pan><span class="char">'named_type'</span></code>
      which, passed an enclosing type, returns the named type if it exists, else
      a marker type if it does not.
    </p>
<p>
      As with our other macros we can use the alternative form of the macro <code class="computeroutput"><a class="link" href="../BOOST_TTI_TRAIT_ME_idm6453.html" title="Macro BOOST_TTI_TRAIT_MEMBER_TYPE">BOOST_TTI_TRAIT_MEMBER_TYPE</a></code> to
      pass first the name of the metafunction to be generated and then the name of
  