   @doc """
   Performs a depth-first, pre-order traversal of quoted expressions.
 
-  Returns a new ast where each node is the result of invoking `fun` on each
+  Returns a new AST where each node is the result of invoking `fun` on each
   corresponding node of `ast`.
 
   ## Examples

  @doc """
  Performs a depth-first traversal of quoted expressions
  using an accumulator.
  """
  @spec traverse(t, any, (t, any -> {t, any}), (t, any -> {t, any})) :: {t, any}
  def traverse(ast, acc, pre, post) when is_function(pre, 2) and is_function(post, 2) do

      ...>   {:*, meta, children} -> {:+, meta, children}
      ...>   other -> other
      ...> end)
      iex> {:*, _, [5, {:+, _, [3, 7]}]} = new_ast
      iex> Code.eval_quoted(ast)
      {26, []}
      iex> Code.eval_quoted(new_ast)
