A type that provides a bidirectional iterator that can read or modify an element in a reversed map.
A type reverse_iterator cannot modify the value of an element and is use to iterate through the map in reverse.
The reverse_iterator defined by map points to elements that are objects of value_type, that is of type pair<const Key, Type>, whose first member is the key to the element and whose second member is the mapped datum held by the element.
To dereference a reverse_iterator rIter pointing to an element in a map, use the -> operator.
To access the value of the key for the element, use rIter -> first, which is equivalent to (*rIter).first. To access the value of the mapped datum for the element, use rIter -> second, which is equivalent to (*rIter).first.
See example for rbegin for an example of how to declare and use reverse_iterator.