some freer manipulations

freer_transformer.hs

{-#LANGUAGE GADTs, TypeApplications, DataKinds, TypeOperators #-}
import Control.Monad.Freer
import qualified Control.Monad.Freer as F
import Control.Monad.Trans.Writer
import Control.Monad.IO.Class
type Loc = Int
type LogSource = Int
type LogLevel = Int
type LogStr = String

data Logger v where
  Log :: Loc -> LogSource -> LogLevel -> LogStr -> Logger ()
  
f1 :: (Member (WriterT [String] IO) r) => String -> Eff r ()
f1 str = send (tell [str] :: WriterT [String] IO ()) 

f2 :: (Member (WriterT [String] IO) r) => String -> Eff r ()
f2 str = send (tell @IO [str]) 

g :: (Member Logger r) => String -> Eff r ()
g str = send (Log 0 0 0 str)

h1 :: (Member (WriterT [String] IO) r, Member Logger r) => Eff r ()
h1 = do
  g  "hi"
  f2 "hi" 
  f1 "hi"

main1 = do 
     ls <- execWriterT $ runM $ writerLogger h1 :: IO [String]
     mapM_ putStrLn ls
  
h2 :: (Member (WriterT [String] IO) r, Member Logger r) => Eff r ()
h2 = do
  send $ (liftIO $ putStrLn "interpolated IO!" :: WriterT [String] IO ())
  h1 
  send $ (liftIO $ putStrLn "more IO!" :: WriterT [String] IO ())
  
main2 = do 
   ls <- execWriterT $ runM $ writerLogger h2 :: IO [String]
   mapM_ putStrLn ls
  
writerLogger :: (Member (WriterT [String] IO) r) => Eff (Logger:r) a -> Eff r a
writerLogger = handleRelay return (\(Log _ _ _ str) f -> f1 str >>= f)

program :: Member Logger r => Eff r ()
program = g "hi" >> g "ho"

  
main3 = do 
   ls <- execWriterT $ runM $ writerLogger program :: IO [String]
   mapM_ putStrLn ls
   

program_with_io :: (Member Logger r, Member IO r) => Eff r ()
program_with_io = do
 send (putStrLn "interpolated IO" :: IO ())
 program 

main4 = do 
    ls <- execWriterT $ runM 
                      $ runNat (liftIO @(WriterT [String] IO))
                      $ writerLogger program_with_io :: IO [String]
    mapM_ putStrLn ls