[rules-users] Finicky eval statements

[Bagwell, Allen F]

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
phone:  505/284-4517
fax:  505/ 844-7886


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