26 Ranges library [ranges]

26.3 Range access [range.access]

26.3.8 ranges::crbegin [range.access.crbegin]

The name ranges::crbegin denotes a customization point object ([customization.point.object]).

Given a subexpression E with type T, let t be an lvalue that denotes the reified object for E.

Then:

(1.1)
If E is an rvalue and enable_borrowed_range<remove_cv_t<T>> is false, ranges::crbegin(E) is ill-formed.
(1.2)
Otherwise, let U be ranges::rbegin(possibly-const-range(t)).

ranges::crbegin(E) is expression-equivalent to const_iterator<decltype(U)>(U).

[Note 1:

Whenever ranges::crbegin(E) is a valid expression, its type models input_or_output_iterator and constant-iterator.

— end note]