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

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Ranges library
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(C++23)
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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)>{});

Contents

[edit] Parameters

(none)

[edit] Return value

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

[edit] 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.

[edit] Example

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);
}

[edit] See also

returns an integer equal to the size of a range
(customization point object) [edit]
returns a signed integer equal to the size of a range
(customization point object) [edit]