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