MeTTa Task

; Task: A function that takes a grandchild and a result set and updates the guard set accordingly.

; Components

;;;;;;;;; Component 1 ;;;;;;;;;;;;

; find-object: accepts a list and and an instance, iterates through it, and returns True if object is available, else False
; (: find-object (-> List TreeNode Bool))

(= (find-object $list $instance)
   (
    case $list (
        (Nil False)
        ((Cons $x $xs) (
            if (== $x $instance) True (find-object $xs $instance)
        ))
        ($_ ERROR)
    )
   )
)

! (find-object (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil)))) 7)
! (find-object (Cons 1 (Cons 2 (Cons 3 (Cons 4 Nil)))) 4)


;;;;;; Component 2: Set Difference Calculator Returns $list1 - $list2 (A-B in mathematical terms) ;;;;;;;;;;;;;;;

; LOGIC: Iterate over objects of $list1, if they don't exist in $list2 add them to our list

; (:set-difference (-> List List List))
(= (set-difference $list1 $list2)
    (
        case $list1 (
            (Nil Nil) ; Base Case: Reaches the end of the list
           
            ((Cons $x $xs) ( ; Destructure the list, one value to $x the rest of the list to $xs
                             if (find-object $list2 $x) ; if condition
                                (set-difference $xs $list2) ; pass if object found in @list2
                                (Cons $x (set-difference $xs $list2)) ; add to our result and continue if not found in $list2
            ))
        )   
    )
)

! (set-difference (Cons 1 (Cons 2 (Cons 7 (Cons 4 Nil))))  (Cons 1 (Cons 2 (Cons 3 (Cons 5 Nil)))))

(TreeNode $nodeValue $left $right $guardSet $children)

; LOGIC: destructure grandChild and get the $guardSet, then calculate its set difference with result set

; ( : compute-grandchild-guardset (-> TreeNode List))
( = (compute-grandchild-guardset $grandChild $resultset)
    (
        case $grandChild (
               ((TreeNode $nodeValue $left $right $guardSet $children) (TreeNode $nodeValue $left $right (set-difference $guardSet $resultset) $children))
               ($_ ERROR)
        )
    )
)

; ! (compute-grandchild-guardset )