1 // Types used in iterator implementation -*- C++ -*-
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56 /** @file stl_iterator_base_types.h
57 * This is an internal header file, included by other library headers.
58 * You should not attempt to use it directly.
60 * This file contains all of the general iterator-related utility types,
61 * such as iterator_traits and struct iterator.
64 #ifndef _ITERATOR_BASE_TYPES_H
65 #define _ITERATOR_BASE_TYPES_H 1
67 #pragma GCC system_header
73 * @defgroup iterator_tags Iterator Tags
74 * These are empty types, used to distinguish different iterators. The
75 * distinction is not made by what they contain, but simply by what they
76 * are. Different underlying algorithms can then be used based on the
77 * different operations supporetd by different iterator types.
79 /// Marking input iterators.
80 struct input_iterator_tag
{};
81 /// Marking output iterators.
82 struct output_iterator_tag
{};
83 /// Forward iterators support a superset of input iterator operations.
84 struct forward_iterator_tag
: public input_iterator_tag
{};
85 /// Bidirectional iterators support a superset of forward iterator
87 struct bidirectional_iterator_tag
: public forward_iterator_tag
{};
88 /// Random-access iterators support a superset of bidirectional iterator
90 struct random_access_iterator_tag
: public bidirectional_iterator_tag
{};
95 * @brief Common %iterator class.
97 * This class does nothing but define nested typedefs. %Iterator classes
98 * can inherit from this class to save some work. The typedefs are then
99 * used in specializations and overloading.
101 * In particular, there are no default implementations of requirements
102 * such as @c operator++ and the like. (How could there be?)
104 template<typename _Category
, typename _Tp
, typename _Distance
= ptrdiff_t,
105 typename _Pointer
= _Tp
*, typename _Reference
= _Tp
&>
108 /// One of the @link iterator_tags tag types@endlink.
109 typedef _Category iterator_category
;
110 /// The type "pointed to" by the iterator.
111 typedef _Tp value_type
;
112 /// Distance between iterators is represented as this type.
113 typedef _Distance difference_type
;
114 /// This type represents a pointer-to-value_type.
115 typedef _Pointer pointer
;
116 /// This type represents a reference-to-value_type.
117 typedef _Reference reference
;
121 * This class does nothing but define nested typedefs. The general
122 * version simply "forwards" the nested typedefs from the Iterator
123 * argument. Specialized versions for pointers and pointers-to-const
124 * provide tighter, more correct semantics.
126 template<typename _Iterator
>
127 struct iterator_traits
129 typedef typename
_Iterator::iterator_category iterator_category
;
130 typedef typename
_Iterator::value_type value_type
;
131 typedef typename
_Iterator::difference_type difference_type
;
132 typedef typename
_Iterator::pointer pointer
;
133 typedef typename
_Iterator::reference reference
;
136 template<typename _Tp
>
137 struct iterator_traits
<_Tp
*>
139 typedef random_access_iterator_tag iterator_category
;
140 typedef _Tp value_type
;
141 typedef ptrdiff_t difference_type
;
142 typedef _Tp
* pointer
;
143 typedef _Tp
& reference
;
146 template<typename _Tp
>
147 struct iterator_traits
<const _Tp
*>
149 typedef random_access_iterator_tag iterator_category
;
150 typedef _Tp value_type
;
151 typedef ptrdiff_t difference_type
;
152 typedef const _Tp
* pointer
;
153 typedef const _Tp
& reference
;
158 * This function is not a part of the C++ standard but is syntactic
159 * sugar for internal library use only.
162 template<typename _Iter
>
163 inline typename iterator_traits
<_Iter
>::iterator_category
164 __iterator_category(const _Iter
&)
165 { return typename iterator_traits
<_Iter
>::iterator_category(); }
169 #endif /* _ITERATOR_BASE_TYPES_H */