Clean up HW2 code.

HW2.fedorind.hs

@@ -32,7 +32,7 @@ instance Functor Tree where
 
 -- | Map a function over a tree. Applies the given function to every label
 --   in the tree, preserving the tree's structure.
---   
+--
 --   >>> mapTree odd End
 --   End
 --
@@ -92,12 +92,12 @@ valueAt (x:xs) (Node a l r) = valueAt xs $ if x == L then l else r
 --   >>> pathTo 10 ex
 --   Nothing
 --
+
 pathTo :: Eq a => a -> Tree a -> Maybe Path
 pathTo v End = Nothing
 pathTo v (Node a l r) = orElse currentNode $ orElse (pathHelper v l L) $ pathHelper v r R
     where
         currentNode = if a == v then Just [] else Nothing
-        pathHelper v tree dir = (pathTo v tree) >>= (Just . (dir:))
-        orElse m1 m2 = case m1 of
-            Just _ -> m1
-            Nothing -> m2
+        pathHelper v tree dir = fmap (dir:) (pathTo v tree)
+        orElse m1 m2 = if isJust m1 then m1 else m2
+        isJust mx = mx /= Nothing