Hello,
I have a question about the multislots. I have a rule that basically
tries to match two cars that having black color.
/(defrule get-black-cars
(car (id ?id1) (color "black"))
(car (id ?id2 &:(~= ?id1 ?id2)) (color "black"))
(and (not (black-cars (car-id ?id1 ?id2)) (not (black-cars (car-id
?id2 ?id1)))
=>
(assert (black-cars (car-id ?id1 ?id2)))/
The important thing is that the cars should be diferent, so this is why
i use the /&:(~= ?id1 ?id2))/ expression. I even use the "/not/"
expression to avoid duplication, like:
car A and car B are black, meaning that i will have a fact:
/ black-cars (car-id A B)/
but the same is true
/black-cars (car-id B A)/
My question is: There is a matching way of avoid this comparison? The
only thing i want to know is which are the black cars, not the order.
Moreover, when matching a multislot, a simillar problem arises:
/(defrule matching-multislot
(car (id ?id1) (color "black"))
(car (id ?id2 &:(~= ?id1 ?id2)) (color "black"))
(not (black-cars (car-id ?id1 ?id2)))
=>..../
Depending on how jess schedule the matching facts, this rule might be
eroneous, because i can have a fact /black-cars (car-id A B)/, which is
not the same as /black-cars (car-id B A)/. This means that for pair of
elements in the multislot a check must follow, replacing the last /not/ with
/ (and (not (black-cars (car-id ?id1 ?id2))) (not (black-cars (car-id
?id2 ?id1)))).
/While this is not a problem with two elements, can become a very
diffult problem with 3 or more elements. Can anyone tell me techniques
to avoid this situation?
Regards,
Joao
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