[rules-users] [rule-users] rule comparison

[Edson Tirelli]

   Yes, that is the correct behavior and checking of equality will not help
on that. If you want facts to match only in one way but not the reverse, you
need to have some kind of "ordering" between them and must add a constraint
to your rules to avoid that. Note that this is not a rules engine issue, but
a model design issue.
    Example of how to solve that is:

* if your facts have an attribute with an ID/code/whatever that may be
ordered, you can do:

when
    MyFact( $id : id )
    MyFact( id > $id )
then
   ...
end

   So the ">" constraint will prevent facts matching both ways.
   If you don't have such attribute, you can use system id, but that is
ugly, and you probably could find a better modeling for your facts. Anyway,
it would be like:

when
   $f1 : MyFact()
   $f2 : MyFact()
   eval( System.identityHashCode( $f1 ) > System.identityHashCode( $f2 ) )
then
  ...
end

   Again, the above works, but is damn ugly... :)

   []s
   Edson



2007/5/20, Sikkandar Nawabjan <Sikkandar.Nawabjan at ustri.com>:
>
> Edson,
> am getting the following output
> [ b, a ]
> [ a, b ]
> only the order of the output is different. so if i check a equal to b
> according to the cross product law the then part execute 2 times?
> thats y i check the reference in the then part.
>
> how to use eval to  variable comparison of objects in a single line
>
> Thanks and  regs,
> Basha
>
>
>
>
>
>
>
>
>
>
>
>
> /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
> Message: 3
> Date: Sat, 19 May 2007 09:53:29 -0300
> From: "Edson Tirelli" <tirelli at post.com>
> Subject: Re: [rules-users] [rule-users]how to create object properties
>         in      single stmnt
> To: "Rules Users List" <rules-users at lists.jboss.org>
> Message-ID:
>         <e6dd5ba30705190553p1f5f794ct91ad250fb1ad3753 at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
>     Sikkandar,
>
>     In 3.0.6, if you have 2 strings in the working memory ("a" and "b" )
> and
> you write:
>
> rule "cross product"
> when
>     $s1: String()
>     $s2: String()
> then
>     System.out.println("[ "+$s1+", "+$s2+" ]");
> end
>
>    The result MUST be:
>
> [ a, b ]
> [ b, a ]
>
>    If it is not that, then we have a bug, but our integration tests that
> test this specific situation are working fine. Plz let us know if it is
> different for you.
>    In 4.0, the result must be:
>
> [ a, b ]
> [ b, a ]
> [ a, a ]
> [ b, b ]
>
>    So a fact (by default) may match multiple simultaneous patterns.
>
>    Regarding your second question, comparing properties of the same object
> is also something we added for 4.0. In 3.0.x you need eval() too.
>
>    []s
>    Edson
>
> 2007/5/19, Sikkandar Nawabjan <Sikkandar.Nawabjan at ustri.com>:
> >
> > Hi ,
> > The very reason i used to compare two object reference is that i got
> then
> > executed multiple time when i do duplicate check between object
> properties.
> > so i beleive the pattern match happen more than a time
> > for example
> >  when
> >      $obj1:object($code:code,$stdate:startdate);
> >      $obj2:object(code==$code,startdate=$stdate);
> >  then
> > if(obj1!=obj2)
> >      System.out.println("Fired");
> >
> > My questions are
> >
> > 1) In 3.0.6 is there any other way to avoid this multiple check other
> than
> > using eval(which affects performance i beleive). i can't use this
> operator
> > in 3.0.6
> >
> > 2) related to this i have one more query. how to check properties within
> > the object itself
> >
> > for example i want to do
> >  when
> >      $obj1:object($code:code,$stdate:startdate,$enddate:enddate >
> $stdate,
> > reasoncode == $code);
> >  then
> >      System.out.println("Fired");
> > i beleive the above throws error in 3.0.6 (nullpointer related to alpha
> > node)
> >
> > Earlier reply is highly appreciated
> >
> > Thanks and Regs,
> > Bassha
> >
> >
>
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> rules-users at lists.jboss.org
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>
>


-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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