text: ///////////////////////////////////////////////////////////////////////////////
  // grammar.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_GRAMMAR_HPP_EAN_11_12_2006
  #define BOOST_XPRESSIVE_DETAIL_STATIC_GRAMMAR_HPP_EAN_11_12_2006
  
  // MS compatible compilers support #pragma once
  #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  # pragma once
  #endif
  
  #include <boost/mpl/if.hpp>
  #include <boost/mpl/bool.hpp>
  #include <boost/mpl/assert.hpp>
  #include <boost/proto/core.hpp>
  #include <boost/xpressive/detail/static/is_pure.hpp>
  #include <boost/xpressive/detail/static/transforms/as_matcher.hpp>
  #include <boost/xpressive/detail/static/transforms/as_alternate.hpp>
  #include <boost/xpressive/detail/static/transforms/as_sequence.hpp>
  #include <boost/xpressive/detail/static/transforms/as_quantifier.hpp>
  #include <boost/xpressive/detail/static/transforms/as_marker.hpp>
  #include <boost/xpressive/detail/static/transforms/as_set.hpp>
  #include <boost/xpressive/detail/static/transforms/as_independent.hpp>
  #include <boost/xpressive/detail/static/transforms/as_modifier.hpp>
  #include <boost/xpressive/detail/static/transforms/as_inverse.hpp>
  #include <boost/xpressive/detail/static/transforms/as_action.hpp>
  #include <boost/xpressive/detail/detail_fwd.hpp>
  
  #define BOOST_XPRESSIVE_CHECK_REGEX(Expr, Char)\
      BOOST_MPL_ASSERT\
      ((\
          typename boost::mpl::if_c<\
              boost::xpressive::is_valid_regex<Expr, Char>::value\
            , boost::mpl::true_\
            , boost::xpressive::INVALID_REGULAR_EXPRESSION\
          >::type\
      ));
  
  //////////////////////////////////////////////////////////////////////////
  //**********************************************************************//
  //*                            << NOTE! >>                             *//
  //*                                                                    *//
  //* Whenever you change this grammar, you MUST also make corresponding *//
  //* changes to width_of.hpp and is_pure.hpp.                           *//
  //*                                                                    *//
  //**********************************************************************//
  //////////////////////////////////////////////////////////////////////////
  
  namespace boost { namespace xpressive
  {
      template<typename Char>
      struct Grammar;
  
      template<typename Char>
      struct ActionableGrammar;
  
      namespace grammar_detail
      {
          ///////////////////////////////////////////////////////////////////////////
          // CharLiteral
          template<typename Char>
          struct CharLiteral;
  
          ///////////////////////////////////////////////////////////////////////////
          // ListSet
          template<typename Char>
          struct ListSet;
  
          ///////////////////////////////////////////////////////////////////////////
          // as_repeat
          template<typename Char, typename Gram, typename Greedy>
          struct as_repeat
            : if_<
                  make<detail::use_simple_repeat<_child, Char> >
                , as_simple_quantifier<Gram, Greedy>
                , as_default_quantifier<Greedy>
              >
          {};
  
          ///////////////////////////////////////////////////////////////////////////
          // NonGreedyRepeatCases
          template<typename Gram>
          struct NonGreedyRepeatCases
          {
              template<typename Tag, typename Dummy = void>
              struct case_
                : not_<_>
              {};
  
              template<typename Dummy>
              struct case_<tag::dereference, Dummy>
                : dereference<Gram>
              {};
  
              template<typename Dummy>
              struct case_<tag::unary_plus, Dummy>
                : unary_plus<Gram>
              {};
  
              template<typename Dummy>
              struct case_<tag::logical_not, Dummy>
                : logical_not<Gram>
              {};
  
              template<uint_t Min, uint_t Max, typename Dummy>
              struct case_<detail::generic_quant_tag<Min, Max>, Dummy>
                : unary_expr<detail::generic_quant_tag<Min, Max>, Gram>
              {};
          };
  
          ///////////////////////////////////////////////////////////////////////////
          // InvertibleCases
          template<typename Char, typename Gram>
          struct InvertibleCases
          {
              template<typename Tag, typename Dummy = void>
              struct case_
                : not_<_>
              {};
  
              template<typename Dummy>
              struct case_<tag::comma, Dummy>
                : when<ListSet<Char>, as_list_set_matcher<Char> >
              {};
  
              template<typename Dummy>
              struct case_<tag::assign, Dummy>
                : when<ListSet<Char>, as_list_set_matcher<Char> >
              {};
  
              template<typename Dummy>
              struct case_<tag::subscript, Dummy>
                : when<subscript<detail::set_initializer_type, Gram>, call<as_set_matcher<Gram>(_right)> >
              {};
  
              template<typename Dummy>
              struct case_<detail::lookahead_tag, Dummy>
                : when<
                      unary_expr<detail::lookahead_tag, Gram>
                    , as_lookahead<Gram>
                  >
              {};
  
              template<typename Dummy>
              struct case_<detail::lookbehind_tag, Dummy>
                : when<
                      unary_expr<detail::lookbehind_tag, Gram>
                    , as_lookbehind<Gram>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::terminal, Dummy>
                : when<
                      or_<
                          CharLiteral<Char>
                        , terminal<detail::posix_charset_placeholder>
                        , terminal<detail::range_placeholder<_> >
                        , terminal<detail::logical_newline_placeholder>
                        , terminal<detail::assert_word_placeholder<detail::word_boundary<mpl::true_> > >
                      >
                    , as_matcher
                  >
              {};
          };
  
