;
- : int -> point =
# let p = new point 7;;
val p : point =