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Is it legal to use a reverse_iterator with std::equal?
For example, are any of these legal?
std::equal(v.begin(), v.end(), w.rbegin())
std::equal(v.rbegin(), v.rend(), w.begin())
std::equal(v.rbegin(), v.rend(), w.rbegin())
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C++ Iterators Reverse Iterators A reverse iterator is made from a bidirectional, or random access iterator which it keeps as a member which can be accessed through base() . To iterate backwards use rbegin() and rend() as the iterators for the end of the collection, and the start of the collection respectively.
The C++ function std::map::rbegin() returns a reverse iterator which points to the last element of the map. Reverse iterator iterates in reverse order that is why incrementing them moves towards beginning of map.
The rbegin() is a function in C++ STL. It returns a reverse iterator which points to the last element of the map. The reverse iterator iterates in reverse order and incrementing it means moving towards beginning of map.
Description. A Bidirectional Iterator is an iterator that can be both incremented and decremented. The requirement that a Bidirectional Iterator can be decremented is the only thing that distinguishes Bidirectional Iterators from Forward Iterators.
All are valid, because reverse iterators are, in fact, forward iterators.
"Reverse iterator" is not an iterator category. Remember some iterator categories:
*) and incremented (++) is a forward iterator.+ and - operators.On the other hand, a reverse iterator is a bidirectional iterator or a random access iterator that looks at a collection in reverse. Look at
http://www.cplusplus.com/reference/std/iterator/reverse_iterator/
... especially what it says about iterator_category under the "Member types" heading.
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