gistfile1.clj

(defn monoid?
  ([op zero example-vals check]
  (and (= zero (op zero zero))
       (every? (fn [val] (= val (op zero val) (op val zero)))
	       example-vals)
       (closure-under? op example-vals check)
       (a-associative? op (conj example-vals zero)))))

(monoid? clojure.set/union #{} [#{:d :g} #{2 3}] set?)
(monoid? concat nil [[:a :b] [1 2 3][""]'(a b c d e)] seq?)