primitive recursion

z :: [Int] -> Int
z _ = 0

n :: [Int] -> Int
n [x] = x + 1
n _ = error "Bad argument" {- yep, not very informative, but who fcking cares? -}

u :: Int -> [Int] -> Int
u index l
    | index < (length l) = l !! index
    | otherwise = error "Bad index"


s :: ([Int] -> Int) -> [([Int] -> Int)] -> [Int] -> Int
s f gl args = f $ map ($args) gl

r :: ([Int] -> Int) -> ([Int] -> Int) -> Int -> [Int] -> Int
r f g 0 args = f args
r f g y args = g $ [y - 1] ++ args ++ [r f g (y - 1) args]

main = do
    putStrLn "hello"