text: ///////////////////////////////////////////////////////////////////////////////
  // logical_newline_matcher.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_CORE_MATCHER_LOGICAL_NEWLINE_MATCHER_HPP_EAN_10_04_2005
  #define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_LOGICAL_NEWLINE_MATCHER_HPP_EAN_10_04_2005
  
  // MS compatible compilers support #pragma once
  #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  # pragma once
  #endif
  
  #include <boost/xpressive/detail/detail_fwd.hpp>
  #include <boost/xpressive/detail/core/quant_style.hpp>
  #include <boost/xpressive/detail/core/state.hpp>
  
  namespace boost { namespace xpressive { namespace detail
  {
  
      //////////////////////////////////////////////////////////////////////////
      // logical_newline_matcher
      //
      template<typename Traits>
      struct logical_newline_matcher
        : quant_style_variable_width
      {
          typedef typename Traits::char_type char_type;
          typedef typename Traits::char_class_type char_class_type;
  
          logical_newline_matcher(Traits const &traits)
            : newline_(lookup_classname(traits, "newline"))
            , nl_(traits.widen('\n'))
            , cr_(traits.widen('\r'))
          {
          }
  
          template<typename BidiIter, typename Next>
          bool match(match_state<BidiIter> &state, Next const &next) const
          {
              if(state.eos())
              {
                  return false;
              }
  
              char_type ch = *state.cur_;
              if(traits_cast<Traits>(state).isctype(ch, this->newline_))
              {
                  ++state.cur_;
                  if(this->cr_ == ch && !state.eos() && this->nl_ == *state.cur_)
                  {
                      ++state.cur_;
                      if(next.match(state))
                      {
                          return true;
                      }
                      --state.cur_;
                  }
                  else if(next.match(state))
                  {
                      return true;
                  }
  
                  --state.cur_;
              }
              return false;
          }
  
          char_class_type newline() const
          {
              return this->newline_;
          }
  
      private:
          char_class_type newline_;
          char_type nl_, cr_;
      };
  
  }}}
  
  #endif
  