SyncStitch:Train Gate Controll ref: http://qiita.com/kencoba/items/82a0ff70737a6c150148

Definitions

(define-event f.enter)
(define-event f.exit)
(define-event b.enter)
(define-event b.exit)
(define-event c.open)
(define-event c.close)

SYS

(define-channel ch-fc (x) '((0)))
(define-channel ch-bc (x) '((0)))
(define-channel ch-cg (x) '((0) (1)))

(define-process SYS
  (par '() FRONT BACK CTRL-CLOSE))

(define-process FRONT
  (! f.enter (! ch-fc (0) (! f.exit FRONT))))
(define-process BACK
  (! b.enter (! b.exit (! ch-bc (0) BACK))))

(define-process CTRL-CLOSE
    (? ch-fc (x) (! c.open
      (? ch-bc (x) (! c.close CTRL-CLOSE)))))