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

NAME
     std::ranges::max_element - std::ranges::max_element

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

		  std::indirect_strict_weak_order<std::projected<I,  Proj>> Comp
     (1) (since
	=			      ranges::less			       >
     C++20)
	constexpr I

	    max_element( I first, S last, Comp comp = {}, Proj proj = {} );
	template< ranges::forward_range R, class Proj = std::identity,

		  std::indirect_strict_weak_order<
		      std::projected<ranges::iterator_t<R>,    Proj>>	Comp   =
     (2) (since
	ranges::less							       >
     C++20)
	constexpr ranges::borrowed_iterator_t<R>

	    max_element( R&& r, Comp comp = {}, Proj proj = {} );

	1) Finds the greatest element in the range [first, last).
	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 pair denoting the range to examine
	r	    - the range to examine
	comp	    - comparison to apply to the projected elements
	proj	    - projection to apply to the elements

Return value
	Iterator  to the greatest element in the range [first, last). If several
     elements in
	the range are equivalent to the greatest element, returns  the	iterator
     to the first
	such  element.	Returns  last  if  the	range is empty (i.e. if first ==
     last).

Complexity
	Exactly max(N - 1, 0) comparisons,  where  N  =  ranges::distance(first,
     last).

Possible implementation
     struct max_element_fn {
	 template<std::forward_iterator  I, std::sentinel_for<I> S, class Proj =
     std::identity,
		  std::indirect_strict_weak_order<std::projected<I, Proj>>  Comp
     = ranges::less>
	 constexpr I operator()(I first, S last, Comp comp = {}, Proj proj = {})
     const
	 {
	     if (first == last)
		 return last;

	     auto largest = first;
	     while (++first != last)
		 if  (std::invoke(comp,  std::invoke(proj,  *largest),	std::in-
     voke(proj, *first)))
		     largest = first;
	     return largest;
	 }

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

     inline constexpr max_element_fn max_element;

Example
     // Run this code

      #include <algorithm>
      #include <cmath>
      #include <iostream>

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

	  const auto v = {3, 1, -14, 1, 5, 9, -14, 9};

	  auto result = ranges::max_element(v.begin(), v.end());
	  std::cout << "Max element at pos " << ranges::distance(v.begin(),  re-
     sult) << '\n';

	  auto	 abs_compare   =  [](int  a,  int  b)  {  return  std::abs(a)  <
     std::abs(b); };
	  result = ranges::max_element(v, abs_compare);
	  std::cout << "Absolute max element at pos "
		    << ranges::distance(v.begin(), result) << '\n';
      }

Output:
      Max element at pos 5
      Absolute max element at pos 2

See also
	ranges::min_element    returns the smallest element in a range
	(C++20) 	       (niebloid)
	ranges::minmax_element returns the smallest and the largest elements  in
     a range
	(C++20) 	       (niebloid)
	ranges::max	       returns the greater of the given values
	(C++20) 	       (niebloid)
	max_element	       returns the largest element in a range
			       (function template)

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