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std::ranges::upper_bound(3)    C++ Standard Libary   std::ranges::upper_bound(3)

NAME
     std::ranges::upper_bound - std::ranges::upper_bound

Synopsis
	Defined in header <algorithm>
	Call signature
	template< std::forward_iterator I, std::sentinel_for<I> S,

		  class       T,      class	 Proj	   =	  std::identity,
     (since
		  std::indirect_strict_weak_order
     C++20)
		      <const	T*,    std::projected<I,    Proj>>    Comp     =
     (until
	ranges::less							       >
     C++26)
	constexpr I upper_bound( I first, S last, const T& value,

				 Comp comp = {}, Proj proj = {} );
	template< std::forward_iterator I, std::sentinel_for<I> S,

		  class Proj = std::identity,
		  class T = std::projected_value_t<I, Proj>,
		  std::indirect_strict_weak_order
     (since
		      <const	T*,    std::projected<I,    Proj>>    Comp     =
     C++26)
	ranges::less >
	constexpr I upper_bound( I first, S last, const T& value,

				 Comp comp = {}, Proj proj = {} );
	template< ranges::forward_range R,

		  class T, class Proj = std::identity,
		  std::indirect_strict_weak_order		     (1)
		      <const						     T*,
     (since
	std::projected<ranges::iterator_t<R>,
     C++20)
						Proj>>		Comp	       =
     (until
	ranges::less							       >
     C++26)
	constexpr ranges::borrowed_iterator_t<R>

	    upper_bound( R&& r, const T& value, Comp comp = {}, Proj
	proj = {} );
	template< ranges::forward_range R,				 (2)

		  class Proj = std::identity,
		  class T =
	std::projected_value_t<ranges::iterator_t<R>, Proj>,
		  std::indirect_strict_weak_order
		      <const						     T*,
     (since
	std::projected<ranges::iterator_t<R>,
     C++26)
						Proj>> Comp =
	ranges::less >
	constexpr ranges::borrowed_iterator_t<R>

	    upper_bound( R&& r, const T& value, Comp comp = {}, Proj
	proj = {} );

	1)  Returns  an  iterator  pointing  to  the  first element in the range
     [first, last) that
	is greater than value, or last if no such element is  found.  The  range
     [first, last)
	must  be partitioned with respect to the expression or !comp(value, ele-
     ment), i.e.,
	all elements for which the expression is true must precede all	elements
     for which
	the expression is false. A fully-sorted range meets this criterion.
	2)  Same as (1), but uses r as the source range, as if using ranges::be-
     gin(r) as
	first and ranges::end(r) as last.

	The function-like entities described on this page  are	niebloids,  that
     is:

	  *  Explicit  template  argument lists cannot be specified when calling
     any of them.
	  * None of them are visible to argument-dependent lookup.
	  * When any of them are found by normal unqualified lookup as the  name
     to the left
	    of	the  function-call operator, argument-dependent lookup is inhib-
     ited.

	In practice, they may be implemented as function objects, or  with  spe-
     cial compiler
	extensions.

Parameters
	first,	last - iterator-sentinel defining the partially-ordered range to
     examine
	r	    - the partially-ordered range to examine
	value	    - value to compare the elements to
	pred	    - predicate to apply to the projected elements
	proj	    - projection to apply to the elements

Return value
	Iterator pointing to the first element that is greater	than  value,  or
     last if no
	such element is found.

Complexity
	The  number  of comparisons and applications of the projection performed
     are
	logarithmic in the distance between first and last (at most log
	2(last - first) + O(1) comparisons and applications of the  projection).
     However, for
	an  iterator  that  does not model random_access_iterator, the number of
     iterator
	increments is linear.

Possible implementation
	struct upper_bound_fn
	{
	    template<std::forward_iterator I, std::sentinel_for<I> S,
		     class  Proj  =   std::identity,   class   T   =   std::pro-
     jected_value_t<I, Proj>,
		     std::indirect_strict_weak_order
			 <const    T*,	  std::projected<I,    Proj>>	Comp   =
     ranges::less>
	    constexpr I operator()(I first, S last, const T& value,
				   Comp comp = {}, Proj proj = {}) const
	    {
		I it;
		std::iter_difference_t<I> count, step;
		count = ranges::distance(first, last);

		while (count > 0)
		{
		    it = first;
		    step = count / 2;
		    ranges::advance(it, step, last);
		    if (!comp(value, std::invoke(proj, *it)))
		    {
			first = ++it;
			count -= step + 1;
		    }
		    else
			count = step;
		}
		return first;
	    }

	    template<ranges::forward_range R, class Proj = std::identity,
		     class  T  =   std::projected_value_t<ranges::iterator_t<R>,
     Proj>,
		     std::indirect_strict_weak_order
			 <const T*, std::projected<ranges::iterator_t<R>,
						   Proj>> Comp = ranges::less>
	    constexpr ranges::borrowed_iterator_t<R>
		operator()(R&&	r,  const  T& value, Comp comp = {}, Proj proj =
     {}) const
	    {
		return (*this)(ranges::begin(r), ranges::end(r), value,
			       std::ref(comp), std::ref(proj));
	    }
	};

	inline constexpr upper_bound_fn upper_bound;

Notes
		  Feature-test macro	       Value	Std		 Feature
	__cpp_lib_algorithm_default_value_type 202403  (C++26)	List-initializa-
     tion for
							      algorithms (1,2)

Example
     // Run this code

      #include <algorithm>
      #include <cassert>
      #include <complex>
      #include <iostream>
      #include <iterator>
      #include <vector>

      int main()
      {
	  namespace ranges = std::ranges;

	  std::vector<int> data{1, 1, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 6};

	  {
	      auto lower = ranges::lower_bound(data.begin(), data.end(), 4);
	      auto upper = ranges::upper_bound(data.begin(), data.end(), 4);

	      ranges::copy(lower, upper, std::ostream_iterator<int>(std::cout, "
     "));
	      std::cout << '\n';
	  }
	  {
	      auto lower = ranges::lower_bound(data, 3);
	      auto upper = ranges::upper_bound(data, 3);

	      ranges::copy(lower, upper, std::ostream_iterator<int>(std::cout, "
     "));
	      std::cout << '\n';
	  }

	  using CD = std::complex<double>;
	  std::vector<CD> nums{{1, 0}, {2, 2}, {2, 1}, {3, 0}, {3, 1}};
	  auto cmpz = [](CD x, CD y) { return x.real() < y.real(); };
	  #ifdef __cpp_lib_algorithm_default_value_type
	      auto it = ranges::upper_bound(nums, {2, 0}, cmpz);
	  #else
	      auto it = ranges::upper_bound(nums, CD{2, 0}, cmpz);
	  #endif
	  assert((*it == CD{3, 0}));
      }

Output:
      4 4 4
      3 3 3 3

See also
	ranges::equal_range returns range of elements matching a specific key
	(C++20) 	    (niebloid)
	ranges::lower_bound  returns  an  iterator to the first element not less
     than the given
	(C++20) 	    value
			    (niebloid)
	ranges::partition   divides a range of elements into two groups
	(C++20) 	    (niebloid)
			    returns an iterator to  the  first	element  greater
     than a certain
	upper_bound	    value
			    (function template)

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