Modularise graph functions

src/Dodge/Path.hs

@@ -1,6 +1,7 @@
 module Dodge.Path where
 import Dodge.Data
 import Dodge.Base
+import Dodge.Graph
 
 import Geometry
 
@@ -160,12 +161,3 @@ maybeToEither :: a -> Maybe b -> Either a b
 maybeToEither _ (Just x) = Right x
 maybeToEither y Nothing  = Left y
 
-pairsToIncidence :: (Eq a,Ord a) => [(a,a)] -> [(a,[a])]
-pairsToIncidence = map ((\(xs,ys) -> (head xs,ys)) . unzip)
-                     . groupBy ( (==) `on` fst)
-                     . sort
-
-incidenceToFunction :: Eq a => [(a,[a])] -> a -> [a]
-incidenceToFunction xs a = case lookup a xs of Just ys -> ys
-                                               Nothing -> []
-