(C++17) | ||||
| Sequence | ||||
(C++11) | ||||
(C++26) | ||||
(C++26) | ||||
(C++11) | ||||
| Associative | ||||
| Unordered associative | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
| Adaptors | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
| Views | ||||
(C++20) | ||||
(C++23) | ||||
| Tables | ||||
| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
template<class...Args> iterator emplace( Args&&...args); | (since C++23) (constexpr since C++26) | |
Inserts a new element into the container constructed in-place with the givenargs.
Initializes an objectt of typestd::pair<key_type, mapped_type> withstd::forward<Args>(args)...; if the map already contains an element whose key is equivalent tot.first,*this is unchanged. Otherwise, equivalent to:
auto key_it=ranges::upper_bound(c.keys, t.first, compare);auto value_it= c.values.begin()+std::distance(c.keys.begin(), key_it);c.keys.insert(key_it, std::move(t.first));c.values.insert(value_it, std::move(t.second));
This overload participates in overload resolution only ifstd::is_constructible_v<std::pair<key_type, mapped_type>, Args...> istrue.
Ifvalue_type is notEmplaceConstructible intoflat_multimap fromargs, the behavior is undefined.
| Information on iterator invalidation is copied fromhere |
Contents |
| args | - | arguments to forward to the constructor of the element |
An iterator to the inserted element.
If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).
Linear in the size of the container
Careful use ofemplace allows the new element to be constructed while avoiding unnecessary copy or move operations.
#include <iostream>#include <string>#include <utility>#include <flat_map> 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(constauto& p: m)std::cout<< p.first<<" => "<< p.second<<'\n';}
Output:
a => ab => abcdc => ccccccccccd => dddd => DDD
| constructs elements in-place using a hint (public member function)[edit] | |
| inserts elements (public member function)[edit] |
