[rules-users] Finicky eval statements
Bagwell, Allen F
afbagwe at sandia.gov
Wed Dec 10 13:24:46 EST 2008
That's probably it, but my mind is blanking on the definition of time-constant as it would apply here.
howOld() is doing a simple calculation of the difference between the current time and the timestamp value that was set in statusRequested however many x seconds ago. So based on your feedback, I'm assuming the inline eval isn't seeing proper timestamp value since its last change. But the top-leve eval can.
-A
________________________________
From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Edson Tirelli
Sent: Wednesday, December 10, 2008 10:45 AM
To: Rules Users List
Subject: Re: [rules-users] Finicky eval statements
Is your inline eval() time-constant? I would guess that "howOld()" is returning different values when executed at different times. Inline evals MUST be time-constant. Top level evals can deal with non-time-constant expressions.
[]s
Edson
2008/12/10 Bagwell, Allen F <afbagwe at sandia.gov<mailto:afbagwe at sandia.gov>>
I'm puzzled over the proper use of in-line evals. I've used them successfully in some places. But it seems that on occasion something doesn't work when I think it should.
First, this is a when clause that works properly using a separate eval statement. The rule activates and fires when expected:
$rt : RuleTimer(uniqueName == "Hardware Status Request", timedOut == true)
$hw : Hardware($activelyMonitored : activelyMonitored, command == null)
AttrBoolean(this == $activelyMonitored, currentValue == true)
eval($hw.getStatusRequested().howOld() > $hw.getStatusPeriod())
However, this re-write changing to an in-line eval never fires.
$rt : RuleTimer(uniqueName == "Hardware Status Request", timedOut == true)
$hw : Hardware($activelyMonitored : activelyMonitored, command == null, eval(statusRequested.howOld() > statusPeriod) )
AttrBoolean(this == $activelyMonitored, currentValue == true)
Likewise, this re-write doesn't fire either where I sought to bind the more complex statusRequested object to a Drools variable before using it in the eval. The field statusPeriod just holds a primitive double.
$rt : RuleTimer(uniqueName == "Hardware Status Request", timedOut == true)
$hw : Hardware($activelyMonitored : activelyMonitored, $sr : statusRequested, command == null,
eval($sr.howOld() > statusPeriod) )
AttrBoolean(this == $activelyMonitored, currentValue == true)
I haven't been able to find anything in the manual that says these other two syntaxes are wrong. Furthermore, the Drools compiler has no issues with them.
Thanks!
Allen F. Bagwell
e-mail: afbagwe at sandia.gov<mailto:afbagwe at sandia.gov>
phone: 505/284-4517
fax: 505/ 844-7886
Ask your doctor if medical advice from a TV commercial is right for you.
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Edson Tirelli
JBoss Drools Core Development
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