std::ranges::crbegin

Since C++20

Header: <ranges>

const std::remove_reference_t& if the argument is an lvalue (i.e. T is an lvalue reference type),

# Declarations

inline namespace /* unspecified */ {
inline constexpr /* unspecified */ crbegin = /* unspecified */;
}

(since C++20) (customization point object)

Call signature

template< class T >
requires /* see below */
constexpr /* see below */ auto crbegin( T&& t );

(since C++20)

# Example

#include <cassert>
#include <iterator>
#include <span>
#include <vector>
 
int main()
{
    std::vector<int> v{3, 1, 4};
    auto vi = std::ranges::crbegin(v);
    assert(*vi == 4);
    ++vi; // OK, iterator object is mutable
    assert(*vi == 1);
    // *vi = 13; // Error: underlying element is read-only
 
    int a[]{-5, 10, 15};
    auto ai = std::ranges::crbegin(a);
    assert(*ai == 15);
 
    // auto x_x = std::ranges::crbegin(std::vector<int>{6, 6, 6});
    // ill-formed: the argument is an rvalue (see Notes ↑)
 
    auto si = std::ranges::crbegin(std::span{a}); // OK
    assert(*si == 15);
    static_assert
    (
        std::ranges::enable_borrowed_range<std::remove_cv_t<decltype(std::span{a})>>
    );
}

# See also