A quine in Haskell

Q.hs

module Main where

a, b :: String
a = "module Main where\n\na, b :: String\na = \""
b = "\"\n\nexpand :: Char -> String\nexpand '\\n' = \"\\\\n\"\nexpand '\"' = \"\\\\\\\"\"\nexpand '\\\\' = \"\\\\\\\\\"\nexpand c = [c]\n\nmain :: IO ()\nmain = do\n  putStr a\n  putStr $ a >>= expand\n  putStr \"\\\"\\nb = \\\"\"\n  putStr $ b >>= expand\n  putStr b\n"

expand :: Char -> String
expand '\n' = "\\n"
expand '"' = "\\\""
expand '\\' = "\\\\"
expand c = [c]

main :: IO ()
main = do
  putStr a
  putStr $ a >>= expand
  putStr "\"\nb = \""
  putStr $ b >>= expand
  putStr b