Dear Jess users,
I am still learning the ropes, and cannot find an answer to the following
question either online or in the 'Jess in action' book. Is there a way to
match facts in a LHS based on the presence of a slot?
For example, I have two templates:
(deftemplate A (slot score))
(deftemplate
Dear Jess users,
I am wondering how to write a rule that would dynamically match multiple
facts based on their names.
Let say I have two types of facts; one representing the information that an
item (with a given name) exists, and the other one representing a list of
items (e.g., as a list of
The short answer is no. Templates are like Java classes, and so this is akin
to asking if you can write Java code that reads the value of a score member
variable in any class.
But you can use template inheritance to achieve your goal. Templates can extend
other templates; just put your score
Not sure what dynamic means in this context. But you can use the forall
conditional element to implement this rule. You could read the LHS here as For
all values of ?name in bag-of-items, there's a corresponding item fact.
(defrule check-bag-valid
(forall
(bag-of-items (names $?
Another old skool way of doing it using predicate constraints is...
(clear)
(deftemplate item (slot name))
(deftemplate bag-of-items (multislot item-names))
(defrule fire-for-all-members-in-bag
; If you have a bag of item names ...
(bag-of-items (item-names $?item-names))
; and there is an
Thank you very much for this answer. It seems like 'forall' will fire the rule
only if all the 'bag-of-items' facts are validated (i.e., if all of them have
'item' facts with the names listed in their 'names' slot). Is that correct?
If yes, then what I am trying to do is slightly different. I
