The following function retracts and reasserts all facts in the engine.
Except for the fact ids, the working memory should be the same after the
call, but all rules will fire over again.
(deffunction rewind ()
(bind ?e (engine))
(bind ?it (?e listFacts))
(while (?it hasNext)
(bind ?fact (?it next))
(?e assertFact (?e retract ?fact) )
)
)
-W
On Thu, Jul 23, 2009 at 4:22 PM, Ernest Friedman-Hill <[email protected]>wrote:
> I can't think of any other way to achieve that behavior, so I guess you can
> go ahead and do it. You might tell us *why* you want that behavior, though,
> because maybe there's another solution.
>
>
>
>
> On Jul 23, 2009, at 5:02 AM, [email protected] wrote:
>
> Dear Jess users,
>>
>> I have been looking in the manual and mailing list for some time but
>> couldn't find an answer. Maybe you could help me on this one.
>>
>> Rules only fire once each time their condition is true, provided that the
>> facts the condition refers to are not modified, i.e. if I only have one
>> rule:
>>
>> (defrule test
>> (fact)
>> =>
>> (printout t "fired!" crlf))
>>
>> it will only fire once as (fact) is not modified.
>>
>> I am running Jess from Java. Even when I invoke the rete.run() method
>> twice the rule still fires once. I want a behavior in which the rule fires
>> once each time I call the run() method. What I mean is that two
>> consecutive calls to run should produce as output:
>> fired!
>> fired!
>>
>> Resetting the engine (rete.reset()) is not a satisfactory solution,
>> because I don't want to reset my working memory also. Neither is
>> implementing a rule:
>>
>> (defrule test
>> ?f <- (fact)
>> =>
>> (retract ?f)
>> (printout t "fired!" crlf)
>> (assert ?f))
>>
>> as this will result in firing the rule ad infinitum during one run.
>>
>> I considered enriching the LHS of all my rules with a special designated
>> fact, say (fire-again) and retract and assert it in between each call to
>> run, i.e.:
>>
>> (defrule test
>> (fire-again)
>> (fact)
>> =>
>> (printout t "fired!" crlf)
>> )
>>
>> (reset)
>> (assert (fire-again))
>> (run)
>> (retract-string "(fire-again)")
>> (assert (fire-again))
>> (run)
>>
>> and this seems to get me the behavior I want.
>>
>> Before I rush to preprocessing all my rules in Java I wondered if there
>> are other (better) ways to get the behavior I want?
>>
>> Kind regards,
>>
>> Nick.
>>
>>
>>
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>> .
>> --------------------------------------------------------------------
>>
>
> ---------------------------------------------------------
> Ernest Friedman-Hill
> Informatics & Decision Sciences, Sandia National Laboratories
> PO Box 969, MS 9012, Livermore, CA 94550
> http://www.jessrules.com
>
>
>
>
>
>
>
>
> --------------------------------------------------------------------
> To unsubscribe, send the words 'unsubscribe jess-users [email protected]'
> in the BODY of a message to [email protected], NOT to the list
> (use your own address!) List problems? Notify [email protected].
> --------------------------------------------------------------------
>
>
