[rules-users] counting facts of a kind

[Wolfgang Laun]

2010/8/24 Edson Tirelli <tirelli at post.com>

>
>     Wolfgang,
>
>     The requirement for serializable classes even when not using
> persistence was a "mistake" made several versions ago and I believed it was
> fixed. What version of Drools are you using? If that is trunk, we need to
> fix it.
>
> The latest official release 5.1.



>     Anyway, workaround: for count(), you can simply write "count(1)"
> instead of using the actual variable,
>

Good to know. OTOH, is there any good reason for count() having an argument
at all? Just because all others have an argument? Nowadays, the uniform
signature could be (Object... objs) which would, e.g., permit you to write
count() without the dummy argument. Others, such as sum, average and
especially min and max could easily handle more than one argument. Not a
bonanza, but being general is not a bad thing...

-W



>
>     Edson
>
> 2010/8/23 Wolfgang Laun <wolfgang.laun at gmail.com>
>
> No, not knowingly :-) I'm using the simplest possible setup for
>> KnowledgeBase, KnowledgeBuilder, StatefulKnowledgeSession.
>>
>> Why should accumulate/count effect persistence?
>>
>> -W
>>
>>
>> 2010/8/23 Swindells, Thomas <TSwindells at nds.com>
>>
>>>   You’ve probably configured your system to be using persistence?
>>>
>>> In which case what you are persisting needs to be serializable so that it
>>> can be persisted
>>>
>>>
>>>
>>> Thomas
>>>
>>>
>>>
>>> *From:* rules-users-bounces at lists.jboss.org [mailto:
>>> rules-users-bounces at lists.jboss.org] *On Behalf Of *Wolfgang Laun
>>> *Sent:* 23 August 2010 12:17
>>> *To:* Rules Users List
>>> *Subject:* [rules-users] counting facts of a kind
>>>
>>>
>>>
>>> As simple as it gets:
>>>
>>> rule countHigh
>>> when
>>>     $n : Number() from accumulate ( $sgc : StartGoalConn() count( $sgc )
>>> )
>>> then
>>>     System.out.println( "plain routes: " + $n );
>>> end
>>>
>>> And yet, it fails:
>>>
>>> Exception in thread "main" org.drools.RuntimeDroolsException:
>>> java.lang.ClassCastException: rss.ixl.route.TrainStartGoalConn cannot be
>>> cast to java.io.Serializable
>>>
>>> Sure, adding "implements Serializable" to StartGoalConn fixes this. But
>>> why is this necessary?
>>>
>>> FYI, StartGoalConn is abstract superclass of TrainStartGoalConn - just in
>>> case this has some bearing on this issue.
>>>
>>> Best
>>> -W
>>>
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>>
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>
>
> --
>   Edson Tirelli
>   JBoss Drools Core Development
>   JBoss by Red Hat @ www.jboss.com
>
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