Maybe we need a MonadState s m => MonadReader s m instance some day ?

src/PDF/Box.hs

@@ -17,10 +17,22 @@ module PDF.Box (
 import Control.Monad.Except (ExceptT(..), runExceptT)
 import Control.Monad.Fail (MonadFail(..))
 import Control.Monad.State (MonadState(..))
+--import Control.Monad.Reader (MonadReader(..))
 import Data.Map (Map)
 import qualified Data.Map as Map (insert, lookup, member)
 import Prelude hiding (fail)
 
+{-
+instance (Monad m, MonadState s m) => MonadReader s m where
+  ask = get
+  local f m = do
+    backup <- get
+    put $ f backup
+    result <- m
+    put backup
+    return result
+-}
+
 newtype Index = Index Int
 newtype Maybe_ x = Maybe_ x
 newtype Either_ b x = Either_ x