NAME¶

deductionguidesforstd::unordered_multiset - deductionguidesforstd::unordered_multiset

Synopsis¶

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> > (1) (since C++17)
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>;
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>, (2) (since C++17)
typename /* see below */::size_type = /* see
below */,
Hash = Hash(), Pred = Pred(), Alloc = Alloc()
)

-> unordered_multiset<T, Hash, Pred, Alloc>;
template< class InputIt, class Alloc >

unordered_multiset( InputIt, InputIt, typename /* see below
*/::size_type, Alloc )
-> unordered_multiset<typename
std::iterator_traits<InputIt>::value_type, (3) (since C++17)
std::hash<typename
std::iterator_traits<InputIt>::value_type>,
std::equal_to<typename
std::iterator_traits<InputIt>::value_type>,

Alloc>;
template< class InputIt, class Hash, class Alloc >

unordered_multiset( InputIt, InputIt, typename /* see below
*/::size_type, Hash, Alloc )
-> unordered_multiset<typename (4) (since C++17)
std::iterator_traits<InputIt>::value_type, Hash,
std::equal_to<typename
std::iterator_traits<InputIt>::value_type>,

Alloc>;
template< class T, class Alloc >

unordered_multiset( std::initializer_list<T>, typename /* see
below */::size_type, Alloc ) (5) (since C++17)

-> unordered_multiset<T, std::hash<T>, std::equal_to<T>,
Alloc>;
template< class T, class Hash, class Alloc >

unordered_multiset( std::initializer_list<T>, typename /* see
below */::size_type, (6) (since C++17)
Hash, Alloc )

-> unordered_multiset<T, Hash, std::equal_to<T>, Alloc>;
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&&, (7) (since C++23)
typename /* see below */::size_type = /* see
below */,
Hash = Hash(), Pred = Pred(), Alloc = Alloc()
)

-> unordered_multiset<ranges::range_value_t<R>, Hash, Pred,
Alloc>;
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>, (8) (since C++23)
hash<ranges::range_value_t<R>>,

std::equal_to<ranges::range_value_t<R>>, Alloc>;
template< ranges::input_range R, class Alloc >

unordered_multiset( std::from_range_t, R&&, Alloc )
-> unordered_multiset<ranges::range_value_t<R>, (9) (since C++23)
hash<ranges::range_value_t<R>>,

std::equal_to<ranges::range_value_t<R>>, Alloc>;
template< ranges::input_range R, class Hash, class Alloc >

unordered_multiset( std::from_range_t, R&&,
typename /* see below */::size_type, Hash,
Alloc ) (10) (since C++23)
-> unordered_multiset<ranges::range_value_t<R>, Hash,

std::equal_to<ranges::range_value_t<R>>, Alloc>;

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 is not an integral type.
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{}) must be well-formed when treated as
an unevaluated operand.

The size_type parameter type in these guides refers to the size_type member type of
the type deduced by the deduction guide.

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());
}