Filtering on specific slot while retrieving multislot values

Question

I'd like to retrieve a multislot containing object, and filter on a specific slot at the same time (fetching time). This is a code example:

(defclass OBJECT (is-a USER)
    (slot uuid
        (type STRING))
    (slot enable
        (type NUMBER)
        (allowed-integers 0 1) (default 0)))


(defclass GROUP (is-a USER)
    (slot uuid
        (type STRING))
    (multislot objects
        (type INSTANCE)))

(defrule my-rule  
    ?group <- (object (is-a GROUP) (uuid ?uuid) (objects $?objects&:(eq enable 1)))  ;; I want only enable rooms 
=>
(printout t "done" crlf))

Is it possible in CLIPS?

Thank you Nicola

Answer 1

You can filter the objects on the RHS of the rule:

CLIPS> 
(defclass OBJ
   (is-a USER)
   (slot uuid
      (type STRING))
   (slot enable
      (type NUMBER)
      (allowed-integers 0 1) 
      (default 0)))
CLIPS> 
(defclass GROUP (is-a USER)
   (slot uuid
      (type STRING))
   (multislot objects
      (type INSTANCE-NAME)))
CLIPS> 
(definstances initial
   ([o1] of OBJ (enable 1))
   ([o2] of OBJ (enable 0))
   ([o3] of OBJ (enable 1))
   ([o4] of OBJ (enable 0))
   ([g1] of GROUP (objects [o1] [o2] [o3] [o4])))
CLIPS>    
(deffunction filter (?objects ?slot ?value)
   (bind ?result (create$))
   (progn$ (?o ?objects)
      (if (eq (send ?o (sym-cat get- ?slot)) ?value)
         then
         (bind ?result (create$ ?result ?o))))
   ?result)
CLIPS>    
(defrule my-rule  
   ?group <- (object (is-a GROUP)
                     (uuid ?uuid)
                     (objects $?objects)) 
   =>
   (bind ?objects (filter ?objects enable 1))
   (printout t "Objects = " ?objects crlf))
CLIPS> (reset)
CLIPS> (run)
Objects = ([o1] [o3])
CLIPS>