std::ranges::views::cartesian_product,std::ranges::cartesian_product_view(3)

NAME
std::ranges::views::cartesian_product,std::ranges::cartesian_product_view - std::ranges::views::cartesian_product,std::ranges::cartesian_product_view

Synopsis
   Defined in header <ranges>
   template< ranges::input_range First, ranges::forward_range... Vs
   >
       requires (ranges::view<First> && ... && ranges::view<Vs>) (1) (since C++23)
   class cartesian_product_view
       : public ranges::view_interface<cartesian_product_view<First,
   Vs...>>
   namespace views {
       inline constexpr /*unspecified*/ cartesian_product = (2) (since C++23)
   /*unspecified*/;
   }
   Call signature
   template< ranges::viewable_range... Rs >
       requires /* see below */ (since C++23)
   constexpr auto cartesian_product( Rs&&... rs );
   Helper concepts
   template< bool Const, class First, class... Vs >
   concept __cartesian_product_is_random_access =
       (ranges::random_access_range<__maybe_const<Const, First>> && (3) (exposition
   ... && only*)
           (ranges::random_access_range<__maybe_const<Const, Vs>> &&
               ranges::sized_range<__maybe_const<Const, Vs>>));
   template< class R >
   concept __cartesian_product_common_arg = (exposition
       ranges::common_range<R> || (4) only*)
           (ranges::sized_range<R> &&
   ranges::random_access_range<R>);
   template< bool Const, class First, class... Vs >
   concept __cartesian_product_is_bidirectional =
       (ranges::bidirectional_range<__maybe_const<Const, First>> && (exposition
   ... && (5) only*)
           (ranges::bidirectional_range<__maybe_const<Const, Vs>> &&
               __cartesian_product_common_arg<__maybe_const<Const,
   Vs>>));
   template< class First, class... Vs >
                        (exposition
   concept __cartesian_product_is_common = (6) only*)
       __cartesian_product_common_arg<First>;
   template< class... Vs >
                        (exposition
   concept __cartesian_product_is_sized = (7) only*)
       (ranges::sized_range<Vs> && ...);
   template< bool Const, template<class> class FirstSent, class
   First, class... Vs >
   concept __cartesian_is_sized_sentinel =
       (ranges::sized_sentinel_for<FirstSent<__maybe_const<Const,
   First>>,
           ranges::iterator_t<__maybe_const<Const, First>>> && ... (8) (exposition
   && only*)
               (ranges::sized_range<__maybe_const<Const, Vs>> &&
   ranges::sized_sentinel_for<iterator_t<__maybe_const<Const, Vs>>,
                       ranges::iterator_t<__maybe_const<Const,
   Vs>>>));
   Helper function templates
   template< __cartesian_product_common_arg R >
   constexpr auto __cartesian_common_arg_end( R& r ) {
       if constexpr (ranges::common_range<R>) (exposition
           return ranges::end(r); (9) only*)
       else
           return ranges::begin(r) + ranges::distance(r);
   }
   1) cartesian_product_view is a range adaptor that takes n views, where n > 0, and
   produces a view of tuples calculated by the n-ary cartesian product of the provided
   ranges. The size of produced view is a multiple of sizes of provided ranges, while
   each element is a tuple (of references) of the size n.
   2) views::cartesian_product is a customization point object.
     * When calling with no argument, views::cartesian_product() is
       expression-equivalent to views::single(std::tuple()).
     * Otherwise, views::cartesian_product(rs...) is expression-equivalent to
       ranges::cartesian_product_view<views::all_t<decltype((rs))>...>(rs...).
   3) Determines if cartesian_product is a random access range (see also
   random_access_range).
   4) Determines if cartesian_product is a common range (see also common_range).
   5) Determines if cartesian_product is a bidirectional range (see also
   bidirectional_range).
   6) Determines if cartesian_product satisfies the helper concept
   __cartesian_product_is_common (see also common_range).
   7) Determines if cartesian_product is a sized range (see also sized_range).
   8) Determines if cartesian_product uses sized sentinel.
   9) Returns the end of the produced view. Participates in overload resolution only if
   cartesian_product satisfies the helper concept __cartesian_product_common_arg.
   The First range passed to cartesian_product_view is treated specially, since it is
   only passed through a single time. As a result, several constrains are relaxed on
   it:
     * First is an input_range instead of forward_range;
     * First does not have to be a sized_range in order for the cartesian_product_view
       to be random_access_range or common_range;
     * First does not have to be common_range in order for the cartesian_product_view
       to be bidirectional_range.

Member functions
   constructor constructs a cartesian_product_view
   (C++23) (public member function)
   begin returns an iterator to the beginning
   (C++23) (public member function)
   end returns an iterator or a sentinel to the end
   (C++23) (public member function)
   size returns the number of elements. Provided only if the underlying
   (C++23) (adapted) range satisfies sized_range.
                 (public member function)
         Inherited from std::ranges::view_interface
   empty returns whether the derived view is empty. Provided if it satisfies
   (C++20) sized_range or forward_range.
                 (public member function of std::ranges::view_interface<D>)
   cbegin returns a constant iterator to the beginning of the range.
   (C++23) (public member function of std::ranges::view_interface<D>)
   cend returns a sentinel for the constant iterator of the range.
   (C++23) (public member function of std::ranges::view_interface<D>)
   operator bool returns whether the derived view is not empty. Provided if
   (C++20) ranges::empty is applicable to it.
                 (public member function of std::ranges::view_interface<D>)
   front returns the first element in the derived view. Provided if it
   (C++20) satisfies forward_range.
                 (public member function of std::ranges::view_interface<D>)
   back returns the last element in the derived view. Provided if it satisfies
   (C++20) bidirectional_range and common_range.
                 (public member function of std::ranges::view_interface<D>)
   operator[] returns the n^th element in the derived view. Provided if it satisfies
   (C++20) random_access_range.
                 (public member function of std::ranges::view_interface<D>)
   Deduction guides
   Nested classes
   iterator the iterator type
   (C++23) (exposition-only member class template*)

Notes
           Feature-test macro Value Std Feature
   __cpp_lib_ranges_cartesian_product 202207L (C++23) std::ranges::cartesian_product_view

Example
// Run this code
 #include <array>
 #include <iostream>
 #include <list>
 #include <ranges>
 #include <string>
 #include <vector>
 void print(std::tuple<char const&, int const&, std::string const&> t, int pos)
 {
     const auto& [a, b, c] = t;
     std::cout << '(' << a << ' ' << b << ' ' << c << ')' << (pos % 4 ? " " : "\n");
 }
 int main()
 {
     const auto x = std::array{'A', 'B'};
     const auto y = std::vector{1, 2, 3};
     const auto z = std::list<std::string>{"α", "β", "γ", "δ"};
     for (int i{1}; auto const& tuple : std::views::cartesian_product(x, y, z))
         print(tuple, i++);
 }

Output:
 (A 1 α) (A 1 β) (A 1 γ) (A 1 δ)
 (A 2 α) (A 2 β) (A 2 γ) (A 2 δ)
 (A 3 α) (A 3 β) (A 3 γ) (A 3 δ)
 (B 1 α) (B 1 β) (B 1 γ) (B 1 δ)
 (B 2 α) (B 2 β) (B 2 γ) (B 2 δ)
 (B 3 α) (B 3 β) (B 3 γ) (B 3 δ)

References
     * C++23 standard (ISO/IEC 14882:2023):
     * 26.7.31 Cartesian product view [range.stride]

See also
   ranges::zip_view a view consisting of tuples of references to corresponding elements
   views::zip of the adapted views
   (C++23) (class template) (customization point object)