Re: [rules-users] "not exists MyObject" - is it a valid LHS condition?
Vlad,
The conditional element "not" is the oposite of "exists". It means
exactly what you want:
not MyObject( <constraints> )
Will evaluate to true if and only if there is no instance of MyObject in
the working memory that match the given <constraints>.
Exists will evaluate to true if there is at least one object that
matches the constraints:
exists MyObject( <constraints> )
So, you don't need to write "not exists"... write simply "not".
Having said that, 3.0.x will trigger an error if you write "not exists".
Trunk will "optimize" and remove your "exists" effectivelly using only
the "not".
[]s
Edson
Olenin, Vladimir (MOH) wrote:
Hi,
I wonder if the combination of ‘not’ and ‘exists’ keywords is a valid
one and therefore the construct like
rule “myrule”
when
not exist MyObject(param matches “somepattern”)
then
System.out.println(“Object for pattern ‘somepattern’ doesn’t exisit”);
End
Thanks.
Vlad
PS: basically I need to trigger a rule if some set of facts is NOT
found and I need to trigger it only once.
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Edson Tirelli
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