text: 
  #ifndef BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
  #define BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
  
  // Copyright Aleksey Gurtovoy 2000-2004
  //
  // Distributed under the Boost Software License, Version 1.0. 
  // (See accompanying file LICENSE_1_0.txt or copy at 
  // http://www.boost.org/LICENSE_1_0.txt)
  //
  // See http://www.boost.org/libs/mpl for documentation.
  
  // $Id$
  // $Date$
  // $Revision$
  
  #include <boost/mpl/sequence_tag_fwd.hpp>
  #include <boost/mpl/aux_/has_tag.hpp>
  #include <boost/mpl/aux_/has_begin.hpp>
  #include <boost/mpl/aux_/na_spec.hpp>
  #include <boost/mpl/aux_/is_msvc_eti_arg.hpp>
  #include <boost/mpl/aux_/config/eti.hpp>
  #include <boost/mpl/aux_/yes_no.hpp>
  #include <boost/mpl/aux_/config/workaround.hpp>
  
  namespace boost { namespace mpl {
  
  // agurt, 27/nov/02: have to use a simplistic 'sequence_tag' implementation
  // on MSVC to avoid dreadful "internal structure overflow" error
  #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) \
      || defined(BOOST_MPL_CFG_NO_HAS_XXX)
  
  template<
        typename BOOST_MPL_AUX_NA_PARAM(Sequence)
      >
  struct sequence_tag
  {
      typedef typename Sequence::tag type;
  };
  
  #elif BOOST_WORKAROUND(BOOST_MSVC, == 1300)
  
  // agurt, 07/feb/03: workaround for what seems to be MSVC 7.0-specific ETI issue
  
  namespace aux {
  
  template< bool >
  struct sequence_tag_impl
  {
      template< typename Sequence > struct result_
      {
          typedef typename Sequence::tag type;
      };
  };
  
  template<>
  struct sequence_tag_impl<false>
  {
      template< typename Sequence > struct result_
      {
          typedef int type;
      };
  };
  
  } // namespace aux
  
  template<
        typename BOOST_MPL_AUX_NA_PARAM(Sequence)
      >
  struct sequence_tag
      : aux::sequence_tag_impl< !aux::is_msvc_eti_arg<Sequence>::value >
          ::template result_<Sequence>
  {
  };
  
  #else
  
  namespace aux {
  
  template< bool has_tag_, bool has_begin_ >
  struct sequence_tag_impl
  {
      // agurt 24/nov/02: MSVC 6.5 gets confused in 'sequence_tag_impl<true>' 
      // specialization below, if we name it 'result_' here
      template< typename Sequence > struct result2_;
  };
  
  #   define AUX_CLASS_SEQUENCE_TAG_SPEC(has_tag, has_begin, result_type) \
  template<> struct sequence_tag_impl<has_tag,has_begin> \
  { \
      template< typename Sequence > struct result2_ \
      { \
          typedef result_type type; \
      }; \
  }; \
  /**/
  
  AUX_CLASS_SEQUENCE_TAG_SPEC(true, true, typename Sequence::tag)
  AUX_CLASS_SEQUENCE_TAG_SPEC(true, false, typename Sequence::tag)
  AUX_CLASS_SEQUENCE_TAG_SPEC(false, true, nested_begin_end_tag)
  AUX_CLASS_SEQUENCE_TAG_SPEC(false, false, non_sequence_tag)
  
  #   undef AUX_CLASS_SEQUENCE_TAG_SPEC
  
  } // namespace aux
  
  template<
        typename BOOST_MPL_AUX_NA_PARAM(Sequence)
      >
  struct sequence_tag
      : aux::sequence_tag_impl<
            ::boost::mpl::aux::has_tag<Sequence>::value
          , ::boost::mpl::aux::has_begin<Sequence>::value
          >::template result2_<Sequence>
  {
  };
  
  #endif // BOOST_MSVC
  
  BOOST_MPL_AUX_NA_SPEC(1, sequence_tag)
  
  }}
  
  #endif // BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
  