Delete cruft, add Reader monad to some internal ai

src/Dodge/Graph.hs

@@ -1,18 +1,20 @@
 module Dodge.Graph
   where
 import Data.Function (on)
-import Data.List
+import Data.List.Extra
 
+import Data.Bifunctor (first)
 import Data.Graph
+import Data.Maybe
 
 pairsToIncidence :: (Eq a,Ord a) => [(a,a)] -> [(a,[a])]
-pairsToIncidence = map ((\(xs,ys) -> (head xs,ys)) . unzip)
-                     . groupBy ( (==) `on` fst)
-                     . sort
+pairsToIncidence 
+    = map (first head . unzip)
+    . groupOn fst
+    . sort
 
 incidenceToFunction :: Eq a => [(a,[a])] -> a -> [a]
-incidenceToFunction xs a = case lookup a xs of Just ys -> ys
-                                               Nothing -> []
+incidenceToFunction xs a = fromMaybe [] $ lookup a xs
 
 mkNode :: (a,[a]) -> (a,a,[a])
 mkNode (x,xs) = (x,x,xs)