libstdc++-v3/include/ext/iterator

// HP/SGI iterator extensions -*- C++ -*-

// Copyright (C) 2001-2025 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/>.

/*
 *
 * 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 ext/iterator
 *  This file is a GNU extension to the Standard C++ Library (possibly
 *  containing extensions from the HP/SGI STL subset).
 */

#ifndef _EXT_ITERATOR
#define _EXT_ITERATOR 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/concept_check.h>
#include <iterator>

namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // There are two signatures for distance.  In addition to the one
  // taking two iterators and returning a result, there is another
  // taking two iterators and a reference-to-result variable, and
  // returning nothing.  The latter seems to be an SGI extension.
  // -- pedwards
  template<typename _InputIterator, typename _Distance>
    inline void
    __distance(_InputIterator __first, _InputIterator __last,
	       _Distance& __n, std::input_iterator_tag)
    {
      // concept requirements
      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
      while (__first != __last)
	{
	  ++__first;
	  ++__n;
	}
    }

  template<typename _RandomAccessIterator, typename _Distance>
    inline void
    __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
	       _Distance& __n, std::random_access_iterator_tag)
    {
      // concept requirements
      __glibcxx_function_requires(_RandomAccessIteratorConcept<
				  _RandomAccessIterator>)
      __n += __last - __first;
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _InputIterator, typename _Distance>
    inline void
    distance(_InputIterator __first, _InputIterator __last,
             _Distance& __n)
    {
      // concept requirements -- taken care of in __distance
      __distance(__first, __last, __n, std::__iterator_category(__first));
    }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif