 
   """
   def seq(first, last) when is_integer(first) and is_integer(last) and first <= last + 1 do
-    do_seq(last - first + 1, last, [])
+    Erlang.lists.seq(first, last)
   end
 
   @doc """

      #=> -2

  """
  def foldr(list, acc, function) do
    Erlang.lists.foldr(function, acc, list)
  end


      #=> 2

  """
  def foldl(list, acc, function) when is_list(list) and is_function(function) do
    Erlang.lists.foldl(function, acc, list)
  end

