;; Object oriented version of Tree
;; a preview of CS61B

(define-class (tree datum children)

  (method (tree-map! fn)
	     (set! datum (fn datum))
	     (for-each (lambda (t) (ask t 'tree-map! fn))
			children))

  
  (method (count)
	  (if (null? children) 1
	      (+ 1 (count-forest children))))
  
  )

(define (count-forest ls)
  (if (null? ls) 0
      (+ (ask (car ls) 'count)
	 (count-forest (cdr ls)))))


(define english-kings
  (instantiate tree 'HenryII
	       (list (instantiate tree 'RichardI '())
		     (instantiate tree 'John
				(list (instantiate tree 'HenryIII '()))))))