A handy macro for replacing vars with atoms and vice versa

gistfile1.ex

defmodule Atomize do
  @doc """
  Given an expression, replaces all variables with atoms and atoms with
  variables.

  For example,

      a = 1; b = "string"
      Atomize.invert {a, :a, {{b, :b}, [c, d]}}
      #=> {:a, 1, {{:b, "string"}, [:c, :d]}}

  It can be useful when passing large amounts of atoms between Elixir and
  Erlang.
  """
  defmacro invert(expr) do
    vars_to_atoms expr
  end

  defp vars_to_atoms({atom, _, nil}), do: atom
  defp vars_to_atoms(atom) when is_atom(atom), do: {atom, 0, nil}

  defp vars_to_atoms({atom, _line, args}) when is_list(args) do
    {atom, _line, vars_to_atoms(args)}
  end

  defp vars_to_atoms(tuple) when is_tuple(tuple) do
    list_to_tuple(vars_to_atoms tuple_to_list(tuple))
  end

  defp vars_to_atoms(list) when is_list(list) do
    lc arg in list, do: vars_to_atoms(arg)
  end

  defp vars_to_atoms(other), do: other
end