std::flat_multimap<Key,T,Compare,KeyContainer,MappedContainer>::emplace
(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 |
| Member types | ||||
| Member functions | ||||
| Non-member functions | ||||
| Helper classes | ||||
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| Deduction guides | ||||
template< class... Args > iterator emplace( Args&&... args ); |
(since C++23) (constexpr since C++26) |
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Inserts a new element into the container constructed in-place with the given args.
Initializes an object t of type std::pair<key_type, mapped_type> with std::forward<Args>(args)...; if the map already contains an element whose key is equivalent to t.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 if std::is_constructible_v<std::pair<key_type, mapped_type>, Args...> is true.
If value_type is not EmplaceConstructible into flat_multimap from args, the behavior is undefined.
| Information on iterator invalidation is copied from here |
Contents |
[edit] Parameters
| args | - | arguments to forward to the constructor of the element |
[edit] Return value
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
Linear in the size of the container
[edit] Notes
Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations.
[edit] Example
#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 (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 elements (public member function) [edit] |
