constexpr iterator<false> begin()
requires (!__simple_view<First> || ... || !__simple_view<Vs>);
| (1) | (since C++23) |
constexpr iterator<true> begin() const
requires (ranges::range<const First> && ... && ranges::range<const Vs>);
| (2) | (since C++23) |
Returns an iterator to the first element of the cartesian_product_view.
Let bases_ be the tuple of underlying views.
return /*iterator*/<false>(__tuple_transform(ranges::begin, bases_));.return /*iterator*/<true>(__tuple_transform(ranges::begin, bases_));.(none).
Iterator to the first element.
Can be checked online with Compiler Explorer.
#include <array>
#include <print>
#include <ranges>
#include <string_view>
#include <tuple>
using namespace std::literals;
int main()
{
constexpr auto a = std::array{ "Curiously"sv, "Recurring"sv, "Template"sv, "Pattern"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&> first { *v.begin() };
std::println("{}{}{}{}",
std::get<0>(first),
std::get<1>(first),
std::get<2>(first),
std::get<3>(first));
}Output:
CRTP
|
(C++23) | returns an iterator or a sentinel to the end (public member function) |
|
(C++20) | returns an iterator to the beginning of a range (customization point object) |
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https://en.cppreference.com/w/cpp/ranges/cartesian_product_view/begin