std::multimap<Key,T,Compare,Allocator>:: emplace

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 ) ... .

If value_type is not EmplaceConstructible into multimap from args , the behavior is undefined.

No iterators or references are invalidated.

Parameters

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.

Notes

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

Example

#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';
}

a => a
b => abcd
c => cccccccccc
d => ddd
d => DDD

See also