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

From cppreference.com
 
 
 
std::flat_multimap
 
containers extract() &&;
(since C++23)

Extracts adapted containers c. Equivalent to return std::move(c);.

After this operation *this is empty, even if an exception is thrown.

[edit] Return value

std::move(c).

[edit] Complexity

Constant.

[edit] Example

Run this code
#include <cassert>
#include <flat_map>
#include <print>
#include <type_traits>
#include <utility>
#include <vector>
 
int main()
{
 std::flat_multimap <int, double> map{{1, 1.1}, {2, 2.2}, {3, 3.3}};
 const auto size{map.size()};
 
 auto c{std::move(map).extract()};
 assert (c.keys.size() == size);
 assert (c.values.size() == size);
 assert (map.empty());
 assert (map.keys().empty());
 assert (map.values().empty());
 
 // The default keys and values containers are std::vector:
 static_assert(std::is_same_v <decltype(c.keys), std::vector <int>>);
 static_assert(std::is_same_v <decltype(c.values), std::vector <double>>);
 
 std::println ("keys: {}", c.keys);
 std::println ("values: {}", c.values);
}

Output:

keys: [1, 2, 3]
values: [1.1, 2.2, 3.3]

[edit] See also

replaces the underlying containers
(public member function) [edit]
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