37 lines
1.5 KiB
Racket
37 lines
1.5 KiB
Racket
#lang syndicate/core
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;; Test case for a historical bug in Syndicate.
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;;
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;; When the bug existed, this program received four SCN events in
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;; total, whereas it should receive only two.
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;;
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;; While metamessages were "echo cancelled", and receivers only ever
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;; got one copy of a sent metamessage no matter how many metas there
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;; were, state changes were not. Issuing a quick enough "pulse" of
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;; metaassertion while maintaining interest in it led to an "echo":
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;; multiple receipts of the pulse.
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;;
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;; The fix was to adjust the implementation of state change
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;; notifications to cancel the echo for metaassertions.
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;;
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;; 20160730 I'm in the process of revising the design of dataspace
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;; relaying to avoid this problem in a different way. Instead of just
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;; having `at-meta` for both inbound and outbound assertions, there
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;; are now two constructors, `inbound` and `outbound`, and the relay
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;; function of the dataspace pays attention to each in a different
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;; way. Now there cannot be (accidental) routing loops: asserting
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;; something `outbound`, no matter how briefly, will only ever result
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;; in a pulse of an `inbound` assertion.
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(require syndicate/pretty)
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(dataspace-actor
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(actor (lambda (e counter)
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(and e
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(let ((new-counter (+ counter 1)))
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(printf "Received event ~a:\n~a\n" new-counter (syndicate-pretty-print->string e))
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(transition (+ counter 1) '()))))
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0
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(list (patch-seq (assert (outbound 'x))
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(sub (inbound 'x)))
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(retract (outbound 'x)))))
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