ets of round parenthesis must be used: The parenthesis
      to invoke the macro <code class="computeroutput"><span class="identifier">BOOST_IDENTITY_TYPE</span><span class="special">(...)</span></code> plus the inner parenthesis to wrap the
      type passed to the macro <code class="computeroutput"><span class="identifier">BOOST_IDENTITY_TYPE</span><span class="special">((...))</span></code>.
    </p><p>
      This macro works on any <a href="http://www.open-std.org/JTC1/SC22/WG21/docs/standards" target="