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std::ranges::rend

From cppreference.com
< cpp‎ | ranges
 
C++
 
Ranges library
Range adaptors
 
Defined in header <ranges>
Defined in header <iterator>
inline namespace /* unspecified */ {

    inline constexpr /* unspecified */ rend = /* unspecified */;

}
 (since C++20)
(customization point object)
Call signature
template< class T >

    requires /* see below */
constexpr std::sentinel_for<

    decltype(ranges::rbegin(std::declval<T>()))> auto rend( T&& t );
 (since C++20)

Returns a sentinel indicating the end of a reversed range.

range-rbegin-rend.svg

If T is an array type and std::remove_all_extents_t<std::remove_reference_t<T>> is incomplete, then the call to ranges::rend 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::rend is expression-equivalent to:

  1. decay-copy(t.rend())(until C++23)auto(t.rend())(since C++23), if that expression is valid and its type models std::sentinel_for<decltype(ranges::rbegin(std::declval<T>()))>.
  2. Otherwise, decay-copy(rend(t))(until C++23)auto(rend(t))(since C++23), if T is a class or enumeration type, that expression is valid and its type models std::sentinel_for<decltype(ranges::rbegin(std::declval<T>()))>, where the meaning of rend is established as if by performing argument-dependent lookup only.
  3. Otherwise, std::make_reverse_iterator(ranges::begin(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::rend is ill-formed, which can result in substitution failure when ranges::rend(t) appears in the immediate context of a template instantiation.

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