1 files changed, 38 insertions, 0 deletions
diff --git a/treebanks/PennTreebank/PennFormat.hs b/treebanks/PennTreebank/PennFormat.hs
new file mode 100644
index 000000000..2aaf0a6b6
--- /dev/null
+++ b/treebanks/PennTreebank/PennFormat.hs
@@ -0,0 +1,38 @@
+module PennFormat(parseTreebank, showTree) where
+
+import Text.PrettyPrint
+import Data.Tree
+import Data.Char
+
+parseTreebank :: String -> [Tree String]
+parseTreebank []     = []
+parseTreebank (c:cs)
+  | isSpace c        = parseTreebank cs
+  | c == '('         = let (ts,cs1) = parseTrees cs
+                       in ts ++ parseTreebank cs1
+
+parseTrees []     = ([],[])
+parseTrees (c:cs)
+  | isSpace c     = parseTrees cs
+  | c == ')'      = ([],cs)
+  | c == '('      = let (w,       cs1) = parseWord  cs
+                        (children,cs2) = parseTrees cs1
+                        (rest,    cs3) = parseTrees cs2
+                    in (Node (normalize w) children : rest,cs3)
+  | otherwise     = let (w,       cs1) = parseWord  (c:cs)
+                        (rest,    cs2) = parseTrees cs1
+                    in (Node w [] : rest,cs2)
+
+normalize tag =
+  let (tag0,mod) = break (=='-') tag
+  in if null tag0
+       then tag
+       else tag0
+
+parseWord = break (\c -> isSpace c || c == '(' || c == ')')
+
+printTree (Node w [])       = text w
+printTree (Node l children) = parens (text l <+> hsep (map printTree children))
+
+showTree :: Tree String -> String
+showTree = render . printTree