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      deduction guides forstd::set

      From cppreference.com
      <cpp‎ |container‎ |set

      [edit template]
       
       
       
       
      Defined in header<set>
      template<

         class InputIt,
         class Comp=std::less<typenamestd::iterator_traits<InputIt>::value_type>,
         class Alloc=std::allocator<typenamestd::iterator_traits<InputIt>::value_type>>
      set( InputIt, InputIt, Comp= Comp(), Alloc= Alloc())

         -> set<typenamestd::iterator_traits<InputIt>::value_type, Comp, Alloc>;
      		 (1)(since C++17)
      template<

         class Key,class Comp=std::less<Key>,
         class Alloc=std::allocator<Key>>
      set(std::initializer_list<Key>, Comp= Comp(), Alloc= Alloc())

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

      set( InputIt, InputIt, Alloc)
         -> set<typenamestd::iterator_traits<InputIt>::value_type,

                 std::less<typenamestd::iterator_traits<InputIt>::value_type>, Alloc>;
      		 (3)(since C++17)
      template<class Key,class Alloc>

      set(std::initializer_list<Key>, Alloc)

         -> set<Key,std::less<Key>, Alloc>;
      		 (4)(since C++17)
      template<ranges::input_range R,class Compare= less<ranges::range_value_t<R>>,

               class Alloc=std::allocator<ranges::range_value_t<R>>>
      set(std::from_range_t, R&&, Compare= Compare(), Alloc= Alloc())

         -> set<ranges::range_value_t<R>, Compare, Alloc>;
      		 (5)(since C++23)
      template<ranges::input_range R,class Alloc>

      set(std::from_range_t, R&&, Alloc)

         -> set<ranges::range_value_t<R>,std::less<ranges::range_value_t<R>>, Alloc>;
      		 (6)(since C++23)
      1-4) Thesededuction guides are provided forset to allow deduction from an iterator range (overloads(1,3)) andstd::initializer_list (overloads(2,4)).
      5,6) These deduction guides are provided forset 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 <set> int main(){// guide #2 deduces std::set<int>std::set s={1,2,3,4}; // guide #1 deduces std::set<int>std::set s2(s.begin(), s.end());}
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