std::ranges::views::cartesian_product, std::ranges::cartesian_product_view

 

C++

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Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

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Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (C++26)(C++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators std::generator (C++23)

Range adaptor closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::cartesian_product_view

Member functions

cartesian_product_view::cartesian_product_view

cartesian_product_view::begin

cartesian_product_view::end

cartesian_product_view::size

Deduction guides

Iterator

Member functions

cartesian_product_view::iterator::iterator

cartesian_product_view::iterator::operator*

cartesian_product_view::iterator::operator[]

cartesian_product_view::iterator::operator++ cartesian_product_view::iterator::operator++(int) cartesian_product_view::iterator::operator-- cartesian_product_view::iterator::operator--(int) cartesian_product_view::iterator::operator+= cartesian_product_view::iterator::operator-=

cartesian_product_view::iterator::next

cartesian_product_view::iterator::prev

cartesian_product_view::iterator::distance_from

Non-member functions

operator==(cartesian_product_view::iterator) operator<=>(cartesian_product_view::iterator)

operator+(cartesian_product_view::iterator) operator-(cartesian_product_view::iterator)

iter_move(cartesian_product_view::iterator)

iter_swap(cartesian_product_view::iterator)

 

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:

• 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. 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.

Data members

Member	Definition
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)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
size	returns the number of elements. Provided only if the underlying (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 sized_range or forward_range. (public member function of std::ranges::view_interface<D>)
cbegin (C++23)	returns a constant iterator to the beginning of the range. (public member function of std::ranges::view_interface<D>)
cend (C++23)	returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D>)
operator bool	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>)
front	returns the first element in the derived view. Provided if it 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 bidirectional_range and common_range. (public member function of std::ranges::view_interface<D>)
operator[]	returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>)

Nested classes

iterator

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

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 14882:2024):

• 26.7.31 Cartesian product view [range.stride]

See also

ranges::zip_viewviews::zip (C++23)

a view consisting of tuples of references to corresponding elements of the adapted views (class template) (customization point object)