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deduction guides for std::set

Defined in header <set> 
template<
  class InputIt,
  class Comp = std::less<typename std::iterator_traits<InputIt>::value_type>,
  class Alloc = std::allocator<typename std::iterator_traits<InputIt>::value_type>>
set( InputIt, InputIt, Comp = Comp(), Alloc = Alloc() )
  -> set<typename std::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<typename std::iterator_traits<InputIt>::value_type,
         std::less<typename std::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) These deduction guides are provided for set to allow deduction from an iterator range (overloads (1,3)) and std::initializer_list (overloads (2,4)).
5,6) These deduction guides are provided for set to allow deduction from a std::from_range_t tag and an input_range.

These overloads participate in overload resolution only if InputIt satisfies LegacyInputIterator, Alloc satisfies Allocator, and Comp does not satisfy Allocator.

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.

Notes

Feature-test macro Value Std Comment
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overload (5,6)

Example

#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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