NAME¶

std::flat_map::extract - std::flat_map::extract

Synopsis¶

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.

Parameters¶

(none)

Return value¶

std::move(c).

Complexity¶

Constant.

Example¶

// Run this code

#include <cassert>
#include <flat_map>
#include <print>
#include <type_traits>
#include <vector>

int main()
{
std::flat_map<int, double> map{{1, 1.1}, {2, 2.2}, {3, 3.3}};
const auto size = map.size();

auto c = 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.value), std::vector<int>>);

std::println("keys: {}", c.keys);
std::println("values: {}", c.values);
}

Output:¶

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

See also¶

replace replaces the underlying containers
(public member function)