1 // Types used in iterator implementation -*- C++ -*-
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52 /** @file stl_iterator_base_types.h
53 * This is an internal header file, included by other library headers.
54 * You should not attempt to use it directly.
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 _GLIBCXX_BEGIN_NAMESPACE(std)
70 * @defgroup iterators Iterators
71 * Abstractions for uniform iterating through various underlying types.
76 * @defgroup iterator_tags Iterator Tags
77 * These are empty types, used to distinguish different iterators. The
78 * distinction is not made by what they contain, but simply by what they
79 * are. Different underlying algorithms can then be used based on the
80 * different operations supported by different iterator types.
83 /// Marking input iterators.
84 struct input_iterator_tag { };
86 /// Marking output iterators.
87 struct output_iterator_tag { };
89 /// Forward iterators support a superset of input iterator operations.
90 struct forward_iterator_tag : public input_iterator_tag { };
92 /// Bidirectional iterators support a superset of forward iterator
94 struct bidirectional_iterator_tag : public forward_iterator_tag { };
96 /// Random-access iterators support a superset of bidirectional
97 /// iterator operations.
98 struct random_access_iterator_tag : public bidirectional_iterator_tag { };
102 * @brief Common %iterator class.
104 * This class does nothing but define nested typedefs. %Iterator classes
105 * can inherit from this class to save some work. The typedefs are then
106 * used in specializations and overloading.
108 * In particular, there are no default implementations of requirements
109 * such as @c operator++ and the like. (How could there be?)
111 template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
112 typename _Pointer = _Tp*, typename _Reference = _Tp&>
115 /// One of the @link iterator_tags tag types@endlink.
116 typedef _Category iterator_category;
117 /// The type "pointed to" by the iterator.
118 typedef _Tp value_type;
119 /// Distance between iterators is represented as this type.
120 typedef _Distance difference_type;
121 /// This type represents a pointer-to-value_type.
122 typedef _Pointer pointer;
123 /// This type represents a reference-to-value_type.
124 typedef _Reference reference;
128 * @brief Traits class for iterators.
130 * This class does nothing but define nested typedefs. The general
131 * version simply @a forwards the nested typedefs from the Iterator
132 * argument. Specialized versions for pointers and pointers-to-const
133 * provide tighter, more correct semantics.
135 template<typename _Iterator>
136 struct iterator_traits
138 typedef typename _Iterator::iterator_category iterator_category;
139 typedef typename _Iterator::value_type value_type;
140 typedef typename _Iterator::difference_type difference_type;
141 typedef typename _Iterator::pointer pointer;
142 typedef typename _Iterator::reference reference;
145 /// Partial specialization for pointer types.
146 template<typename _Tp>
147 struct iterator_traits<_Tp*>
149 typedef random_access_iterator_tag iterator_category;
150 typedef _Tp value_type;
151 typedef ptrdiff_t difference_type;
152 typedef _Tp* pointer;
153 typedef _Tp& reference;
156 /// Partial specialization for const pointer types.
157 template<typename _Tp>
158 struct iterator_traits<const _Tp*>
160 typedef random_access_iterator_tag iterator_category;
161 typedef _Tp value_type;
162 typedef ptrdiff_t difference_type;
163 typedef const _Tp* pointer;
164 typedef const _Tp& reference;
168 * This function is not a part of the C++ standard but is syntactic
169 * sugar for internal library use only.
171 template<typename _Iter>
172 inline typename iterator_traits<_Iter>::iterator_category
173 __iterator_category(const _Iter&)
174 { return typename iterator_traits<_Iter>::iterator_category(); }
178 // If _Iterator has a base returns it otherwise _Iterator is returned
180 template<typename _Iterator, bool _HasBase>
183 typedef _Iterator iterator_type;
184 static iterator_type _S_base(_Iterator __it)
188 template<typename _Iterator>
189 struct _Iter_base<_Iterator, true>
191 typedef typename _Iterator::iterator_type iterator_type;
192 static iterator_type _S_base(_Iterator __it)
193 { return __it.base(); }
196 _GLIBCXX_END_NAMESPACE
198 #endif /* _STL_ITERATOR_BASE_TYPES_H */