Rules with Builtin : listLength can not trigger

[Wang Darrell]

Hello there

I got the link that have many builtin function and I want to use the
listLength( ?l , ?len) in my own rules.

Here is my rules :

 [TestList:    ( ?x   yago:created  ?l)
               listLength(?l, ?len)
                ->
                (?x  yago:HasCreated ?len)
                ]

I count it manually , there should be more than ten facts can be triggered
by this rules.

Can someone give some example to deal with listLength(?l , ?len)