Endless loop

[maacl]

Below results in an endless loop. I would expect the rule to stop matching -> nothing inserted -> steady state after the first match.

I am using:

[org.clojure/clojure "1.10.1"]
[com.cerner/clara-rules "0.20.0"]]

(defrule test-rule
    "test guard"
    [:not [:guard (= (:active this) true)]]
    =>
    (do
      (println "Inserting guard!")
      (insert! {:type :guard :active true})))
  (-> (mk-session [test-rule]
                  :fact-type-fn :type)
      (fire-rules))

[maacl]

Got answer from slack:

the rules attempt to find a logical consistency balance

1:30
Your rule Left side condition is invalidated when the right side inserts.
1:31
The engine then retracts that’s fact because it is no longer logically supported.
1:31
It’s called the truth maintenance system
1:31
Then it can activate again and re insert. And again it invalidates itself. So it’s logical looping