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std::is_heap_until(3)	       C++ Standard Libary	   std::is_heap_until(3)

NAME
     std::is_heap_until - std::is_heap_until

Synopsis
	Defined in header <algorithm>
	template<  class  RandomIt  >				     (1)  (since
     C++11)
	RandomIt is_heap_until( RandomIt first, RandomIt last );      (constexpr
     since C++20)
	template< class ExecutionPolicy, class RandomIt >

	RandomIt  is_heap_until(  ExecutionPolicy&&  policy,	     (2)  (since
     C++17)

				RandomIt first, RandomIt last );
	template< class  RandomIt,  class  Compare  >			  (since
     C++11)
	RandomIt  is_heap_until( RandomIt first, RandomIt last,   (3) (constexpr
     since C++20)
	Compare comp );
	template< class ExecutionPolicy, class RandomIt, class
	Compare >

	RandomIt  is_heap_until(  ExecutionPolicy&&  policy,	     (4)  (since
     C++17)

				RandomIt first, RandomIt last,
	Compare comp );

	Examines  the  range [first, last) and finds the largest range beginning
     at first
	which is a heap.

	1) The heap property to be checked is with respect to
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3) The heap property to be checked is with respect to comp.
	2,4) Same as (1,3), but executed according to policy.
	These overloads participate in overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

Parameters
	first, last -  the range of elements to examine
	policy	    -  the execution policy to use. See execution policy for de-
     tails.
		       comparison function object (i.e. an object that satisfies
     the
		       requirements of Compare) which returns true if the  first
     argument is
		       less than the second.

		       The signature of the comparison function should be equiv-
     alent to the
		       following:

		       bool cmp(const Type1& a, const Type2& b);
	comp	    -
		       While  the  signature  does  not need to have const&, the
     function must
		       not modify the objects passed to it and must be	able  to
     accept all
		       values  of  type (possibly const) Type1 and Type2 regard-
     less of value
		       category (thus, Type1& is not allowed
		       , nor is Type1 unless for Type1 a move is equivalent to a
     copy
		       (since C++11)).
		       The types Type1 and Type2 must be such that an object  of
     type
		       RandomIt  can  be  dereferenced	and then implicitly con-
     verted to both of
		       them.

Type requirements
	-
	RandomIt must meet the requirements of LegacyRandomAccessIterator.
	-
	Compare must meet the requirements of Compare.

Return value
	The last iterator it for which range [first, it) is a heap.

Complexity
	Given \(\scriptsize N\)N as std::distance(first, last):

	1,2) \(\scriptsize O(N)\)O(N) comparisons using
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3,4) \(\scriptsize O(N)\)O(N) applications of  the  comparison	function
     comp.

Exceptions
	The overloads with a template parameter named ExecutionPolicy report er-
     rors as
	follows:

	  *  If  execution of a function invoked as part of the algorithm throws
     an exception
	    and ExecutionPolicy is one of the standard policies,  std::terminate
     is called.
	    For  any  other  ExecutionPolicy, the behavior is implementation-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Example
     // Run this code

      #include <algorithm>
      #include <iostream>
      #include <vector>

      int main()
      {
	  std::vector<int> v{3, 1, 4, 1, 5, 9};

	  std::make_heap(v.begin(), v.end());

	  // probably mess up the heap
	  v.push_back(2);
	  v.push_back(6);

	  auto heap_end = std::is_heap_until(v.begin(), v.end());

	  std::cout << "all of v:  ";
	  for (const auto& i : v)
	      std::cout << i << ' ';
	  std::cout << '\n';

	  std::cout << "only heap: ";
	  for (auto i = v.begin(); i != heap_end; ++i)
	      std::cout << *i << ' ';
	  std::cout << '\n';
      }

Output:
      all of v:  9 5 4 1 1 3 2 6
      only heap: 9 5 4 1 1 3 2

See also
	is_heap 	      checks if the given range is a max heap
	(C++11) 	      (function template)
	make_heap	      creates a max heap out of a range of elements
			      (function template)
	push_heap	      adds an element to a max heap
			      (function template)
	pop_heap	      removes the largest element from a max heap
			      (function template)
			      turns a max heap into a range of	elements  sorted
     in ascending
	sort_heap	      order
			      (function template)
	ranges::is_heap_until finds the largest subrange that is a max heap
	(C++20) 	      (niebloid)

http://cppreference.com 	   2024.06.10		   std::is_heap_until(3)
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