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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...).

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:

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

Member functions

constructs a cartesian_product_view
(public member function) [edit]
returns an iterator to the beginning
(public member function) [edit]
returns an iterator or a sentinel to the end
(public member function) [edit]
returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range
(public member function) [edit]
Inherited from ranges::view_interface
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]

(C++23)

 returns a constant iterator to the beginning of the range
(public member function of std::ranges::view_interface<D>) [edit]

(C++23)

 returns a sentinel for the constant iterator of the range
(public member function of std::ranges::view_interface<D>) [edit]
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]
returns the first element in the derived view, provided if it satisfies forward_range
(public member function of std::ranges::view_interface<D>) [edit]
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]
returns the nth 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]

See also