2016-01-16 19:32:04 +00:00
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#lang prospect
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;; Hello-worldish "bank account" example.
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(struct account (balance) #:prefab)
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2016-01-18 22:38:58 +00:00
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(struct deposit (amount) #:prefab)
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2016-01-16 19:32:04 +00:00
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2016-01-18 22:38:58 +00:00
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(define (manager e balance)
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2016-03-01 21:45:29 +00:00
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(match-event e
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2016-01-18 22:38:58 +00:00
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[(message (deposit amount))
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(transition (+ balance amount) (patch-seq (retract (account balance))
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2016-03-01 21:45:29 +00:00
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(assert (account (+ balance amount)))))]))
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2016-01-16 19:32:04 +00:00
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2016-01-18 22:38:58 +00:00
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(define (observer e _)
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2016-02-29 18:44:45 +00:00
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(when (patch? e) (for [(balance (project-assertions (patch-added e) (account (?!))))]
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2016-03-01 21:45:29 +00:00
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(printf "Balance changed to ~a\n" balance))))
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2016-01-16 19:32:04 +00:00
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2016-01-18 22:38:58 +00:00
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(define (updater e _)
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2016-03-01 21:48:28 +00:00
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(when (patch/added? e)
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2016-03-01 21:45:29 +00:00
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(quit (list (message (deposit +100))
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(message (deposit -30))))))
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2016-01-18 22:38:58 +00:00
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(spawn manager 0 (patch-seq (assert (observe (deposit ?))) (assert (account 0))))
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(spawn observer (void) (assert (observe (account ?))))
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(spawn updater (void) (assert (observe (observe (deposit ?)))))
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