;;;
;;; Part IV
;;;


(define x 0)
  (define (f) 
    (set! x (+ x 1))
  x
)

(define (repeatl f k)
  (if (<= k 0)
       '()
       ;; make sure (f) gets called before making tail of list.
       (let ((x (f)))   
            (cons x (repeatl f (- k 1)))
       )
   )
)

(define (repeatr f k)
  (reverse (repeatl f k))
)

;; Tail-recursive implementation of same

(define (my-repeatl f k)
  (define (my-repeatl-helper f k collect)
    (if (<= k 0)
	collect
	(let ((x (f)))
	  (my-repeatl-helper f (- k 1) (cons x collect)))))
  (my-repeatl-helper f k '())
)

(define (my-repeatr f k)
  (reverse (my-repeatl f k)))