stl_iterator_base_types.h

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// Types used in iterator implementation -*- C++ -*-

// Copyright (C) 2001, 2002, 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
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// any later version.

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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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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
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 * representations about the suitability of this software for any
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 * 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
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/** @file stl_iterator_base_types.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 types,
 *  such as iterator_traits and struct iterator.
 */

#ifndef _ITERATOR_BASE_TYPES_H
#define _ITERATOR_BASE_TYPES_H 1

#pragma GCC system_header

namespace std
{
  //@{
  /**
   *  @defgroup iterator_tags Iterator Tags
   *  These are empty types, used to distinguish different iterators.  The
   *  distinction is not made by what they contain, but simply by what they
   *  are.  Different underlying algorithms can then be used based on the
   *  different operations supporetd by different iterator types.
  */
  ///  Marking input iterators.
  struct input_iterator_tag {};
  ///  Marking output iterators.
  struct output_iterator_tag {};
  /// Forward iterators support a superset of input iterator operations.
  struct forward_iterator_tag : public input_iterator_tag {};
  /// Bidirectional iterators support a superset of forward iterator
  /// operations.
  struct bidirectional_iterator_tag : public forward_iterator_tag {};
  /// Random-access iterators support a superset of bidirectional iterator
  /// operations.
  struct random_access_iterator_tag : public bidirectional_iterator_tag {};
  //@}


  /**
   *  @brief  Common %iterator class.
   *
   *  This class does nothing but define nested typedefs.  %Iterator classes
   *  can inherit from this class to save some work.  The typedefs are then
   *  used in specializations and overloading.
   *
   *  In particular, there are no default implementations of requirements
   *  such as @c operator++ and the like.  (How could there be?)
  */
  template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
           typename _Pointer = _Tp*, typename _Reference = _Tp&>
    struct iterator
    {
      /// One of the @link iterator_tags tag types@endlink.
      typedef _Category  iterator_category;
      /// The type "pointed to" by the iterator.
      typedef _Tp        value_type;
      /// Distance between iterators is represented as this type.
      typedef _Distance  difference_type;
      /// This type represents a pointer-to-value_type.
      typedef _Pointer   pointer;
      /// This type represents a reference-to-value_type.
      typedef _Reference reference;
    };

  /**
   *  This class does nothing but define nested typedefs.  The general
   *  version simply "forwards" the nested typedefs from the Iterator
   *  argument.  Specialized versions for pointers and pointers-to-const
   *  provide tighter, more correct semantics.
  */
  template<typename _Iterator>
    struct iterator_traits
    {
      typedef typename _Iterator::iterator_category iterator_category;
      typedef typename _Iterator::value_type        value_type;
      typedef typename _Iterator::difference_type   difference_type;
      typedef typename _Iterator::pointer           pointer;
      typedef typename _Iterator::reference         reference;
    };

  template<typename _Tp>
    struct iterator_traits<_Tp*>
    {
      typedef random_access_iterator_tag iterator_category;
      typedef _Tp                         value_type;
      typedef ptrdiff_t                   difference_type;
      typedef _Tp*                        pointer;
      typedef _Tp&                        reference;
    };

  template<typename _Tp>
    struct iterator_traits<const _Tp*>
    {
      typedef random_access_iterator_tag iterator_category;
      typedef _Tp                         value_type;
      typedef ptrdiff_t                   difference_type;
      typedef const _Tp*                  pointer;
      typedef const _Tp&                  reference;
    };

  /**
   *  @if maint
   *  This function is not a part of the C++ standard but is syntactic
   *  sugar for internal library use only.
   *  @endif
  */
  template<typename _Iter>
    inline typename iterator_traits<_Iter>::iterator_category
    __iterator_category(const _Iter&)
    { return typename iterator_traits<_Iter>::iterator_category(); }

} // namespace std

#endif /* _ITERATOR_BASE_TYPES_H */

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