deduction guides for std::multiset

From cppreference.com

C++
Containers library
std::multiset
Member functions
Non-member functions
Deduction guides (C++17)
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 >>
multiset ( InputIt, InputIt, Comp = Comp ( ) , Alloc = Alloc ( ) )

- > multiset < 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 > >
multiset ( std:: initializer_list < Key > , Comp = Comp ( ) , Alloc = Alloc ( ) )

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

multiset ( InputIt, InputIt, Alloc )
- > multiset < 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 >

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

- > multiset < 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 >> >
multiset ( std:: from_range_t , R && , Compare = Compare ( ) , Alloc = Alloc ( ) )

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

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

- > multiset < 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 multiset 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 multiset 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 Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overload (5,6)

Example

Run this code 
#include <set>
 
int main()
{
    // guide #2 deduces std::multiset<int>
    std::multiset s = {1, 2, 3, 4};
 
    // guide #1 deduces std::multiset<int>
    std::multiset s2(s.begin(), s.end());
}
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