mipsel-buildroot-linux-uclibc/include/c++/4.9.1/bits/regex_executor.tcc - toolchains/bruno - Git at Google

 // class template regex -*- C++ -*-

 // Copyright (C) 2013-2014 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
 // software; you can redistribute it and/or modify it under the
 // terms of the GNU General Public License as published by the
 // Free Software Foundation; either version 3, or (at your option)
 // any later version.

 // This library is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 // GNU General Public License for more details.

 // Under Section 7 of GPL version 3, you are granted additional
 // permissions described in the GCC Runtime Library Exception, version
 // 3.1, as published by the Free Software Foundation.

 // You should have received a copy of the GNU General Public License and
 // a copy of the GCC Runtime Library Exception along with this program;
 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 // <http://www.gnu.org/licenses/>.

 /**
  *  @file bits/regex_executor.tcc
  *  This is an internal header file, included by other library headers.
  *  Do not attempt to use it directly. @headername{regex}
  */

 namespace std _GLIBCXX_VISIBILITY(default)
 {
 namespace __detail
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION

   template<typename _BiIter, typename _Alloc, typename _TraitsT,
     bool __dfs_mode>
     bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_search()
     {
       if (_M_flags & regex_constants::match_continuous)
 	return _M_search_from_first();
       auto __cur = _M_begin;
       do
 	{
 	  _M_current = __cur;
 	  if (_M_main<false>())
 	    return true;
 	}
       // Continue when __cur == _M_end
       while (__cur++ != _M_end);
       return false;
     }

   // This function operates in different modes, DFS mode or BFS mode, indicated
   // by template parameter __dfs_mode. See _M_main for details.
   //
   // ------------------------------------------------------------
   //
   // DFS mode:
   //
   // It applies a Depth-First-Search (aka backtracking) on given NFA and input
   // string.
   // At the very beginning the executor stands in the start state, then it tries
   // every possible state transition in current state recursively. Some state
   // transitions consume input string, say, a single-char-matcher or a
   // back-reference matcher; some don't, like assertion or other anchor nodes.
   // When the input is exhausted and/or the current state is an accepting state,
   // the whole executor returns true.
   //
   // TODO: This approach is exponentially slow for certain input.
   //       Try to compile the NFA to a DFA.
   //
   // Time complexity: \Omega(match_length), O(2^(_M_nfa.size()))
   // Space complexity: \theta(match_results.size() + match_length)
   //
   // ------------------------------------------------------------
   //
   // BFS mode:
   //
   // Russ Cox's article (http://swtch.com/~rsc/regexp/regexp1.html)
   // explained this algorithm clearly.
   //
   // It first computes epsilon closure (states that can be achieved without
   // consuming characters) for every state that's still matching,
   // using the same DFS algorithm, but doesn't re-enter states (find a true in
   // _M_visited), nor follows _S_opcode_match.
   //
   // Then apply DFS using every _S_opcode_match (in _M_match_queue) as the start
   // state.
   //
   // It significantly reduces potential duplicate states, so has a better
   // upper bound; but it requires more overhead.
   //
   // Time complexity: \Omega(match_length * match_results.size())
   //                  O(match_length * _M_nfa.size() * match_results.size())
   // Space complexity: \Omega(_M_nfa.size() + match_results.size())
   //                   O(_M_nfa.size() * match_results.size())
   template<typename _BiIter, typename _Alloc, typename _TraitsT,
     bool __dfs_mode>
   template<bool __match_mode>
     bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_main()
     {
       if (__dfs_mode)
 	{
 	  _M_has_sol = false;
 	  _M_cur_results = _M_results;
 	  _M_dfs<__match_mode>(_M_start_state);
 	  return _M_has_sol;
 	}
       else
 	{
 	  _M_match_queue->push_back(make_pair(_M_start_state, _M_results));
 	  bool __ret = false;
 	  while (1)
 	    {
 	      _M_has_sol = false;
 	      if (_M_match_queue->empty())
 		break;
 	      _M_visited->assign(_M_visited->size(), false);
 	      auto __old_queue = std::move(*_M_match_queue);
 	      for (auto& __task : __old_queue)
 		{
 		  _M_cur_results = std::move(__task.second);
 		  _M_dfs<__match_mode>(__task.first);
 		}
 	      if (!__match_mode)
 		__ret |= _M_has_sol;
 	      if (_M_current == _M_end)
 		break;
 	      ++_M_current;
 	    }
 	  if (__match_mode)
 	    __ret = _M_has_sol;
 	  return __ret;
 	}
     }

