n class='arg-name'>class</span> is not <span class='other-name'>nil</span>, create an instance of that
class.  Otherwise, create a fluid object whose class has the given
<span class='arg-name'>superclasses</span> (null list by default).  In either case, populate the
resulting object using <span class='arg-name'>bindings</span> (an alist of slot names and
values).
</p>
  </div>

<p>To maintain the mapping between lists of superclass names and fluid classes, the decoder maintains a class registry.  Thus, usin