The CircularDeque type implements a double-ended queue using a circular buffer of fixed capacity. This data structure supports constant-time insertion/removal of elements at both ends of a sequence.


a = CircularDeque{Int}(n)   # allocate a deque with maximum capacity n
isempty(a)          # test whether the deque is empty
empty!(a)           # reset the deque
capacity(a)         # return capacity
length(a)           # get the number of elements currently in the deque
push!(a, 10)        # add an element to the back
pop!(a)             # remove an element from the back
pushfirst!(a, 20)   # add an element to the front
popfirst!(a)        # remove an element from the front
first(a)            # get the element at the front
last(a)             # get the element at the back
eltype(a)           # return type of items

Note: Julia's Vector type also provides this interface, and thus can be used as a deque. However, the CircularDeque type in this package is implemented as a circular buffer, and thus avoids copying elements when modifications are made to the front of the vector.

Benchmarks show that the performance of CircularDeque is several times faster than Deque.