r>;</li>
  <li>for any Lisp value <var>X</var>, <code>(setf (slot-value <var>F</var> <var>R</var>) <var>X</var>)</code> adds the slot <var>R</var> to the class <var>K</var> and then sets its value in <var>F</var> to <var>X</var>.</li>
</ul>
This makes fluid objects somewhat like objects in prototype-based languages, in that the user may add new slots to an object without concerning himself with the object's class membership.  Yet fluid objects are little more that &ldquo;poor man's JavaScript&rdquo; as ther