# 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) Equivalent to
auto check = [](auto& rng) { return __begin_or_first_end(rng); };
return iterator<__is_const>(/*tuple-transform*/(check, bases_));,
where:

- __is_const is true for the const-qualified overload, and false otherwise.
- __is_empty is true if the expression ranges::empty (rng) is true for any rng among the underlying ranges except the first one and false otherwise.
- __begin_or_first_end(rng) is 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.

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

Run this code

    #include <array>
    #include <format>
    #include <iostream>
    #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::cout << std::format("{}{}{}{}{}",
                                 std::get<0>(last),
                                 std::get<1>(last),
                                 std::get<2>(last),
                                 std::get<3>(last), '\n');
    }

Output:

    long

### See also

begin | 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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