   // Return whether now match the given sub-NFA.
   template<typename _BiIter, typename _Alloc, typename _TraitsT,
     bool __dfs_mode>
     bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_lookahead(_State<_TraitsT> __state)
     {
       _ResultsVec __what(_M_cur_results.size());
       auto __sub = std::unique_ptr<_Executor>(new _Executor(_M_current,
 							    _M_end,
 							    __what,
 							    _M_re,
 							    _M_flags));
       __sub->_M_start_state = __state._M_alt;
       if (__sub->_M_search_from_first())
 	{
 	  for (size_t __i = 0; __i < __what.size(); __i++)
 	    if (__what[__i].matched)
 	      _M_cur_results[__i] = __what[__i];
 	  return true;
 	}
       return false;
     }

   // TODO: Use a function vector to dispatch, instead of using switch-case.
   template<typename _BiIter, typename _Alloc, typename _TraitsT,
     bool __dfs_mode>
   template<bool __match_mode>
     void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_dfs(_StateIdT __i)
     {
       if (!__dfs_mode)
 	{
 	  if ((*_M_visited)[__i])
 	    return;
 	  (*_M_visited)[__i] = true;
 	}

       const auto& __state = _M_nfa[__i];
       // Every change on _M_cur_results and _M_current will be rolled back after
       // finishing the recursion step.
       switch (__state._M_opcode)
 	{
 	// _M_alt branch is "match once more", while _M_next is "get me out
 	// of this quantifier". Executing _M_next first or _M_alt first don't
 	// mean the same thing, and we need to choose the correct order under
 	// given greedy mode.
 	case _S_opcode_alternative:
 	  // Greedy.
 	  if (!__state._M_neg)
 	    {
 	      // "Once more" is preferred in greedy mode.
 	      _M_dfs<__match_mode>(__state._M_alt);
 	      // If it's DFS executor and already accepted, we're done.
 	      if (!__dfs_mode || !_M_has_sol)
 		_M_dfs<__match_mode>(__state._M_next);
 	    }
 	  else // Non-greedy mode
 	    {
 	      if (__dfs_mode)
 		{
 		  // vice-versa.
 		  _M_dfs<__match_mode>(__state._M_next);
 		  if (!_M_has_sol)
 		    _M_dfs<__match_mode>(__state._M_alt);
 		}
 	      else
 		{
 		  // DON'T attempt anything, because there's already another
 		  // state with higher priority accepted. This state cannot be
 		  // better by attempting its next node.
 		  if (!_M_has_sol)
 		    {
 		      _M_dfs<__match_mode>(__state._M_next);
 		      // DON'T attempt anything if it's already accepted. An
 		      // accepted state *must* be better than a solution that
 		      // matches a non-greedy quantifier one more time.
 		      if (!_M_has_sol)
 			_M_dfs<__match_mode>(__state._M_alt);
 		    }
 		}
 	    }
 	  break;
 	case _S_opcode_subexpr_begin:
 	  // If there's nothing changed since last visit, do NOT continue.
 	  // This prevents the executor from get into infinite loop when using
 	  // "()*" to match "".
 	  if (!_M_cur_results[__state._M_subexpr].matched
 	      || _M_cur_results[__state._M_subexpr].first != _M_current)
 	    {
 	      auto& __res = _M_cur_results[__state._M_subexpr];
 	      auto __back = __res.first;
 	      __res.first = _M_current;
 	      _M_dfs<__match_mode>(__state._M_next);
 	      __res.first = __back;
 	    }
