Knutsel

(define (knutsel n sterren sneeuwmannen)
  (define output '())
  (define (add-sterren output n)
    (define (iter output n)
      (if (or (null? sterren) (<= n 0))
          output
          (let ((rest (cdr sterren)))
            (cond ((null? output)
                   (set! output sterren)
                   (set-cdr! sterren '()))
                  (else
                   (set-cdr! (last output) sterren)
                   (set-cdr! sterren '())))
            (set! sterren rest)
            (iter output (- n 1)))))
    (iter output n))
  (define (iter sneeuwmannen)
    (display "sterren: ")(display sterren)(newline)
    (display "sneeuwmannen: ")(display sneeuwmannen)(newline)
    (display "output: ")(display output)(newline)
    (cond
      ((null? sterren)
       (set-cdr! (last output) sneeuwmannen)
       (set-cdr! (last output) output)
       (display sterren)(newline)
       output
       )
      ((null? sneeuwmannen)
       (set-cdr! (last output) sterren)
       (set-cdr! (last output) output)
       output
       (display "sterren: ")(display sterren)(newline)
       (display "sneeuwmannen: ")(display sneeuwmannen)(newline)
       (display "output: ")(display output)(newline))
      (else
       (let ((ster sterren)
             (sneeuwman sneeuwmannen)
             (restsneeuw (cdr sneeuwmannen)))
         ;sneeuwman aanhangen
         (if (null? output)
             (begin (set! output sneeuwman)
                    (set-cdr! output '()))
             (begin (set-cdr! sneeuwman '())
                    (set-cdr! (last output) sneeuwman)))
         ;n sterren aanhangen
         (add-sterren output n)
         ;itereren
         (iter restsneeuw)))))
  (iter sneeuwmannen))