class.rkt

#lang racket

(define (Pt x y)
  (let ([self 0])
    (begin
      (define (obj method)
        (case method
          [("getX") (lambda () x)]
          [("getY") (lambda () y)]
          [("moveX") (lambda (newx) (Pt (+ newx ((self "getX"))) y))]))
      (set! self obj)
      
      obj)))

(define pt (Pt 6 7))
((pt "getX"))
((pt "getY"))
(define pt2 ((pt "moveX") 67))
(list ([pt2 "getX"]) ([pt2 "getY"]))