(meditations
 "Sets are another important data structure in clojure"
 (= #{} (set nil))

 "Remember that a set is a 'set'"
 (= __ (set '(1 1 2 2 3 3 4 4 5 5)))

 "You can ask clojure for the union of two sets"
 (= __ (clojure.set/union #{1 2 3 4} #{2 3 5}))

 "And also the intersection"
 (= __ (clojure.set/intersection #{1 2 3 4} #{2 3 5}))

 "But don't forget about the difference"
 (= __ (clojure.set/difference #{1 2 3 4 5} #{2 3 5})))