Clojure var18

;Params:
;   a, b, c, d - input sets
;   state - variable for state saving
;   elm - single element used in contains subfunction
(defn megaTask [a b c d  &{:keys [state, elm] :or {state 0 elm 0}}]
    (cond
        ;Subfunction contains
        ;Checks if elm is in list a
        ;Non empty list mean true, empty list - false
        (= state 1) (cond
                            (empty? a) nil
                            (= elm (first a)) '(0)
                            true (megaTask (rest a) b c d :state 1 :elm elm)
                        )
        ;Subfunction union
        ;Creates union of two sets - a and b
        (= state 2) (cond
                        (empty? b) a
                        (megaTask a () () () :state 1 :elm (first b)) (megaTask a (rest b) () () :state 2)
                        true (cons (first b) (megaTask a (rest b) '() '() :state 2))
                      )
        ;Subfunction difference
        ;Computes difference of two sets - a and b
        (= state 3) (cond
                          (empty? a) ()
                          (megaTask b () () () :state 1 :elm (first a)) (megaTask (rest a) b () () :state 3)
                          true (cons (first a) (megaTask (rest a) b '() '() :state 3))
                      )
        ;Subfunction intersection
        ;Computes intersection of two sets - a and b
        (= state 4) (cond
                          (empty? a) ()
                          (megaTask b () () () :state 1 :elm (first a)) (cons (first a) (megaTask (rest a) b () () :state 4))
                          true (megaTask (rest a) b () () :state 4)
                    )
        ;Computes target result - A union (B difference (C union D))
        true (megaTask (megaTask (megaTask a b () () :state 3) c () () :state 2) d () () :state 3)
    )
)

(print (megaTask '(1 2 3 4 5) '(4 5 6 7 8 9) '(7 8 9 10 11 12) '(9 10 11 12)))