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CLIPS: counting different products

I have some facts in the form of a list: (list day1 apple milk bread) (list day 2 bread milk) and I would like to count the different products in that facts for each day. How can I count them? The result that I want is (list day1 3) (list day2 2)

Solution 
  •          CLIPS (6.4 2/9/21)
CLIPS> 
(defrule list-count
   (list ?day $?items)
   =>
   (assert (count ?day (length$ ?items))))
CLIPS> 
(assert (list day1 apple milk bread)
        (list day2 bread milk))
<Fact-2>
CLIPS> (agenda)
0      list-count: f-2
0      list-count: f-1
For a total of 2 activations.
CLIPS> (run)
CLIPS> (facts)
f-1     (list day1 apple milk bread)
f-2     (list day2 bread milk)
f-3     (count day2 2)
f-4     (count day1 3)
For a total of 4 facts.
CLIPS>