generators.ET0LTreeGrammar:
( { H, A },
  {F:7, G:1, line:0, cap:0, shift:1 },
  {
    {
      H -> F[H,A,H,A,H,A,H],
      A -> G[A]
    },
    {
      H -> cap,
      A -> line
    }
  },
  shift[H] % shift has been added only to centre the picture
           % in the display.
)
