tle="Struct template valid_member_metafunction">boost::tti::valid_member_metafunction</a></code>
              </p>
              <p>
                class T = a metafunction type
              </p>
              <p>
                returns = true if the return 'type' of the metafunction exists, false
                if it does not.'Existence' is determined by whether the return 'type'
                does not equal the marker type of BOOST_TTI_MEMBER_TYPE.
              </p>
            </td>
<td>
        