std::stack<T,Container>::emplace - cppreference.com (original) (raw)
| 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 on top of the stack. 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
| (none) | (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
#include
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::stack stack;
const S& s = stack.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) |
[edit] See also
| | inserts element at the top (public member function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | removes the top element (public member function) [edit] |