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std::reverse_iterator

Defined in header <iterator>

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

template< class Iter >
class reverse_iterator : public std::iterator<
                           typename std::iterator_traits<Iter>::iterator_category,
                           typename std::iterator_traits<Iter>::value_type,
                           typename std::iterator_traits<Iter>::difference_type,
                           typename std::iterator_traits<Iter>::pointer,
                           typename std::iterator_traits<Iter>::reference >

(until C++17)

template< class Iter >
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 types

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

These member types are required to be obtained by inheriting from std::iterator< std::iterator_traits<Iter>::iterator_category , std::iterator_traits<Iter>::value_type , std::iterator_traits<Iter>::difference_type , std::iterator_traits<Iter>::pointer , std::iterator_traits<Iter>::reference >.

(until C++17)

Member type	Definition
`iterator_type`	`Iter`

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)

Member objects

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

Non-member functions

make_reverse_iterator (C++14)	creates a `std::reverse_iterator` of type inferred from the argument (function template)
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)

Notes

std::reverse_iterator does not work with iterators that return a reference to a member object (so-called "stashing iterators"). An example of stashing iterator is std::filesystem::path::iterator.

Example

#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