ker type, then the type generated
      is not the nested type we had hoped for. If it is not the marker type, then
      the type generated is the nested type we had hoped for. This is easy enough
      to do for the template metaprogrammer but TTI makes it easier by providing
      either of two metafunctions to do this calculation. These two metafunctions
      are 'boost::tti::valid_member_type' and 'boost::tti::valid_member_metafunction':
    </p>
<div class="table">
<a name="the_type_traits_introspect