Great Clojure feature:<p><pre><code>    user=&gt; (source even?)
    (defn even?
      &quot;Returns true if n is even, throws an exception if n is not an integer&quot;
      {:added &quot;1.0&quot;
       :static true}
       [n] (if (integer? n)
            (zero? (bit-and (clojure.lang.RT&#x2F;uncheckedLongCast n) 1))
            (throw (IllegalArgumentException. (str &quot;Argument must be an integer: &quot; n)))))</code></pre>