[rules-users] finding matching entries in parallel arrays

[Aaron Dixon]

The "from" conditional element solves part of my problem:

rule "Find matching entry in parallel arrays (alternate)"
    when
        $first : ArrayList( )
        $second : ArrayList( this != $first )
        $fi : Object() from $first
        $si : Object() from $second
        eval( $fi == $si )
    then
        System.out.println ( " Found match at index ? : " + $fi + "!" );
end

I do want reference equality (==) in my eval. But I understand that object
equality would look just like:

eval( $fi .equals( $si ) )


Thanks!

Aaron


On 8/7/07, Mike D <mike.dalaker at kewill.com> wrote:
>
>
> Mark,
>
> Just to be sure I read this correctly:
>
> eval( $fi == $si )
>
> means it's checking objects, not values within the object?
> If a compare of values is needed, another eval would have to be written to
> compare temp value.
>
> Thanks,
> Mike
>
>
> Oh, and can we change the documenatation examples please?
>
> Somthing like...
>
> rule
>     when
>         Team( $team : name == "ManU" )
>         $person : Person( favouriteTeam == $team )
>     then
>         System.out.println( $person.getName() + " likes Manchester" );
>     end
>
> rule
>     when
>         Team( $team : name == "Chelsea" )
>         $person : Person( favouriteTeam != $team )
>     then
>         System.out.println( $person.getName() + " does not like Chelsea at
> all" );
>     end
>
>
>
> Mark Proctor wrote:
> >
> > We don't really recommend you assert ArrayLists etc as facts, as they
> > have no contextual meaning
> >
> > $first : ArrayList( )
> > $second : ArrayList( this != $first )
> > $fi Object() from $first
> > $si Object from $second
> > eval( $fi == $si )
> >
> > 'from' allows iteration of lists, so you could potentially do it this
> > way, although it doesn't provide an index number for you.... You could
> > possibly have a global that as part of a function in eval get
> > incremented and that global is available in the consequence. But you'll
> > have to be very careful with concurrency.... Might be easier to have a
> > hashmap of indexes where the key is made up of $first and $second. Btw
> > == checks for same instances, not an equality check, is that what you
> > wanted?
> >
> > Mark
> >
> > Aaron Dixon wrote:
> >> My problem boils down to finding matching entries in parallel arrays.
> >>
> >> Here is a rule that succesfully does just that:
> >>
> >> rule "Find matching entry in parallel arrays"
> >>     when
> >>         $first : ArrayList( )
> >>         $second : ArrayList( this != $first )
> >>         $i : Integer( this < $first.size )
> >>         eval( $first.get($i) == $second.get($i) )
> >>     then
> >>         System.out.println ( "Found match at index " + $i + "!" );
> >> end
> >>
> >>
> >> To execute this rule, I must insert (assert) the two ArrayList facts
> >> as well as at least as many Integer facts as there are items in the
> >> ArrayLists.
> >>
> >> What I don't like about this rule is that
> >>
> >>     (1) I have to assert the Integers
> >>     (2) I can't support arbitrarily-sized lists in my rules (without
> >> asserting that many Integer facts)
> >>
> >> So -- Is there a better way?
> >>
> >> What if a future version of Drools supported implicit Number facts
> >> that allowed for these kinds of indexing rules?
> >>
> >> Aaron
> >>
> >>
> >>
> >>
> >>
> ------------------------------------------------------------------------
> >>
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users at lists.jboss.org
> >> https://lists.jboss.org/mailman/listinfo/rules-users
> >>
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
> --
> View this message in context:
> http://www.nabble.com/finding-matching-entries-in-parallel-arrays-tf4225120.html#a12034578
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>
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