generators.ET0LTreeGrammar:
( { 0, 1, 2, 3, Ha, Va, Hb, Vb },
  { h:2, v:2, c:1, a:0, b:0 },
  {
    {
      0 -> v[1,c[Ha]],
      1 -> h[2,c[Va]],
      2 -> v[c[Ha],3],
      3 -> h[c[Va],0],
      0 -> v[1,c[Hb]],
      1 -> h[2,c[Vb]],
      2 -> v[c[Hb],3],
      3 -> h[c[Vb],0],
      Ha -> h[a,Ha],
      Va -> v[a,Va],
      Hb -> h[b,Hb],
      Vb -> v[b,Vb]
    },
    {
      0 -> c[v[a,a]],
      1 -> c[h[a,a]],
      2 -> c[v[a,a]],
      3 -> c[h[a,a]],
      Ha -> h[a,a],
      Va -> v[a,a],
      0 -> c[v[b,b]],
      1 -> c[h[b,b]],
      2 -> c[v[b,b]],
      3 -> c[h[b,b]],
      Hb -> h[b,b],
      Vb -> v[b,b]
    }
  },
  0
)
