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std::ranges...ound_result(3)   C++ Standard Libary  std::ranges...ound_result(3)

NAME
     std::ranges::in_found_result - std::ranges::in_found_result

Synopsis
	Defined in header <algorithm>
	template< class I >	       (since C++20)
	struct in_found_result;

	ranges::in_found_result is a class template that provides a way to store
     an iterator
	and a boolean flag as a single unit.

	This  class  template has no base classes or declared members other than
     those shown
	below. Thus it is suitable for use with structured bindings.

	All special member functions of this class template are  implicitly  de-
     clared, which
	makes specializations be aggregate classes, and propagate triviality,
	potentially-throwing-ness,  and  constexpr-ness  of corresponding opera-
     tions on data
	members.

Template parameters
	I - the type of the iterator that the ranges::in_found_result stores.

	Data members

	Member name Definition
		    a value (that is supposed to be an iterator) of type  I.  It
     is declared
	in	    with [[no_unique_address]] attribute.
		    (public member object)
		    a  boolean	flag (that may show whether an appropriate range
     can be found)
	found	    of type bool.
		    (public member object)

Member functions
     std::ranges::in_found_result::operator in_found_result<I2>

	template<class I2>

	requires std::convertible_to<const I&, I2>	  (1)

	constexpr operator in_found_result<I2>() const &;
	template<class I2>

	requires std::convertible_to<I, I2>		  (2)

	constexpr operator in_found_result<I2>() &&;

	Converts *this to the result by constructing every data  member  of  the
     result from
	the corresponding member of *this.

	1) Equivalent to return {in, found};.
	2) Equivalent to return {std::move(in), found};.

Standard library
	The  following standard library functions use ranges::in_found_result as
     the return
	type:

	      Algorithm functions
	ranges::next_permutation generates the next greater lexicographic permu-
     tation of a
	(C++20) 		 range of elements
				 (niebloid)
	ranges::prev_permutation generates the next smaller lexicographic permu-
     tation of a
	(C++20) 		 range of elements
				 (niebloid)

Synopsis
      namespace std::ranges
      {
	  template<class I>
	  struct in_found_result
	  {
	      [[no_unique_address]] I in;
	      bool found;

	      template<class I2>
	      requires std::convertible_to<const I&, I2>
	      constexpr operator in_found_result<I2>() const &
	      {
		  return {in, found};
	      }

	      template<class I2>
	      requires std::convertible_to<I, I2>
	      constexpr operator in_found_result<I2>() &&
	      {
		  return {std::move(in), found};
	      }
	  };
      }

Notes
	Each standard library algorithm that uses this family  of  return  types
     declares a new
	alias type, e.g. using merge_result = in_in_out_result<I1, I2, O>;.

	The  names for such aliases are formed by adding the suffix "_result" to
     the
	algorithm's name. So, the return type of std::ranges::merge can be named
     as
	std::ranges::merge_result.

	Unlike std::pair and std::tuple, this class template has data members of
     meaningful
	names.

Example
     // Run this code

      #include <algorithm>
      #include <iostream>
      #include <iterator>
      #include <ranges>

      int main()
      {
	  int v[] {1, 2, 3};

	  const auto result = std::ranges::next_permutation(v);

	  std::ranges::for_each(std::cbegin(v), result.in, [](int e)  {std::cout
     << e << ' ';});

	  std::cout  <<  std::boolalpha << "\n" "result.found: " << result.found
     << '\n';
      }

Output:
      1 3 2
      result.found = true

See also
	pair	implements binary tuple, i.e. a pair of values
		(class template)
	tuple	implements fixed size container, which holds elements of  possi-
     bly different
	(C++11) types
		(class template)

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