std::ranges...t_view::size(3)

std::ranges::cartesian_product_view::size(3) 🎀

okay bestie, this is the glow-up of the C++ Standard Libary manual page for std::ranges::cartesian_product_view::size — section (3), no cap. It's the size() member of cartesian_product_view, and yes we're keeping every little detail. 💅

💖 NAME

• std::ranges::cartesian_product_view::size — literally std::ranges::cartesian_product_view::size. That's the whole name, bestie. ✨

✨ Synopsis

Here's the signature slate, copied exactly — including the (1) and (2) tags and the requires clauses. Don't come for me about the line breaks, they're part of the original vibe:

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

okay so what does it do? It 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. Like, actually undefined, bestie — do not go there in production 😭.

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) — no parameters. Zero. Nada. The function takes nothing, and honestly? iconic. 🎀

🦋 Return value

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

💜 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. That's the whole note, bestie. 🫶

🔥 Example

Run this code, it's cute:

       // 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 — returns an integer equal to the size of a range. (C++20) (customization point object) ✨
• ranges::ssize — returns a signed integer equal to the size of a range. (C++20) (customization point object) 💅

okay bye bestie, hope this ate 💅 — source/version: http://cppreference.com · date: 2024.06.10 · footer page label: std::ranges...t_view::size(3) 🎀