function Dequeue: T; inline;
T __fastcall Dequeue();
Removes the item from the beginning of the queue.
Dequeue is the same as Extract except for the event code indicating an element was removed rather than extracted. Extract is a more generic method, common to all collections, whereas Dequeue is specialized for TQueue. You can use either of the two functions to obtain and remove the item at the beginning of the queue.
This is a O(1) operation.