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

From: CSchr <christian.schrinner(a)sbb.ch&gt; Subject: Re: [rules-users] Newbie question on accessing predecessor and successor in a list To: rules-users(a)lists.jboss.org Date: Tuesday, November 4, 2008, 1:45 AM Thanks Greg for your fast reply. Unfortunately I do not get this to work: $preSegment : Segment ( $journey.segmentList.indexOf(this) == ($journey.segmentList.indexOf($segment) - 1), countries not contains Country.Switzerland && ... ) from $journey.segmentList Compiler throws: [36,48]: unknown:36:48 Unexpected token 'this'[36,98]: unknown:36:98 Unexpected token '$segment' Is it possible to use eval() inside Segment ()? With eval the compiler throws something like this: $journey.segmentList cannot be resolved to a type Cannot use this in a static context I don't know how matching works in drools, but wouldn't this also be very expensive? As for every match of Segment ( ) the segmentList has to be iterated two times. These lists can get very long. A cheap approach would be if the from statement would "know" the index of the Segment () matched. I was hoping this would be possible. Regards, Chris Greg Barton wrote: > > 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(a)sbb.ch&gt; wrote: > >> From: CSchr <christian.schrinner(a)sbb.ch&gt; >> Subject: [rules-users] Newbie question on accessing predecessor and >> successor in a list >> To: rules-users(a)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 >> >> >> -- >> View this message in context: >> http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes... >> Sent from the drools - user mailing list archive at >> Nabble.com. >> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users > > > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > -- View this message in context: http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes... Sent from the drools - user mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users