std::reverse_iterator<Iter>::operator[]

#include <array>
#include <cstddef>
#include <iostream>
#include <iterator>
#include <list>
#include <vector>
 
int main()
{
    {
        int a[]{0, 1, 2, 3};
        std::reverse_iterator<int*> iter{std::rbegin(a)};
        for (std::size_t i{}; i != std::size(a); ++i)
            std::cout << iter[i] << ' '; // decltype(iter[i]) is `int&`
        std::cout << '\n';
    }
    {
        std::vector v{0, 1, 2, 3};
        std::reverse_iterator<std::vector<int>::iterator> iter{std::rbegin(v)};
        for (std::size_t i{}; i != std::size(v); ++i)
            std::cout << iter[i] << ' '; // decltype(iter[i]) is `int&`
        std::cout << '\n';
    }
    {
        // constexpr context
        constexpr static std::array<int, 4> z{0, 1, 2, 3};
        constexpr std::reverse_iterator<decltype(z)::const_iterator> it{std::crbegin(z)};
        static_assert(it[1] == 2);
    }
    {
        std::list li{0, 1, 2, 3};
        std::reverse_iterator<std::list<int>::iterator> iter{std::rbegin(li)};
        *iter = 42; // OK
    //  iter[0] = 13; // compilation error ~ the underlying iterator
                      // does not model the random access iterator
    }
}