ocaml example at http://w3.one.net/~jweirich/oostuff/

[Pixel <pixel@mandrakesoft.com>]

(* 

Here is little rework of the example that i find nicer :) 

- it now shows the ability to subtype when inheriting...
- use of printf for cleanup
- use of List.iter instead of explicitly doing it via recursion
- removed the "int" typing of class constructors, caml doesn't need any help,
even if keeping them may be clearer


cu Pixel.

*)

class virtual shape initx inity =
   object (self)
      val mutable x = initx
      val mutable y = inity

      (* get the x & y coordinates for the object *)
      method getX = x
      method getY = y

      (* set the x & y coordinates for the object *)
      method setX newx = x <- newx
      method setY newy = y <- newy

      (* move the x & y position of the object *)
      method moveTo newx newy =
         self#setX newx;
         self#setY newy
      method rMoveTo deltax deltay =
         self#setX (self#getX + deltax);
         self#setY (self#getY + deltay)

      (* draw method is effectively abstract *)
      method virtual draw : unit
   end

class rectangle initx inity initwidth initheight =
   object (self)
      inherit shape initx inity
      val mutable width = initwidth
      val mutable height = initheight

      (* get the width & height of the object *)
      method getWidth = width
      method getHeight = height

      (* set the width & height of the object *)
      method setWidth newwidth = width <- newwidth
      method setHeight newheight = height <- newheight

      (* draw the rectangle *)
      method draw =
        Printf.printf "Drawing a Rectangle at:(%d,%d), width %d, height %d\n"
           self#getX
	   self#getY
	   self#getWidth
	   self#getHeight
   end

class circle initx inity initradius =
   object (self)
      inherit shape initx inity
      val mutable radius = initradius

      (*  get the radius of the object *)
      method getRadius = radius

      (*  set the radius of the object *)
      method setRadius newradius = radius <- newradius

      (* draw the circle *)
      method draw =
         Printf.printf "Drawing a Circle at:(%d,%d), radius %d\n"
           self#getX
	   self#getY
           self#getRadius
   end

let main () =
   (* set up lists to hold the shapes *)
   let (scribble : shape list) = [
     (new rectangle 10 20 5 6 :> shape) ; 
     (new circle 15 25 8 :> shape)
   ] in

   (* iterate through the lists and handle shapes polymorphically *)
   List.iter (fun o ->
     o#draw; 
     o#rMoveTo 100 100; 
     o#draw
   ) scribble;

   (* call a rectangle specific instance *)
   let arectangle = new rectangle 0 0 15 15 in
   arectangle#draw;
   arectangle#setWidth 30;
   arectangle#draw;;

main ();;