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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
       declared, which
	  makes	specializations	be aggregate classes, and  propagate  trivial-
       ity,
	  potentially-throwing-ness, and constexpr-ness	of corresponding oper-
       ations 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
       permutation of a
	  (C++20)		   range of elements
				   (niebloid)
	  ranges::prev_permutation generates the  next	smaller	 lexicographic
       permutation 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 mem-
       bers 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:  "	<< re-
       sult.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
       possibly	different
	  (C++11) types
		  (class template)

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

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