(define (make-state)
  (define next-0 #f)
  (define next-1 #f)
  (define weight 0)
  (define id #f)

  (define (set-pointers! p1 p2)
    (set! next-0 p1)
    (set! next-1 p2))

  (define (select-next)
    (lambda(t)
    (cond((eq? t' 0) next-0)
         ((eq? t' 1) next-1))))

  (define (heaviest-next)
    (if(= (next-0 'weight) (next-1 'weight))
       0
       (if(> (next-0 'weight)(next-1 'weight)) 0 1)))

  (define (set-id! new-id)
    (set! id new-id))

  (lambda (m)
    (cond((eq? m 'set-pointers!) set-pointers!)
         ((eq? m 'select-next) (select-next))
         ((eq? m 'heaviest-next) (heaviest-next))
         ((eq? m 'increase-weight!) (set! weight (+ weight 1)))
         ((eq? m 'weight) weight)
         ;((eq? m 'next-0) next-0)
         ;((eq? m 'next-1) next-1)
         ((eq? m 'get-id) id)
         ((eq? m 'set-id!) set-id!)
         (else "Unknown request"))))