29 lines
1.1 KiB
Racket
29 lines
1.1 KiB
Racket
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#lang racket/base
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(require racket/set)
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(require "core.rkt")
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(require "pattern.rkt")
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(provide (except-out (struct-out presence-detector) presence-detector)
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(rename-out [make-presence-detector presence-detector])
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presence-detector-update
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presence-exists-for?)
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(struct presence-detector (route-set) #:transparent)
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(define (make-presence-detector [initial-routes '()])
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(presence-detector (list->set initial-routes)))
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(define (presence-detector-update p rs)
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(define old-route-set (presence-detector-route-set p))
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(define new-route-set (list->set rs))
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(values (struct-copy presence-detector p [route-set new-route-set])
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(set-subtract new-route-set old-route-set)
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(set-subtract old-route-set new-route-set)))
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(define (presence-exists-for? p probe-route)
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(for/or ((existing-route (in-set (presence-detector-route-set p))))
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(and (equal? (route-subscription? probe-route) (route-subscription? existing-route))
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(equal? (route-meta-level probe-route) (route-meta-level existing-route))
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(intersect? (route-pattern probe-route) (route-pattern existing-route)))))
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