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

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C++
Ranges library
Range adaptors
(C++23) (C++23)
(C++23)
(C++23) (C++23)
(C++23)
(C++23) (C++23)
(C++23) (C++23)
(C++23) (C++23)
(C++23) (C++23)
cartesian_product_view views::cartesian_product
(C++23) (C++23)

std::ranges::cartesian_product_view
Member functions
Deduction guides
Iterator
Member functions
Non-member functions
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 view s , 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.
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. 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

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

constructs a cartesian_product_view
(public member function)
returns an iterator to the beginning
(public member function)
returns an iterator or a sentinel to the end
(public member function)
returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range .
(public member function)
Inherited from std::ranges::view_interface
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> )
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> )
returns the first element in the derived view. Provided if it satisfies forward_range .
(public member function of std::ranges::view_interface<D> )
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> )
returns the n th element in the derived view. Provided if it satisfies random_access_range .
(public member function of std::ranges::view_interface<D> )

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

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

(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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