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)