# std::ranges::cartesian_product_view<First, Vs...>::end

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< cpp‎ | ranges‎ | cartesian product view

constexpr iterator<false> end() requires ((!__simple_view<First> || ... || !__simple_view<Vs>) && __cartesian_product_is_common<First, Vs...>); | (1) | (since C++23)
constexpr iterator<true> end() const requires __cartesian_product_is_common<const First, const Vs...>; | (2) | (since C++23)
constexpr std::default_sentinel_t end() const noexcept; | (3) | (since C++23)

Returns an iterator or a sentinel representing the end of the `cartesian_product_view`.

Let `bases_` be the underlying tuple of views.

1-2) Let:

- __is_const be true for the const-qualified overload, and false otherwise;
- __is_empty be true if the expression ranges::empty(rng) is true for any rng among the underlying ranges except the first one and false otherwise; and
- __begin_or_first_end(rng) be expression-equivalent to __is_empty ? ranges::begin(rng) : __cartesian_common_arg_end(rng) if rng is the first underlying range and ranges::begin(rng) otherwise.

Equivalent to:

    auto check = [](auto& rng) { return __begin_or_first_end(rng); };
    return iterator<__is_const>(__tuple_transform(check, bases_));

3) Equivalent to: return std::default_sentinel;.

### Parameters

(none)

### Return value

An iterator to the element following the last element, or a sentinel which compares equal to the end iterator.

### Example

Can be checked online with Compiler Explorer.

Run this code

    #include <array>
    #include <print>
    #include <ranges>
    #include <string_view>
    #include <tuple>
    using namespace std::literals;

    int main()
    {
        constexpr auto a = std::array{ "bool"sv, "goto"sv, "extern"sv, "long"sv };      /*
                                           ^         ^           ^         ^            */
        constexpr auto v = std::ranges::cartesian_product_view(a[0], a[1], a[2], a[3]);

        constexpr std::tuple<char const&,
                             char const&,
                             char const&,
                             char const&> last { *(v.end() - 1) };

        std::println("{}{}{}{}",
                     std::get<0>(last),
                     std::get<1>(last),
                     std::get<2>(last),
                     std::get<3>(last));
    }

Output:

    long

### See also

begin (C++23) | returns an iterator to the beginning (public member function)
ranges::end (C++20) | returns a sentinel indicating the end of a range (customization point object)

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