1 // Types used in iterator implementation -*- C++ -*-
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52 /** @file bits/stl_iterator_base_types.h
53 * This is an internal header file, included by other library headers.
54 * Do not attempt to use it directly. @headername{iterator}
56 * This file contains all of the general iterator-related utility types,
57 * such as iterator_traits and struct iterator.
60 #ifndef _STL_ITERATOR_BASE_TYPES_H
61 #define _STL_ITERATOR_BASE_TYPES_H 1
63 #pragma GCC system_header
65 #include <bits/c++config.h>
67 #ifdef __GXX_EXPERIMENTAL_CXX0X__
68 # include <type_traits> // For _GLIBCXX_HAS_NESTED_TYPE
71 namespace std _GLIBCXX_VISIBILITY(default)
73 _GLIBCXX_BEGIN_NAMESPACE_VERSION
76 * @defgroup iterators Iterators
77 * Abstractions for uniform iterating through various underlying types.
82 * @defgroup iterator_tags Iterator Tags
83 * These are empty types, used to distinguish different iterators. The
84 * distinction is not made by what they contain, but simply by what they
85 * are. Different underlying algorithms can then be used based on the
86 * different operations supported by different iterator types.
89 /// Marking input iterators.
90 struct input_iterator_tag { };
92 /// Marking output iterators.
93 struct output_iterator_tag { };
95 /// Forward iterators support a superset of input iterator operations.
96 struct forward_iterator_tag : public input_iterator_tag { };
98 /// Bidirectional iterators support a superset of forward iterator
100 struct bidirectional_iterator_tag : public forward_iterator_tag { };
102 /// Random-access iterators support a superset of bidirectional
103 /// iterator operations.
104 struct random_access_iterator_tag : public bidirectional_iterator_tag { };
108 * @brief Common %iterator class.
110 * This class does nothing but define nested typedefs. %Iterator classes
111 * can inherit from this class to save some work. The typedefs are then
112 * used in specializations and overloading.
114 * In particular, there are no default implementations of requirements
115 * such as @c operator++ and the like. (How could there be?)
117 template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
118 typename _Pointer = _Tp*, typename _Reference = _Tp&>
121 /// One of the @link iterator_tags tag types@endlink.
122 typedef _Category iterator_category;
123 /// The type "pointed to" by the iterator.
124 typedef _Tp value_type;
125 /// Distance between iterators is represented as this type.
126 typedef _Distance difference_type;
127 /// This type represents a pointer-to-value_type.
128 typedef _Pointer pointer;
129 /// This type represents a reference-to-value_type.
130 typedef _Reference reference;
134 * @brief Traits class for iterators.
136 * This class does nothing but define nested typedefs. The general
137 * version simply @a forwards the nested typedefs from the Iterator
138 * argument. Specialized versions for pointers and pointers-to-const
139 * provide tighter, more correct semantics.
141 #ifdef __GXX_EXPERIMENTAL_CXX0X__
143 _GLIBCXX_HAS_NESTED_TYPE(iterator_category)
145 template<typename _Iterator,
146 bool = __has_iterator_category<_Iterator>::value>
147 struct __iterator_traits { };
149 template<typename _Iterator>
150 struct __iterator_traits<_Iterator, true>
152 typedef typename _Iterator::iterator_category iterator_category;
153 typedef typename _Iterator::value_type value_type;
154 typedef typename _Iterator::difference_type difference_type;
155 typedef typename _Iterator::pointer pointer;
156 typedef typename _Iterator::reference reference;
159 template<typename _Iterator>
160 struct iterator_traits
161 : public __iterator_traits<_Iterator> { };
163 template<typename _Iterator>
164 struct iterator_traits
166 typedef typename _Iterator::iterator_category iterator_category;
167 typedef typename _Iterator::value_type value_type;
168 typedef typename _Iterator::difference_type difference_type;
169 typedef typename _Iterator::pointer pointer;
170 typedef typename _Iterator::reference reference;
174 /// Partial specialization for pointer types.
175 template<typename _Tp>
176 struct iterator_traits<_Tp*>
178 typedef random_access_iterator_tag iterator_category;
179 typedef _Tp value_type;
180 typedef ptrdiff_t difference_type;
181 typedef _Tp* pointer;
182 typedef _Tp& reference;
185 /// Partial specialization for const pointer types.
186 template<typename _Tp>
187 struct iterator_traits<const _Tp*>
189 typedef random_access_iterator_tag iterator_category;
190 typedef _Tp value_type;
191 typedef ptrdiff_t difference_type;
192 typedef const _Tp* pointer;
193 typedef const _Tp& reference;
197 * This function is not a part of the C++ standard but is syntactic
198 * sugar for internal library use only.
200 template<typename _Iter>
201 inline typename iterator_traits<_Iter>::iterator_category
202 __iterator_category(const _Iter&)
203 { return typename iterator_traits<_Iter>::iterator_category(); }
207 // If _Iterator has a base returns it otherwise _Iterator is returned
209 template<typename _Iterator, bool _HasBase>
212 typedef _Iterator iterator_type;
213 static iterator_type _S_base(_Iterator __it)
217 template<typename _Iterator>
218 struct _Iter_base<_Iterator, true>
220 typedef typename _Iterator::iterator_type iterator_type;
221 static iterator_type _S_base(_Iterator __it)
222 { return __it.base(); }
225 _GLIBCXX_END_NAMESPACE_VERSION
228 #endif /* _STL_ITERATOR_BASE_TYPES_H */