NAME¶

std::multimap::emplace - std::multimap::emplace

Synopsis¶

template< class... Args > (since C++11)
iterator emplace( Args&&... args );

Inserts a new element into the container constructed in-place with the given args.

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)....

Careful use of emplace allows the new element to be constructed while avoiding
unnecessary copy or move operations.

No iterators or references are invalidated.

Parameters¶

args - arguments to forward to the constructor of the element

Return value¶

An iterator to the inserted element.

Exceptions¶

If an exception is thrown for any reason, this function has no effect (strong
exception safety guarantee).

Complexity¶

Logarithmic in the size of the container.

Example¶

// Run this code

#include <iostream>
#include <string>
#include <utility>
#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");

// emplace with duplicate key
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
d => DDD

See also¶

emplace_hint constructs elements in-place using a hint
(C++11) (public member function)
inserts in-place if the key does not exist, does nothing if the key
try_emplace exists
(public member function)
inserts elements
insert or nodes
(since C++17)
(public member function)