From cppreference.com
template<class...Args>std::pair<iterator,bool>emplace(Args&&...args);(since C++23)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.
First, initializes an object t of type
with std::forward<Args>(args)..., then inserts t as if by
autoit=ranges::upper_bound(c,t,compare);c.insert(it,std::move(t));This overload participates in overload resolution only if std::is_constructible_v<value_type,Args...> is true.
Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations.
Parameters
args - arguments to forward to the constructor of the element Return value
A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool value set to true if and only if the insertion took place.
Exceptions
If an exception is thrown for any reason, this function has no effect (
strong exception safety guarantee
).
Complexity
Logarithmic in the size of the container.
Example
See also