std::reverse_iterator

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (deprecated in C++17)	incrementable_traits (C++20) indirectly_readable_traits (C++20) iter_value_titer_difference_titer_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++20)(C++20)
Iterator adaptors
reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) back_inserter front_inserter inserter
Stream iterators
istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
Iterator customization points
ranges::iter_move (C++20)
ranges::iter_swap (C++20)
Iterator operations
advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
Range access
begincbegin (C++11)(C++14) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

std::reverse_iterator

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>=operator<=> (C++20)

operator+

operator-

iter_move (C++20)

iter_swap (C++20)

 

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)

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

Member types iterator_category, value_type, difference_type, pointer and reference 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 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>=operator<=> (C++20)	compares the underlying iterators (function template)
operator+	advances the iterator (function template)
operator-	computes the distance between two iterator adaptors (function template)
iter_move (C++20)	casts the result of dereferencing the adjusted underlying iterator to its associated rvalue reference type (function template)
iter_swap (C++20)	swap the objects pointer by two adjusted underlying iterators (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

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

See also

iterator (deprecated in C++17)

base class to ease the definition of required types for simple iterators (class template)