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      deduction guides forstd::multimap

      From cppreference.com
      <cpp‎ |container‎ |multimap

      [edit template]
       
       
       
      std::multimap
      Member functions
      Non-member functions
      (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
      Deduction guides(C++17)
       
      Defined in header<map>
      template<class InputIt,

               class Comp=std::less</*iter-key-t*/<InputIt>>,
               class Alloc=std::allocator</*iter-to-alloc-t*/<InputIt>>>
      multimap( InputIt, InputIt, Comp= Comp(), Alloc= Alloc())

         -> multimap</*iter-key-t*/<InputIt>,/*iter-val-t*/<InputIt>, Comp, Alloc>;
      		 (1)(since C++17)
      template<class Key,

               class T,
               class Comp=std::less<Key>,
               class Alloc=std::allocator<std::pair<const Key, T>>>
      multimap(std::initializer_list<std::pair<Key, T>>, Comp= Comp(), Alloc= Alloc())

         -> multimap<Key, T, Comp, Alloc>;
      		 (2)(since C++17)
      template<class InputIt,class Alloc>

      multimap( InputIt, InputIt, Alloc)
         -> multimap</*iter-key-t*/<InputIt>,/*iter-val-t*/<InputIt>,

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

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

         -> multimap<Key, T,std::less<Key>, Alloc>;
      		 (4)(since C++17)
      template<ranges::input_range R,class Compare=std::less</*range-key-t*/<R>,

               class Alloc=std::allocator</*range-to-alloc-t*/<R>>>
      multimap(std::from_range_t, R&&, Compare= Compare(), Alloc= Alloc())

         -> multimap</*range-key-t*/<R>, range_mapped_t<R>, Compare, Alloc>;
      		 (5)(since C++23)
      template<ranges::input_range R,class Alloc>

      multimap(std::from_range_t, R&&, Alloc)
         -> multimap</*range-key-t*/<R>, range_mapped_t<R>,

             multimapstd::less</*range-key-t*/<R>>, Alloc>;
      		 (6)(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*)
      1-4) Thesededuction guides are provided formultimap to allow deduction from an iterator range (overloads(1,3)) andstd::initializer_list (overloads(2,4)).
      5,6) These deduction guides are provided formultimap to allow deduction from astd::from_range_t tag and aninput_range.

      These overloads participate in overload resolution only ifInputIt satisfiesLegacyInputIterator,Alloc satisfiesAllocator, andComp does not satisfyAllocator.

      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.

      [edit]Notes

      Feature-test macroValueStdFeature
      __cpp_lib_containers_ranges202202L(C++23)Ranges-aware construction and insertion; overload(5,6)

      [edit]Example

      Run this code
      #include <map> int main(){// std::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::multimap m1={std::pair{"foo",2},{"bar",3}};// guide #2std::multimap 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(2,4) takestd::pair<const Key, T>usestd::pair<Key, T>
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