std::multimap::emplace
From cppreference.com
| template< class... Args >
iterator emplace( Args&&... args ); |
(since C++11) | |
Inserts a new element into the container by constructing it in-place with the given args .
Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations.
The constructor of the new element (i.e. std::pair<const Key, T>) is called with exactly the same arguments as supplied to emplace, forwarded via std::forward<Args>(args)....
No iterators or references are invalidated.
Contents |
[edit] Parameters
| args | - | arguments to forward to the constructor of the element |
[edit] Return value
Returns an iterator to the inserted element.
[edit] Exceptions
If an exception is thrown by any operation, this function has no effect.
[edit] Complexity
Logarithmic in the size of the container.
[edit] Example
Run this code
#include <iostream> #include <utility> #include <string> #include <map> int main() { std::multimap<std::string, std::string> m; // uses pair's move constructor m.emplace(std::make_pair(std::string("a"), std::string("a"))); // uses pair's converting move constructor m.emplace(std::make_pair("b", "abcd")); // uses pair's template constructor m.emplace("d", "ddd"); // uses pair's piecewise constructor m.emplace(std::piecewise_construct, std::forward_as_tuple("c"), std::forward_as_tuple(10, 'c')); for (const auto &p : m) { std::cout << p.first << " => " << p.second << '\n'; } }
Output:
a => a b => abcd c => cccccccccc d => ddd
[edit] See also
| (C++11)
|
constructs elements in-place using a hint (public member function) |
| inserts elements (public member function) |