std::queue emplace() method

since C++17

// Non const version only
template< class... Args >
decltype(auto) emplace( Args&&... args );

since C++11

// Non const version only
template< class... Args >
void emplace( Args&&... args );

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.

note

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

Parameters

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

Return value

since C++17

(none)

until C++17

The value or reference, if any, returned by the above call to the underlying container's emplace_back.

Complexity

Equivalent to that of emplace_back of the underlying container.

Example

Main.cpp

#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