home | help 
std::ranges...tor_closure(3)   C++ Standard Libary  std::ranges...tor_closure(3)

NAME
     std::ranges::range_adaptor_closure - std::ranges::range_adaptor_closure

Synopsis
	Defined in header <ranges>
	template< class D >

	    requires	    std::is_object_v<D>        &&	 std::same_as<D,
     (since C++23)
	std::remove_cv_t<D>>

	class range_adaptor_closure {};

	std::ranges::range_adaptor_closure is a helper class template for defin-
     ing a
	RangeAdaptorClosureObject.

	Let t be the object of type T, the implementation ensures that	t  is  a
     range adaptor
	closure object if all the requirements are met:

	  * t is a unary function object that takes one range argument.
	  *  T	has  exactly  one  public  base class ranges::range_adaptor_clo-
     sure<T>, and T has
	    no base classes of	type  ranges::range_adaptor_closure<U>	for  any
     other type U.
	  * T does not satisfy range.

Example
     // Run this code

      #include <ranges>
      #include <string_view>

      // Define Slice as a range adaptor closure
      struct Slice : std::ranges::range_adaptor_closure<Slice>
      {
	  std::size_t start = 0;
	  std::size_t end = std::string_view::npos;

	  constexpr std::string_view operator()(std::string_view sv) const
	  {
	      return sv.substr(start, end - start);
	  }
      };

      int main()
      {
	  constexpr std::string_view str = "01234567";

	  constexpr Slice slicer{.start = 1, .end = 6};

	  constexpr  auto  sv1 = slicer(str); // use slicer as a normal function
     object
	  constexpr auto sv2 = str | slicer; // use slicer as  a  range  adaptor
     closure object
	  static_assert(sv1 == "12345");
	  static_assert(sv2 == "12345");

	  // range adaptor closures can be composed
	  constexpr auto slice_and_drop
	      = slicer
	      | std::views::drop_while([](char ch) { return ch != '3'; });
	  static_assert(std::string_view(str | slice_and_drop) == "345");
      }

http://cppreference.com 	   2024.06.10	    std::ranges...tor_closure(3)
home | help