CLIPS defrules compare the value of two variables

0
votes

I want to write a rule that says the following 

if x > y => assert x

where x and y are variables and their values are given as facts.

How do I do it?

1
clips

1 Answers

2
votes

If x already exists as a fact, then asserting it again from the actions of the rule would be unnecessary, but if you want to assert a fact indicating that x is greater than y then you could do it this way:

CLIPS> 
(defrule greater-than
   (x ?x)
   (y ?y)
   (test (> ?x ?y))
   =>
   (assert (x-is-greater-than-y)))
CLIPS> (assert (x 4))
<Fact-1>
CLIPS> (assert (y 1))
<Fact-2>
CLIPS> (agenda)
0      greater-than: f-1,f-2
For a total of 1 activation.
CLIPS> (run)
CLIPS> (facts)
f-0     (initial-fact)
f-1     (x 4)
f-2     (y 1)
f-3     (x-is-greater-than-y)
For a total of 4 facts.
CLIPS>