std::multimap<Key,T,Compare,Allocator>::emplace (3) - Linux Man Pages

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

NAME

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

Parameters


args - arguments to forward to the constructor of the element

Return value


Returns an iterator to the inserted element.

Exceptions


If an exception is thrown by any operation, this function has no effect.

Complexity


Logarithmic in the size of the container.

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

See also


emplace_hint constructs elements in-place using a hint
             (public member function)
(C++11)
             inserts elements
             or nodes
insert (since C++17)
             (public member function)