list flattening

flatten.ex

defmodule Flatten do
  def flatten(deep_list), do: collect_flattened([], deep_list)

  defp collect_flattened(acc, []), do: acc
  defp collect_flattened(acc, [h | t]) do
    acc
    |> collect_flattened(t)
    |> flatten(h)
  end

  defp flatten(acc, []), do: acc
  defp flatten(acc, [_|_] = list), do: collect_flattened(acc, list)
  defp flatten(acc, element), do: [element | acc]
end

IO.inspect Flatten.flatten([])
IO.inspect Flatten.flatten([1,2,3])
IO.inspect Flatten.flatten([1,[[2,[[[3]]]]],[[[4], 5], 6], [], [[[]]]])