Simple implementation of a breadth-first tree traversal written in Elixir

breadth_first_traversal.ex

defmodule Tree do
  @moduledoc """
  Simple implementation of a breadth-first tree traversal.
  
  Author: William Carroll
  
  """
  
  @type value :: any
  @type tree :: {value [tree]}
  
  @spec bf_print_tree(tree) :: :ok
  def bf_print_tree(tree) do
    queue =
      :queue.in(tree, :queue.new())

    do_bf_print_tree(queue)
  end

  @spec do_bf_print_tree(:queue.queue(tree)) :: :ok
  defp do_bf_print_tree(queue) do
    case :queue.out(queue) do
      {{:value, {value, children}}, queue} ->
        IO.inspect(value)

        queue =
          case children do
            nil ->
              queue

            children when is_list(children) ->
              children
              |> Enum.reduce(queue, & :queue.in(&1, &2))
          end

        do_bf_print_tree(queue)

      {:empty, _} ->
        nil
    end
  end

end