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_.
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)>{});(none).
The number of elements, that is, the product of the sizes of all the underlying ranges.
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.
Can be checked online with Compiler Explorer.
#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);
}|
(C++20) | returns an integer equal to the size of a range (customization point object) |
|
(C++20) | returns a signed integer equal to the size of a range (customization point object) |
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