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std::ranges::adjacent_view<V,N>::size

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_ be the underlying view. Equivalent to:

using SizeType = decltype(ranges::size(base_));
using CommonType = ranges::common_type_t<SizeType, std::size_t>;
auto size = static_cast<CommonType>(ranges::size(base_));
size -= std::min<CommonType>(size, N - 1);
return static_cast<SizeType>(size);

Parameters

(none).

Return value

The number of elements, may be ​0​ if ranges::size(base_) is less than N.

Example

A link to test: Compiler Explorer/g++-13.

#include <ranges>
 
int main()
{
    constexpr static auto v = {1, 2, 3, 4, 5, 6};
 
    constexpr int width1 {4};
    constexpr auto view1 {std::views::adjacent<width1>(v)};
    static_assert(view1.size() == 3);
    static_assert(view1.size() == (v.size() - width1 + 1));
 
    constexpr int width2 {8};
    constexpr auto view2 {std::views::adjacent<width2>(v)};
    // window is too wide, so view2 has no elements:
    static_assert(view2.size() == 0);
}

See also

(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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