[rules-users] Re: Usage of 'exists' keyword to get the number of occurance?

[Edson Tirelli]

   Yes, the "from collect" is new to 4.0.
   If you are using 3.0.6, you must use 2 rules and a helper class to do the
count:

rule "counting"
salience 10
when
    $counter : Counter()
    Student( name == "Drools" )
then
    $counter.setValue( $counter.getValue() + 1 );
end

rule "Total instances"
when
    $counter : Counter( )
then
    System.out.println( "Total instances = "+$counter.getValue() );
end

   Please not the higher salience value in the first rule. Also, remember to
assert all your objects into the working memory, not only the list.
   The Counter class is a simple java bean to help you do the count.

   Hope it helps.

   []s
   Edson

2007/6/1, rajesh_sachin10 at yahoo.co.in <rajesh_sachin10 at yahoo.co.in>:
>
> Hi
> I'm working on Drools 3.06. I am not able to decipher the drl snippet you
> have posted.
> I'am not clear about the <b>'from collect'</b> Keywords. My problem
> statement is to get the number of
> occurance of a Student(Name =="Drools") in a collection.
>
> Please find below a small java snippet which is equivalent to what I'm
> tring to do.
>
> int count = 0;
> List<Student> nameList = getListofNames();
> while(nameList.iterator().hasNext())
> {
>         Student student = (Student)nameList.iterator().next();
>         if(Student.getName.equals("Drools"))
>        {
>              count++;
>         }
> }
> System.out.println("Occurance Count" + count);
>
>
> Edson Tirelli-3 wrote:
> >
> >    Nope, if you want actual instances you must use "collect":
> >
> > when
> >   context : Context(state == Context:START_UP)
> >   list : ArrayList( size > 0 ) from collect( ClassName(varName =="value"
> )
> > )
> > then
> >   // list has your matching ClassName objects
> > end
> >
> >    []s
> >    Edson
> >
> >
> >
> > 2007/6/1, Rajesh.Sachin10 <rajesh_sachin10 at yahoo.co.in>:
> >>
> >>
> >> Its possible to use 'exists' keyword to get the number of occurance?
> >>
> >> Eg:
> >>
> >> context : Context(state == Context:START_UP) exists ClassName(varName
> ==
> >> "value")
> >>
> >>
> >> The ClassName is an Object array..... So to get the number of occurance
> >> of
> >> the "value" in varName, we have any method or keywords?
> >> --
> >> View this message in context:
> >>
> http://www.nabble.com/Usage-of-%27exists%27-keyword-to-get-the-number-of-occurance--tf3853750.html#a10917875
> >> Sent from the drools - user mailing list archive at Nabble.com.
> >>
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users at lists.jboss.org
> >> https://lists.jboss.org/mailman/listinfo/rules-users
> >>
> >
> >
> >
> > --
> >   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
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> Quoted from:
>
> http://www.nabble.com/Usage-of-%27exists%27-keyword-to-get-the-number-of-occurance--tf3853750.html#a10918988
>
>


-- 
  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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