;; Stream-Netzwerke in CML mit selektiver Kommunikation

(define (combine proc in-1 in-2 out)
  (spawn
   (lambda ()
     (let loop ()
       (let ((pair
	      (select
	       (list 
		(wrap (receive-rv in-1)
		      (lambda (a)
			(cons a (receive in-2))))
		(wrap (receive-rv in-2)
		      (lambda (b)
			(cons (receive in-1) b)))))))
       (send out (proc (car pair) (cdr pair)))
       (loop))))))

(define (delay init in out)
  (spawn
   (lambda ()
     (let loop ((message init))
       (send out message)
       (loop (receive in))))))

(define (copy in out-1 out-2)
  (spawn
   (lambda ()
     (let loop ()
       (let ((message (receive in)))
	 (select
	  (list
	   (wrap (send-rv out-1 message)
		 (lambda (ignore)
		   (send out-2 message)))
	   (wrap (send-rv out-2 message)
		 (lambda (ignore)
		   (send out-1 message)))))
	 (loop))))))

(define (make-fib-channel)
  (let ((out (make-channel))
	(c1 (make-channel))
	(c2 (make-channel))
	(c3 (make-channel))
	(c4 (make-channel))
	(c5 (make-channel)))
    (delay 0 c4 c5)
    (copy c2 c3 c4)
    (combine + c3 c5 c1)
    (copy c1 c2 out)
    (send c1 1)
    out))

(define (write-channel channel)
  (let loop ()
    (write (receive channel))
    (newline)
    (loop)))