[rules-users] finding matching entries in parallel arrays

[Aaron Dixon]

I spoke too soon. The from will match items in the two Lists that are not at
the same index.

As for asserting ArrayList( ) facts -- in my actual application I have facts
that have Collections attributes for which I need this behavior. I just made
the problem simpler for this post.


On 8/7/07, Aaron Dixon <atdixon at gmail.com> wrote:
>
> 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
> >
> > 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
> >
>
>
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