std::ranges::cartesian_product_view<First, Vs...>::size

 

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std::ranges::cartesian_product_view

Member functions

cartesian_product_view::cartesian_product_view (C++23)

cartesian_product_view::begin (C++23)

cartesian_product_view::end (C++23)

cartesian_product_view::size (C++23)

Deduction guides

Iterator

Member functions

cartesian_product_view::iterator::iterator (C++23)

cartesian_product_view::iterator::operator* (C++23)

cartesian_product_view::iterator::operator[] (C++23)

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-= (C++23)(C++23)(C++23)(C++23)(C++23)(C++23)

cartesian_product_view::iterator::next (C++23)

cartesian_product_view::iterator::prev (C++23)

cartesian_product_view::iterator::distance_from (C++23)

Non-member functions

operator==(cartesian_product_view::iterator) operator<=>(cartesian_product_view::iterator) (C++23)(C++23)

operator+(cartesian_product_view::iterator) operator-(cartesian_product_view::iterator) (C++23)(C++23)

iter_move(cartesian_product_view::iterator) (C++23)

iter_swap(cartesian_product_view::iterator) (C++23)

 

constexpr /* see description */ size()     requires __cartesian_product_is_sized<First, Vs...>;	(1)	(since C++23)
constexpr /* see description */ size() const     requires __cartesian_product_is_sized<const First, const Vs...>;	(2)	(since C++23)

Returns the number of elements. The return type is an implementation-defined unsigned-integer-like type U.

Let bases_ be the underlying tuple of views, and prod be the product of the sizes of all the ranges in bases_.

1-2) Returns prod. The behavior is undefined if prod cannot be represented by the return type U.

Equivalent to:

return [&]<std::size_t... Is>(std::index_sequence<Is...>)
{
    auto prod = static_cast<U>(1);
    prod = (static_cast<U>(ranges::size(std::get<Is>(bases_))) * ...);
    return prod;
}
(std::make_index_sequence<1U + sizeof...(Vs)>{});

Parameters

(none)

Return value

The number of elements, that is, the product of the sizes of all the underlying ranges.

Notes

The return type is the smallest unsigned-integer-like type that is sufficiently wide to store the product of the maximum sizes of all the underlying ranges, if such a type exists.

Example

Can be checked online with Compiler Explorer.

Run this code

#include <ranges>
 
int main()
{
    constexpr static auto w = { 1 };
    constexpr static auto x = { 2, 3 };
    constexpr static auto y = { 4, 5, 6 };
    constexpr static auto z = { 7, 8, 9, 10, 11, 12, 13 };
    constexpr auto v = std::ranges::cartesian_product_view(w, x, y, z);
    static_assert(v.size() == w.size() * x.size() * y.size() * z.size() and v.size() == 42);
}

See also

ranges::size (C++20)	returns an integer equal to the size of a range (customization point object)
ranges::ssize (C++20)	returns a signed integer equal to the size of a range (customization point object)