diff --git a/tests/playground/deriv.hs b/tests/playground/deriv.hs
new file mode 100644
index 0000000000..be2a3ca37a
--- /dev/null
+++ b/tests/playground/deriv.hs
@@ -0,0 +1,80 @@
+data Expr =
+    Val Int
+  | Var String
+  | Add Expr Expr
+  | Mul Expr Expr
+  | Pow Expr Expr
+  | Ln  Expr
+
+pown :: Int -> Int -> Int
+pown a 0 = 1
+pown a 1 = a
+pown a n =
+  let b = pown a (n `div` 2) in
+  b * b * (if n `mod` 2 == 0 then 1 else a)
+
+add :: Expr -> Expr -> Expr
+add (Val n)   (Val m)         = Val (n + m)
+add (Val 0)   f               = f
+add f         (Val 0)         = f
+add f         (Val n)         = add (Val n) f
+add (Val n)   (Add (Val m) f) = add (Val (n+m)) f
+add f         (Add (Val n) g) = add (Val n) (add f g)
+add (Add f g) h               = add f (add g h)
+add f         g               = Add f g
+
+mul :: Expr -> Expr -> Expr
+mul (Val n)   (Val m)         = Val (n*m)
+mul (Val 0)   _               = Val 0
+mul _         (Val 0)         = Val 0
+mul (Val 1)   f               = f
+mul f         (Val 1)         = f
+mul f         (Val n)         = mul (Val n) f
+mul (Val n)   (Mul (Val m) f) = mul (Val (n*m)) f
+mul f         (Mul (Val n) g) = mul (Val n) (mul f g)
+mul (Mul f g) h               = mul f (mul g h)
+mul f         g               = Mul f g
+
+pow :: Expr -> Expr -> Expr
+pow (Val m) (Val n) = Val (pown m n)
+pow _       (Val 0) = Val 1
+pow f       (Val 1) = f
+pow (Val 0) _       = Val 0
+pow f       g       = Pow f g
+
+ln :: Expr -> Expr
+ln (Val 1) = Val 0
+ln f       = Ln f
+
+d :: String -> Expr -> Expr
+d x (Val _)   = Val 0
+d x (Var y)   = if x == y then Val 1 else Val 0
+d x (Add f g) = add (d x f) (d x g)
+d x (Mul f g) = add (mul f (d x g)) (mul g (d x f))
+d x (Pow f g) = mul (pow f g) (add (mul (mul g (d x f)) (pow f (Val (-1)))) (mul (ln f) (d x g)))
+d x (Ln f)    = mul (d x f) (pow f (Val (-1)))
+
+count :: Expr -> Integer
+count (Val _) = 1
+count (Var _) = 1
+count (Add f g) = count f + count g
+count (Mul f g) = count f + count g
+count (Pow f g) = count f + count g
+count (Ln f)    = count f
+
+nest_aux :: Int -> (Int -> Expr -> IO Expr) -> Int -> Expr -> IO Expr
+nest_aux s f 0 x = pure x
+nest_aux s f m x = f (s - m) x >>= nest_aux s f (m-1)
+
+nest f n e = nest_aux n f n e
+
+deriv :: Int -> Expr -> IO Expr
+deriv i f = do
+  let f' = d "x" f
+  putStrLn (show (i+1) ++ " count: " ++ (show $ count f'))
+  pure f'
+
+main = do
+  let x = Var "x"
+  let f = pow x x
+  nest deriv 10 f