Hi Hal, Peter & Wolfgang,
>> The proposed solution does not compare a length with foo.desired, and
binding of a multislot vaue should use a variable starting with $?.
Hal, since you said you were satisfied with Peter's solution, I never posted
my reply which anticipated Wolfgang's almost verbatim.
However, if you really want what Peter was advocating then there is a bit
more to it I think. You have to recall that Jess doesn't allow multiple
facts to have identical slot values -- that means that no two foo facts
could have the exact same multislot list and desired value. You may need
this in your application, so you'd need some other slot like (slot id) to
differentiate your facts. Also, Peter's version would fire twice for each
pair of foo facts that had the same slot length, which is not what you want
I'd think.
The implementation below addresses these issues.
Cheers,
Jason
;;;;;;;;;;;;;;;;;;
;; list-len.clp ;;
;;;;;;;;;;;;;;;;;;
(clear)
(watch all)
(deftemplate foo (slot id) (multislot my-list) (slot desired))
(deffacts init
(foo (id 1) (my-list 1 2 3 4))
(foo (id 2) (my-list a b c d))
(foo (id 3) (my-list 5 6 7 8))
(foo (id 4) (my-list e f g h)))
(defrule myrule
; Find a foo fact...
(foo (id ?id1) (my-list $?list1))
; ...and another fact of different id where the list lengths are the
same...
(foo (id ?id2&~?id1) (my-list $?list2&:(= (length$ ?list2) (length$
?list1))))
; ...such that we have not examined this pair of foo facts before.
(not (has-fired ?id1 ?id2))
=>
; Assert that this pair has been processed with a little logic trick.
(assert (has-fired ?id2 ?id1))
(printout t "Lists lengths in foo facts " ?id1 " and " ?id2 " are
equal!" crlf))
:: Program
(reset)
(run)
;MAIN::myrule: +1+1+1+2+1+1+2+t
; ==> Focus MAIN
; ==> f-0 (MAIN::initial-fact)
; ==> f-1 (MAIN::foo (id 1) (my-list 1 2 3 4) (desired nil))
; ==> f-2 (MAIN::foo (id 2) (my-list a b c d) (desired nil))
;==> Activation: MAIN::myrule : f-2, f-1,
;==> Activation: MAIN::myrule : f-1, f-2,
; ==> f-3 (MAIN::foo (id 3) (my-list 5 6 7 8) (desired nil))
;==> Activation: MAIN::myrule : f-3, f-1,
;==> Activation: MAIN::myrule : f-3, f-2,
;==> Activation: MAIN::myrule : f-1, f-3,
;==> Activation: MAIN::myrule : f-2, f-3,
; ==> f-4 (MAIN::foo (id 4) (my-list e f g h) (desired nil))
;==> Activation: MAIN::myrule : f-4, f-1,
;==> Activation: MAIN::myrule : f-4, f-2,
;==> Activation: MAIN::myrule : f-4, f-3,
;==> Activation: MAIN::myrule : f-1, f-4,
;==> Activation: MAIN::myrule : f-2, f-4,
;==> Activation: MAIN::myrule : f-3, f-4,
;FIRE 1 MAIN::myrule f-3, f-4,
; ==> f-5 (MAIN::has-fired 4 3)
;<== Activation: MAIN::myrule : f-4, f-3,
;Lists lengths in foo facts 3 and 4 are equal!
;FIRE 2 MAIN::myrule f-4, f-2,
; ==> f-6 (MAIN::has-fired 2 4)
;<== Activation: MAIN::myrule : f-2, f-4,
;Lists lengths in foo facts 4 and 2 are equal!
;FIRE 3 MAIN::myrule f-1, f-4,
; ==> f-7 (MAIN::has-fired 4 1)
;<== Activation: MAIN::myrule : f-4, f-1,
;Lists lengths in foo facts 1 and 4 are equal!
;FIRE 4 MAIN::myrule f-3, f-2,
; ==> f-8 (MAIN::has-fired 2 3)
;<== Activation: MAIN::myrule : f-2, f-3,
;Lists lengths in foo facts 3 and 2 are equal!
;FIRE 5 MAIN::myrule f-3, f-1,
; ==> f-9 (MAIN::has-fired 1 3)
;<== Activation: MAIN::myrule : f-1, f-3,
;Lists lengths in foo facts 3 and 1 are equal!
;FIRE 6 MAIN::myrule f-1, f-2,
; ==> f-10 (MAIN::has-fired 2 1)
;<== Activation: MAIN::myrule : f-2, f-1,
;Lists lengths in foo facts 1 and 2 are equal!
; <== Focus MAIN
--
-----------------------------------------------------------
Jason Morris
Morris Technical Solutions LLC
http://www.morris-technical-solutions.com
