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 <[EMAIL PROTECTED]>:
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" <[EMAIL PROTECTED]>
Subject: Re: [rules-users] [rule-users]how to create object properties
in single stmnt
To: "Rules Users List"
Message-ID:
<[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>:
>
> 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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Edson Tirelli
Software Engineer - JBoss Rules Core Developer
Office: +55 11 3529-6000
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