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

// Copyright (C) 2001, 2002 Free Software Foundation, Inc.
//
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/*
 *
 * 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 __GLIBCPP_INTERNAL_ITERATOR_BASE_FUNCS_H
#define __GLIBCPP_INTERNAL_ITERATOR_BASE_FUNCS_H

#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
      __glibcpp_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
      __glibcpp_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 __distance(__first, __last, __iterator_category(__first));
    }
  
  template<typename _InputIter, typename _Distance>
    inline void
    __advance(_InputIter& __i, _Distance __n, input_iterator_tag)
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter>)
      while (__n--) ++__i;
    }
  
  template<typename _BidirectionalIterator, typename _Distance>
    inline void
    __advance(_BidirectionalIterator& __i, _Distance __n,
              bidirectional_iterator_tag)
    {
      // concept requirements
      __glibcpp_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
      __glibcpp_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
      __advance(__i, __n, __iterator_category(__i));
    }
} // namespace std

#endif /* __GLIBCPP_INTERNAL_ITERATOR_BASE_FUNCS_H */
