generators.ET0LTreeGrammar("DT0L version"):
  ( { p, pl, pr },
    { F:2, F1:1, F2:1, G:2, G1:1, G2:1, p:0, pl:0, pr:0, move:1 },
    { { p -> F[p,pr], pl -> G1[pl], pr -> F1[pr] },
      { p -> G[pl,p], pl -> G2[pl], pr -> F2[pr] }
    },
    move[p] )
% Note: Move only translates the picture downwards, so that its postion
% fits nicer with the display.