std::ranges::rbegin

 

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Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted to_input_viewviews::to_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators std::generator (C++23)

Range adaptor closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

Defined in header <ranges>
Defined in header <iterator>
inlinenamespace/* unspecified */{     inlineconstexpr/* unspecified */ rbegin =/* unspecified */; }		(since C++20) (customization point object)
Call signature
template<class T >     requires /* see below */ constexprstd::input_or_output_iteratorauto rbegin( T&& t );		(since C++20)

Returns an iterator to the last element of the argument.

If T is an array type and std::remove_all_extents_t<std::remove_reference_t<T>> is incomplete, then the call to ranges::rbegin is ill-formed, no diagnostic required.

If the argument is an lvalue or ranges::enable_borrowed_range<std::remove_cv_t<T>> is true, then a call to ranges::rbegin is expression-equivalent to:

1. decay-copy(t.rbegin())(until C++23)auto(t.rbegin())(since C++23), if that expression is valid and its type models std::input_or_output_iterator.
2. Otherwise, decay-copy(rbegin(t))(until C++23)auto(rbegin(t))(since C++23), if T is a class or enumeration type, that expression is valid and its type models std::input_or_output_iterator, where the meaning of rbegin is established as if by performing argument-dependent lookup only.
3. Otherwise, std::make_reverse_iterator(ranges::end(t)) if both ranges::begin(t) and ranges::end(t) are valid expressions, have the same type, and that type models std::bidirectional_iterator.

In all other cases, a call to ranges::rbegin is ill-formed, which can result in substitution failure when ranges::rbegin(t) appears in the immediate context of a template instantiation.

Customization point objects

The name ranges::rbegin denotes a customization point object, which is a const function object of a literalsemiregular class type. See CustomizationPointObject for details.

Notes

If the argument is an rvalue (i.e. T is an object type) and ranges::enable_borrowed_range<std::remove_cv_t<T>> is false, the call to ranges::rbegin is ill-formed, which also results in substitution failure.

The return type models std::input_or_output_iterator in all cases.

The C++20 standard requires that if the underlying rbegin function call returns a prvalue, the return value is move-constructed from the materialized temporary object. All implementations directly return the prvalue instead. The requirement is corrected by the post-C++20 proposal P0849R8 to match the implementations.

Example

Run this code

#include <iostream>#include <ranges>#include <span>#include <vector>   int main(){std::vector<int> v ={3, 1, 4};auto vi = std::ranges::rbegin(v);std::cout<<*vi <<'\n';*vi =42;// OK   int a[]={-5, 10, 15};auto ai = std::ranges::rbegin(a);std::cout<<*ai <<'\n';*ai =42;// OK   // auto x_x = std::ranges::rbegin(std::vector{6, 6, 6});// ill-formed: the argument is an rvalue (see Notes ↑)   auto si = std::ranges::rbegin(std::span{a});// OK static_assert(std::ranges::enable_borrowed_range<std::remove_cv_t<decltype(std::span{a})>>);*si =42;// OK}

Output:

4 15

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P2602R2	C++20	there's machinery to prohibit certain non-member rbegin found by ADL	removed such machinery

See also

ranges::crbegin (C++20)	returns a reverse iterator to a read-only range (customization point object)
rbegincrbegin (C++14)	returns a reverse iterator to the beginning of a container or array (function template)