Imperative Programming in Haskell

{-

...but what if we need state?
How would we write this imperative pseudocode in Haskell without the IO monad or any other monad?

x = 1
y = 2
x = x + y        comment: x == 3
y = x * y        comment: y == 3 * 2 = 6
result = x + y   comment: 3 + 6 = 9

-}

type LineLabel = Int
type Program t = LineLabel -> t

p :: Program (Int -> Int -> Int -> Int)
p 0  x y r  =  p 1  1 y r       -- x = 1
p 1  x y r  =  p 2  x 2 r       -- y = 2
p 2  x y r  =  p 3  (x + y) y r -- x = x + y
p 3  x y r  =  p 4  x (x * y) r -- y = x * y
p 4  x y r  =  p 5  x y (x + y) -- r = x + y
p 5  x y r  =  r

program :: Int
program = p 0 0 0 0

-- program == 9