;;;; -*- Scheme -*-
;;
;; Beacons example for HLSIM
;;
;; David DeRoure June 12 1997, revised Sep 10 1997
;; dder@martigny.ai.mit.edu
;;
;; This definition file is used by beacons1.scm.  It should be compiled 
;; with (cf "beacons1d") and loaded with (load "beacons1d").  See 
;; beacons1s.scm for the simulation setup.  See the HLSIM documentation 
;; for further details.

(declare (usual-integrations))

;; The message constructor and accessors.  We use the message format
;; defined in util1d.scm.

(define (make-message source id ttl color)    
  (vector 'beacon source color ttl id))

(define message-source message.source)  ; processor id of originator
(define message-id     message.id)      ; message id 
(define message-ttl    message.ttl)     ; ttl = time-to-live = hopcount
(define message-color  message.data)    ; message color

;; To keep track of messages that have already been rebroadcast by the 
;; propagators, the procedure new-message? checks for the message source
;; and id in a table which is updated when new messages first arrive.
;; If present in the table, new-message? returns #F, else it updates 
;; the table of messages-received and returns #T so that the rebroadcast
;; occurs. 

(define (make-table) (make-eqv-hash-table 2))

(define (new-message? message message-table)
  (let ((ids (hash-table/get message-table (message-source message) '())))
    (if (member (message-id message) ids)
	#F
	(begin 
	  (hash-table/put! message-table 
			   (message-source message)
			   (cons (message-id message) ids))
	  #T))))

;; end of beacons1d.scm