Nitpicking, but: // of type B. ">>=" instead takes in something of type M[A], // a function from (A -> B) and produces something of type // M[B]. The ty

Nitpicking, but: // of type B. ">>=" instead takes in something of type M[A], // a function from (A -> B) and produces something of type // M[B]. The type of ">>=" is M a -> (a -> M b) -> M b, which lets you 'chain' the result of one monadic function (a -> M b) to another monadic function. So, for example: return :: String -> IO String putStrLn :: String -> IO () getLine :: IO String return "foo" >>= putStrLn :: IO () -- prints "foo" getLine >>= putStrLn :: IO () -- gets a line of input, then prints it