 	  break;
 	case _S_opcode_subexpr_end:
 	  if (_M_cur_results[__state._M_subexpr].second != _M_current
 	      || _M_cur_results[__state._M_subexpr].matched != true)
 	    {
 	      auto& __res = _M_cur_results[__state._M_subexpr];
 	      auto __back = __res;
 	      __res.second = _M_current;
 	      __res.matched = true;
 	      _M_dfs<__match_mode>(__state._M_next);
 	      __res = __back;
 	    }
 	  else
 	    _M_dfs<__match_mode>(__state._M_next);
 	  break;
 	case _S_opcode_line_begin_assertion:
 	  if (_M_at_begin())
 	    _M_dfs<__match_mode>(__state._M_next);
 	  break;
 	case _S_opcode_line_end_assertion:
 	  if (_M_at_end())
 	    _M_dfs<__match_mode>(__state._M_next);
 	  break;
 	case _S_opcode_word_boundary:
 	  if (_M_word_boundary(__state) == !__state._M_neg)
 	    _M_dfs<__match_mode>(__state._M_next);
 	  break;
 	// Here __state._M_alt offers a single start node for a sub-NFA.
 	// We recursively invoke our algorithm to match the sub-NFA.
 	case _S_opcode_subexpr_lookahead:
 	  if (_M_lookahead(__state) == !__state._M_neg)
 	    _M_dfs<__match_mode>(__state._M_next);
 	  break;
 	case _S_opcode_match:
 	  if (__dfs_mode)
 	    {
 	      if (_M_current != _M_end && __state._M_matches(*_M_current))
 		{
 		  ++_M_current;
 		  _M_dfs<__match_mode>(__state._M_next);
 		  --_M_current;
 		}
 	    }
 	  else
 	    if (__state._M_matches(*_M_current))
 	      _M_match_queue->push_back(make_pair(__state._M_next,
 						  _M_cur_results));
 	  break;
 	// First fetch the matched result from _M_cur_results as __submatch;
 	// then compare it with
 	// (_M_current, _M_current + (__submatch.second - __submatch.first)).
 	// If matched, keep going; else just return and try another state.
 	case _S_opcode_backref:
 	  {
 	    _GLIBCXX_DEBUG_ASSERT(__dfs_mode);
 	    auto& __submatch = _M_cur_results[__state._M_backref_index];
 	    if (!__submatch.matched)
 	      break;
 	    auto __last = _M_current;
 	    for (auto __tmp = __submatch.first;
 		 __last != _M_end && __tmp != __submatch.second;
 		 ++__tmp)
 	      ++__last;
 	    if (_M_re._M_traits.transform(__submatch.first,
 						__submatch.second)
 		== _M_re._M_traits.transform(_M_current, __last))
 	      {
 		if (__last != _M_current)
 		  {
 		    auto __backup = _M_current;
 		    _M_current = __last;
 		    _M_dfs<__match_mode>(__state._M_next);
 		    _M_current = __backup;
 		  }
 		else
 		  _M_dfs<__match_mode>(__state._M_next);
 	      }
 	  }
 	  break;
 	case _S_opcode_accept:
 	  if (__dfs_mode)
 	    {
 	      _GLIBCXX_DEBUG_ASSERT(!_M_has_sol);
 	      if (__match_mode)
 		_M_has_sol = _M_current == _M_end;
 	      else
 		_M_has_sol = true;
 	      if (_M_current == _M_begin
 		  && (_M_flags & regex_constants::match_not_null))
 		_M_has_sol = false;
 	      if (_M_has_sol)
 		_M_results = _M_cur_results;
 	    }
 	  else
 	    {
 	      if (_M_current == _M_begin
 		  && (_M_flags & regex_constants::match_not_null))
 		break;
 	      if (!__match_mode || _M_current == _M_end)
 		if (!_M_has_sol)
 		  {
 		    _M_has_sol = true;
 		    _M_results = _M_cur_results;
 		  }
 	    }
 	  break;
 	default:
 	  _GLIBCXX_DEBUG_ASSERT(false);
 	}
     }

