limited_queue

limited_queue is a simple Elixir queue, with a constant-time size/1 and a maximum capacity.

Usage

Add it to mix.exs

defp deps do
  [{:limited_queue, "~> 0.1.0"}]
end

Create a new queue with a capacity and drop strategy, then push and pop values from it.

queue = 
  LimitedQueue.new(2, :drop_newest)
  |> LimitedQueue.push("a")
  |> LimitedQueue.push("b")
  |> LimitedQueue.push("c")

{:ok, queue, "a"} = LimitedQueue.pop(queue)
{:ok, queue, "b"} = LimitedQueue.pop(queue)
{:error, :empty} = LimitedQueue.pop(queue)
0 = LimitedQueue.size(queue)
2 = LimitedQueue.capacity(queue)

You can also append/2 multiple values to a queue at once, and get information about how many were dropped.

queue = LimitedQueue.new(2, :drop_newest)

{queue, dropped} = LimitedQueue.append(queue, ["a", "b", "c"])
1 = dropped
2 = LimitedQueue.size(queue)

{:ok, queue, "a"} = LimitedQueue.pop(queue)
{:ok, queue, "b"} = LimitedQueue.pop(queue)
{:error, :empty} = LimitedQueue.pop(queue)

split/2 allows getting multiple values from the queue at once.

queue = LimitedQueue.new(10, :drop_newest)

{queue, 0} = LimitedQueue.append(queue, ["a", "b", "c"])

{queue, values} = LimitedQueue.split(queue, 2)
["a", "b"] = values
1 = LimitedQueue.size(queue)

Documentation

This library contains internal documentation. Documentation is available on HexDocs, or you can generate the documentation from source:

$ mix deps.get
$ mix docs

Running the Tests

Tests can be run by running mix test in the root directory of the library.

Compared to `deque`

LimitedQueue has similar performance to deque depending on the situation (see Benchmarks). It has a more special-purpose limited interface, it is a single-sided queue, and its internals are built on Erlang's :queue.