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 auto cartesian_product( Rs&&... rs );
| (since C++23) | |
| Helper concepts | ||
template< bool Const, class First, class... Vs >
concept __cartesian_product_is_random_access = // exposition only
(ranges::random_access_range<__maybe_const<Const, First>> && ... &&
(ranges::random_access_range<__maybe_const<Const, Vs>> &&
ranges::sized_range<__maybe_const<Const, Vs>>));
| (3) | (since C++23) |
template< class R >
concept __cartesian_product_common_arg = // exposition only
ranges::common_range<R> ||
(ranges::sized_range<R> && ranges::random_access_range<R>);
| (4) | (since C++23) |
template< bool Const, class First, class... Vs >
concept __cartesian_product_is_bidirectional = // exposition only
(ranges::bidirectional_range<__maybe_const<Const, First>> && ... &&
(ranges::bidirectional_range<__maybe_const<Const, Vs>> &&
__cartesian_product_common_arg<__maybe_const<Const, Vs>>));
| (5) | (since C++23) |
template< class First, class... Vs >
concept __cartesian_product_is_common = // exposition only
__cartesian_product_common_arg<First>;
| (6) | (since C++23) |
template< class... Vs >
concept __cartesian_product_is_sized = // exposition only
(ranges::sized_range<Vs> && ...);
| (7) | (since C++23) |
template< bool Const, template<class> class FirstSent, class First, class... Vs >
concept __cartesian_is_sized_sentinel = // exposition only
(ranges::sized_sentinel_for<FirstSent<__maybe_const<Const, First>>,
ranges::iterator_t<__maybe_const<Const, First>>> && ... &&
(ranges::sized_range<__maybe_const<Const, Vs>> &&
ranges::sized_sentinel_for<iterator_t<__maybe_const<Const, Vs>>,
ranges::iterator_t<__maybe_const<Const, Vs>>>));
| (8) | (since C++23) |
| Helper function templates | ||
template< __cartesian_product_common_arg R >
constexpr auto __cartesian_common_arg_end( R& r ) { // exposition only
if constexpr (ranges::common_range<R>)
return ranges::end(r);
else
return ranges::begin(r) + ranges::distance(r);
}
| (9) | (since C++23) |
| Helper alias templates | ||
template< class... Ts >
using __tuple_or_pair = /* see description */; // exposition only
| (10) | (since C++23) |
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.views::cartesian_product is a customization point object. views::cartesian_product() is expression-equivalent to views::single(std::tuple()). views::cartesian_product(rs...) is expression-equivalent to ranges::cartesian_product_view<views::all_t<decltype((rs))>...>(rs...).cartesian_product satisfies the helper concept __cartesian_product_is_common (see also common_range).cartesian_product uses sized sentinel.view. Participates in overload resolution only if cartesian_product satisfies the helper concept __cartesian_product_common_arg.Ts be some pack of types, then __tuple_or_pair<Ts...> denotes: std::pair<Ts...>, if sizeof...(Ts) is 2, std::tuple<Ts...> otherwise.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. The name views::cartesian_product denotes a customization point object, which is a const function object of a literal semiregular class type. For exposition purposes, the cv-unqualified version of its type is denoted as __cartesian_product_fn.
All instances of __cartesian_product_fn are equal. The effects of invoking different instances of type __cartesian_product_fn on the same arguments are equivalent, regardless of whether the expression denoting the instance is an lvalue or rvalue, and is const-qualified or not (however, a volatile-qualified instance is not required to be invocable). Thus, views::cartesian_product can be copied freely and its copies can be used interchangeably.
Given a set of types Args..., if std::declval<Args>()... meet the requirements for arguments to views::cartesian_product above, __cartesian_product_fn models
.
std::invocable<__cartesian_product_fn, Args...>, std::invocable<const __cartesian_product_fn, Args...>, std::invocable<__cartesian_product_fn&, Args...>, and std::invocable<const __cartesian_product_fn&, Args...>.Otherwise, no function call operator of __cartesian_product_fn participates in overload resolution.
Typical implementations of cartesian_product_view hold only one non-static data member (shown here as base_ for exposition only) of type std::tuple<First, Vs...> that holds all adapted view objects.
|
(C++23) | constructs a cartesian_product_view (public member function) |
|
(C++23) | returns an iterator to the beginning (public member function) |
|
(C++23) | returns an iterator or a sentinel to the end (public member function) |
|
(C++23) | returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range. (public member function) |
Inherited from |
|
|
(C++20) | returns whether the derived view is empty. Provided if it satisfies sized_range or forward_range. (public member function of std::ranges::view_interface<D>) |
|
(C++23) | returns a constant iterator to the beginning of the range. (public member function of std::ranges::view_interface<D>) |
|
(C++23) | returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns whether the derived view is not empty. Provided if ranges::empty is applicable to it. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range. (public member function of std::ranges::view_interface<D>) |
|
(C++20) | returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>) |
|
(C++23) | the iterator type (exposition-only member class template) |
| Feature-test macro | Value | Std | Comment |
|---|---|---|---|
__cpp_lib_ranges_cartesian_product | 202207L | (C++23) |
std::ranges::cartesian_product_view |
Can be checked online with Compiler Explorer.
#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)
|
(C++23) | a view consisting of tuples of references to corresponding elements of the adapted views (class template) (customization point object) |
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