MONAD HELL

gistfile1.hs

type App = ReaderT (AcidState Database) (ServerPartT IO)

processForm :: App Response
processForm =
    do method POST
       db <- ask
       (games, _) <- query db (GetState) ----- this part explodes
       prefs <- sequence $ map (runText . fst) prefMap
       ok $ template "form" $ H.p "success!"

main :: IO ()
main =
    do database <- openLocalState $ Database [] []
       simpleHTTP nullConf $ do
             decodeBody (defaultBodyPolicy "/tmp/" 4096 4096 4096)
             runReaderT processForm database

gistfile2.txt

src/Haystack/Web/Preferences.hs:79:28:
    Couldn't match type `IO'
                  with `ReaderT (AcidState Database) (ServerPartT IO)'
    Expected type: ReaderT
                     (AcidState Database) (ServerPartT IO) (EventResult GetState)
      Actual type: IO (EventResult GetState)
    In the return type of a call of `query'
    In a stmt of a 'do' block: (games, _) <- query db (GetState)
    In the expression:
      do { method POST;
           db <- ask;
           (games, _) <- query db (GetState);
           prefs <- sequence $ map (runText . fst) prefMap;
           .... }