防止夹子规则射击两次

Question

如果不收回最初的事实，我如何才能防止以下规则两次开火？

CLIPS> 
(defrule cf_calculation
   (CF ?cf1)
   (CF ?cf2&~?cf1)
   =>
   (bind ?fCF (+ ?cf1 ?cf2))
   (printout t "the final CF is " ?fCF crlf))
CLIPS> (assert (CF 10))
<Fact-1>
CLIPS> (assert (CF 5))
<Fact-2>
CLIPS> (run)
the final CF is 15
the final CF is 15
CLIPS>

Answer 1

与其检查两个值的不等式，不如检查第一个值大于第二个值：

CLIPS> 
(defrule cf_calculation
   (CF ?cf1)
   (CF ?cf2&:(> ?cf1 ?cf2))
   =>
   (bind ?fCF (+ ?cf1 ?cf2))
   (printout t "the final CF is " ?fCF crlf))
CLIPS> (assert (CF 10))
<Fact-1>
CLIPS> (assert (CF 5))
<Fact-2>
CLIPS> (run)
the final CF is 15
CLIPS>