Sneeuwmannen

;Vraag 3
(define doos (cons '() '()))
(define slinger '(sneeuwman sneeuwman ster ster sneeuwman ster ster sneeuwman sneeuwman ster))

(define (sneeuwman? x)
  (eq? 'sneeuwman x))
(define (ster? x)
  (eq? 'ster x))

(define (berg-op slinger doos)
  (cond
    ((null? slinger)
     '())
    (else
     (let iter
       ((view slinger)
        (rest (cdr slinger))
        (lastsnm '())
        (laststr '()))
       (display doos)(newline)
       (cond
         ((eq? rest slinger)
          doos)
         ((sneeuwman? (car view))
          (if (null? (car doos))
              (begin (set-car! doos view)
                     (set-cdr! view '())
                     (iter rest (cdr rest) view laststr))
              (begin (set-cdr! lastsnm view)
                     (set-cdr! view '())
                     (iter rest (cdr rest) view laststr))))
         ((ster? (car view))
          (if (null? (cdr doos))
              (begin (set-cdr! doos view)
                     (set-cdr! view '())
                     (iter rest (cdr rest) lastsnm view))
              (begin (set-cdr! laststr view)
                     (set-cdr! view '())
                     (iter rest (cdr rest) lastsnm view)))))))))