   // Return whether now is at some word boundary.
   template<typename _BiIter, typename _Alloc, typename _TraitsT,
     bool __dfs_mode>
     bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_word_boundary(_State<_TraitsT> __state) const
     {
       // By definition.
       bool __ans = false;
       auto __pre = _M_current;
       --__pre;
       if (!(_M_at_begin() && _M_at_end()))
 	{
 	  if (_M_at_begin())
 	    __ans = _M_is_word(*_M_current)
 	      && !(_M_flags & regex_constants::match_not_bow);
 	  else if (_M_at_end())
 	    __ans = _M_is_word(*__pre)
 	      && !(_M_flags & regex_constants::match_not_eow);
 	  else
 	    __ans = _M_is_word(*_M_current)
 	      != _M_is_word(*__pre);
 	}
       return __ans;
     }

 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace __detail
 } // namespace
	// class template regex -- C++ --

	// Copyright (C) 2013-2014 Free Software Foundation, Inc.
	//
	// This file is part of the GNU ISO C++ Library. This library is free
	// software; you can redistribute it and/or modify it under the
	// terms of the GNU General Public License as published by the
	// Free Software Foundation; either version 3, or (at your option)
	// any later version.

	// This library is distributed in the hope that it will be useful,
	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	// GNU General Public License for more details.

	// Under Section 7 of GPL version 3, you are granted additional
	// permissions described in the GCC Runtime Library Exception, version
	// 3.1, as published by the Free Software Foundation.

	// You should have received a copy of the GNU General Public License and
	// a copy of the GCC Runtime Library Exception along with this program;
	// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
	// <http://www.gnu.org/licenses/>.

	/**
	* @file bits/regex_executor.tcc
	* This is an internal header file, included by other library headers.
	* Do not attempt to use it directly. @headername{regex}
	*/

	namespace std _GLIBCXX_VISIBILITY(default)
	{
	namespace __detail
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION

	template<typename _BiIter, typename _Alloc, typename _TraitsT,
	bool __dfs_mode>
	bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
	_M_search()
	{
	if (_M_flags & regex_constants::match_continuous)
	return _M_search_from_first();
	auto __cur = _M_begin;
	do
	{
	_M_current = __cur;
	if (_M_main<false>())
	return true;
	}
	// Continue when __cur == _M_end
	while (__cur++ != _M_end);
	return false;
	}

	// This function operates in different modes, DFS mode or BFS mode, indicated
	// by template parameter __dfs_mode. See _M_main for details.
	//
	// ------------------------------------------------------------
	//
	// DFS mode:
	//
	// It applies a Depth-First-Search (aka backtracking) on given NFA and input
	// string.
	// At the very beginning the executor stands in the start state, then it tries
	// every possible state transition in current state recursively. Some state
	// transitions consume input string, say, a single-char-matcher or a
	// back-reference matcher; some don't, like assertion or other anchor nodes.
	// When the input is exhausted and/or the current state is an accepting state,
	// the whole executor returns true.
	//
	// TODO: This approach is exponentially slow for certain input.
	// Try to compile the NFA to a DFA.
	//
	// Time complexity: \Omega(match_length), O(2^(_M_nfa.size()))
	// Space complexity: \theta(match_results.size() + match_length)
	//
	// ------------------------------------------------------------
	//
	// BFS mode:
	//
	// Russ Cox's article (http://swtch.com/~rsc/regexp/regexp1.html)
	// explained this algorithm clearly.
	//
	// It first computes epsilon closure (states that can be achieved without
	// consuming characters) for every state that's still matching,
	// using the same DFS algorithm, but doesn't re-enter states (find a true in
	// _M_visited), nor follows _S_opcode_match.
	//
	// Then apply DFS using every _S_opcode_match (in _M_match_queue) as the start
	// state.
	//
	// It significantly reduces potential duplicate states, so has a better
	// upper bound; but it requires more overhead.
	//
	// Time complexity: \Omega(match_length * match_results.size())
	// O(match_length * _M_nfa.size() * match_results.size())
	// Space complexity: \Omega(_M_nfa.size() + match_results.size())
	// O(_M_nfa.size() * match_results.size())
	template<typename _BiIter, typename _Alloc, typename _TraitsT,
	bool __dfs_mode>
	template<bool __match_mode>
	bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
	_M_main()
	{
	if (__dfs_mode)
	{
	_M_has_sol = false;
	_M_cur_results = _M_results;
	_M_dfs<__match_mode>(_M_start_state);
	return _M_has_sol;
	}
	else
	{
	_M_match_queue->push_back(make_pair(_M_start_state, _M_results));
	bool __ret = false;
	while (1)
	{
	_M_has_sol = false;
	if (_M_match_queue->empty())
	break;
	_M_visited->assign(_M_visited->size(), false);
	auto __old_queue = std::move(*_M_match_queue);
	for (auto& __task : __old_queue)
	{
	_M_cur_results = std::move(__task.second);
	_M_dfs<__match_mode>(__task.first);
	}
	if (!__match_mode)
	__ret \|= _M_has_sol;
	if (_M_current == _M_end)
	break;
	++_M_current;
	}
	if (__match_mode)
	__ret = _M_has_sol;
	return __ret;
	}
	}

