1 // Types used in iterator implementation -*- C++ -*-
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51 /** @file bits/stl_iterator_base_types.h
52 * This is an internal header file, included by other library headers.
53 * Do not attempt to use it directly. @headername{iterator}
55 * This file contains all of the general iterator-related utility types,
56 * such as iterator_traits and struct iterator.
59 #ifndef _STL_ITERATOR_BASE_TYPES_H
60 #define _STL_ITERATOR_BASE_TYPES_H 1
62 #pragma GCC system_header
64 #include <bits/c++config.h>
66 #if __cplusplus >= 201103L
67 # include <type_traits> // For __void_t, is_convertible
70 namespace std
_GLIBCXX_VISIBILITY(default)
72 _GLIBCXX_BEGIN_NAMESPACE_VERSION
75 * @defgroup iterators Iterators
76 * Abstractions for uniform iterating through various underlying types.
81 * @defgroup iterator_tags Iterator Tags
82 * These are empty types, used to distinguish different iterators. The
83 * distinction is not made by what they contain, but simply by what they
84 * are. Different underlying algorithms can then be used based on the
85 * different operations supported by different iterator types.
88 /// Marking input iterators.
89 struct input_iterator_tag
{ };
91 /// Marking output iterators.
92 struct output_iterator_tag
{ };
94 /// Forward iterators support a superset of input iterator operations.
95 struct forward_iterator_tag
: public input_iterator_tag
{ };
97 /// Bidirectional iterators support a superset of forward iterator
99 struct bidirectional_iterator_tag
: public forward_iterator_tag
{ };
101 /// Random-access iterators support a superset of bidirectional
102 /// iterator operations.
103 struct random_access_iterator_tag
: public bidirectional_iterator_tag
{ };
107 * @brief Common %iterator class.
109 * This class does nothing but define nested typedefs. %Iterator classes
110 * can inherit from this class to save some work. The typedefs are then
111 * used in specializations and overloading.
113 * In particular, there are no default implementations of requirements
114 * such as @c operator++ and the like. (How could there be?)
116 template<typename _Category
, typename _Tp
, typename _Distance
= ptrdiff_t,
117 typename _Pointer
= _Tp
*, typename _Reference
= _Tp
&>
120 /// One of the @link iterator_tags tag types@endlink.
121 typedef _Category iterator_category
;
122 /// The type "pointed to" by the iterator.
123 typedef _Tp value_type
;
124 /// Distance between iterators is represented as this type.
125 typedef _Distance difference_type
;
126 /// This type represents a pointer-to-value_type.
127 typedef _Pointer pointer
;
128 /// This type represents a reference-to-value_type.
129 typedef _Reference reference
;
133 * @brief Traits class for iterators.
135 * This class does nothing but define nested typedefs. The general
136 * version simply @a forwards the nested typedefs from the Iterator
137 * argument. Specialized versions for pointers and pointers-to-const
138 * provide tighter, more correct semantics.
140 #if __cplusplus >= 201103L
141 // _GLIBCXX_RESOLVE_LIB_DEFECTS
142 // 2408. SFINAE-friendly common_type/iterator_traits is missing in C++14
143 template<typename _Iterator
, typename
= __void_t
<>>
144 struct __iterator_traits
{ };
146 template<typename _Iterator
>
147 struct __iterator_traits
<_Iterator
,
148 __void_t
<typename
_Iterator::iterator_category
,
149 typename
_Iterator::value_type
,
150 typename
_Iterator::difference_type
,
151 typename
_Iterator::pointer
,
152 typename
_Iterator::reference
>>
154 typedef typename
_Iterator::iterator_category iterator_category
;
155 typedef typename
_Iterator::value_type value_type
;
156 typedef typename
_Iterator::difference_type difference_type
;
157 typedef typename
_Iterator::pointer pointer
;
158 typedef typename
_Iterator::reference reference
;
161 template<typename _Iterator
>
162 struct iterator_traits
163 : public __iterator_traits
<_Iterator
> { };
165 template<typename _Iterator
>
166 struct iterator_traits
168 typedef typename
_Iterator::iterator_category iterator_category
;
169 typedef typename
_Iterator::value_type value_type
;
170 typedef typename
_Iterator::difference_type difference_type
;
171 typedef typename
_Iterator::pointer pointer
;
172 typedef typename
_Iterator::reference reference
;
176 /// Partial specialization for pointer types.
177 template<typename _Tp
>
178 struct iterator_traits
<_Tp
*>
180 typedef random_access_iterator_tag iterator_category
;
181 typedef _Tp value_type
;
182 typedef ptrdiff_t difference_type
;
183 typedef _Tp
* pointer
;
184 typedef _Tp
& reference
;
187 /// Partial specialization for const pointer types.
188 template<typename _Tp
>
189 struct iterator_traits
<const _Tp
*>
191 typedef random_access_iterator_tag iterator_category
;
192 typedef _Tp value_type
;
193 typedef ptrdiff_t difference_type
;
194 typedef const _Tp
* pointer
;
195 typedef const _Tp
& reference
;
199 * This function is not a part of the C++ standard but is syntactic
200 * sugar for internal library use only.
202 template<typename _Iter
>
203 inline typename iterator_traits
<_Iter
>::iterator_category
204 __iterator_category(const _Iter
&)
205 { return typename iterator_traits
<_Iter
>::iterator_category(); }
209 // If _Iterator has a base returns it otherwise _Iterator is returned
211 template<typename _Iterator
, bool _HasBase
>
214 typedef _Iterator iterator_type
;
215 static iterator_type
_S_base(_Iterator __it
)
219 template<typename _Iterator
>
220 struct _Iter_base
<_Iterator
, true>
222 typedef typename
_Iterator::iterator_type iterator_type
;
223 static iterator_type
_S_base(_Iterator __it
)
224 { return __it
.base(); }
227 #if __cplusplus >= 201103L
228 template<typename _InIter
>
229 using _RequireInputIter
= typename
230 enable_if
<is_convertible
<typename
231 iterator_traits
<_InIter
>::iterator_category
,
232 input_iterator_tag
>::value
>::type
;
235 _GLIBCXX_END_NAMESPACE_VERSION
238 #endif /* _STL_ITERATOR_BASE_TYPES_H */