Deque (double-ended queue) is a data structure which promises the same speed of operation wether you’re modifying or reading from the front or back of the deque. This in comparison with the builtin List, which is only fast if reading/modifiying from the start of the list.
In this version I’ve added initialize, repeat and range to make it easier and faster to construct a deque.
In addition, the performance of the structure is now more stable than before, and the performance of left, right, dropLeft and dropRight has increased by 4-5x.
Another use case for Dequeue might be if you want a FIFO (first-in first-out) data structure in order to implement a breadth-first search. Same as (1) above really.
Use a List for LIFO (last-in first-out) for a depth first search.