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

okay bestie, this is the std::ranges..._view::size(3) page from the C++ Standard Library 💅 and we’re gonna make drop_view::size make sense, fr fr.

💖 NAME 💖

std::ranges::drop_view::size — std::ranges::drop_view::size

Like… it tells you how many elements are left after the drop. iconic behavior.

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✨ 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 you got two overloads, both constexpr, both since C++20:

• (1) — constexpr auto size() requires ranges::sized_range<V>;
• (2) — constexpr auto size() const requires ranges::sized_range<const V>;

They return the number of elements. That’s the whole vibe 🎀

Let base_ be the underlying view, and let count_ be the stored count — usually the number passed to the constructor, or 0 if *this is default constructed. It’s equivalent to:

const auto s = ranges::size(base_);
const auto c = static_cast<decltype(s)>(count_);
return s < c ? 0 : s - c;

The way that little s < c ? 0 : s - c handles the “drop more than we have” situation? lowkey elegant 💀✨

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🫶 Parameters 🫶

(none) — no parameters, bestie. Not a single one. 🫶

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🎀 Return value 🎀

The number of elements. That’s it. That’s the return value. 🌸

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🧚 Example 🧚

// Run this code

#include <array>
#include <ranges>

int main()
{
    constexpr std::array a{42, 43, 44};
    static_assert(std::ranges::drop_view{std::views::all(a), 0}.size() == 3);
    static_assert(std::ranges::drop_view{std::views::all(a), 1}.size() == 2);
    static_assert(std::ranges::drop_view{std::views::all(a), 2}.size() == 1);
    static_assert(std::ranges::drop_view{std::views::all(a), 3}.size() == 0);
    static_assert(std::ranges::drop_view{std::views::all(a), 4}.size() == 0);
}

Not the static_asserts proving every drop count from 0 to 4? Obsessed. The 4 case still gives 0, not negative, because the ternary said “bestie, no” 😭💅

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🌈 See also 🌈

• ranges::size — returns an integer equal to the size of a range; it’s a customization point object since C++20.
• ranges::ssize — returns a signed integer equal to the size of a range; it’s also a customization point object since C++20.

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source: http://cppreference.com 🫶 dated 2024.06.10 ✨ periodt, go count your elements 💜