std::reverse_iterator<Iter>::operator[]

 

C++

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Feature test macros (C++20)

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Iterators library

Ranges library (C++20)

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Symbols index

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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_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)
Algorithm concepts and utilities
Indirect callable concepts
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)   indirect_unary_predicate (C++20)	indirect_binary_predicate (C++20) indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20) indirectly_copyable_storable (C++20)	indirectly_swappable (C++20) indirectly_comparable (C++20) permutable (C++20) mergeable (C++20) sortable (C++20)
Utilities
indirect_result_t (C++20)	projected (C++20)
Iterator adaptors
reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) 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) make_const_iterator (C++23) make_const_sentinel (C++23) 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)

make_reverse_iterator (C++14)

 

/*unspecified*/ operator[]( difference_type n ) const;		(until C++17)
constexpr /*unspecified*/ operator[]( difference_type n ) const;		(since C++17)

Returns a reference to the element at specified relative location.

Parameters

n

-

position relative to current location.

Return value

A reference to the element at relative location, that is, base()[-n-1].

Example

Run this code

#include <array>
#include <cstddef>
#include <iostream>
#include <iterator>
#include <list>
#include <vector>
 
int main()
{
    {
        int a[]{0, 1, 2, 3};
        std::reverse_iterator<int*> iter{std::rbegin(a)};
        for (std::size_t i{}; i != std::size(a); ++i)
            std::cout << iter[i] << ' '; // decltype(iter[i]) is `int&`
        std::cout << '\n';
    }
    {
        std::vector v{0, 1, 2, 3};
        std::reverse_iterator<std::vector<int>::iterator> iter{std::rbegin(v)};
        for (std::size_t i{}; i != std::size(v); ++i)
            std::cout << iter[i] << ' '; // decltype(iter[i]) is `int&`
        std::cout << '\n';
    }
    {
        // constexpr context
        constexpr static std::array<int, 4> z{0, 1, 2, 3};
        constexpr std::reverse_iterator<decltype(z)::const_iterator> it{std::crbegin(z)};
        static_assert(it[1] == 2);
    }
    {
        std::list li{0, 1, 2, 3};
        std::reverse_iterator<std::list<int>::iterator> iter{std::rbegin(li)};
        *iter = 42; // OK
    //  iter[0] = 13; // compilation error ~ the underlying iterator
                      // does not model the random access iterator
    }
}

Output:

3 2 1 0
3 2 1 0

See also

operator*operator->

accesses the pointed-to element (public member function)