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

NAME
     std::includes - std::includes

Synopsis
	Defined in header <algorithm>
	template< class InputIt1, class InputIt2 >

	bool  includes( InputIt1 first1, InputIt1 last1,	  (1) (constexpr
     since C++20)

		       InputIt2 first2, InputIt2 last2 );
	template< class ExecutionPolicy,

		  class ForwardIt1, class ForwardIt2 >
	bool  includes(  ExecutionPolicy&&  policy,		     (2)  (since
     C++17)
		       ForwardIt1 first1, ForwardIt1 last1,

		       ForwardIt2 first2, ForwardIt2 last2 );
	template< class InputIt1, class InputIt2, class Compare
	>

	bool  includes( InputIt1 first1, InputIt1 last1,	  (3) (constexpr
     since C++20)

		       InputIt2 first2, InputIt2 last2, Compare
	comp );
	template< class ExecutionPolicy,

		  class ForwardIt1, class ForwardIt2, class
	Compare >
	bool  includes(  ExecutionPolicy&&  policy,		     (4)  (since
     C++17)
		       ForwardIt1 first1, ForwardIt1 last1,

		       ForwardIt2 first2, ForwardIt2 last2,
	Compare comp );

	Returns true if the sorted range [first2, last2) is a subsequence of the
     sorted
	range [first1, last1) (a subsequence need not be contiguous).

	1) If [first1, last1) or [first2, last2) is not sorted with respect to
	operator<
	(until C++20)
	std::less{}
	(since C++20), the behavior is undefined.
	3)  If	[first1, last1) or [first2, last2) is not sorted with respect to
     comp, the
	behavior is undefined.
	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
	first1, last1 - the sorted range of elements to examine
	first2, last2 - the sorted range of elements to search for
	policy	      - the execution policy to use. See  execution  policy  for
     details.
			comparison  function  object (i.e. an object that satis-
     fies the
			requirements of Compare) which returns true if the first
     argument is
			less than (i.e. is ordered before) the second.

			The signature  of  the	comparison  function  should  be
     equivalent 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
			InputIt  can  be  dereferenced	and then implicitly con-
     verted to both of
			them.

Type requirements
	-
	InputIt1, InputIt2 must meet the requirements of LegacyInputIterator.
	-
	ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardItera-
     tor.
	-
	Compare must meet the requirements of Compare.

Return value
	true if [first2, last2) is a subsequence of [first1,  last1);  otherwise
     false.

	An  empty sequence is a subsequence of any sequence, so true is returned
     if
	[first2, last2) is empty.

Complexity
	Given \(\scriptsize N_1\)N
	1 as std::distance(first1, last1) and \(\scriptsize N_2\)N
	2 as std::distance(first2, last2):

	1,2) At most \(\scriptsize 2 \cdot (N_1+N_2)-1\)2a(N
	1+N
	2)-1 comparisons using
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3,4) At most \(\scriptsize 2 \cdot (N_1+N_2)-1\)2a(N
	1+N
	2)-1 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.

Possible implementation
				include (1)
	template<class InputIt1, class InputIt2>
	bool includes(InputIt1 first1, InputIt1 last1,
		      InputIt2 first2, InputIt2 last2)
	{
	    for (; first2 != last2; ++first1)
	    {
		if (first1 == last1 || *first2 < *first1)
		    return false;
		if (!(*first1 < *first2))
		    ++first2;
	    }
	    return true;
	}
				include (3)
	template<class InputIt1, class InputIt2, class Compare>
	bool includes(InputIt1 first1, InputIt1 last1,
		      InputIt2 first2, InputIt2 last2, Compare comp)
	{
	    for (; first2 != last2; ++first1)
	    {
		if (first1 == last1 || comp(*first2, *first1))
		    return false;
		if (!comp(*first1, *first2))
		    ++first2;
	    }
	    return true;
	}

Example
     // Run this code

      #include <algorithm>
      #include <cctype>
      #include <iostream>

      template<class Os, class Co>
      Os& operator<<(Os& os, const Co& v)
      {
	  for (const auto& i : v)
	      os << i << ' ';
	  return os << '\t';
      }

      int main()
      {
	  const auto
	      v1 = {'a', 'b', 'c', 'f', 'h', 'x'},
	      v2 = {'a', 'b', 'c'},
	      v3 = {'a', 'c'},
	      v4 = {'a', 'a', 'b'},
	      v5 = {'g'},
	      v6 = {'a', 'c', 'g'},
	      v7 = {'A', 'B', 'C'};

	  auto	no_case  =  [](char  a,  char  b)  {  return  std::tolower(a)  <
     std::tolower(b); };

	  std::cout
	  << v1 << "\nincludes:\n" << std::boolalpha
	  << v2 <<  ":	"  <<  std::includes(v1.begin(),  v1.end(),  v2.begin(),
     v2.end()) << '\n'
	  <<  v3  <<  ":  "  <<  std::includes(v1.begin(), v1.end(), v3.begin(),
     v3.end()) << '\n'
	  << v4 <<  ":	"  <<  std::includes(v1.begin(),  v1.end(),  v4.begin(),
     v4.end()) << '\n'
	  <<  v5  <<  ":  "  <<  std::includes(v1.begin(), v1.end(), v5.begin(),
     v5.end()) << '\n'
	  << v6 <<  ":	"  <<  std::includes(v1.begin(),  v1.end(),  v6.begin(),
     v6.end()) << '\n'
	  <<  v7  <<  ":  "  <<  std::includes(v1.begin(), v1.end(), v7.begin(),
     v7.end(), no_case)
		<< " (case-insensitive)\n";
      }

Output:
      a b c f h x
      includes:
      a b c   : true
      a c     : true
      a a b   : false
      g       : false
      a c g   : false
      A B C   : true (case-insensitive)

	Defect reports

	The following behavior-changing defect	reports  were  applied	retroac-
     tively to
	previously published C++ standards.

	   DR	  Applied  to		 Behavior as published		    Cor-
     rect behavior
	LWG 1205 C++98	    the return value was unclear if		 returns
     true in this
			    [first2, last2) is empty			case

See also
	set_difference	 computes the difference between two sets
			 (function template)
	search		 searches for a range of elements
			 (function template)
	ranges::includes  returns  true  if one sequence is a subsequence of an-
     other
	(C++20) 	 (niebloid)

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