generators.ET0LTreeGrammar:
(
  { A, F },
  { F:0, conc:5, conc:2, enc2+:1, enc3-:1, -:1, enc:2, empty:0 },
  {
    {
      A -> conc[F, enc2+[A], F, enc3-[A], enc[F, -[A]]],
      F -> conc[F,F]
    },
    {
      A -> empty,
      F -> F
    }
  },
  A, 1+ 2
)
