text: ///////////////////////////////////////////////////////////////////////////////
  // as_modifier.hpp
  //
  //  Copyright 2008 Eric Niebler. 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)
  
  #ifndef BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_MODIFIER_HPP_EAN_04_05_2007
  #define BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_MODIFIER_HPP_EAN_04_05_2007
  
  // MS compatible compilers support #pragma once
  #if defined(_MSC_VER)
  # pragma once
  #endif
  
  #include <boost/mpl/sizeof.hpp>
  #include <boost/xpressive/detail/detail_fwd.hpp>
  #include <boost/xpressive/detail/static/static.hpp>
  #include <boost/proto/core.hpp>
  
  #define UNCV(x) typename remove_const<x>::type
  #define UNREF(x) typename remove_reference<x>::type
  #define UNCVREF(x) UNCV(UNREF(x))
  
  namespace boost { namespace xpressive { namespace detail
  {
      ///////////////////////////////////////////////////////////////////////////////
      // regex operator tags
      struct modifier_tag
      {};
  
  }}}
  
  namespace boost { namespace xpressive { namespace grammar_detail
  {
  
      ///////////////////////////////////////////////////////////////////////////////
      // as_modifier
      template<typename Grammar, typename Callable = proto::callable>
      struct as_modifier : proto::transform<as_modifier<Grammar, Callable> >
      {
          template<typename Expr, typename State, typename Data>
          struct impl : proto::transform_impl<Expr, State, Data>
          {
              typedef
                  typename proto::result_of::value<
                      typename proto::result_of::left<typename impl::expr>::type
                  >::type
              modifier_type;
  
              typedef
                  typename modifier_type::template apply<typename impl::data>::type
              visitor_type;
  
              typedef
                  typename proto::result_of::right<Expr>::type
              expr_type;
  
              typedef
                  typename Grammar::template impl<expr_type, State, visitor_type &>::result_type
              result_type;
  
              result_type operator ()(
                  typename impl::expr_param expr
                , typename impl::state_param state
                , typename impl::data_param data
              ) const
              {
                  visitor_type new_visitor(proto::value(proto::left(expr)).call(data));
                  return typename Grammar::template impl<expr_type, State, visitor_type &>()(
                      proto::right(expr)
                    , state
                    , new_visitor
                  );
              }
          };
      };
  
  }}}
  
  #undef UNCV
  #undef UNREF
  #undef UNCVREF
  
  #endif
  