transformers.hs

module Transformer where

import Control.Monad.Reader
import Control.Monad.Trans

data Config = Config { filename :: String } deriving (Show)

c = Config { filename = "a.txt" }

loadFile :: ReaderT Config IO String
loadFile = do
     fname <- asks filename
     liftIO $ readFile fname

module ReaderMClark where

import Control.Monad.Reader
import Control.Monad.Trans

data Config = Config { filename :: String } deriving (Show)

c = Config { filename = "a.txt" }

loadFile :: ReaderT Config IO String
loadFile = do
     -- This is how I assume I get the filename from the config
     -- fname <- ask filename
     fname <- asks filename
     -- can use let bindings to assert a type and see what it is
     let f :: IO String
         f = fname
     -- How am I supposed to provide the fname to loadFile so that I can end up with a ReaderT Config IO String?
     return loadFile fname

Updated with the correct solution. Thanks!