在Haskell中使用monad transformer RWST

newtype RWST r w s m a = RWST { runRWST :: r -> s -> m (a, s, w) }

import Control.Monad.Trans.RWS.Strict

type AppConfig = String
type AppState = Int
type AppLog = [String]

-- 处理请求的函数
handleRequest :: String -> RWST AppConfig AppLog AppState IO ()
handleRequest request = do
  config <- ask -- 读取配置
  logMsg $ "Handling request: " ++ request
  -- 处理请求的逻辑
  -- ...
  -- 更新状态
  modify (+1)

-- 记录日志的函数
logMsg :: String -> RWST AppConfig AppLog AppState IO ()
logMsg msg = tell [msg]

-- 运行计算过程的函数
runApp :: RWST AppConfig AppLog AppState IO () -> IO ((), AppState, AppLog)
runApp app = runRWST app "config" 0

main :: IO ()
main = do
  result <- runApp $ do
    handleRequest "GET /"
    handleRequest "POST /login"
  print result