For simplicity, this is a toy version of the actual problem: given a set of integers, find the longest sequence of consecutive numbers from that set.
I looked at CLIPS and other expert systems, and they seem ill-suited to express this kind of problem. Specifically, I don't see a list like data structure, which seems to be necessary to implement a solution. I'm looking for an example of implementation using logic programming.
One way:
CLIPS (6.4 2/9/21)
CLIPS>
(deffacts start
(set 1 9 2 10 4 3 11 13 5 14))
CLIPS>
(defrule combine-1
?f <- (set $?b ?n $?e)
=>
(retract ?f)
(assert (combine ?n))
(assert (set ?b ?e)))
CLIPS>
(defrule combine-2
?f1 <- (combine $?b ?j1)
?f2 <- (combine ?j2&=(+ ?j1 1) $?e)
=>
(retract ?f1 ?f2)
(assert (combine ?b ?j1 ?j2 ?e)))
CLIPS>
(defrule longest
(declare (salience -10))
(combine $?c)
(not (combine $?o&:(> (length$ ?o) (length$ ?c))))
=>
(println "Longest is " ?c))
CLIPS> (reset)
CLIPS> (run)
Longest is (1 2 3 4 5)
CLIPS> (facts)
f-21 (set)
f-22 (combine 13 14)
f-26 (combine 1 2 3 4 5)
f-28 (combine 9 10 11)
For a total of 4 facts.
CLIPS>
Another way:
CLIPS> (clear)
CLIPS>
(deffacts start
(set 1 9 2 10 4 3 11 13 5 14))
CLIPS>
(defrule sort
?f <- (set $?s)
(test (neq ?s (sort > ?s)))
=>
(retract ?f)
(assert (set (sort > ?s))))
CLIPS>
(deffunction consecutive ($?s)
(loop-for-count (?i (- (length$ ?s) 1))
(if (<> (+ (nth$ ?i ?s) 1) (nth$ (+ ?i 1) ?s))
then (return FALSE)))
(return TRUE))
CLIPS>
(defrule longest
(set $? $?s&:(consecutive $?s) $?)
(not (set $? $?s2&~$?s&:(consecutive $?s2)&:(> (length$ ?s2) (length$ ?s)) $?))
=>
(println "Longest is " ?s))
CLIPS> (reset)
CLIPS> (run)
Longest is (1 2 3 4 5)
CLIPS> (facts)
f-2 (set 1 2 3 4 5 9 10 11 13 14)
For a total of 1 fact.
CLIPS>
