Bubble sort: terser and faster

sp :: [Integer] -> [Integer]
sp (x:y:ys)
  | x > y = y : sp (x : ys)
  | otherwise = x : sp (y : ys)
sp xs = xs

srt :: [Integer] -> [Integer]
srt xs
  | xs == sp xs = xs
  | otherwise = srt $ sp xs

main :: IO [Integer]
main = return $ srt [500,499 .. 0]

-- real    0m0,003s
-- user    0m0,000s
-- sys 0m0,003s