std::ranges::views::all, std::ranges::views::all_t

inline constexpr /* unspecified */ all = /* unspecified */;

template< ranges::viewable_range R >
using all_t = decltype(views::all(std::declval<R>()));

#include <iostream>
#include <ranges>
#include <type_traits>
#include <vector>
 
int main()
{
    std::vector<int> v{0, 1, 2, 3, 4, 5};
    for (int n : std::views::all(v) | std::views::take(2))
        std::cout << n << ' ';
    std::cout << '\n';
 
    static_assert(std::is_same<
        decltype(std::views::single(42)),
        std::ranges::single_view<int>
        >{});
 
    static_assert(std::is_same<
        decltype(std::views::all(v)),
        std::ranges::ref_view<std::vector<int, std::allocator<int>>>
        >{});
 
    int a[]{1, 2, 3, 4};
    static_assert(std::is_same<
        decltype(std::views::all(a)),
        std::ranges::ref_view<int[4]>
        >{});
 
    static_assert(std::is_same<
        decltype(std::ranges::subrange{std::begin(a) + 1, std::end(a) - 1}),
        std::ranges::subrange<int*, int*, std::ranges::subrange_kind(1)>
        >{});
}