Modularise graph functions

src/Dodge/Graph.hs

@@ -0,0 +1,21 @@
+module Dodge.Graph
+  where
+import Data.Function (on)
+import Data.List
+
+import Data.Graph
+
+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 -> []
+
+mkNode :: (a,[a]) -> (a,a,[a])
+mkNode (x,xs) = (x,x,xs)
+
+pairsToSCC :: (Eq a, Ord a) => [(a,a)] -> [SCC a]
+pairsToSCC = stronglyConnComp . map mkNode . pairsToIncidence