nd form,
      <TT>Collision</TT> <TT><I>y</I></TT> will be raised. In the third form,
      <TT><I>f</I></TT> is applied to <TT><I>y</I></TT> before the set is
      returned as in the first form. The following equivalences hold:</P>
      <PRE>
      insert         = insertWith ignore
      insertDisjoint = insertWith (fn y => raise Collision y)</PRE>
    </DD>

    <DT>
      <TT>remove (<I>s</I>, <I>x</I>)</TT> <BR>
      <TT>removeExistent (<I>s</I>, <I>x</I>)</TT> <BR>
      <TT>removeWith <I>f</I> (<