servant-examples/tutorial/T7.hs · typeable/servant

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1{-# LANGUAGE DataKinds #-}

2{-# LANGUAGE TypeFamilies #-}

3{-# LANGUAGE TypeOperators #-}

4module T7 where

6import Control.Monad.Trans.Except

7import Control.Monad.Trans.Reader

8import Network.Wai

9import Servant

11type ReaderAPI = "a" :> Get '[JSON] Int

12 :<|> "b" :> Get '[JSON] String

14readerAPI :: Proxy ReaderAPI

15readerAPI = Proxy

17readerServerT :: ServerT ReaderAPI (Reader String)

18readerServerT = a :<|> b

20 where a :: Reader String Int

21 a = return 1797

23 b :: Reader String String

24 b = ask

26readerServer :: Server ReaderAPI

27readerServer = enter readerToEither readerServerT

29 where readerToEither :: Reader String :~> ExceptT ServantErr IO

30 readerToEither = Nat $ \r -> return (runReader r "hi")

32app :: Application

33app = serve readerAPI readerServer