Control.Monad.MultiLift

MultiLift class

class MultiLift mIn mOut where

MultiLift provides an mlift method that invokes the lift method of MonadTrans multiple times, based on the requested argument and result type. You will usually have to specify the type of the argument explicitly.

Note that mlift only works with up to 9 levels of nested monad transformer.

Methods

mlift :: mIn a -> mOut a

Instances

MultiLift m m

(MonadTrans t9, Monad (t9 (t8 (t7 (t6 (t5 (t4 (t3 (t2 (t1 m))))))))), MonadTrans t8, Monad (t8 (t7 (t6 (t5 (t4 (t3 (t2 (t1 m)))))))), MonadTrans t7, Monad (t7 (t6 (t5 (t4 (t3 (t2 (t1 m))))))), MonadTrans t6, Monad (t6 (t5 (t4 (t3 (t2 (t1 m)))))), MonadTrans t5, Monad (t5 (t4 (t3 (t2 (t1 m))))), MonadTrans t4, Monad (t4 (t3 (t2 (t1 m)))), MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t9 (t8 (t7 (t6 (t5 (t4 (t3 (t2 (t1 m)))))))))

(MonadTrans t8, Monad (t8 (t7 (t6 (t5 (t4 (t3 (t2 (t1 m)))))))), MonadTrans t7, Monad (t7 (t6 (t5 (t4 (t3 (t2 (t1 m))))))), MonadTrans t6, Monad (t6 (t5 (t4 (t3 (t2 (t1 m)))))), MonadTrans t5, Monad (t5 (t4 (t3 (t2 (t1 m))))), MonadTrans t4, Monad (t4 (t3 (t2 (t1 m)))), MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t8 (t7 (t6 (t5 (t4 (t3 (t2 (t1 m))))))))

(MonadTrans t7, Monad (t7 (t6 (t5 (t4 (t3 (t2 (t1 m))))))), MonadTrans t6, Monad (t6 (t5 (t4 (t3 (t2 (t1 m)))))), MonadTrans t5, Monad (t5 (t4 (t3 (t2 (t1 m))))), MonadTrans t4, Monad (t4 (t3 (t2 (t1 m)))), MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t7 (t6 (t5 (t4 (t3 (t2 (t1 m)))))))

(MonadTrans t6, Monad (t6 (t5 (t4 (t3 (t2 (t1 m)))))), MonadTrans t5, Monad (t5 (t4 (t3 (t2 (t1 m))))), MonadTrans t4, Monad (t4 (t3 (t2 (t1 m)))), MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t6 (t5 (t4 (t3 (t2 (t1 m))))))

(MonadTrans t5, Monad (t5 (t4 (t3 (t2 (t1 m))))), MonadTrans t4, Monad (t4 (t3 (t2 (t1 m)))), MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t5 (t4 (t3 (t2 (t1 m)))))

(MonadTrans t4, Monad (t4 (t3 (t2 (t1 m)))), MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t4 (t3 (t2 (t1 m))))

(MonadTrans t3, Monad (t3 (t2 (t1 m))), MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t3 (t2 (t1 m)))

(MonadTrans t2, Monad (t2 (t1 m)), MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t2 (t1 m))

(MonadTrans t1, Monad (t1 m), Monad m) => MultiLift m (t1 m)

Example

 module Main where
 
 import Control.Monad.MultiLift
 import Control.Monad.MultiWrap
 import Control.Monad.Reader
 import Control.Monad.Trans
 import Control.Monad.Wrap
 
 newtype Type1 = Type1 { unType1 :: String }
 type Reader1 = ReaderT Type1 IO
 
 newtype Type2 = Type2 { unType2 :: String }
 type Reader2 = ReaderT Type2 Reader1
 
 r2 :: Reader2 ()
 r2 = do
   -- Note that you have to specify the inner type
   s1 <- mlift (asks unType1 :: Reader1 String)
   liftIO $ putStrLn $ "s1: " ++ s1 ++ "\n"
   s2 <- asks unType2
   liftIO $ putStrLn $ "s2: " ++ s2 ++ "\n"
 
 r1 :: Reader1 ()
 r1 = do
   runReaderT r2 $ Type2 "this is the Reader2 contents"
 
 main :: IO ()
 main = do
   runReaderT r1 $ Type1 "this is the Reader1 contents"