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// Functions used by iterators -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004 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 2, 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.

// You should have received a copy of the GNU General Public License along

// with this library; see the file COPYING.  If not, write to the Free

// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,

// USA.

// As a special exception, you may use this file as part of a free software

// library without restriction.  Specifically, if other files instantiate

// templates or use macros or inline functions from this file, or you compile

// this file and link it with other files to produce an executable, this

// file does not by itself cause the resulting executable to be covered by

// the GNU General Public License.  This exception does not however

// invalidate any other reasons why the executable file might be covered by

// the GNU General Public License.

/*

 *

 * Copyright (c) 1994

 * Hewlett-Packard Company

 *

 * Permission to use, copy, modify, distribute and sell this software

 * and its documentation for any purpose is hereby granted without fee,

 * provided that the above copyright notice appear in all copies and

 * that both that copyright notice and this permission notice appear

 * in supporting documentation.  Hewlett-Packard Company makes no

 * representations about the suitability of this software for any

 * purpose.  It is provided "as is" without express or implied warranty.

 *

 *

 * Copyright (c) 1996-1998

 * Silicon Graphics Computer Systems, Inc.

 *

 * Permission to use, copy, modify, distribute and sell this software

 * and its documentation for any purpose is hereby granted without fee,

 * provided that the above copyright notice appear in all copies and

 * that both that copyright notice and this permission notice appear

 * in supporting documentation.  Silicon Graphics makes no

 * representations about the suitability of this software for any

 * purpose.  It is provided "as is" without express or implied warranty.

 */

/** @file stl_iterator_base_funcs.h

 *  This is an internal header file, included by other library headers.

 *  You should not attempt to use it directly.

 *

 *  This file contains all of the general iterator-related utility

 *  functions, such as distance() and advance().

 */

#ifndef _ITERATOR_BASE_FUNCS_H

#define _ITERATOR_BASE_FUNCS_H 1

#pragma GCC system_header

#include <bits/concept_check.h>

namespace std

{

  template<typename _InputIterator>

    inline typename iterator_traits<_InputIterator>::difference_type

    __distance(_InputIterator __first, _InputIterator __last,

               input_iterator_tag)

    {

      // concept requirements

      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)

      typename iterator_traits<_InputIterator>::difference_type __n = 0;

      while (__first != __last)

        {

          ++__first;

          ++__n;

        }

      return __n;

    }

  template<typename _RandomAccessIterator>

    inline typename iterator_traits<_RandomAccessIterator>::difference_type

    __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,

               random_access_iterator_tag)

    {

      // concept requirements

      __glibcxx_function_requires(_RandomAccessIteratorConcept<

                                  _RandomAccessIterator>)

      return __last - __first;

    }

  /**

   *  @brief A generalization of pointer arithmetic.

   *  @param  first  An input iterator.

   *  @param  last  An input iterator.

   *  @return  The distance between them.

   *

   *  Returns @c n such that first + n == last.  This requires that @p last

   *  must be reachable from @p first.  Note that @c n may be negative.

   *

   *  For random access iterators, this uses their @c + and @c - operations

   *  and are constant time.  For other %iterator classes they are linear time.

  */

  template<typename _InputIterator>

    inline typename iterator_traits<_InputIterator>::difference_type

    distance(_InputIterator __first, _InputIterator __last)

    {

      // concept requirements -- taken care of in __distance

      return std::__distance(__first, __last,

                             std::__iterator_category(__first));

    }

  template<typename _InputIterator, typename _Distance>

    inline void

    __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)

    {

      // concept requirements

      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)

      while (__n--)

        ++__i;

    }

  template<typename _BidirectionalIterator, typename _Distance>

    inline void

    __advance(_BidirectionalIterator& __i, _Distance __n,

              bidirectional_iterator_tag)

    {

      // concept requirements

      __glibcxx_function_requires(_BidirectionalIteratorConcept<

                                  _BidirectionalIterator>)

      if (__n > 0)

        while (__n--)

          ++__i;

      else

        while (__n++)

          --__i;

    }

  template<typename _RandomAccessIterator, typename _Distance>

    inline void

    __advance(_RandomAccessIterator& __i, _Distance __n,

              random_access_iterator_tag)

    {

      // concept requirements

      __glibcxx_function_requires(_RandomAccessIteratorConcept<

                                  _RandomAccessIterator>)

      __i += __n;

    }

  /**

   *  @brief A generalization of pointer arithmetic.

   *  @param  i  An input iterator.

   *  @param  n  The "delta" by which to change @p i.

   *  @return  Nothing.

   *

   *  This increments @p i by @p n.  For bidirectional and random access

   *  iterators, @p n may be negative, in which case @p i is decremented.

   *

   *  For random access iterators, this uses their @c + and @c - operations

   *  and are constant time.  For other %iterator classes they are linear time.

  */

  template<typename _InputIterator, typename _Distance>

    inline void

    advance(_InputIterator& __i, _Distance __n)

    {

      // concept requirements -- taken care of in __advance

      std::__advance(__i, __n, std::__iterator_category(__i));

    }

} // namespace std

#endif /* _ITERATOR_BASE_FUNCS_H */