[Haskell-cafe] Libraries to compare trees?

[dokondr]

Please advise on Haskell libraries to compare trees in textual
representation.
I need to compare both structure and node contents of two trees, find
similar sub-trees, and need some metric to measure distance between two
trees.
Also need advice on simple parser to convert textual tree representation
into a data type convenient for tree manipulation (comparison, matching,
etc.) What data type to use for trees with arbitrary structure?

Example trees:

*** Tree 1:
(ROOT
  (S
    (NP (DT The) (NN voice) (NN quality))
    (VP (VBD was)
      (ADJP (JJ clear) (RB too)))
    (. .)))


*** Tree 2:
(ROOT
  (S
    (SBAR (IN Although)
      (S
        (NP (DT the) (NN battery) (NN life))
        (VP (VBD was) (RB not)
          (ADJP (JJ long)))))
    (, ,)
    (NP (DT that))
    (VP (VBZ is)
      (VP (VBN ok)
        (PP (IN for)
          (NP (PRP me)))))
    (. .)))

Thanks!
Dmitri
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