# std::queue<T,Container>::emplace

From cppreference.com
< 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)...);

### Parameters

args | - | arguments to forward to the constructor of the element

### Return value

(none) | (until C++17)
The value or reference, if any, returned by the above call to Container::emplace_back. | (since C++17)

### Complexity

Identical to the complexity of Container::emplace_back.

### Example

Run this code

    #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> adaptor;

        const S& s = adaptor.emplace(42, 3.14, "C++"); // for return value C++17 required

        std::cout << "id = " << s.id << '\n';
    }

Output:

    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)`

### See also

push | inserts element at the end (public member function)
pop | removes the first element (public member function)

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