26 lines
815 B
Racket
26 lines
815 B
Racket
#lang racket/base
|
|
|
|
(require racket/set)
|
|
(require racket/match)
|
|
(require "core.rkt")
|
|
|
|
(provide (except-out (struct-out presence-detector) presence-detector)
|
|
(rename-out [make-presence-detector presence-detector])
|
|
presence-detector-update
|
|
presence-detector-routes)
|
|
|
|
(struct presence-detector (route-set) #:transparent)
|
|
|
|
(define (make-presence-detector [initial-routes '()])
|
|
(presence-detector (list->set initial-routes)))
|
|
|
|
(define (presence-detector-update p rs)
|
|
(define old-route-set (presence-detector-route-set p))
|
|
(define new-route-set (list->set rs))
|
|
(values (struct-copy presence-detector p [route-set new-route-set])
|
|
(set-subtract new-route-set old-route-set)
|
|
(set-subtract old-route-set new-route-set)))
|
|
|
|
(define (presence-detector-routes p)
|
|
(set->list (presence-detector-route-set p)))
|