NAME¶

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

Synopsis¶

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.

Equivalent to:

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

Parameters¶

(none)

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_.

Example¶

// Run this code

#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)