user=> (source even?)
    (defn even?
      "Returns true if n is even, throws an exception if n is not an integer"
      {:added "1.0"
       :static true}
       [n] (if (integer? n)
            (zero? (bit-and (clojure.lang.RT/uncheckedLongCast n) 1))
            (throw (IllegalArgumentException. (str "Argument must be an integer: " n)))))