29 lines
910 B
Racket
29 lines
910 B
Racket
#lang prospect
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;; Hello-worldish "bank account" example.
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(struct account (balance) #:prefab)
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(struct deposit (amount) #:prefab)
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(define (manager e balance)
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(match e
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[(message (deposit amount))
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(transition (+ balance amount) (patch-seq (retract (account balance))
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(assert (account (+ balance amount)))))]
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[_ #f]))
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(define (observer e _)
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(when (patch? e)
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(for-trie ([(account $balance) (patch-added e)])
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(printf "Balance changed to ~a\n" balance)))
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#f)
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(define (updater e _)
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(if (and (patch? e) (trie-non-empty? (patch-added e)))
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(quit (list (message (deposit +100))
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(message (deposit -30))))
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#f))
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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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