t in set <TT><I>s</I></TT>.
      For red-black trees, this happens in increasing order. Equivalent
      to <TT>List.app <I>f</I> (toList <I>s</I>)</TT>.</P>
    </DD>

    <DT>
      <TT>map <I>f</I> <I>s</I></TT>
    </DT>
    <DD>
      <P>Returns the set which contains the results of applying <TT><I>f</I></TT>
      to each element in set <TT><I>s</I></TT>.
      For red-black trees, the function is applied in increasing order.
      Raises <TT>Collision</TT> <TT><I>x</I></TT>, if two applications of
 