title: Process n items from a list at a time in Lisp
body: <p>Given a list, how do I process <em>N</em> items at a time? Ruby has <a href="http://ruby-doc.org/core-2.0/Enumerable.html#method-i-each_slice" rel="noreferrer"><code>each_slice</code></a> method on the <code>Enumerable</code> that does this; what would be the Lisp equivalent?</p>