big tidy

Logic/Graph.hs

@@ -2,23 +2,31 @@ module Logic.Graph where
 
 import Data.Set (Set, insert)
 
-bfs :: (Eq a, Ord a) => a -> a -> (a -> [(edge, a)]) -> Maybe [edge]
-bfs goal start getEdges = reverse <$> aux [([], start)] mempty
+type GetEdges vertex edge = vertex -> [(vertex, edge)]
+type GetEdgesCosts vertex edge cost = vertex -> [((vertex, edge), cost)]
+
+bfs
+  :: (Eq vertex, Ord vertex)
+  => GetEdges vertex edge
+  -> vertex
+  -> vertex
+  -> Maybe [edge]
+bfs getEdges goal start = reverse <$> aux [(start, [])] mempty
   where
     aux [] _ = Nothing
-    aux ((path, vertex):queue) visited
+    aux ((vertex, path):queue) visited
       | vertex == goal = Just path
       | otherwise =
         let new = getUnvisitedAdjacent vertex visited
         in
-          case filter (\(_, v) -> v == goal) new of
+          case filter (\(v, _) -> v == goal) new of
             [] ->
-              let queue' = queue ++ map (\(edge, next) -> (edge:path, next)) new
+              let queue' = queue ++ map (\(next, edge) -> (next, edge:path)) new
               in aux queue' $ insert vertex visited
-            ((edge, _):_) -> Just (edge:path)
+            ((_, edge):_) -> Just (edge:path)
 
     getUnvisitedAdjacent vertex visited =
-      filter (\(edge, next) -> not $ next `elem` visited) $
+      filter (\(next, edge) -> not $ next `elem` visited) $
       getEdges vertex
 
 {-