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

NAME
     std::ranges::enumerate_view::size - std::ranges::enumerate_view::size

Synopsis
	constexpr  auto  size() requires ranges::sized_range<V>;	     (1)
     (since C++23)
	constexpr auto size() const requires ranges::sized_range<const	V>;  (2)
     (since C++23)

	Returns    the	  number    of	  elements.    Equivalent    to   return
     ranges::size(base_);, where
	base_ is the underlying view.

Parameters
	(none)

Return value
	The number of elements.

Example
     // Run this code

      #include <cassert>
      #include <forward_list>
      #include <ranges>
      #include <string_view>

      int main()
      {
	  constexpr static auto v1 = {1, 2, 3, 4, 5};
	  constexpr auto ev1{v1 | std::views::enumerate};
	  static_assert(ev1.size() == 5);
	  static_assert(std::ranges::sized_range<decltype(v1)>);

	  auto v2 = std::forward_list{1, 2, 3, 4, 5};
	  auto ev2 {v2 | std::views::enumerate};
	  static_assert(not std::ranges::sized_range<decltype(v2)>);
	  // auto size = ev2.size(); // Error: v2 is not a sized range
	  assert(std::ranges::distance(v2) == 5); // OK, distance does	not  re-
     quire sized
						  //  range,  but  has O(N) com-
     plexity here
      }

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...e_view::size(3)
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