Add asks function same as Control.Monad.Reader.

src/Control/Monad/Freer/Reader.hs

@@ -24,6 +24,7 @@ module Control.Monad.Freer.Reader (
   Reader(..),
 
   ask,
+  asks,
   runReader,
   local
 ) where
@@ -38,6 +39,10 @@ data Reader e v where
 ask :: (Member (Reader e) r) => Eff r e
 ask = send Reader
 
+-- | Request a value from the environment and applys as function
+asks :: (b -> a) -> Eff '[Reader b] a
+asks f = ask >>= return . f
+
 -- | Handler for reader effects
 runReader :: Eff (Reader e ': r) w -> e -> Eff r w
 runReader m e = handleRelay return (\Reader k -> k e) m