	// Return whether now match the given sub-NFA.
	template<typename _BiIter, typename _Alloc, typename _TraitsT,
	bool __dfs_mode>
	bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
	_M_lookahead(_State<_TraitsT> __state)
	{
	_ResultsVec __what(_M_cur_results.size());
	auto __sub = std::unique_ptr<_Executor>(new _Executor(_M_current,
	_M_end,
	__what,
	_M_re,
	_M_flags));
	__sub->_M_start_state = __state._M_alt;
	if (__sub->_M_search_from_first())
	{
	for (size_t __i = 0; __i < __what.size(); __i++)
	if (__what[__i].matched)
	_M_cur_results[__i] = __what[__i];
	return true;
	}
	return false;
	}

	// TODO: Use a function vector to dispatch, instead of using switch-case.
	template<typename _BiIter, typename _Alloc, typename _TraitsT,
	bool __dfs_mode>
	template<bool __match_mode>
	void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
	_M_dfs(_StateIdT __i)
	{
	if (!__dfs_mode)
	{
	if ((*_M_visited)[__i])
	return;
	(*_M_visited)[__i] = true;
	}

	const auto& __state = _M_nfa[__i];
	// Every change on _M_cur_results and _M_current will be rolled back after
	// finishing the recursion step.
	switch (__state._M_opcode)
	{
	// _M_alt branch is "match once more", while _M_next is "get me out
	// of this quantifier". Executing _M_next first or _M_alt first don't
	// mean the same thing, and we need to choose the correct order under
	// given greedy mode.
	case _S_opcode_alternative:
	// Greedy.
	if (!__state._M_neg)
	{
	// "Once more" is preferred in greedy mode.
	_M_dfs<__match_mode>(__state._M_alt);
	// If it's DFS executor and already accepted, we're done.
	if (!__dfs_mode \|\| !_M_has_sol)
	_M_dfs<__match_mode>(__state._M_next);
	}
	else // Non-greedy mode
	{
	if (__dfs_mode)
	{
	// vice-versa.
	_M_dfs<__match_mode>(__state._M_next);
	if (!_M_has_sol)
	_M_dfs<__match_mode>(__state._M_alt);
	}
	else
	{
	// DON'T attempt anything, because there's already another
	// state with higher priority accepted. This state cannot be
	// better by attempting its next node.
	if (!_M_has_sol)
	{
	_M_dfs<__match_mode>(__state._M_next);
	// DON'T attempt anything if it's already accepted. An
	// accepted state must be better than a solution that
	// matches a non-greedy quantifier one more time.
	if (!_M_has_sol)
	_M_dfs<__match_mode>(__state._M_alt);
	}
	}
	}
	break;
	case _S_opcode_subexpr_begin:
	// If there's nothing changed since last visit, do NOT continue.
	// This prevents the executor from get into infinite loop when using
	// "()*" to match "".
	if (!_M_cur_results[__state._M_subexpr].matched
	\|\| _M_cur_results[__state._M_subexpr].first != _M_current)
	{
	auto& __res = _M_cur_results[__state._M_subexpr];
	auto __back = __res.first;
	__res.first = _M_current;
	_M_dfs<__match_mode>(__state._M_next);
	__res.first = __back;
	}
	break;
	case _S_opcode_subexpr_end:
	if (_M_cur_results[__state._M_subexpr].second != _M_current
	\|\| _M_cur_results[__state._M_subexpr].matched != true)
	{
	auto& __res = _M_cur_results[__state._M_subexpr];
	auto __back = __res;
	__res.second = _M_current;
	__res.matched = true;
	_M_dfs<__match_mode>(__state._M_next);
	__res = __back;
	}
	else
