std::stack<T,Container>:: emplace
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 ) ... ) ; .
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
#include <iostream> #include <stack> 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<S> 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)
|
See also
inserts element at the top
(public member function) |
|
removes the top element
(public member function) |