inside of a pattern == is in equality. Inside of an eval it all depends
if you are using the java or mvel dialect - its just an expression, so
it obeys the host expression language.
Mark
Aaron Dixon 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* <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> 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
>>
>>
>>
>>
>>
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>>
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>>
>
>
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>
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