[add sccForest, dff, and dfs
John Meacham <john@repetae.net>**20061130061901] hunk ./Util/Graph.hs 62
+
+sccForest :: Graph n k -> Forest n
+sccForest (Graph g ln kv fn) = map (fmap ln) forest where
+    forest = Data.Graph.scc g
+
+dff :: Graph n k -> Forest n
+dff (Graph g ln kv fn) = map (fmap ln) forest where
+    forest = Data.Graph.dff g
+
+dfs :: Graph n k -> [k] -> Forest n
+dfs (Graph g ln kv fn) ks = map (fmap ln) forest where
+    forest = Data.Graph.dfs g [ v | Just v <- map kv ks]