Added a collapse function to Trie

src/GF/Data/Map.hs

@@ -12,6 +12,7 @@ module Map
            (
            Map,
            empty,
+           isEmpty,	   
 	   (!),     -- lookup operator.
 	   (!+),    -- lookupMany operator.
 	   (|->),   -- insert operator.

src/GF/Data/RedBlack.hs

@@ -10,6 +10,7 @@
 
 module RedBlack (
                 emptyTree,
+		isEmpty,		
 		Tree,
 		lookupTree,
 		insertTree,
@@ -32,6 +33,10 @@ balance color a x b = T color a x b
 emptyTree :: Tree key el
 emptyTree = E
 
+isEmpty :: Tree key el -> Bool
+isEmpty (E) = True
+isEmpty _   = False
+
 lookupTree :: Ord a => a -> Tree a b -> Maybe b
 lookupTree _ E = Nothing
 lookupTree x (T _ a (y,z) b)

src/GF/Data/Trie.hs

@@ -10,6 +10,7 @@
 
 module Trie (
              tcompile,
+	     collapse,
              Trie,
 	     trieLookup,
 	     decompose,
@@ -35,6 +36,14 @@ optimize :: TrieT -> Trie
 optimize (TrieT (xs,res)) = Trie ([(c,optimize t) | (c,t) <- xs] |->+ empty,
 				  res)
 
+collapse :: Trie -> [(String,[(Attr,String)])]
+collapse trie = collapse' trie []
+  where collapse' (Trie (map,(x:xs))) s = if (isEmpty map) then [(reverse s,(x:xs))]
+	                                   else (reverse s,(x:xs)):
+					    concat [ collapse' trie (c:s) | (c,trie) <- flatten map]
+	collapse' (Trie (map,[])) s
+	 = concat [ collapse' trie (c:s) | (c,trie) <- flatten map]
+
 tcompile :: [(String,[(Attr,String)])] -> Trie
 tcompile xs = optimize $ build xs emptyTrie