std::reverse_iterator

Defined in header `<iterator>`
template< class Iterator > class reverse_iterator : public std::iterator< typename std::iterator_traits<Iterator>::iterator_category, typename std::iterator_traits<Iterator>::value_type, typename std::iterator_traits<Iterator>::difference_type, typename std::iterator_traits<Iterator>::pointer, typename std::iterator_traits<Iterator>::reference >		(until C++17)
template< class Iterator > class reverse_iterator;		(since C++17)

std::reverse_iterator is an iterator adaptor that reverses the direction of a given iterator. In other words, when provided with a bidirectional iterator, std::reverse_iterator produces a new iterator that moves from the end to the beginning of the sequence defined by the underlying bidirectional iterator.

For a reverse iterator r constructed from an iterator i, the relationship &*r == &*(i-1) is always true (as long as r is dereferenceable); thus a reverse iterator constructed from a one-past-the-end iterator dereferences to the last element in a sequence.

This is the iterator returned by member functions rbegin() and rend() of the standard library containers.

Member type	Definition
`value_type`	std::iterator_traits<Iterator>::value_type
`difference_type`	std::iterator_traits<Iterator>::difference_type
`pointer`	std::iterator_traits<Iterator>::pointer
`reference`	std::iterator_traits<Iterator>::reference
`iterator_category`	std::iterator_traits<Iterator>::iterator_category

Note: before C++17, these member types are required to be obtained by inheriting from std::iterator< std::iterator_traits<Iterator>::iterator_category
, std::iterator_traits<Iterator>::value_type
, std::iterator_traits<Iterator>::difference_type
, std::iterator_traits<Iterator>::pointer
, std::iterator_traits<Iterator>::reference
>.

Member type	Definition
`iterator_type`	`Iterator`

[edit] Member functions

(constructor)	constructs a new iterator adaptor (public member function)
operator=	assigns another iterator (public member function)
base	accesses the underlying iterator (public member function)
operator*operator->	accesses the pointed-to element (public member function)
operator[]	accesses an element by index (public member function)
operator++operator++(int)operator+=operator+operator--operator--(int)operator-=operator-	advances or decrements the iterator (public member function)

[edit] Member objects

Member name	Definition
`current` (protected)	a copy of the base() iterator

[edit] Non-member functions

operator==operator!=operator<operator<=operator>operator>=	compares the underlying iterators (function template)
operator+	advances the iterator (function template)
operator-	computes the distance between two iterator adaptors (function template)

[edit] Example

Run this code

#include <iostream>
#include <string>
#include <iterator>
 
int main()
{
    std::string s = "Hello, world";
    std::reverse_iterator<std::string::iterator> r = s.rbegin();
    r[7] = 'O'; // replaces 'o' with 'O' 
    r += 7; // iterator now points at 'O'
    std::string rev(r, s.rend());
    std::cout << rev << '\n';
}

Output:

OlleH

[edit] See also

iterator

the basic iterator
(class template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Technical Specifications

Member functions
reverse_iterator::reverse_iterator
reverse_iterator::operator=
reverse_iterator::base
reverse_iterator::operator*reverse_iterator::operator->
reverse_iterator::operator[]
reverse_iterator::operator++reverse_iterator::operator+reverse_iterator::operator+=reverse_iterator::operator--reverse_iterator::operator-reverse_iterator::operator-=
Non-member functions
operator==operator!=operator<operator>
operator+
operator-