	_M_dfs<__match_mode>(__state._M_next);
	break;
	case _S_opcode_line_begin_assertion:
	if (_M_at_begin())
	_M_dfs<__match_mode>(__state._M_next);
	break;
	case _S_opcode_line_end_assertion:
	if (_M_at_end())
	_M_dfs<__match_mode>(__state._M_next);
	break;
	case _S_opcode_word_boundary:
	if (_M_word_boundary(__state) == !__state._M_neg)
	_M_dfs<__match_mode>(__state._M_next);
	break;
	// Here __state._M_alt offers a single start node for a sub-NFA.
	// We recursively invoke our algorithm to match the sub-NFA.
	case _S_opcode_subexpr_lookahead:
	if (_M_lookahead(__state) == !__state._M_neg)
	_M_dfs<__match_mode>(__state._M_next);
	break;
	case _S_opcode_match:
	if (__dfs_mode)
	{
	if (_M_current != _M_end && __state._M_matches(*_M_current))
	{
	++_M_current;
	_M_dfs<__match_mode>(__state._M_next);
	--_M_current;
	}
	}
	else
	if (__state._M_matches(*_M_current))
	_M_match_queue->push_back(make_pair(__state._M_next,
	_M_cur_results));
	break;
	// First fetch the matched result from _M_cur_results as __submatch;
	// then compare it with
	// (_M_current, _M_current + (__submatch.second - __submatch.first)).
	// If matched, keep going; else just return and try another state.
	case _S_opcode_backref:
	{
	_GLIBCXX_DEBUG_ASSERT(__dfs_mode);
	auto& __submatch = _M_cur_results[__state._M_backref_index];
	if (!__submatch.matched)
	break;
	auto __last = _M_current;
	for (auto __tmp = __submatch.first;
	__last != _M_end && __tmp != __submatch.second;
	++__tmp)
	++__last;
	if (_M_re._M_traits.transform(__submatch.first,
	__submatch.second)
	== _M_re._M_traits.transform(_M_current, __last))
	{
	if (__last != _M_current)
	{
	auto __backup = _M_current;
	_M_current = __last;
	_M_dfs<__match_mode>(__state._M_next);
	_M_current = __backup;
	}
	else
	_M_dfs<__match_mode>(__state._M_next);
	}
	}
	break;
	case _S_opcode_accept:
	if (__dfs_mode)
	{
	_GLIBCXX_DEBUG_ASSERT(!_M_has_sol);
	if (__match_mode)
	_M_has_sol = _M_current == _M_end;
	else
	_M_has_sol = true;
	if (_M_current == _M_begin
	&& (_M_flags & regex_constants::match_not_null))
	_M_has_sol = false;
	if (_M_has_sol)
	_M_results = _M_cur_results;
	}
	else
	{
	if (_M_current == _M_begin
	&& (_M_flags & regex_constants::match_not_null))
	break;
	if (!__match_mode \|\| _M_current == _M_end)
	if (!_M_has_sol)
	{
	_M_has_sol = true;
	_M_results = _M_cur_results;
	}
	}
	break;
	default:
	_GLIBCXX_DEBUG_ASSERT(false);
	}
	}

	// Return whether now is at some word boundary.
	template<typename _BiIter, typename _Alloc, typename _TraitsT,
	bool __dfs_mode>
	bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
	_M_word_boundary(_State<_TraitsT> __state) const
	{
	// By definition.
	bool __ans = false;
	auto __pre = _M_current;
	--__pre;
	if (!(_M_at_begin() && _M_at_end()))
	{
	if (_M_at_begin())
	__ans = _M_is_word(*_M_current)
	&& !(_M_flags & regex_constants::match_not_bow);
	else if (_M_at_end())
	__ans = _M_is_word(*__pre)
	&& !(_M_flags & regex_constants::match_not_eow);
	else
	__ans = _M_is_word(*_M_current)
	!= _M_is_word(*__pre);
	}
	return __ans;
	}

	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace __detail
	} // namespace