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 __GLIBCPP_INTERNAL_ITERATOR_BASE_TYPES_H
65 #define __GLIBCPP_INTERNAL_ITERATOR_BASE_TYPES_H
67 #pragma GCC system_header
72 * @defgroup iterator_tags Iterator Tags
73 * These are empty types, used to distinguish different iterators. The
74 * distinction is not made by what they contain, but simply by what they
75 * are. Different underlying algorithms can then be used based on the
76 * 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 operations.
86 struct bidirectional_iterator_tag
: public forward_iterator_tag
{};
87 /// Random-access iterators support a superset of bidirectional iterator operations.
88 struct random_access_iterator_tag
: public bidirectional_iterator_tag
{};
93 * This class does nothing but define nested typedefs. %Iterator classes
94 * can inherit from this class to save some work. The typedefs are then
95 * used in specializations and overloading.
97 * In particular, there are no default implementations of requirements
98 * such as @c operator++ and the like. (How could there be?)
100 template<typename _Category
, typename _Tp
, typename _Distance
= ptrdiff_t,
101 typename _Pointer
= _Tp
*, typename _Reference
= _Tp
&>
103 /// One of the @link iterator_tags tag types@endlink.
104 typedef _Category iterator_category
;
105 /// The type "pointed to" by the iterator.
106 typedef _Tp value_type
;
107 /// Distance between iterators is represented as this type.
108 typedef _Distance difference_type
;
109 /// This type represents a pointer-to-value_type.
110 typedef _Pointer pointer
;
111 /// This type represents a reference-to-value_type.
112 typedef _Reference reference
;
116 * This class does nothing but define nested typedefs. The general
117 * version simply "forwards" the nested typedefs from the Iterator
118 * argument. Specialized versions for pointers and pointers-to-const
119 * provide tighter, more correct semantics.
121 template<typename _Iterator
>
122 struct iterator_traits
{
123 typedef typename
_Iterator::iterator_category iterator_category
;
124 typedef typename
_Iterator::value_type value_type
;
125 typedef typename
_Iterator::difference_type difference_type
;
126 typedef typename
_Iterator::pointer pointer
;
127 typedef typename
_Iterator::reference reference
;
130 template<typename _Tp
>
131 struct iterator_traits
<_Tp
*> {
132 typedef random_access_iterator_tag iterator_category
;
133 typedef _Tp value_type
;
134 typedef ptrdiff_t difference_type
;
135 typedef _Tp
* pointer
;
136 typedef _Tp
& reference
;
139 template<typename _Tp
>
140 struct iterator_traits
<const _Tp
*> {
141 typedef random_access_iterator_tag iterator_category
;
142 typedef _Tp value_type
;
143 typedef ptrdiff_t difference_type
;
144 typedef const _Tp
* pointer
;
145 typedef const _Tp
& reference
;
150 * This function is not a part of the C++ standard but is syntactic
151 * sugar for internal library use only.
154 template<typename _Iter
>
155 inline typename iterator_traits
<_Iter
>::iterator_category
156 __iterator_category(const _Iter
&)
157 { return typename iterator_traits
<_Iter
>::iterator_category(); }
161 #endif /* __GLIBCPP_INTERNAL_ITERATOR_BASE_TYPES_H */