home | help 
deductiongu...ordered_set(3)   C++ Standard Libary  deductiongu...ordered_set(3)

NAME
     deductionguidesforstd::unordered_set - deductionguidesforstd::unordered_set

Synopsis
	Defined in header <unordered_set>
	template<

	    class InputIt,
	    class Hash = std::hash<typename
	std::iterator_traits<InputIt>::value_type>,
	    class Pred = std::equal_to<typename
	std::iterator_traits<InputIt>::value_type>,
	    class Alloc = std::allocator<typename
	std::iterator_traits<InputIt>::value_type>   >			     (1)
     (since C++17)
	unordered_set( InputIt, InputIt,
		       typename /* see below */::size_type = /* see below
	*/,
		       Hash = Hash(), Pred = Pred(), Alloc = Alloc() )
	    -> unordered_set<typename
	std::iterator_traits<InputIt>::value_type,

			     Hash, Pred, Alloc>;
	template< class T,

		  class Hash = std::hash<T>,
		  class Pred = std::equal_to<T>,
		  class Alloc = std::allocator<T> >
	unordered_set(	std::initializer_list<T>,			     (2)
     (since C++17)
		       typename /* see below */::size_type = /* see below
	*/,
		       Hash = Hash(), Pred = Pred(), Alloc = Alloc() )

	    -> unordered_set<T, Hash, Pred, Alloc>;
	template< class InputIt, class Alloc >

	unordered_set( InputIt, InputIt, typename /* see below
	*/::size_type, Alloc )
	    -> unordered_set<typename
	std::iterator_traits<InputIt>::value_type,			     (3)
     (since C++17)
			     std::hash<typename
	std::iterator_traits<InputIt>::value_type>,
			     std::equal_to<typename
	std::iterator_traits<InputIt>::value_type>,

			     Alloc>;
	template< class InputIt, class Hash, class Alloc >

	unordered_set( InputIt, InputIt, typename /* see below
	*/::size_type, Hash, Alloc )
	    ->	unordered_set<typename					     (4)
     (since C++17)
	std::iterator_traits<InputIt>::value_type, Hash,
			     std::equal_to<typename
	std::iterator_traits<InputIt>::value_type>,

			     Alloc>;
	template< class T, class Alloc >

	unordered_set(	std::initializer_list<T>,  typename  /* see below    (5)
     (since C++17)
	*/::size_type, Alloc )

	    -> unordered_set<T, std::hash<T>, std::equal_to<T>, Alloc>;
	template< class T, class Hash, class Alloc >

	unordered_set( std::initializer_list<T>, typename /* see below
	*/::size_type,							     (6)
     (since C++17)
		       Hash, Alloc )

	    -> unordered_set<T, Hash, std::equal_to<T>, Alloc>;
	template< ranges::input_range R,

		  class Hash = std::hash<ranges::range_value_t<R>>,
		  class Pred = std::equal_to<ranges::range_value_t<R>>,
		  class Alloc = std::allocator<ranges::range_value_t<R>>
	>
	unordered_set(	std::from_range_t,  R&&,			     (7)
     (since C++23)
		       typename /* see below */::size_type = /* see below
	*/,
		       Hash = Hash(), Pred = Pred(), Alloc = Alloc() )

	    -> unordered_set<ranges::range_value_t<R>, Hash, Pred,
	Alloc>;
	template< ranges::input_range R, class Alloc >

	unordered_set( std::from_range_t, R&&,
		       typename /* see below */::size_type, Alloc )
	    ->	unordered_set<ranges::range_value_t<R>, 		     (8)
     (since C++23)
	hash<ranges::range_value_t<R>>,

			     std::equal_to<ranges::range_value_t<R>>,
	Alloc>;
	template< ranges::input_range R, class Alloc >

	unordered_set( std::from_range_t, R&&, Alloc )
	    ->	 unordered_set<ranges::range_value_t<R>,		     (9)
     (since C++23)
	hash<ranges::range_value_t<R>>,

			     std::equal_to<ranges::range_value_t<R>>,
	Alloc>;
	template< ranges::input_range R, class Hash, class Alloc >

	unordered_set( std::from_range_t, R&&,
		       typename /* see below */::size_type, Hash, Alloc  )  (10)
     (since C++23)
	    -> unordered_set<ranges::range_value_t<R>, Hash,

			     std::equal_to<ranges::range_value_t<R>>,
	Alloc>;

	1-6)  These deduction guides are provided for unordered_set to allow de-
     duction from
	an iterator range (overloads (1,3,4)) and  std::initializer_list  (over-
     loads (2,5,6)).
	This overload participates in overload resolution only if InputIt satis-
     fies
	LegacyInputIterator,  Alloc  satisfies	Allocator, neither Hash nor Pred
     satisfy
	Allocator, Hash is not an integral type.
	7-10) These deduction guides are provided for unordered_set to allow de-
     duction from
	a std::from_range_t tag and an input_range.

	Note: the extent to which the library determines that a  type  does  not
     satisfy
	LegacyInputIterator  is  unspecified,  except that as a minimum integral
     types do not
	qualify as input iterators. Likewise, the extent to which it  determines
     that a type
	does  not satisfy Allocator is unspecified, except that as a minimum the
     member type
	Alloc::value_type must exist and the expression
	std::declval<Alloc&>().allocate(std::size_t{}) must be well-formed  when
     treated as
	an unevaluated operand.

	The  size_type	parameter  type  in these guides refers to the size_type
     member type of
	the type deduced by the deduction guide.

Notes
	    Feature-test macro	     Value    Std		    Feature
	__cpp_lib_containers_ranges 202202L  (C++23)  Ranges-aware  construction
     and insertion;
						    overloads (7-10)

Example
     // Run this code

      #include <unordered_set>

      int main()
      {
	  // guide #2 deduces std::unordered_set<int>
	  std::unordered_set s = {1, 2, 3, 4};

	  // guide #1 deduces std::unordered_set<int>
	  std::unordered_set s2(s.begin(), s.end());
      }

http://cppreference.com 	   2024.06.10	    deductiongu...ordered_set(3)
home | help