elixir: merge two sorted list

merge_list.ex

defmodule MergeSoredList do
  def merge(l1, []), do: l1
  def merge([], l2), do: l2

  def merge(l1, l2), do: merge(l1, l2, [])
  def merge([], l2, acc), do: acc ++ l2
  def merge(l1, [], acc), do: acc ++ l1

  def merge([head1| tail1], [head2 | _] = l2, acc) when head1 <= head2 do
    merge(tail1, l2, acc ++ [head1])
  end

  def merge([head1| _] = l1, [head2 | tail2], acc) when head2 < head1 do
    merge(l1, tail2, acc ++ [head2])
  end
end

r = MergeSoredList.merge([1, 3, 5, 7, 10], [2, 4, 6, 8])
IO.puts inspect(r)
# [1, 2, 3, 4, 5, 6, 7, 8, 10]