constexpr auto size() requires ranges::sized_range<V>; | (since C++23) | |
constexpr auto size() const requires ranges::sized_range<const V>; | (since C++23) |
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);(none).
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_.
A link to test: Compiler Explorer.
#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
|
(C++20) | returns an integer equal to the size of a range (customization point object) |
|
(C++20) | returns a signed integer equal to the size of a range (customization point object) |
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