home | help 
std::ranges::includes(3)       C++ Standard Libary	std::ranges::includes(3)

NAME
     std::ranges::includes - std::ranges::includes

Synopsis
	Defined in header <algorithm>
	Call signature
	template< std::input_iterator I1, std::sentinel_for<I1> S1,

		  std::input_iterator I2, std::sentinel_for<I2> S2,
		  class Proj1 = std::identity, class Proj2 =
	std::identity,
		  std::indirect_strict_weak_order<			     (1)
     (since C++20)
		      std::projected<I1, Proj1>,
		      std::projected<I2, Proj2>> Comp = ranges::less >
	constexpr bool
	    includes( I1 first1, S1 last1, I2 first2, S2 last2,

		      Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )
	template< ranges::input_range R1, ranges::input_range R2,

		  class Proj1 = std::identity, class Proj2 =
	std::identity,
		  std::indirect_strict_weak_order<
		      std::projected<ranges::iterator_t<R1>,  Proj1>,	     (2)
     (since C++20)
		      std::projected<ranges::iterator_t<R2>, Proj2>> Comp
	= ranges::less >
	constexpr bool

	    includes( R1&& r1, R2&& r2, Comp comp = {}, Proj1 proj1 = {},
	Proj2 proj2 = {} )

	1)  Returns  true if the projections of the sorted range [first2, last2)
     is a
	subsequence of the projections of the sorted range [first1, last1).
	2) Same as (1), but uses r1 and r2 as the source ranges, as if by using
	ranges::begin(r1) and ranges::begin(r2) as  first1  and  first2  respec-
     tively, and
	ranges::end(r1) and ranges::end(r2) as last1 and last2 respectively.

	Both  ranges  must  be sorted with the given comparison function comp. A
     subsequence
	need not be contiguous.

	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
	first1, last1 - the sorted range of elements to examine
	r1	      - the sorted range of elements to examine
	first2, last2 - the sorted range of elements to search for
	r2	      - the sorted range of elements to search for
	comp	      - comparison function to apply to the projected elements
	proj1	      - projection to apply to the elements in the first range
	proj2	      - projection to apply to the elements in the second range

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

Complexity
	At most \(\scriptsize 2 \cdot (N_1+N_2-1)\)2A.(N[1]+N[2]-1) comparisons,
     where
	\(\scriptsize  N_1\)N[1]  is  ranges::distance(r1)   and   \(\scriptsize
     N_2\)N[2] is
	ranges::distance(r2).

Possible implementation
	struct includes_fn
	{
	    template<std::input_iterator I1, std::sentinel_for<I1> S1,
		     std::input_iterator I2, std::sentinel_for<I2> S2,
		     class Proj1 = std::identity, class Proj2 = std::identity,
		     std::indirect_strict_weak_order<
			 std::projected<I1, Proj1>,
			 std::projected<I2, Proj2>> Comp = ranges::less>
	    constexpr bool operator()(I1 first1, S1 last1, I2 first2, S2 last2,
				      Comp  comp  =  {}, Proj1 proj1 = {}, Proj2
     proj2 = {}) const
	    {
		for (; first2 != last2; ++first1)
		{
		    if (first1 == last1 || comp(*first2, *first1))
			return false;
		    if (!comp(*first1, *first2))
			++first2;
		}
		return true;
	    }

	    template<ranges::input_range R1, ranges::input_range R2,
		     class Proj1 = std::identity, class Proj2 = std::identity,
		     std::indirect_strict_weak_order<
			 std::projected<ranges::iterator_t<R1>, Proj1>,
			 std::projected<ranges::iterator_t<R2>, Proj2>>  Comp  =
     ranges::less>
	    constexpr bool operator()(R1&& r1, R2&& r2, Comp comp = {},
				      Proj1 proj1 = {}, Proj2 proj2 = {}) const
	    {
		return (*this)(ranges::begin(r1), ranges::end(r1),
			       ranges::begin(r2), ranges::end(r2),
			       std::ref(comp),			std::ref(proj1),
     std::ref(proj2));
	    }
	};

	inline constexpr auto includes = includes_fn {};

Example
     // Run this code

      #include <algorithm>
      #include <cctype>
      #include <initializer_list>
      #include <iomanip>
      #include <iostream>
      #include <locale>
      #include <string>

      template<class T>
      std::ostream& operator<<(std::ostream& os, std::initializer_list<T> const&
     list)
      {
	  for (os << "{ "; auto const& elem : list)
	      os << elem << ' ';
	  return os << "} ";
      }

      struct true_false : std::numpunct<char>
      {
	  std::string do_truename() const { return "? Yes\n"; }
	  std::string do_falsename() const { return "? No\n"; }
      };

      int main()
      {
	  std::cout.imbue(std::locale(std::cout.getloc(), new true_false));

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

	  const auto
	      a = {'a', 'b', 'c'},
	      b = {'a', 'c'},
	      c = {'a', 'a', 'b'},
	      d = {'g'},
	      e = {'a', 'c', 'g'},
	      f = {'A', 'B', 'C'},
	      z = {'a', 'b', 'c', 'f', 'h', 'x'};

	  std::cout
	      << z << "includes\n" << std::boolalpha
	      <<   a  <<  std::ranges::includes(z.begin(),  z.end(),  a.begin(),
     a.end())
	      << b << std::ranges::includes(z, b)
	      << c << std::ranges::includes(z, c)
	      << d << std::ranges::includes(z, d)
	      << e << std::ranges::includes(z, e)
	      << f << std::ranges::includes(z, f, ignore_case);
      }

Output:
      { a b c f h x } includes
      { a b c } ? Yes
      { a c } ? Yes
      { a a b } ? No
      { g } ? No
      { a c g } ? No
      { A B C } ? Yes

See also
	ranges::set_difference	  computes the difference between two sets
	(C++20) 		  (niebloid)
	ranges::search		  searches for a range of elements
	(C++20) 		  (niebloid)
	ranges::contains
	ranges::contains_subrange checks if the range contains the given element
     or subrange
	(C++23) 		  (niebloid)
	(C++23)
	includes		  returns true if one sequence is a  subsequence
     of another
				  (function template)

http://cppreference.com 	   2024.06.10		std::ranges::includes(3)
home | help