     <TT><I>f</I></TT> return equal values <TT><I>x</I></TT>.
      Equivalent to <TT>fromList(List.map <I>f</I> (toList <I>s</I>))</TT>.</P>
    </DD>

    <DT>
      <TT>mapPartial <I>f</I> <I>s</I></TT>
    </DT>
    <DD>
      <P>Applies <TT><I>f</I></TT> to each element in set <TT><I>s</I></TT> and
      returns the set of defined results.
      For red-black trees, the function is applied in increasing order.
      Raises <TT>Collision</TT> <TT><I>x</I></TT>, if two applications of
      <TT><I>f</I><