[rules-users] Newbie question on accessing predecessor and successor in a list

[Greg Barton]

You can't do $journey.segmentList.indexOf(this) and $journey.segmentList.indexOf($segment), even in an eval?

--- On Mon, 11/3/08, CSchr <christian.schrinner at sbb.ch> wrote:

> From: CSchr <christian.schrinner at sbb.ch>
> Subject: [rules-users] Newbie question on accessing predecessor and successor in a list
> To: rules-users at lists.jboss.org
> Date: Monday, November 3, 2008, 9:56 AM
> Hi everyone!
> 
> I'm relatively new to Drools and rule languages.
> 
> I'm wondering if it is possible to access the
> predecessor and successor in a
> match using from operator on an (Array)List. I have
> something like this
> (simplified):
> 
> ...
> $segment : Segment( countries contains Country.Switzerland
> && ... ) from
> $journey.segmentList
> 
> $preSegment : Segment ( indexOf(this) == indexOf($segment)
> - 1, 
> 			           countries not contains Country.Switzerland
> && ...
> 		    ) from $journey.segmentList
> 
> I need something like indexOf() for the exact predecessor
> of the matched
> segment.
> 
> If the matched business object was an element of a double
> linked list it
> would be easy. Unfortunately I don't have the luxury to
> change the business
> object into knowing it's predecessor or successor. I
> have to prove that we
> could write our java coded business rules in Drools rule
> language without
> changing the business object model.
> 
> Thanks in advance,
> 
> Chris
> 
> 
> -- 
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> http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-successor-in-a-list-tp20302694p20302694.html
> Sent from the drools - user mailing list archive at
> Nabble.com.
> 
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