bubble.exs

defmodule Bubble do
  def sort(list) do
    do_sort list, {[], false}
  end

  defp do_sort([a, b | tail], {acc, _}) when b < a do
    do_sort [a | tail], {[b | acc], true}
  end
  
  defp do_sort([a | tail], {acc, swapped?}) do
    do_sort tail, {[a | acc], swapped?}
  end

  defp do_sort([], {acc, true}) do
    do_sort Enum.reverse(acc), {[], false}
  end

  defp do_sort([], {acc, _}) do
    Enum.reverse acc
  end
end 



ExUnit.start()

defmodule Bubble.Test do
  use ExUnit.Case
  @numbers [3, 2, 1, 4, 5, 9, 8, 7]
  test "basic sorting" do
    assert Enum.sort(@numbers) == Bubble.sort(@numbers)
  end
end