text: 
  #ifndef BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED
  #define BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED
  
  // Copyright Aleksey Gurtovoy 2001-2004
  //
  // 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: is_placeholder.hpp,v 1.3 2009/02/22 01:02:37 wdong-pku Exp $
  // $Date: 2009/02/22 01:02:37 $
  // $Revision: 1.3 $
  
  #include <boost/mpl/arg_fwd.hpp>
  #include <boost/mpl/bool.hpp>
  #include <boost/mpl/aux_/yes_no.hpp>
  #include <boost/mpl/aux_/type_wrapper.hpp>
  #include <boost/mpl/aux_/nttp_decl.hpp>
  #include <boost/mpl/aux_/config/ctps.hpp>
  #include <boost/mpl/aux_/config/static_constant.hpp>
  
  namespace boost { namespace mpl {
  
  #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
  
  template< typename T >
  struct is_placeholder
      : bool_<false>
  {
  };
  
  template< BOOST_MPL_AUX_NTTP_DECL(int, N) >
  struct is_placeholder< arg<N> >
      : bool_<true>
  {
  };
  
  #else
  
  namespace aux {
  
  aux::no_tag is_placeholder_helper(...);
  
  template< BOOST_MPL_AUX_NTTP_DECL(int, N) >
  aux::yes_tag is_placeholder_helper(aux::type_wrapper< arg<N> >*);
  
  } // namespace aux
  
  template< typename T >
  struct is_placeholder
  {
      static aux::type_wrapper<T>* get();
      BOOST_STATIC_CONSTANT(bool, value = 
            sizeof(aux::is_placeholder_helper(get())) == sizeof(aux::yes_tag)
          );
      
      typedef bool_<value> type;
  };
  
  #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  
  }}
  
  #endif // BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED
  