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std::reverse_iterator(3) C++ Standard Libary std::reverse_iterator(3)


std::reverse_iterator - std::reverse_iterator


Defined in header <iterator>
template< class Iter >
class reverse_iterator;

std::reverse_iterator is an iterator adaptor that reverses the direction of a given
iterator, which must be at least a LegacyBidirectionalIterator
or model bidirectional_iterator
(since C++20). 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

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


Member types

Member type Definition
iterator_type Iter
iterator_category std::iterator_traits<Iter>::iterator_category (until
value_type std::iterator_traits<Iter>::value_type C++20)
difference_type std::iterator_traits<Iter>::difference_type
pointer std::iterator_traits<Iter>::pointer
reference std::iterator_traits<Iter>::reference
Member type Definition
iterator_type Iter
If Iter models std::random_access_iterator, this is
iterator_concept std::random_access_iterator_tag. Otherwise, this is
If std::iterator_traits<Iter>::iterator_category models (since
iterator_category std::derived_from<std::random_access_iterator_tag>, this is C++20)
std::random_access_iterator_tag. Otherwise, this is
value_type std::iter_value_t<Iter>
difference_type std::iter_difference_t<Iter>
pointer std::iterator_traits<Iter>::pointer
reference std::iter_reference_t<Iter>

Member types iterator_category, value_type, difference_type, pointer
and reference are required to be obtained by inheriting from
, std::iterator_traits<Iter>::value_type (until C++17)
, std::iterator_traits<Iter>::difference_type
, std::iterator_traits<Iter>::pointer
, std::iterator_traits<Iter>::reference

Member functions

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

Member objects

Member name Definition
current (protected) the underlying iterator of which base() returns a copy

Non-member functions

operator<= compares the underlying iterators
operator> (function template)
operator+ advances the iterator
(function template)
operator- computes the distance between two iterator adaptors
(function template)
iter_move casts the result of dereferencing the adjusted underlying
(C++20) iterator to its associated rvalue reference type
iter_swap swaps the objects pointed to by two adjusted underlying
(C++20) iterators
(function template)
make_reverse_iterator creates a std::reverse_iterator of type inferred from the
(C++14) argument
(function template)

Helper templates

template< class Iterator1, class Iterator2 >

requires (!std::sized_sentinel_for<Iterator1, Iterator2>)
inline constexpr bool disable_sized_sentinel_for< (since C++20)

std::reverse_iterator<Iterator2>> = true;

This partial specialization of std::disable_sized_sentinel_for prevents
specializations of reverse_iterator from satisfying sized_sentinel_for if their
underlying iterators do not satisfy the concept.

Possible implementation

Below is a partial implementation focusing on the way the inner iterator is saved,
calling prev only when the content is fetched via operator*.

template<typename Itr>
class reverse_iterator {
Itr itr;
constexpr explicit reverse_iterator(Itr itr): itr(itr) {}
constexpr auto& operator*() {
return *std::prev(itr); // <== returns the content of prev
constexpr auto& operator++() {
return *this;
constexpr friend bool operator!=(reverse_iterator<Itr> a, reverse_iterator<Itr> b) {
return a.itr != b.itr;


std::reverse_iterator does not work with iterators whose dereference returns a
reference to a member of *this (so-called "stashing iterators").


// Run this code

#include <iostream>
#include <iterator>

template<typename T, size_t SIZE>
class Stack {
T arr[SIZE];
size_t pos = 0;
T pop() {
return arr[--pos];
Stack& push(const T& t) {
arr[pos++] = t;
return *this;
// we wish that looping on Stack would be in LIFO order
// thus we use std::reverse_iterator as an adaptor to existing iterators
// (which are in this case the simple pointers: [arr, arr+pos)
auto begin() {
return std::reverse_iterator(arr + pos);
auto end() {
return std::reverse_iterator(arr);

int main() {
Stack<int, 8> s;
for(int val: s) {
std::cout << val << ' ';


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See also

make_reverse_iterator creates a std::reverse_iterator of type inferred from the
(C++14) argument
(function template)
iterator base class to ease the definition of required types for simple
(deprecated in C++17) iterators
(class template)