The "from" conditional element solves part of my problem:<br><br>rule "Find matching entry in parallel arrays (alternate)"<br> when<br> $first : ArrayList( )<br> $second : ArrayList( this != $first )
<br> $fi : Object() from $first<br> $si : Object() from $second<br> eval( $fi == $si )<br> then<br> System.out.println ( " Found match at index ? : " + $fi + "!" );<br>end
<br><br>I do want reference equality (==) in my eval. But I understand that object equality would look just like:<br><br>eval( $fi .equals( $si ) )<br><br><br>Thanks!<br><br>Aaron<br><br><br><div><span class="gmail_quote">
On 8/7/07, <b class="gmail_sendername">Mike D</b> <<a href="mailto:mike.dalaker@kewill.com">mike.dalaker@kewill.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>Mark,<br><br>Just to be sure I read this correctly:<br><br>eval( $fi == $si )<br><br>means it's checking objects, not values within the object?<br>If a compare of values is needed, another eval would have to be written to
<br>compare temp value.<br><br>Thanks,<br>Mike<br><br><br>Oh, and can we change the documenatation examples please?<br><br>Somthing like...<br><br>rule<br> when<br> Team( $team : name == "ManU" )<br> $person : Person( favouriteTeam == $team )
<br> then<br> System.out.println( $person.getName() + " likes Manchester" );<br> end<br><br>rule<br> when<br> Team( $team : name == "Chelsea" )<br> $person : Person( favouriteTeam != $team )
<br> then<br> System.out.println( $person.getName() + " does not like Chelsea at<br>all" );<br> end<br><br><br><br>Mark Proctor wrote:<br>><br>> We don't really recommend you assert ArrayLists etc as facts, as they
<br>> have no contextual meaning<br>><br>> $first : ArrayList( )<br>> $second : ArrayList( this != $first )<br>> $fi Object() from $first<br>> $si Object from $second<br>> eval( $fi == $si )<br>><br>
> 'from' allows iteration of lists, so you could potentially do it this<br>> way, although it doesn't provide an index number for you.... You could<br>> possibly have a global that as part of a function in eval get
<br>> incremented and that global is available in the consequence. But you'll<br>> have to be very careful with concurrency.... Might be easier to have a<br>> hashmap of indexes where the key is made up of $first and $second. Btw
<br>> == checks for same instances, not an equality check, is that what you<br>> wanted?<br>><br>> Mark<br>><br>> Aaron Dixon wrote:<br>>> My problem boils down to finding matching entries in parallel arrays.
<br>>><br>>> Here is a rule that succesfully does just that:<br>>><br>>> rule "Find matching entry in parallel arrays"<br>>> when<br>>> $first : ArrayList( )<br>>> $second : ArrayList( this != $first )
<br>>> $i : Integer( this < $first.size )<br>>> eval( $first.get($i) == $second.get($i) )<br>>> then<br>>> System.out.println ( "Found match at index " + $i + "!" );
<br>>> end<br>>><br>>><br>>> To execute this rule, I must insert (assert) the two ArrayList facts<br>>> as well as at least as many Integer facts as there are items in the<br>>> ArrayLists.
<br>>><br>>> What I don't like about this rule is that<br>>><br>>> (1) I have to assert the Integers<br>>> (2) I can't support arbitrarily-sized lists in my rules (without<br>
>> asserting that many Integer facts)<br>>><br>>> So -- Is there a better way?<br>>><br>>> What if a future version of Drools supported implicit Number facts<br>>> that allowed for these kinds of indexing rules?
<br>>><br>>> Aaron<br>>><br>>><br>>><br>>><br>>> ------------------------------------------------------------------------<br>>><br>>> _______________________________________________
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