Popfront

Popfront, often written as pop_front, is an operation on a container that removes the first element. Depending on the API, the operation may return the removed element or may discard it; in the latter case, the value may need to be retrieved before the removal.

Common implementations include queues, deques, and linked lists, where pop_front is typically performed in constant time. By contrast, removing the first element from arrays or vectors usually requires shifting or reallocation, resulting in linear time (O(n)) in the size of the container and making frequent front removals less efficient.

Usage examples and behavior vary by language and library. In a typical queue, you may check that it is non-empty, inspect the front element, and then remove it. Pseudo-code: if not q.is_empty(): v = q.front(); q.pop_front(); In some libraries, pop_front returns the removed value (for example, Rust’s VecDeque.pop_front()), while others require a separate front access before removal (as in C++'s deque, where front() can be used before pop_front()).

Notes and related concepts: pop_front is often paired with push_front or push_back to model double-ended queues. In JavaScript, a similar effect is achieved with shift(), which removes the first element from an array. When designing performance-critical code, front removals are best performed on deques or linked structures rather than on arrays or vectors.

See also: push_front, push_back, dequeue, shift, removeFirst.