Oplossing taak 3

(define (make-circular lst)
  (let walk
    ((view lst))
    (cond
      ((null? (cdr view))
       (set-cdr! view lst)
       lst)
      (else
       (walk (cdr view))))))
(define slinger '(ster kerstman ster kerstman ster kerstman ster))
(define slinger-circ (make-circular slinger))

(define (opbergen slinger)
  (define doos (cons '() '()))
  (let walk
    ((view slinger)
     (lastkerstman '())
     (lastster '()))
    (define rest (cdr view))
    (if (and (eq? view slinger)
             (or (not (null? (car doos))) (not (null? (cdr doos)))))
        doos
        (begin (set-cdr! view '())
               (cond
                 ((eq?
                 ((eq? 'kerstman (car view))
                  (if (null? (car doos))
                      (set-car! doos view)
                      (set-cdr! lastkerstman view))
                  (walk rest view lastster))
                 ((eq? 'ster (car view))
                  (if (null? (cdr doos))
                      (set-cdr! doos view)
                      (set-cdr! lastster view))
                  (walk rest lastkerstman view)))))))

    ;kijk eens naar de oefeningen van eline én matthias
    slinger-circ
    (opbergen slinger-circ)