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std::ranges..._view::size(3)   C++ Standard Libary  std::ranges..._view::size(3)

NAME
     std::ranges::adjacent_view::size - std::ranges::adjacent_view::size

Synopsis
	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
     // Run this code

      #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
	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)

http://cppreference.com 	   2024.06.10	    std::ranges..._view::size(3)
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