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

🌸 NAME 🌸

hey bestie, welcome to the C++ Standard Libary manual (yes, the header spells it that way, iykyk), section (3) — this page is std::ranges::slide_view::size, and the NAME line is literally:

std::ranges::slide_view::size - std::ranges::slide_view::size

periodt. 💅

🦋 Synopsis 🦋

okay so there are two size() overloads, both since C++23:

constexpr auto size()                     (since C++23)
  requires ranges::sized_range<V>;
constexpr auto size() const               (since C++23)
  requires ranges::sized_range<const V>;

Returns the number of elements. ✨

Let base_ and n_ be the underlying view and "window size" respectively. (Exact names, no cap.)

Equivalent to:

auto sz = ranges::distance(base_) - n_ + 1;
if (sz < 0)
    sz = 0;
return __to_unsigned_like(sz);

🎀 Parameters 🎀

(none) — literally no parameters, bestie. Zero. Nada. 🫶

💖 Return value 💖

The number of elements. Equals to 0, if the number of elements (ranges::size(base_)) in underlying view base_ is less than "window size" n_. That's the whole vibe. 🌈

🧚 Example 🧚

// Run this code — go off:

#include <forward_list>
#include <iostream>
#include <list>
#include <ranges>

int main()
{
    constexpr static auto v = {1, 2, 3, 4, 5, 6};

    constexpr int width1{4};
    constexpr auto view1{std::views::slide(v, width1)};
    static_assert(view1.size() == 3);
    static_assert(view1.size() == (v.size() - width1 + 1));

    constexpr int width2{8};
    constexpr auto view2{std::views::slide(v, width2)};
    // window is too wide, so view2 has no elements:
    static_assert(view2.size() == 0);

    std::forward_list forward_list = v;
    const auto view3{std::views::slide(forward_list, width1)};
//  auto x = view3.size(); // error: sized_range constraint is not satisfied

    std::list list = v;
    const auto view4{std::views::slide(list, width1)};
    std::cout << view4.size() << '\n'; // prints 3
}

⭐ Output ⭐

3

🌈 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)

mwah 💋 — source/version: http://cppreference.com, dated 2024.06.10. slay and read the docs, bestie! 🎀👑