square :: Int -> Int
square x  =  x * x

add :: Int -> Int -> Int
add x y  =  x + y

factorial :: Int -> Int
cannot conjure

factorial :: Int -> Int
factorial x  =  foldr (*) 1 (enumFromTo 1 x)

second :: [Int] -> Int
second xs  =  head (tail xs)

(++) :: [Int] -> [Int] -> [Int]
xs ++ ys  =  foldr (:) ys xs

reverse :: [Int] -> [Int]
cannot conjure

reverse :: [Int] -> [Int]
reverse xs  =  foldr (foldr (:) . unit) [] xs