std::unordered_set<Key,Hash,KeyEqual,Allocator>::emplace (3) - Linux Man Pages

std::unordered_set<Key,Hash,KeyEqual,Allocator>::emplace: std::unordered_set<Key,Hash,KeyEqual,Allocator>::emplace

NAME

std::unordered_set<Key,Hash,KeyEqual,Allocator>::emplace - std::unordered_set<Key,Hash,KeyEqual,Allocator>::emplace

Synopsis


template< class... Args > (since C++11)
std::pair<iterator,bool> emplace( Args&&... args );


Inserts a new element into the container constructed in-place with the given args if there is no element with the key in the container.
Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations. The constructor of the new element is called with exactly the same arguments as supplied to emplace, forwarded via std::forward<Args>(args).... The element may be constructed even if there already is an element with the key in the container, in which case the newly constructed element will be destroyed immediately.
If rehashing occurs due to the insertion, all iterators are invalidated. Otherwise iterators are not affected. References are not invalidated. Rehashing occurs only if the new number of elements is greater than max_load_factor()*bucket_count().

Parameters


args - arguments to forward to the constructor of the element

Return value


Returns a pair consisting of an iterator to the inserted element, or the already-existing element if no insertion happened, and a bool denoting whether the insertion took place. True for Insertion, False for No Insertion.

Exceptions


If an exception is thrown by any operation, this function has no effect.

Complexity


Amortized constant on average, worst case linear in the size of the container.

Example


 This section is incomplete
 Reason: no example

See also


             constructs elements in-place using a hint
emplace_hint (public member function)
             inserts elements
             or nodes
insert (since C++17)
             (public member function)