deduction guides for std::unordered_multiset

From cppreference.com

C++
Containers library
std::unordered_multiset
Member types
Member functions
Non-member functions
(until C++20)
Deduction guides (C++17)
Defined in header <unordered_set>
template <

class InputIt,
class Hash = std::hash < typename std::iterator_traits <InputIt> :: value_type >,
class Pred = std::equal_to < typename std::iterator_traits <InputIt> :: value_type >,
class Alloc = std::allocator < typename std::iterator_traits <InputIt> :: value_type > >
unordered_multiset( InputIt, InputIt,
typename /* see below */ :: size_type = /* see below */,
                    Hash = Hash( ), Pred = Pred( ), Alloc = Alloc( ) )
- > unordered_multiset< typename std::iterator_traits <InputIt> :: value_type,

                          Hash, Pred, Alloc> ;
(1) (since C++17)
template < class T,

class Hash = std::hash <T>,
class Pred = std::equal_to <T>,
class Alloc = std::allocator <T> >
unordered_multiset( std::initializer_list <T>,
typename /* see below */ :: size_type = /* see below */,
                    Hash = Hash( ), Pred = Pred( ), Alloc = Alloc( ) )

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

unordered_multiset( InputIt, InputIt, typename /* see below */ :: size_type, Alloc )
- > unordered_multiset< typename std::iterator_traits <InputIt> :: value_type,
std::hash < typename std::iterator_traits <InputIt> :: value_type >,
std::equal_to < typename std::iterator_traits <InputIt> :: value_type >,

                          Alloc> ;
(3) (since C++17)
template < class InputIt, class Hash, class Alloc >

unordered_multiset( InputIt, InputIt, typename /* see below */ :: size_type, Hash, Alloc )
- > unordered_multiset< typename std::iterator_traits <InputIt> :: value_type, Hash,
std::equal_to < typename std::iterator_traits <InputIt> :: value_type >,

                          Alloc> ;
(4) (since C++17)
template < class T, class Alloc >

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

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

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

- > unordered_multiset<T, Hash, std::equal_to <T>, Alloc> ;
(6) (since C++17)
template < ranges::input_range R,

class Hash = std::hash < ranges::range_value_t <R>>,
class Pred = std::equal_to < ranges::range_value_t <R>>,
class Alloc = std::allocator < ranges::range_value_t <R>> >
unordered_multiset( std::from_range_t, R&&,
typename /* see below */ :: size_type = /* see below */,
                    Hash = Hash( ), Pred = Pred( ), Alloc = Alloc( ) )

- > unordered_multiset< ranges::range_value_t <R>, Hash, Pred, Alloc> ;
(7) (since C++23)
template < ranges::input_range R, class Alloc >

unordered_multiset( std::from_range_t, R&&,
typename /* see below */ :: size_type, Alloc )
- > unordered_multiset< ranges::range_value_t <R>, hash< ranges::range_value_t <R>>,

std::equal_to < ranges::range_value_t <R>>, Alloc> ;
(8) (since C++23)
template < ranges::input_range R, class Alloc >

unordered_multiset( std::from_range_t, R&&, Alloc )
- > unordered_multiset< ranges::range_value_t <R>, hash< ranges::range_value_t <R>>,

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

unordered_multiset( std::from_range_t, R&&,
typename /* see below */ :: size_type, Hash, Alloc )
- > unordered_multiset< ranges::range_value_t <R>, Hash,

std::equal_to < ranges::range_value_t <R>>, Alloc> ;
(10) (since C++23)
1-6) These deduction guides are provided for unordered_multiset to allow deduction from an iterator range (overloads (1,3,4)) and std::initializer_list (overloads (2,5,6)). This overload participates in overload resolution only if InputIt satisfies LegacyInputIterator, Alloc satisfies Allocator, neither Hash nor Pred satisfy Allocator, Hash
7-10) These deduction guides are provided for unordered_multiset to allow deduction from a std::from_range_t tag and an input_range

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 { } )

The size_type parameter type in these guides refers to the size_type

Notes

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overloads (7-10)

Example

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