polymorph trie added

src/GF/Data/Trie2.hs

@@ -0,0 +1,55 @@
+{- 
+   **************************************************************
+   * Author        : Markus Forsberg                            *
+   *                 markus@cs.chalmers.se                      *
+   ************************************************************** 
+-}
+module Trie2 (
+             tcompile,
+	     collapse,
+             Trie,
+	     trieLookup
+	    ) where
+
+import Map
+
+newtype TrieT a b = TrieT ([(a,TrieT a b)],[b])
+
+newtype Trie a b = Trie (Map a (Trie a b), [b])
+
+emptyTrie = TrieT ([],[])
+
+optimize :: Ord a => TrieT a b -> Trie a b
+optimize (TrieT (xs,res)) = Trie ([(c,optimize t) | (c,t) <- xs] |->+ empty,
+				  res)
+
+collapse :: Ord a => Trie a b -> [([a],[b])]
+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 :: Ord a => [([a],[b])] -> Trie a b
+tcompile xs = optimize $ build xs emptyTrie
+
+build :: Ord a => [([a],[b])] -> TrieT a b -> TrieT a b
+build []     trie = trie
+build (x:xs) trie = build xs (insert x trie)
+ where 
+  insert ([],ys)     (TrieT (xs,res)) = TrieT (xs,ys ++ res)
+  insert ((s:ss),ys) (TrieT (xs,res)) 
+    = case (span (\(s',_) -> s' /= s) xs) of
+       (xs,[])          -> TrieT (((s,(insert (ss,ys) emptyTrie)):xs),res)
+       (xs,(y,trie):zs) -> TrieT (xs ++ ((y,insert (ss,ys) trie):zs),res)
+
+trieLookup :: Ord a => Trie a b -> [a] -> ([a],[b])
+trieLookup trie s = apply trie s s
+
+apply :: Ord a => Trie a b -> [a] -> [a] -> ([a],[b])
+apply (Trie (_,res)) [] inp = (inp,res)
+apply (Trie (map,_)) (s:ss) inp
+ = case map ! s of
+    Just trie -> apply trie ss inp
+    Nothing   -> (inp,[])