{- A multiline comment which can continue for many lines -} 

data Expr = Val Int | Div Expr Expr
-- data Maybe a = Nothing | Just a


eval :: Expr -> Int
eval (Val n) = n
eval (Div x y) = eval x `div`  eval y

safediv :: Int -> Int -> Maybe Int
safediv n m = if m== 0 then Nothing else Just (n `div` m)