(load "ub10-3c.scm")

;;; SIGNATUR
;;; make-traffic-light-group: list(traffic-light) -> traffic-light-group
;;; ERKLÄRUNG
;;; Konstruktorfunktion für Objekte der Klasse traffic-light-group. Das
;;; Argument ist eine Liste von traffic-light-Objekten.
;;; Die Klasse kennt folgende Methoden:
;;; step: -> VOID
;;; (send g 'step) führt dazu, daß alle Ampeln in der Ampelgruppe in den
;;; nächsten Zustand übergehen.
;;; (send g 'reset) setzt alle Ampeln in den Zustand rot.
;;; DEFINITION
(define make-traffic-light-group
  (lambda (traffic-lights)
    (lambda (message)
      (letrec ((send-to-list
                (lambda (lst msg)
                  (if (not (null? lst))
                      (begin
                        (send (car lst) msg)
                        (send-to-list (cdr lst) msg))))))
        (case message
          ((step)
           (lambda (this)
             (send-to-list traffic-lights 'step)))
          ((reset)
           (lambda (this)
             (send-to-list traffic-lights 'reset)))
          (else
           (make-no-method 'traffic-light-group message)))))))
         

(define g (make-traffic-light-group
           (list
            (make-traffic-light "Ampel 1")
            (make-traffic-light "Ampel 2")
            (make-traffic-light-counterpart "Ampel 3"))))

(send g 'step) (newline)
(send g 'reset) (newline)
(send g 'step) (newline)
(send g 'step) (newline)