3 ms·
A small example. class (MonadIO m) => HasLogging m where log :: String -> m () data AppConfig = AppConfig { stuff :: Int } newtype
by mej10 10y ago
A small example.
class (MonadIO m) => HasLogging m where
log :: String -> m ()
data AppConfig = AppConfig { stuff :: Int }
newtype MyApp a = MyApp { runApp :: ReaderT AppConfig IO a}
deriving (Functor, Applicative, Monad, MonadIO, MonadReader AppConfig)
instance HasLogging MyApp where
log s = liftIO (putStrLn s)
function2 :: Int -> MyApp String
function2 x = do
log "hey guys I'm logging"
return (show x)
-- or without specifying the base monad, yay abstraction
function2' x = do
log "heyooo logging here"
return (show x)
-- Haskell will infer this type:
-- function2' :: (HasLogging m, Show a) => a -> m String