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

✨ std::ranges::common_view::size ✨

okay so real talk, this is a page from the C++ Standard Library manpage set, and it's all about std::ranges::common_view::size — literally the member function that tells you how many things are in there. it's giving "just count the elements" but make it constexpr. 💅

---

🌸 NAME 🌸

std::ranges::common_view::size — yes bestie, it's std::ranges::common_view::size. that's the whole name. we love a self-explanatory icon. 👑

---

🎀 Synopsis 🎀

constexpr auto size() requires ranges::sized_range<V>;

(1) (since C++20)

constexpr auto size() const requires ranges::sized_range<const V>;

(2) (since C++20)

so there's two overloads, and both are constexpr (yes, compile-time slay 🫶). notice the requires clauses — overload (1) only shows up if V is a ranges::sized_range, and overload (2) only shows up if const V is a ranges::sized_range. no sized range? no size(). the vibe check is in the constraints, fr fr.

it returns the number of elements. that's it. that's the function. ✨

it's equivalent to return ranges::size(base_);, where base_ is the underlying view. so it's not doing any secret extra math, it's just forwarding to ranges::size on the base. no cap. 💀

---

🦋 Parameters 🦋

• (none) — nothing to pass in, bestie. it takes zero arguments. the way that's the easiest function signature ever. 😌

---

🌈 Return value 🌈

the number of elements. that's the tea. that's the whole return value. 🍓

---

💖 Example 💖

// Run this code

#include <ranges>
#include <string_view>

int main()
{
    constexpr static auto v1 = {1, 2, 3, 4, 5};
    constexpr auto common1 { v1 | std::views::common };
    static_assert(common1.size() == 5);

    constexpr auto take3 { v1 | std::views::reverse | std::views::take(3) };
    constexpr auto common2 { take3 | std::views::common };
    static_assert(common2.size() == 3);

    using namespace std::literals;
    constexpr static auto v2 = { "∧"sv, "∨"sv, "∃"sv, "∀"sv };
    static_assert(std::ranges::views::common(v2).size() == 4);
}

like, look at those static_asserts — everything's checked at compile time and the counts are 5, 3, and 4. iconic behavior honestly. 🔥 the last one uses the logical symbols "∧"sv, "∨"sv, "∃"sv, "∀"sv and yes it still counts to 4, because size is size no matter how cute your elements are. 👑

---

🌟 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)

so if you want the unsigned-ish crowd you hit up ranges::size, and if you want a signed integer you go hang with ranges::ssize. both customization point objects, both C++20, both absolute legends. 🧚

---

later bestie!! this page came from http://cppreference.com and it's dated 2024.06.10 — go read more manpages, ily, periodt 💜🦋