(defmapcatop set-bucket
  ([s v inv]
     (if (contains? s v) (list inv) '()))
  ([s v inv outv]
     (if (contains? s v) (list inv) (list outv)))
  ([s v inv outv bothv]
     (list bothv (if (contains? s v) (list inv) (list outv)))))

(def x (memory-source-tap [["a" 1]
			   ["b" 1]
			   ["c" 1]
			   ["a" 2]
			   ["b" 2]
			   ["c" 2]]))

(?<- (stdout) [?l ?n ?b] (x ?l ?n)
     (set-bucket #{"a" "b"} ?l "a-or-b" "not-a-or-b" "a-or-b-or-not-a-or-b" :> ?b))

;; RESULTS
;; -----------------------
;; a	1	a-or-b
;; a	2	a-or-b
;; b	1	a-or-b
;; b	2	a-or-b
;; a	1	a-or-b-or-not-a-or-b
;; a	2	a-or-b-or-not-a-or-b
;; b	1	a-or-b-or-not-a-or-b
;; b	2	a-or-b-or-not-a-or-b
;; c	1	a-or-b-or-not-a-or-b
;; c	2	a-or-b-or-not-a-or-b
;; c	1	not-a-or-b
;; c	2	not-a-or-b
;; -----------------------

(?<- (stdout) [?l ?n ?b] (x ?l ?n)
     (set-bucket #{"a" "b"} ?l "a-or-b" "not-a-or-b" :> ?b))

;; RESULTS
;; -----------------------
;; a	1	a-or-b
;; a	2	a-or-b
;; b	1	a-or-b
;; b	2	a-or-b
;; c	1	not-a-or-b
;; c	2	not-a-or-b
;; -----------------------