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deductiongu...red_multimap(3)  C++ Standard Libary deductiongu...red_multimap(3)

NAME
     deductionguidesforstd::unordered_multimap	  -   deductionguidesforstd::un-
     ordered_multimap

Synopsis
	Defined in header <unordered_map>
	template< class InputIt,

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

				  Hash, Pred, Alloc>;
	template< class Key, class T, class Hash = std::hash<Key>,

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

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

	unordered_multimap( InputIt, InputIt, typename /*see
	below*/::size_type, Alloc )
	    -> unordered_multimap<iter_key_t<InputIt>,		     (3)  (since
     C++17)
	iter_val_t<InputIt>,
				  std::hash<iter_key_t<InputIt>>,

	std::equal_to<iter_key_t<InputIt>>, Alloc>;
	template< class InputIt, class Alloc >

	unordered_multimap( InputIt, InputIt, Alloc )
	    -> unordered_multimap<iter_key_t<InputIt>,
	iter_val_t<InputIt>,					     (4)  (since
     C++17)
				  std::hash<iter_key_t<InputIt>>,

	std::equal_to<iter_key_t<InputIt>>, Alloc>;
	template< class InputIt, class Hash, class Alloc >

	unordered_multimap( InputIt, InputIt, typename /*see
	below*/::size_type, Hash, Alloc )
	    -> unordered_multimap<iter_key_t<InputIt>,		     (5)  (since
     C++17)
	iter_val_t<InputIt>, Hash,

	std::equal_to<iter_key_t<InputIt>>, Alloc>;
	template< class Key, class T, typename Alloc >

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

	    -> unordered_multimap<Key, T, std::hash<Key>,
	std::equal_to<Key>, Alloc>;
	template< class Key, class T, typename Alloc >

	unordered_multimap( std::initializer_list<std::pair<Key,
	T>>, Alloc )						     (7)  (since
     C++17)

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

	unordered_multimap( std::initializer_list<std::pair<Key,
	T>>,
			    typename /*see below*/::size_type, Hash, (8)  (since
     C++17)
	Alloc )

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

		  class Hash = std::hash<range_key_t<R>>,
		  class Pred = std::equal_to<range_key_t<R>>,
		  class Alloc = std::allocator<range_to_alloc_t<R>>
	>
	unordered_multimap( std::from_range_t, R&&,		     (9)  (since
     C++23)
			    typename /* see description
	*/::size_type = /* see description */,
			    Hash = Hash(), Pred = Pred(), Alloc =
	Alloc() )
	    -> unordered_multimap<range_key_t<R>, range_mapped_t<R>,

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

	unordered_multimap( std::from_range_t, R&&,
			    typename /* see description
	*/::size_type, Alloc )					     (10) (since
     C++23)
	    -> unordered_multimap<range_key_t<R>, range_mapped_t<R>,
				  std::hash<range_key_t<R>>,

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

	unordered_multimap( std::from_range_t, R&&, Alloc )
	    -> unordered_multimap<range_key_t<R>, range_mapped_t<R>, (11) (since
     C++23)
				  std::hash<range_key_t<R>>,

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

	unordered_multimap( std::from_range_t, R&&, typename /* see
	description */::size_type,
			    Hash, Alloc )			     (12) (since
     C++23)
	    -> unordered_multimap<range_key_t<R>, range_mapped_t<R>,
	Hash,

				  std::equal_to<range_key_t<R>>,
	Alloc>;
	Exposition-only helper type aliases
	template< class InputIter >

	using iter_val_t =						  (expo-
     sition only*)

	    typename std::iterator_traits<InputIter>::value_type;
	template< class InputIter >

	using iter_key_t =						  (expo-
     sition only*)

	    std::remove_const_t< std::tuple_element_t<0,
	iter_val_t<InputIter>>>;
	template< class InputIter >

	using iter_mapped_t =						  (expo-
     sition only*)

	    std::tuple_element_t<1, iter_val_t<InputIter>>;
	template< class InputIter >

	using iter_to_alloc_t =
	    std::pair<std::add_const_t<tuple_element_t<0,		  (expo-
     sition only*)
	iter_val_t<InputIter>>>,

		      std::tuple_element_t<1,
	iter_val_t<InputIter>>>;
	template< ranges::input_range Range >

	using range_key_t =						  (since
     C++23)
									  (expo-
     sition only*)
	    std::remove_const_t<typename
	ranges::range_value_t<Range>::first_type>;
	template< ranges::input_range Range >
									  (since
     C++23)
	using range_mapped_t =						  (expo-
     sition only*)

	    typename ranges::range_value_t<Range>::second_type;
	template< ranges::input_range Range >

	using range_to_alloc_t =
	    std::pair<std::add_const_t<typename 			  (since
     C++23)
	ranges::range_value_t<Range>::first_type>,			  (expo-
     sition only*)

		      typename
	ranges::range_value_t<Range>::second_type>;

	1-8) These deduction guide are provided for unordered_multimap to  allow
     deduction
	from  an  iterator  range  (overloads (1,3-5)) and std::initializer_list
     (overloads
	(2,6-8)).
	9-12) These deduction guides are provided for unordered_multimap to  al-
     low deduction
	from a std::from_range_t tag and an input_range.

	These  overloads participate in overload resolution only if InputIt sat-
     isfies
	LegacyInputIterator, Alloc satisfies Allocator, neither  Hash  nor  Pred
     satisfy
	Allocator, and Hash is not an integral type.

	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  in  an  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 (9-12)

Example
     // Run this code

      #include <unordered_map>

      int main()
      {
	  // std::unordered_multimap m1 = {{"foo", 1}, {"bar", 2}};
	      // Error: braced-init-list has no type cannot
	      // deduce pair<Key, T> from {"foo", 1} or {"bar", 2}

	  std::unordered_multimap m1 = {std::pair{"foo",  2},  {"bar",	3}};  //
     guide #2
	  std::unordered_multimap m2(m1.begin(), m1.end()); // guide #1
      }

	Defect reports

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

	   DR	 Applied to	      Behavior as published		 Correct
     behavior
	LWG  3025  C++17       initializer-list  guides  take		     use
     std::pair<Key, T>
			    std::pair<const Key, T>

http://cppreference.com 	   2024.06.10	   deductiongu...red_multimap(3)
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