Rick
One way of doing this is to use the modify function (see
http://herzberg.ca.sandia.gov/jess/docs/70/functions.html#modify) along
with the create$ function
(http://herzberg.ca.sandia.gov/jess/docs/70/functions.html#create$)
similar to the following
g <- (gym-station (ident ?any) (purpose $?alist) )
(modify ?g (purpose (create$ ?alist lower-legs)))
The following rule adds lower-legs to the purpose of any gym-station
that has arms-upperfront in its purpose.
(defrule detect-arms-upperfront
?g <- (gym-station (ident ?any) (purpose $?alist) )
(test (member$ arms-upperfront ?alist))
(test (not (member$ lower-legs ?alist)))
=>
(modify ?g (purpose (create$ ?alist lower-legs)))
(printout t " Found arms-upperfront " ?any crlf ))
Note the test to check that lower-legs isn't already there, if the test
is not there the rule will run forever; maybe Ernest can provide a way
to change the value without having the resulting modified fact retrigger
the rule.
David
ricktee wrote:
Thanks a bunch David & Ernest! That clears up alot!
It's taking me forever to understand this rule-based style. Like in the
"JESS in action" book, the example inside the file "taxes.clp" the "ask
module" part, that part is pretty crazy.
Just one more thing please, how do I add another object into a "multislot"?
After it is created.
Like in the fact
(assert (gym-station (ident s1) (purpose arms-upperfront back)))
How can I add "lower-legs" into the "purpose multislot" so that it becomes.
(gym-station (ident s1) (purpose arms-upperfront back lower-legs))
I have tried the docs, the book, and goggle it, looking for terms like "add"
"multislot" "list" but I can't find any.
Thanks again
Rick
Ernest Friedman-Hill wrote:
Thanks, David, for your excellent reply. Everything you've said is
correct, but I wanted to add something. Rick, you're using an "if-
then" statement on the right-hand side of your rule, and that's often
a sign that the rule isn't conceived right. I imagine you want to
print "None found" only if no gym-stations satisfy your criteria, but
the way you've written things, you'll print "None found" for each gym-
station fact that doesn't contain an arms-upperfront element -- so
both "Found" and "Not found" could be printed on the same run!
Instead of using an if-then, you should instead be more specific
about your pattern matching; and furthermore, you should write a
separate rule for each possible outcome. So, for example, I might write
(defrule detect-arms-upperfront
(gym-station (ident ?any) (purpose $? arms-upperfront $?) )
=>
(printout t " Found arms-upperfront " ?any crlf ))
(defrule no-arms-upperfront
(not (gym-station (purpose $? arms-upperfront $?) ))
=>
(printout t " Not found " crlf ))
On Mar 14, 2007, at 8:39 AM, David Corsar wrote:
Rick
There area two errors in this code that are stopping it from
working: in the deffacts you are using station instead of gym-
station; and in the rule line (gym-station (ident ?any) (purpose ?
alist) ), the ?alist should be $?alist to indicate that it should
be treated as a multislot, which should then cause the member$
function to work correctly. I attach below the revised code that
seems to work fine.
David
(deftemplate gym-station (slot ident) (multislot purpose))
(deftemplate gym-station (slot ident) (multislot purpose))
(deffacts gym-station-data
(gym-station (ident s1) (purpose arms-upperfront back))
(gym-station (ident s2) (purpose legs abs))
(gym-station (ident s3) (purpose abs shoulders arms-upperfront)))
(defrule detect-arms-upperfront
(gym-station (ident ?any) (purpose $?alist) )
=>
(if (member$ arms-upperfront ?alist) then
(printout t " Found arms-upperfront " ?any crlf )
else
(printout t " None found " crlf)))
(reset)(run)
ricktee wrote:
Hi, I'm working on a school project using JESS 6.1 and using the
"JESS in
action" as my manual.
I got 3 "gym-machine" facts, each with 2 slots they are "ident" and
"purpose"
I'm trying to write a rule that checks all 3 facts's "purpose"
slot for the
existent of "arms-upperfront"
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;
(deftemplate gym-station (slot ident) (multislot purpose))
(deffacts gym-station-data
(station (ident s1) (purpose arms-upperfront back))
(station (ident s2) (purpose legs abs))
(station (ident s3) (purpose abs shoulders arms-upperfront)))
(defrule detect-arms-upperfront
(gym-station (ident ?any) (purpose ?alist) )
=>
(if (member$ arms-upperfront ?alist) then
(printout t " Found arms-upperfront " ?any )
else
(printout t " None found " )))
(reset)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;
I'm having trouble at the defrule (gym-station (ident ?any)
it seems I can't use ?any to represent all 3 facts. I'm trying to
get the
rule to cycle through all 3 facts. I have try to remove (ident ?
any) but it
still wont cycle through the 3 facts. Please help me, am I writing
it the
wrong way?
Thank you very much for your time
Rick
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Ernest Friedman-Hill
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David Corsar
Department of Computing Science
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Aberdeen
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Phone +44 (0)1224 274485
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