std::ranges::views::cartesian_product, std::ranges::cartesian_product_view - cppreference.com

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Defined in header `<ranges>`
template< ranges::input_range First, ranges::forward_range... Vs > requires (ranges::view<First> && ... && ranges::view<Vs>) class cartesian_product_view : public ranges::view_interface<cartesian_product_view<First, Vs...>>	(1)	(since C++23)
namespace views { inline constexpr /unspecified/ cartesian_product = /unspecified/; }	(2)	(since C++23)
Call signature
template< ranges::viewable_range... Rs > requires /* see below */ constexpr ranges::view auto cartesian_product( Rs&&... rs );		(since C++23)
Helper concepts
template< bool Const, class First, class... Vs > concept /cartesian-product-is-random-access/ = (ranges::random_access_range</maybe-const/<Const, First>> && ... && (ranges::random_access_range</maybe-const/<Const, Vs>> && ranges::sized_range</maybe-const/<Const, Vs>>));	(3)	(exposition only*)
template< class R > concept /cartesian-product-common-arg/ = ranges::common_range<R> \|\| (ranges::sized_range<R> && ranges::random_access_range<R>);	(4)	(exposition only*)
template< bool Const, class First, class... Vs > concept /cartesian-product-is-bidirectional/ = (ranges::bidirectional_range</maybe-const/<Const, First>> && ... && (ranges::bidirectional_range</maybe-const/<Const, Vs>> && /cartesian-product-common-arg/</maybe-const/<Const, Vs>>));	(5)	(exposition only*)
template< class First, class... Vs > concept /cartesian-product-is-common/ = /cartesian-product-common-arg/<First>;	(6)	(exposition only*)
template< class... Vs > concept /cartesian-product-is-sized/ = (ranges::sized_range<Vs> && ...);	(7)	(exposition only*)
template< bool Const, template<class> class FirstSent, class First, class... Vs > concept /cartesian-is-sized-sentinel/ = (std::sized_sentinel_for<FirstSent</maybe-const/<Const, First>>, ranges::iterator_t</maybe-const/<Const, First>>> && ... && (ranges::sized_range</maybe-const/<Const, Vs>> && std::sized_sentinel_for<ranges::iterator_t< /maybe-const/<Const, Vs>>, ranges::iterator_t</maybe-const/<Const, Vs>>>));	(8)	(exposition only*)
Helper function templates
template< /cartesian-product-common-arg/ R > constexpr auto /cartesian-common-arg-end/( R& r ) { if constexpr (ranges::common_range<R>) return ranges::end(r); else return ranges::begin(r) + ranges::distance(r); }	(9)	(exposition only*)

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...).

4) Determines if cartesian_product is a common range (see also

common_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.

Customization point objects

The name views::cartesian_product denotes a customization point object, which is a const function object of a literal semiregular class type. See CustomizationPointObject for details.

Data members

Member	Description
`std::tuple<First, Vs...>` `base_` (private)	an object that holds all adapted `view` objects (exposition-only member object*)

Member functions

(constructor)	constructs a `cartesian_product_view` (public member function) [edit]
begin	returns an iterator to the beginning (public member function) [edit]
end	returns an iterator or a sentinel to the end (public member function) [edit]
size	returns the number of elements, provided only if the underlying (adapted) range satisfies `sized_range` (public member function) [edit]
Inherited from ranges::view_interface
empty	returns whether the derived view is empty, provided only if it satisfies `sized_range` or `forward_range` (public member function of `std::ranges::view_interface<D>`) [edit]
cbegin (C++23)	returns a constant iterator to the beginning of the range (public member function of `std::ranges::view_interface<D>`) [edit]
cend (C++23)	returns a sentinel for the constant iterator of the range (public member function of `std::ranges::view_interface<D>`) [edit]
operator bool	returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of `std::ranges::view_interface<D>`) [edit]
front	returns the first element in the derived view, provided if it satisfies `forward_range` (public member function of `std::ranges::view_interface<D>`) [edit]
back	returns the last element in the derived view, provided only if it satisfies `bidirectional_range` and `common_range` (public member function of `std::ranges::view_interface<D>`) [edit]
operator[]	returns the `n`^th element in the derived view, provided only if it satisfies `random_access_range` (public member function of `std::ranges::view_interface<D>`) [edit]

Deduction guides

Nested classes

the iterator type
(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

#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 14882:2024):

26.7.31 Cartesian product view [range.stride]