MTL Orphan Instances
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{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Main where
import Counter
import Weather
newtype MyAppM m a = MyAppM { unMyAppM :: MockCounter (MockWeather m) a }
deriving (Functor, Applicative, Monad, CounterT, WeatherT)
instance Monad m => WeatherT (MockCounter (MockWeather m))
runMyAppM :: Int -> MyAppM m a -> m (a, Int)
runMyAppM i = runMockWeather . (`runMockCounter` i) . unMyAppM
myApp :: (Monad m, CounterT m , WeatherT m) => m String
myApp = do
_ <- increment
(WeatherData weather) <- byCity "Amsterdam"
return weather
main :: IO ()
main = runMyAppM 12 myApp >>= print
Haskell
INFO