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std::span<T,Extent>::rend, std::span<T,Extent>::crend - cppreference.com

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constexpr reverse_iterator rend() const noexcept;

 (1) (since C++20)

constexpr const_reverse_iterator crend() const noexcept;

 (2) (since C++23)

Returns a reverse iterator to the element following the last element of the reversed span. It corresponds to the element preceding the first element of the non-reversed span. This element acts as a placeholder, attempting to access it results in undefined behavior.

Return value

Reverse iterator to the element following the last element.

Complexity

Constant.

Example

#include <algorithm>
#include <iostream>
#include <span>
#include <string_view>

void ascending(const std::span<const std::string_view> data,
               const std::string_view term)
{
    std::for_each(data.begin(), data.end(),
        [](const std::string_view x) { std::cout << x << ' '; });
    std::cout << term;
}

void descending(const std::span<const std::string_view> data,
                const std::string_view term)
{
    std::for_each(data.rbegin(), data.rend(),
        [](const std::string_view x) { std::cout << x << ' '; });
    std::cout << term;
}

int main()
{
    constexpr std::string_view bars[]{"▁","▂","▃","▄","▅","▆","▇","█"};
    ascending(bars, " ");
    descending(bars, "\n");
}

Output: 

▁ ▂ ▃ ▄ ▅ ▆ ▇ █  █ ▇ ▆ ▅ ▄ ▃ ▂ ▁

See also

returns a reverse iterator to the beginning
(public member function) [edit]
returns a reverse end iterator for a container or array
(function template) [edit]