RosettaCodeData/Task/Tree-from-nesting-levels/J/tree-from-nesting-levels-6.j

   pnest '((a b) c (d e) f) g (h i)'
┌─────────────────┬─┬─────┐
│┌─────┬─┬─────┬─┐│g│┌─┬─┐│
││┌─┬─┐│c│┌─┬─┐│f││ ││h│i││
│││a│b││ ││d│e││ ││ │└─┴─┘│
││└─┴─┘│ │└─┴─┘│ ││ │     │
│└─────┴─┴─────┴─┘│ │     │
└─────────────────┴─┴─────┘