Name that set operation!

sets.clj

; I'm hoping to find a common name for a particular operation over sets that I've
; been thinking of as a "join" of sorts.
; 
; It's _not_ a relational join -- the values involved aren't relations (for me
; at the moment, they're actually graphs essentially representing
; disjoint recursive sets, but I think that's probably irrelevant
; detail) -- but it feels like it's in the spirit of a full outer join
;
;     Given N sets, recursively produce all unions of those sets that are disjoint.
;
; Does this operation have a name?

(defn- all-pairs [xs]
  (when-let [next (next xs)]
    (concat
     (map list (repeat (first xs)) next)
     (all-pairs next))))

(defn disjoint? [s1 s2]
  (empty? (clojure.set/intersection s1 s2)))

(defn join [sets]
  (let [new (->> (all-pairs sets)
                 (filter (partial apply disjoint?))
                 (map (partial apply clojure.set/union))
                 set)]
    (clojure.set/union
     sets
     (if (seq new)
       (join new)
       new))))

 (join #{#{:a :b} #{:a :c}
              #{:d :e} #{:d :f}})