Movatterモバイル変換

[0]ホーム
URL:

cppreference.com
Namespaces
Variants
    Actions

      deduction guides forstd::unordered_map

      From cppreference.com
      <cpp‎ |container‎ |unordered map

      [edit template]
       
       
       
      std::unordered_map
      Member types
      Member functions
      Non-member functions
      Deduction guides(C++17)
       
      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_map( InputIt, InputIt,
                     typename/* see below */::size_type=/* see below */,
                     Hash= Hash(), Pred= Pred(), Alloc= Alloc())
         -> unordered_map</*iter-key-t*/<InputIt>,/*iter-val-t*/<InputIt>,

                           Hash, Pred, Alloc>;
      		 (1)(since C++17)
      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_map(std::initializer_list<std::pair<Key, T>>,
                     typename/* see below */::size_type=/* see below */,
                     Hash= Hash(), Pred= Pred(), Alloc= Alloc())

         -> unordered_map<Key, T, Hash, Pred, Alloc>;
      		 (2)(since C++17)
      template<class InputIt,class Alloc>

      unordered_map( InputIt, InputIt,typename/* see below */::size_type, Alloc)
         -> unordered_map</*iter-key-t*/<InputIt>,/*iter-val-t*/<InputIt>,
                           std::hash</*iter-key-t*/<InputIt>>,

                           std::equal_to</*iter-key-t*/<InputIt>>, Alloc>;
      		 (3)(since C++17)
      template<class InputIt,class Alloc>

      unordered_map( InputIt, InputIt, Alloc)
         -> unordered_map</*iter-key-t*/<InputIt>,/*iter-val-t*/<InputIt>,
                           std::hash</*iter-key-t*/<InputIt>>,

                           std::equal_to</*iter-key-t*/<InputIt>>, Alloc>;
      		 (4)(since C++17)
      template<class InputIt,class Hash,class Alloc>

      unordered_map( InputIt, InputIt,typename/* see below */::size_type, Hash,
                     Alloc)
         -> unordered_map</*iter-key-t*/<InputIt>,/*iter-val-t*/<InputIt>, Hash,

                           std::equal_to</*iter-key-t*/<InputIt>>, Alloc>;
      		 (5)(since C++17)
      template<class Key,class T,typename Alloc>

      unordered_map(std::initializer_list<std::pair<Key, T>>,
                     typename/* see below */::size_type, Alloc)

         -> unordered_map<Key, T,std::hash<Key>,std::equal_to<Key>, Alloc>;
      		 (6)(since C++17)
      template<class Key,class T,typename Alloc>

      unordered_map(std::initializer_list<std::pair<Key, T>>, Alloc)

         -> unordered_map<Key, T,std::hash<Key>,std::equal_to<Key>, Alloc>;
      		 (7)(since C++17)
      template<class Key,class T,class Hash,class Alloc>

      unordered_map(std::initializer_list<std::pair<Key, T>>,
                     typename/* see below */::size_type, Hash, Alloc)

         -> unordered_map<Key, T, Hash,std::equal_to<Key>, Alloc>;
      		 (8)(since C++17)
      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_map(std::from_range_t, R&&,
                     typename/* see below */::size_type=/* see below */,
                     Hash= Hash(), Pred= Pred(), Alloc= Alloc())
         -> unordered_map</*range-key-t*/<R>,/*range-mapped-t*/<R>,

                           Hash, Pred, Alloc>;
      		 (9)(since C++23)
      template<ranges::input_range R,class Alloc>

      unordered_map(std::from_range_t, R&&,
                     typename/* see below */::size_type, Alloc)
         -> unordered_map</*range-key-t*/<R>,/*range-mapped-t*/<R>,
                           std::hash</*range-key-t*/<R>>,

                           std::equal_to</*range-key-t*/<R>>, Alloc>;
      		 (10)(since C++23)
      template<ranges::input_range R,class Alloc>

      unordered_map(std::from_range_t, R&&, Alloc)
         -> unordered_map</*range-key-t*/<R>,/*range-mapped-t*/<R>,
                           std::hash</*range-key-t*/<R>>,

                           std::equal_to</*range-key-t*/<R>>, Alloc>;
      		 (11)(since C++23)
      template<ranges::input_range R,class Hash,class Alloc>

      unordered_map(std::from_range_t, R&&,typename/* see below */::size_type,
                     Hash, Alloc)
         -> unordered_map</*range-key-t*/<R>,/*range-mapped-t*/<R>, Hash,

                           std::equal_to</*range-key-t*/<R>>, Alloc>;
      		 (12)(since C++23)
      Exposition-only helper type aliases
      template<class InputIt>

      using/*iter-val-t*/=

         typenamestd::iterator_traits<InputIt>::value_type;
      		(exposition only*)
      template<class InputIt>

      using/*iter-key-t*/=

         std::remove_const_t<std::tuple_element_t<0,/*iter-val-t*/<InputIt>>>;
      		(exposition only*)
      template<class InputIt>

      using/*iter-mapped-t*/=

         std::tuple_element_t<1,/*iter-val-t*/<InputIt>>;
      		(exposition only*)
      template<class InputIt>

      using/*iter-to-alloc-t*/=
         std::pair<std::add_const_t<tuple_element_t<0,/*iter-val-t*/<InputIt>>>,

                   std::tuple_element_t<1,/*iter-val-t*/<InputIt>>>;
      		(exposition only*)
      template<ranges::input_range Range>

      using/*range-key-t*/=

         std::remove_const_t<typenameranges::range_value_t<Range>::first_type>;
      		(since C++23)
      (exposition only*)
      template<ranges::input_range Range>

      using/*range-mapped-t*/=

         typenameranges::range_value_t<Range>::second_type;
      		(since C++23)
      (exposition only*)
      template<ranges::input_range Range>

      using/*range-to-alloc-t*/=
         std::pair<std::add_const_t<typenameranges::range_value_t<Range>::first_type>,

                   typenameranges::range_value_t<Range>::second_type>;
      		(since C++23)
      (exposition only*)
      1-8) Thesededuction guide are provided forunordered_map to allow deduction from an iterator range (overloads(1,3-5)) andstd::initializer_list (overloads(2,6-8)).
      9-12) These deduction guides are provided forunordered_map to allow deduction from astd::from_range_t tag and aninput_range.

      These overloads participate in overload resolution only ifInputIt satisfiesLegacyInputIterator,Alloc satisfiesAllocator, neitherHash norPred satisfyAllocator, andHash is not an integral type.

      Note: the extent to which the library determines that a type does not satisfyLegacyInputIterator 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 satisfyAllocator is unspecified, except that as a minimum the member typeAlloc::value_type must exist and the expressionstd::declval<Alloc&>().allocate(std::size_t{}) must be well-formed when treated as an unevaluated operand.

      Thesize_type parameter type in these guides in an refers to thesize_type member type of the type deduced by the deduction guide.

      [edit]Notes

      Feature-test macroValueStdFeature
      __cpp_lib_containers_ranges202202L(C++23)Ranges-aware construction and insertion; overloads(9-12)

      [edit]Example

      Run this code
      #include <unordered_map> int main(){// std::unordered_map 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_map m1={std::pair{"foo",2},{"bar",3}};// guide #2std::unordered_map m2(m1.begin(), m1.end());// guide #1}

      [edit]Defect reports

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

      DRApplied toBehavior as publishedCorrect behavior
      LWG 3025C++17initializer-list guides(2) and(6-8) takestd::pair<const Key, T>usestd::pair<Key, T>
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/container/unordered_map/deduction_guides&oldid=135907"
      [8]ページ先頭
      ©2009-2025 Movatter.jp