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

💖 NAME 💖

std::ranges::enumerate_view::size - std::ranges::enumerate_view::size (yes bestie, the name is the name twice, iconic behavior).

Okay so this is the std::ranges...e_view::size(3) page from the C++ Standard Libary manual. We’re talking about the size() member of std::ranges::enumerate_view, and it is giving “how many elements are in this view?” energy. Periodt. 💅

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✨ Synopsis ✨

Two overloads, both constexpr, both since C++23. Vibe check passed:

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

(1) (since C++23)

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

(2) (since C++23)

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🎀 Parameters 🎀

(none) — literally none, zero, the void. No arguments, no stress. 🫶

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🌸 Return value 🌸

The number of elements. That’s it, that’s the tea. ☕✨

Under the hood it’s equivalent to return ranges::size(base_);, where base_ is the underlying view. Slay. 💅

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🦋 Example 🦋

The page literally says // Run this code, so run it, bestie:

        #include <cassert>
        #include <forward_list>
        #include <ranges>
        #include <string_view>

        int main()
        {
            constexpr static auto v1 = {1, 2, 3, 4, 5};
            constexpr auto ev1{v1 | std::views::enumerate};
            static_assert(ev1.size() == 5);
            static_assert(std::ranges::sized_range<decltype(v1)>);

            auto v2 = std::forward_list{1, 2, 3, 4, 5};
            auto ev2 {v2 | std::views::enumerate};
            static_assert(not std::ranges::sized_range<decltype(v2)>);
            // auto size = ev2.size(); // Error: v2 is not a sized range
            assert(std::ranges::distance(v2) == 5); // OK, distance does not
       require sized
                                                    // range, but has O(N)
       complexity here
        }

Not me pointing at the commented-out line: // auto size = ev2.size(); // Error: v2 is not a sized range — yeah, that one is an error on purpose, because v2 is not a sized range. The assert line is fine because distance does not require sized range, but it has O(N) complexity here. No cap. 😭

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💅 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)

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That’s the whole page, bestie! Source/version: http://cppreference.com; date: 2024.06.10; page: std::ranges...e_view::size(3). Mwah 💋✨