lab06: impl

lab06/functors.lhs

@@ -3,6 +3,10 @@
 >   | Node v (Tree v) (Tree v)
 >   deriving (Show)
 
+> instance Functor Tree where
+>   fmap f (Node v left right) = Node (f v) (fmap f left) (fmap f right)
+>   fmap f Empty = Empty
+
 The findT method shows how we may search through the tree to find a value.
 
 > findT :: Ord v => v -> Tree v -> Maybe v
@@ -18,4 +22,3 @@ The findT method shows how we may search through the tree to find a value.
 Your job is to add support for fmap to this tree, so that the call to fmap below works:
 
 > main = print $ fmap (+1) (Node 3 (Node 1 Empty Empty) (Node 7 (Node 4 Empty Empty) Empty))
-