reverse_iterator<T>

A reverse_iterator is an iterator adapter that converts an iterator into an iterator that traverses in the opposite direction. For example, given a reverse_iterator revItr, writing ++revItr would cause the iterator to point to the element preceding the original element.

Unlike the other iterator adapters, reverse_iterator takes as its template argument an iterator type that represents the type of iterator to reverse. For example, to reverse a vector<int>::iterator, you'd use a reverse_iterator<vector<int>::iterator>. It is highly advised that you use typedef to make shorthands for these types!

reverse_iterator can only reverse iterators that are bidirectional iterators or random iterators. This means, for example, that you can't reverse an ostream_iterator, but that you can reverse a map<string, int>::iterator or a list<double>::iterator.

When constructing a reverse_iterator, it is important to remember that the constructed iterator does not point to the same element as the original iterator. Instead, it points to the element one before the source iterator. This is counterintuitive, but it greatly simplifies many common tasks. For example, suppose you want to iterate over the elements of a vector in reverse order. Then to get a reverse_iterator that points to the last element in the range, you'd create a reverse_iterator<vector<T>::iterator> and initialize it to the value of the vector's end function, since the element one before end is the final element in the vector. Similarly, to get the stopping point, you'd create a reverse_iterator<vector<T>::iterator> initialized to the vector's begin function, since the element one before begin is beyond the beginning of the container and acts in the same way as the end function - defining the place an iterator will reach once it has traversed the entire container.

• reverse_iterator<T> Member Functions
  • Constructor (1)
  • Constructor (2)
  • base