[rules-users] NESTED LOOPS Possible

[Wolfgang Laun]

On 21/07/2012, salt <writemesaltworth at gmail.com> wrote:
> Hi Laune,
>
> Thanks for your comments. But i am not allowed to use eval() as that also
> might have performance issues.

Who forbids this? Bah.

> Actually this is my problem,
>
> $order:Order() Transaction() from $order.transaction
>
> if the list contains A,B,C,D,E,F

Not very lucid.

>
> Please let me know whether nested loops are possible.

There are no "loops" in DRL in the sense you appear to be thinking,
i.e., procedurally.

Here's how to do it:

function boolean cd( List list, Integer c, Integer d ){
    int cPos = list.indexOf( c );
    return cPos != -1 ? list.subList(cPos+1, list.size()).indexOf d)
!= -1 : false;
}
rule cd
when
    $l: List()
    Pair( $c: c, $d: d )
    eval( cd( $l, $c, $d ) )
then
end

This takes, on the average, 0.000014s (2.80GHz) per evaluation for
random combinations of elements that are actually in the list (and a
little less if one or both aren't contained). List length doesn't
really matter; for a list with 1000 elements the average is 0.000016s.

-W

>
> Thanks for your support.
>
>
>
> --
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