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 _GLIBCXX_HAS_NESTED_TYPE, 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
142 _GLIBCXX_HAS_NESTED_TYPE(iterator_category
)
144 template<typename _Iterator
,
145 bool = __has_iterator_category
<_Iterator
>::value
>
146 struct __iterator_traits
{ };
148 template<typename _Iterator
>
149 struct __iterator_traits
<_Iterator
, true>
151 typedef typename
_Iterator::iterator_category iterator_category
;
152 typedef typename
_Iterator::value_type value_type
;
153 typedef typename
_Iterator::difference_type difference_type
;
154 typedef typename
_Iterator::pointer pointer
;
155 typedef typename
_Iterator::reference reference
;
158 template<typename _Iterator
>
159 struct iterator_traits
160 : public __iterator_traits
<_Iterator
> { };
162 template<typename _Iterator
>
163 struct iterator_traits
165 typedef typename
_Iterator::iterator_category iterator_category
;
166 typedef typename
_Iterator::value_type value_type
;
167 typedef typename
_Iterator::difference_type difference_type
;
168 typedef typename
_Iterator::pointer pointer
;
169 typedef typename
_Iterator::reference reference
;
173 /// Partial specialization for pointer types.
174 template<typename _Tp
>
175 struct iterator_traits
<_Tp
*>
177 typedef random_access_iterator_tag iterator_category
;
178 typedef _Tp value_type
;
179 typedef ptrdiff_t difference_type
;
180 typedef _Tp
* pointer
;
181 typedef _Tp
& reference
;
184 /// Partial specialization for const pointer types.
185 template<typename _Tp
>
186 struct iterator_traits
<const _Tp
*>
188 typedef random_access_iterator_tag iterator_category
;
189 typedef _Tp value_type
;
190 typedef ptrdiff_t difference_type
;
191 typedef const _Tp
* pointer
;
192 typedef const _Tp
& reference
;
196 * This function is not a part of the C++ standard but is syntactic
197 * sugar for internal library use only.
199 template<typename _Iter
>
200 inline typename iterator_traits
<_Iter
>::iterator_category
201 __iterator_category(const _Iter
&)
202 { return typename iterator_traits
<_Iter
>::iterator_category(); }
206 // If _Iterator has a base returns it otherwise _Iterator is returned
208 template<typename _Iterator
, bool _HasBase
>
211 typedef _Iterator iterator_type
;
212 static iterator_type
_S_base(_Iterator __it
)
216 template<typename _Iterator
>
217 struct _Iter_base
<_Iterator
, true>
219 typedef typename
_Iterator::iterator_type iterator_type
;
220 static iterator_type
_S_base(_Iterator __it
)
221 { return __it
.base(); }
224 #if __cplusplus >= 201103L
225 template<typename _InIter
>
226 using _RequireInputIter
= typename
227 enable_if
<is_convertible
<typename
228 iterator_traits
<_InIter
>::iterator_category
,
229 input_iterator_tag
>::value
>::type
;
232 _GLIBCXX_END_NAMESPACE_VERSION
235 #endif /* _STL_ITERATOR_BASE_TYPES_H */