[rules-users] Ensure all values in a list are unique?

I have an ArrayList of strings that I need to ensure are all internally unique (ie: {"1","2","3"} = OK, {"1","2","1"} = Error). I've managed to cobble together the code below but I'm running into the "forall w/ an internal from" issue. I don't believe an upgrade is feasible at the moment, so are there any alternative solutions? NOTE: The collection of both $factGroups and $checkGroups is almost definitely redundant, so please keep any laughing to a minimum =) rule "BR033" no-loop true when $fact : MyFact() //# Get 2 copies of all the Groups associated with the $fact $factGroups : ArrayList() from collect ( Group() from $fact.Groups ) $checkGroups : ArrayList() from collect ( Group() from $fact.Groups ) //# Traverse the $factGroups comparing each $currentGroup to the list //# within $checkGroups, erroring out if something other then 1 is found forall ( $currentGroup : Group(this memberOf $factGroups) $test : ArrayList(size != 1) from collect( Group(this == $currentGroup) from $checkGroups ) ) then System.out.println("Failed: BR033"); end I have found a number of postings that seem to be related, namely http://www.nabble.com/Best-practice-for-rules-against-multiple-objects-td... but I've been unable to cobble together a solution thus far. All help is appreciated! Thanks! -- View this message in context: http://www.nabble.com/Ensure-all-values-in-a-list-are-unique--tp23071079p... Sent from the drools - user mailing list archive at Nabble.com.