TT>Collision</TT> <TT><I>x</I></TT> if <TT><I>x</I></TT> is an element in
      the list that is followed by at least one other element equal to
      <TT><I>x</I></TT>.</P>
    </DD>

    <DT>
      <TT>fromVector <I>v</I></TT>
    </DT>
    <DD>
      <P>Returns the set containing the elements from list <TT><I>v</I></TT>.
      Raises <TT>Collision</TT> <TT><I>x</I></TT> if <TT><I>x</I></TT> is an element of
      the vector that is followed by at least one other element equal to
      <TT><I>x</I></TT>. 