deductionguidesforstd::unordered_set(3) | C++ Standard Libary | deductionguidesforstd::unordered_set(3) |
NAME¶
deductionguidesforstd::unordered_set - deductionguidesforstd::unordered_set
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 (1) (since C++17)
std::iterator_traits<InputIt>::value_type>>
unordered_set(InputIt, InputIt,
typename /*see below*/::size_type = /*see below*/,
Hash = Hash(), Pred = Pred(), Alloc = Alloc())
-> unordered_set<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>> (2) (since C++17)
unordered_set(std::initializer_list<T>,
typename /*see below*/::size_type = /*see below*/,
Hash = Hash(), Pred = Pred(), Alloc = Alloc())
-> unordered_set<T, Hash, Pred, Alloc>;
template<class InputIt, class Alloc>
unordered_set(InputIt, InputIt, typename /*see below*/::size_type,
Alloc)
-> unordered_set<typename (3) (since C++17)
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>;
template<class InputIt, class Hash, class Alloc>
unordered_set(InputIt, InputIt, typename /*see below*/::size_type,
Hash, Alloc)
-> unordered_set<typename (4) (since C++17)
std::iterator_traits<InputIt>::value_type, Hash,
std::equal_to<typename
std::iterator_traits<InputIt>::value_type>,
Allocator>;
template<class T, class Allocator>
unordered_set(std::initializer_list<T>, typename /*see (5)
(since C++17)
below*/::size_type, Allocator)
-> unordered_set<T, std::hash<T>, std::equal_to<T>,
Alloc>;
template<class T, class Hash, class Alloc>
unordered_set(std::initializer_list<T>, typename /*see (6)
(since C++17)
below*/::size_type, Hash, Alloc)
-> unordered_set<T, Hash, std::equal_to<T>, Alloc>;
These deduction guides are provided for unordered_set 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
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.
Example¶
// Run this code
#include <unordered_set>
int main() {
std::unordered_set s = {1,2,3,4}; // guide #2 deduces
std::unordered_set<int>
std::unordered_set s2(s.begin(), s.end()); // guide #1 deduces
std::unordered_set<int>
}
2022.07.31 | http://cppreference.com |