*Main> :k Maybe 
Maybe :: * -> *
*Main> :k Maybe Integer 
Maybe Integer :: *
*Main> :k Integer
Integer :: *
*Main> :k Either
Either :: * -> * -> *
*Main> :k Either Bool
Either Bool :: * -> *
*Main> :k Either Bool Integer 
Either Bool Integer :: *
*Main> :t Left
Left :: a -> Either a b
*Main> :k (Int -> Either Int Bool)
(Int -> Either Int Bool) :: *
*Main> :k (->)
(->) :: * -> * -> *
*Main> :k (->) Int
(->) Int :: * -> *
*Main> :k (->) Int Bool
(->) Int Bool :: *
*Main> :k [Int]
[Int] :: *
*Main> :k []
[] :: * -> *
*Main> :t []
[] :: [a]
*Main> :k [] Int
[] Int :: *