HW1.fedorind.hs

@@ -10,7 +10,7 @@ data Tree
 
 -- | An example binary tree, which will be used in tests.
 t1 :: Tree
-t1 = Node 1 (Node 2 (Node 3 (Leaf 4) (Lea 5))
+t1 = Node 1 (Node 2 (Node 3 (Leaf 4) (Leaf 5))
                     (Leaf 6))
             (Node 7 (Leaf 8) (Leaf 9))
 
@@ -62,7 +62,7 @@ treeFold f a (Node i l r) = f i $ treeFold f (treeFold f a r) l
 --   1
 --
 leftmost :: Tree -> Int
-leftmost = treeFoldr1 (\a _ -> a)
+leftmost = treeFoldr1 const
 
 -- | The integer at the right-most node of a binary tree.
 --
@@ -79,7 +79,7 @@ leftmost = treeFoldr1 (\a _ -> a)
 --   9
 --
 rightmost :: Tree -> Int
-rightmost = treeFoldl1 (\a _ -> a)
+rightmost = treeFoldl1 const
 
 -- | Get the maximum integer from a binary tree.
 --

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 = fmap (dir:) (pathTo v tree)
-        orElse m1 m2 = if isJust m1 then m1 else m2
-        isJust mx = mx /= Nothing
+        pathHelper v tree dir = (pathTo v tree) >>= (Just . (dir:))
+        orElse m1 m2 = case m1 of
+            Just _ -> m1
+            Nothing -> m2