Loop

loop.clp

(deftemplate MAIN::meta-fact
   (slot meta-fact)
   (slot name))
 
(defrule MAIN::loop
   ?nil-meta-fact <- (meta-fact (meta-fact nil))
   ?announce-meta-fact <- (meta-fact (name ?name))
   (not (meta-fact (meta-fact ?announce-meta-fact)))
   =>
   (println "Meta-fact: " ?name)
   (modify ?nil-meta-fact (meta-fact ?announce-meta-fact))
   (modify ?announce-meta-fact (meta-fact nil)))

output

CLIPS> (batch* program.bat)
CLIPS> (run 4)
Meta-fact: foo
Meta-fact: bar
Meta-fact: baz
Meta-fact: bat
CLIPS> (run 2)
Meta-fact: foo
Meta-fact: bar
CLIPS> (run 5)
Meta-fact: baz
Meta-fact: bat
Meta-fact: foo
Meta-fact: bar
Meta-fact: baz
CLIPS> (run 1)
FIRE    1 loop: f-2,f-1,*
Meta-fact: bat
<== f-2     (meta-fact (meta-fact nil) ...)
==> f-2     (meta-fact (meta-fact <Fact-1>) ...)
<== f-1     (meta-fact (meta-fact <Fact-4>) ...)
==> f-1     (meta-fact (meta-fact nil) ...)
==> Activation 0      loop: f-1,f-4,*
1 rules fired        Run time is 0.00667309761047363 seconds.
149.855443209832 rules per second.
4 mean number of facts (4 maximum).
0 mean number of instances (0 maximum).
1 mean number of activations (1 maximum).

program.bat

(load loop.clp)
(assert (meta-fact (name foo) (meta-fact
(assert (meta-fact (name bar) (meta-fact
(assert (meta-fact (name baz) (meta-fact
(assert (meta-fact (name bat))))))))))))