          ///////////////////////////////////////////////////////////////////////////
          // Cases
          template<typename Char, typename Gram>
          struct Cases
          {
              template<typename Tag, typename Dummy = void>
              struct case_
                : not_<_>
              {};
  
              template<typename Dummy>
              struct case_<tag::terminal, Dummy>
                : when<
                      _
                    , in_sequence<as_matcher>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::shift_right, Dummy>
                : when<
                      shift_right<Gram, Gram>
                    , reverse_fold<_, _state, Gram>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::bitwise_or, Dummy>
                : when<
                      bitwise_or<Gram, Gram>
                    , in_sequence<
                          as_alternate_matcher<
                              reverse_fold_tree<_, make<fusion::nil>, in_alternate_list<Gram> >
                          >
                      >
                  >
              {};
  
              template<typename Dummy, typename Greedy>
              struct case_<optional_tag<Greedy> , Dummy>
                : when<
                      unary_expr<optional_tag<Greedy>, Gram>
                    , in_sequence<call<as_optional<Gram, Greedy>(_child)> >
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::dereference, Dummy>
                : when<
                      dereference<Gram>
                    , call<Gram(as_repeat<Char, Gram, mpl::true_>)>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::unary_plus, Dummy>
                : when<
                      unary_plus<Gram>
                    , call<Gram(as_repeat<Char, Gram, mpl::true_>)>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::logical_not, Dummy>
                : when<
                      logical_not<Gram>
                    , call<Gram(as_repeat<Char, Gram, mpl::true_>)>
                  >
              {};
  
              template<uint_t Min, uint_t Max, typename Dummy>
              struct case_<detail::generic_quant_tag<Min, Max>, Dummy>
                : when<
                      unary_expr<detail::generic_quant_tag<Min, Max>, Gram>
                    , call<Gram(as_repeat<Char, Gram, mpl::true_>)>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::negate, Dummy>
                : when<
                      negate<switch_<NonGreedyRepeatCases<Gram> > >
                    , call<Gram(call<as_repeat<Char, Gram, mpl::false_>(_child)>)>
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::complement, Dummy>
                : when<
                      complement<switch_<InvertibleCases<Char, Gram> > >
                    , in_sequence<call<as_inverse(call<switch_<InvertibleCases<Char, Gram> >(_child)>)> >
                  >
              {};
  
              template<typename Dummy>
              struct case_<detail::modifier_tag, Dummy>
                : when<binary_expr<detail::modifier_tag, _, Gram>, as_modifier<Gram> >
              {};
  
              template<typename Dummy>
              struct case_<detail::lookahead_tag, Dummy>
                : when<
                      unary_expr<detail::lookahead_tag, Gram>
                    , in_sequence<as_lookahead<Gram> >
                  >
              {};
  
              template<typename Dummy>
              struct case_<detail::lookbehind_tag, Dummy>
                : when<
                      unary_expr<detail::lookbehind_tag, Gram>
                    , in_sequence<as_lookbehind<Gram> >
                  >
              {};
  
              template<typename Dummy>
              struct case_<detail::keeper_tag, Dummy>
                : when<
                      unary_expr<detail::keeper_tag, Gram>
                    , in_sequence<as_keeper<Gram> >
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::comma, Dummy>
                : when<ListSet<Char>, in_sequence<as_list_set_matcher<Char> > >
              {};
  
              template<typename Dummy>
              struct case_<tag::assign, Dummy>
                : or_<
                      when<assign<detail::basic_mark_tag, Gram>, call<Gram(as_marker)> >
                    , when<ListSet<Char>, in_sequence<as_list_set_matcher<Char> > >
                  >
              {};
  
              template<typename Dummy>
              struct case_<tag::subscript, Dummy>
                : or_<
                      when<subscript<detail::set_initializer_type, Gram>, in_sequence<call<as_set_matcher<Gram>(_right)> > >
                    , when<subscript<ActionableGrammar<Char>, _>, call<ActionableGrammar<Char>(as_action)> >
                  >
              {};
          };
  
          ///////////////////////////////////////////////////////////////////////////
          // ActionableCases
          template<typename Char, typename Gram>
          struct ActionableCases
          {
              template<typename Tag, typename Dummy = void>
              struct case_
                : Cases<Char, Gram>::template case_<Tag>
              {};
  
              // Only in sub-expressions with actions attached do we allow attribute assignements
              template<typename Dummy>
              struct case_<proto::tag::assign, Dummy>
                : or_<
                      typename Cases<Char, Gram>::template case_<proto::tag::assign>
                    , when<proto::assign<terminal<detail::attribute_placeholder<_> >, _>, in_sequence<as_attr_matcher> >
                  >
              {};
          };
  
      } // namespace detail
  
      ///////////////////////////////////////////////////////////////////////////
      // Grammar
      template<typename Char>
      struct Grammar
        : proto::switch_<grammar_detail::Cases<Char, Grammar<Char> > >
      {};
  
      template<typename Char>
      struct ActionableGrammar
        : proto::switch_<grammar_detail::ActionableCases<Char, ActionableGrammar<Char> > >
      {};
  
      ///////////////////////////////////////////////////////////////////////////
      // INVALID_REGULAR_EXPRESSION
      struct INVALID_REGULAR_EXPRESSION
        : mpl::false_
      {};
  
      ///////////////////////////////////////////////////////////////////////////
      // is_valid_regex
      template<typename Expr, typename Char>
      struct is_valid_regex
        : proto::matches<Expr, Grammar<Char> >
      {};
  
  }} // namespace boost::xpressive
  
  #endif
  