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std::flat_multimap<Key,T,Compare,KeyContainer,MappedContainer>::emplace

From cppreference.com
 
 
 
 
template< class... Args >
iterator emplace( Args&&... args );
(since C++23)

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

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

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

[edit] Complexity

Logarithmic in the size of the container.

[edit] Example

#include <iostream>
#include <string>
#include <flat_map>
#include <utility>
 
int main()
{
    std::flat_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

[edit] See also

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