"as.rdeque"(x, ...)rdeque.
as.list,
after this an rdeque of the appropriate size is created holding the elements. The element at x[[1]]
becomes the front of the rdeque. Runs in time $O(n)$, in the size of the number of elements contained in the resulting rdeque.
rdeque for info about rdeques, as.rdeque for the generic function.