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

[campbeln]

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-td5621720.html#a5621720
but I've been unable to cobble together a solution thus far. All help is
appreciated!

Thanks!
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