Queues, stacks, and 'deques' are list-like, abstract data types. These are meant to be very cheap to "grow", or insert new objects into. A typical use case involves storing data in a list in a streaming fashion, when you do not necessarily know how may elements need to be stored. Unlike R's lists, the new data structures provided here are not necessarily stored contiguously, making insertions and deletions at the front/end of the structure much faster. The underlying implementation is new and uses a head/tail doubly linked list; thus, we do not rely on R's environments or hashing. To avoid unnecessary data copying, most operations on these data structures are performed via side-effects.