deferences of class definition and usage

clojure.clj

(defprotocol Metric (distance [p1 p2]))

(deftype Point3D [x y z] Metric
  (distance [p1 p2]
    (let [dx (- (.x p1) (.x p2))
          dy (- (.y p1) (.y p2))
          dz (- (.z p1) (.z p2))]
      (Math/sqrt (+ (* dx dx) (* dy dy) (* dz dz))))))

(def p1 (Point3D. 0 0 0))
(def p2 (Point3D. 10 10 10))
(distance p1 p2)

common_lisp.lisp

(defclass point3d ()
  ((x :accessor get-x :initform 0 :initarg :x)
   (y :accessor get-y :initform 0 :initarg :y)
   (z :accessor get-z :initform 0 :initarg :z)))

(defmethod distance ((p1 point3d) (p2 point3d))
  (let ((dx (- (get-x p1) (get-x p2)))
        (dy (- (get-y p1) (get-y p2)))
        (dz (- (get-z p1) (get-z p2))))
    (sqrt (+ (* dx dx) (* dy dy) (* dz dz)))))

(setq p1 (make-instance 'point3d))
(setq p2 (make-instance 'point3d :x 10 :y 10 :z 10))
(distance p1 p2)

ocaml.ml

class point3d (x:float) (y:float) (z:float) = object
  val mutable x : float = x
  val mutable y : float = y
  val mutable z : float = z
  method get_x = x
  method get_y = y
  method get_z = z
  method set_x v = x <- v
  method set_y v = y <- v
  method set_z v = z <- v
  method distance (p:point3d) =
    let dx = x -. p#get_x in
    let dy = y -. p#get_y in
    let dz = z -. p#get_z in
    sqrt (dx*.dx +. dy*.dy +. dz*.dz)
end;;

let p1 = new point3d 0. 0. 0.;;
let p2 = new point3d 10. 10. 10.;;
p1#distance p2;;