std::ranges::slide_view<V>:: size

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

#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
}

3

See also