C++: What is std::hive (P0447)?

1#include <hive>
2
3std::hive<int> h;
4
5// O(1) insert
6auto it1 = h.insert(1);
7auto it2 = h.insert(2);
8auto it3 = h.insert(3);
9
10// O(1) erase — iterators stay valid
11h.erase(it2);
12std::cout << *it1;  // Still valid!
13
14// Iteration (skips erased elements)
15for (int x : h) {
16    std::cout << x << " ";
17}
18
19// Sorted order (by insertion or by predicate)
20std::hive<int, std::less<int>> sorted_hive;
21sorted_hive.insert(3);
22sorted_hive.insert(1);
23sorted_hive.insert(2);
24// Iteration: 1, 2, 3
25
26// Reserve
27h.reserve(1000);
28
29// Size
30std::cout << h.size();