std::multiset<Key,Compare,Allocator>:: emplace
| 
           
            
             template
            
            
             <
            
            
             class
            
            ...
            
             Args
            
            
             >
            
             iterator emplace ( Args && ... args ) ; | (since C++11) | |
Inserts a new element into the container constructed in-place with the given args .
       The constructor of the new element 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
#include <chrono> #include <cstddef> #include <functional> #include <iomanip> #include <iostream> #include <string> #include <set> class Dew { private: int a, b, c; public: Dew(int _a, int _b, int _c) : a(_a), b(_b), c(_c) {} bool operator<(const Dew& other) const { return (a < other.a) || (a == other.a && b < other.b) || (a == other.a && b == other.b && c < other.c); } }; constexpr int nof_operations{101}; std::size_t set_emplace() { std::multiset<Dew> set; for (int i = 0; i < nof_operations; ++i) for (int j = 0; j < nof_operations; ++j) for (int k = 0; k < nof_operations; ++k) set.emplace(i, j, k); return set.size(); } std::size_t set_insert() { std::multiset<Dew> set; for (int i = 0; i < nof_operations; ++i) for (int j = 0; j < nof_operations; ++j) for (int k = 0; k < nof_operations; ++k) set.insert(Dew(i, j, k)); return set.size(); } void time_it(std::function<int()> set_test, std::string what = "") { const auto start = std::chrono::system_clock::now(); const auto the_size = set_test(); const auto stop = std::chrono::system_clock::now(); const std::chrono::duration<double, std::milli> time = stop - start; if (!what.empty() && the_size) std::cout << std::fixed << std::setprecision(2) << time << " for " << what << '\n'; } int main() { time_it(set_insert, "cache warming..."); time_it(set_insert, "insert"); time_it(set_insert, "insert"); time_it(set_emplace, "emplace"); time_it(set_emplace, "emplace"); }
Possible output:
499.61ms for cache warming... 447.89ms for insert 436.77ms for insert 430.62ms for emplace 428.61ms for emplace
See also
| 
           
            
             
              (C++11)
             
            
           
           | constructs elements in-place using a hint (public member function) | 
| inserts elements
         
          
           or nodes
          
          
           
            (since C++17) (public member function) |