Module: Standard C++ Library Library: Iterators
An iterator that can both read and write and can traverse a container in both directions
NOTE -- For a complete discussion of iterators, see the Iterators section of this reference.
Iterators are a generalization of pointers that allow a C++ program to uniformly interact with different data structures. Bidirectional iterators can move both forwards and backwards through a container, and have the ability to both read and write data. These iterators satisfy the requirements listed below.
The following key pertains to the iterator descriptions listed below:
| a and b | values of type X |
| n | value representing a distance between two iterators |
| u, Distance, tmp and m | identifiers |
| r | value of type X& |
| t | value of type T |
A bidirectional iterator must meet all the requirements listed below. Note that most of these requirements are also the requirements for forward iterators.
| X u | u might have a singular value |
| X() | X() might be singular |
| X(a) | copy constructor, a == X(a) |
| X u(a) | copy constructor, u == a |
| X u = a | assignment, u == a |
| r = a | assignment, r == a |
| a == b, a != b | return value convertible to bool |
| a->m | equivalent to (*a).m |
| *a | return value convertible to T& |
| ++r | returns X& |
| r++ | return value convertible to const X& |
| *r++ | returns T& |
| --r | returns X& |
| r-- | return value convertible to const X& |
| *r-- | returns T& |
Like forward iterators, bidirectional iterators have the condition that a == b implies *a== *b.
There are no restrictions on the number of passes an algorithm may make through the structure.
Containers, Iterators, Forward Iterators
ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.1.4
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