tasks a-s

Task/Parametric-polymorphism/Haskell/parametric-polymorphism-1.hs

@@ -0,0 +1,5 @@
+data Tree a = Empty | Node a (Tree a) (Tree a)
+
+mapTree :: (a -> b) -> Tree a -> Tree b
+mapTree f Empty        = Empty
+mapTree f (Node x l r) = Node (f x) (mapTree f l) (mapTree f r)

Task/Parametric-polymorphism/Haskell/parametric-polymorphism-2.hs

@@ -0,0 +1,3 @@
+instance Functor Tree where
+    fmap f Empty        = Empty
+    fmap f (Node x l r) = Node (f x) (fmap f l) (fmap f r)

Task/Parametric-polymorphism/Haskell/parametric-polymorphism-3.hs

@@ -0,0 +1,2 @@
+add1Everywhere :: (Functor f, Num a) => f a -> f a
+add1Everywhere nums = fmap (\x -> x + 1) nums