62 lines
1.2 KiB
Racket
62 lines
1.2 KiB
Racket
#lang syndicate
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;; Expected Output:
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#|
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balance = 0
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balance = 5
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balance = 0
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JEEPERS
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know overdraft!
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balance = -1
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balance = -2
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no longer in overdraft
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balance = 8
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|#
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(assertion-struct balance (v))
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(message-struct deposit (v))
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(spawn
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;; Internal Events
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(message-struct new-transaction (old new))
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(assertion-struct overdraft ())
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(field [account 0])
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(assert (balance (account)))
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(on (message (deposit $v))
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(define prev (account))
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(account (+ v (account)))
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(realize! (new-transaction prev (account))))
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(on (realize (new-transaction $old $new))
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(when (and (negative? new)
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(not (negative? old)))
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(react
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;; (this print is to make sure only one of these facets is created)
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(printf "JEEPERS\n")
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(know (overdraft))
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(on (realize (new-transaction $old $new))
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(when (not (negative? new))
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(stop-current-facet))))))
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(during (know (overdraft))
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(on-start (printf "know overdraft!\n"))
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(on-stop (printf "no longer in overdraft\n"))))
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(spawn
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(on (asserted (balance $v))
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(printf "balance = ~a\n" v)))
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(spawn*
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(send! (deposit 5))
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(flush!)
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(send! (deposit -5))
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(flush!)
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(send! (deposit -1))
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(flush!)
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(send! (deposit -1))
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(flush!)
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(send! (deposit 10)))
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