scope
  variable Natural : Type.
  alias ℕℕ : Natural.
  variable x : Natural.
  print environment 1.
  set_option pp::unicode false.
  print environment 1.
  set_option pp::unicode true.
  print environment 1.
  alias NN : Natural.
  print environment 2.
  alias ℕℕℕ : Natural.
  print environment 3.
  set_option pp::unicode false.
  print environment 3.
pop_scope