Defines a doubly-linked.
(send a-dllist next) → (is-a?/c dllist<%>) (send a-dllist next new-next) → void? new-next : (is-a?/c dllist<%>)
Gets/sets the next field to be the given dllist.
(send a-dllist prev) → (is-a?/c dllist<%>) (send a-dllist prev new-prev) → void? new-prev : (is-a?/c dllist<%>)
Gets/sets the previous item in the list.
Applies f to every element of the dllist.
Creates a Scheme list by applying f to every element
of a-dllist.