std::front_insert_iterator<Container>::front_insert_iterator

From cppreference.com

constexpr front_insert_iterator() noexcept = default;
(1) (since C++20)
(2)
explicit front_insert_iterator( Container& c );
(until C++20)
constexpr explicit front_insert_iterator( Container& c );
(since C++20)
1) Initializes the underlying pointer to container with nullptr.
(since C++20)
2) Initializes the underlying pointer to the container to std::addressof(c).

Parameters

c - container to initialize the inserter with