< cpp‎ | container‎ | queue
template< class... Args >
void emplace( Args&&... args );
(since C++11)
(until C++17)
template< class... Args >
decltype(auto) emplace( Args&&... args );
(since C++17)

Pushes a new element to the end of the queue. The element is constructed in-place, i.e. no copy or move operations are performed. The constructor of the element is called with exactly the same arguments as supplied to the function.

Effectively calls c.emplace_back(std::forward<Args>(args)...);.


[edit] Parameters

args - arguments to forward to the constructor of the element

[edit] Return value


(until C++17)

The value or reference, if any, returned by the above call to Container::emplace_back.

(since C++17)

[edit] Complexity

Identical to the complexity of Container::emplace_back.

[edit] Example

#include <iostream>
#include <queue>
struct S
    int id;
    S(int i, double d, std::string s) : id{i}
        std::cout << "S::S(" << i << ", " << d << ", \"" << s << "\");\n";
int main()
    std::queue<S> queue;
    const S& s = queue.emplace(42, 3.14, "C++"); // for return value C++17 required
    std::cout << "id = " << << '\n';


S::S(42, 3.14, "C++")
id = 42

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2783 C++17 emplace returned reference, breaking compatibility with pre-C++17 containers returns decltype(auto)

[edit] See also

inserts element at the end
(public member function) [edit]
removes the first element
(public member function) [edit]