Remove useless code equivalent to the identity in the right monad (IO)

src/Main.hs

@@ -1,14 +1,11 @@
-{-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE TypeApplications #-}
 module Main where
 
-import Control.Monad.State (execState, execStateT)
 import Data.ByteString.Char8 (ByteString)
 import qualified Data.ByteString.Char8 as BS (readFile, split, intercalate)
 import qualified Data.ByteString.Lazy.Char8 as Lazy (writeFile)
 import PDF (Layers(..), Document(..), UnifiedLayers(..), parseDocument, render)
-import PDF.Box (Index(..), Maybe_(..), at, atAll, edit)
+import PDF.Box (Index(..), Maybe_(..), at, atAll)
 import PDF.Layer (Layer, Objects(..))
 import PDF.Object.Navigation (StreamContent(..))
 import PDF.TextRendering (TextRendering(..), update)
@@ -29,18 +26,14 @@ revealLayer =
     .atAll (Maybe_ StreamContent) $
       return . revealText
 
-reveal :: Document -> Document
-reveal = execState $
-  edit .at UnifiedLayers $ revealLayer
+reveal :: Document -> IO Document
+reveal = at UnifiedLayers $ revealLayer
 
-revealFirst :: Document -> Document
-revealFirst document = maybe document id $ execStateT (
-    edit .at Layers .at(Index 0) $ revealLayer
-  ) document
+revealFirst :: Document -> IO Document
+revealFirst = at Layers .at(Index 0) $ revealLayer
 
-deepReveal :: Document -> Document
-deepReveal = execState $
-  edit .atAll Layers $ revealLayer
+deepReveal :: Document -> IO Document
+deepReveal = atAll Layers $ revealLayer
 
 main :: IO ()
 main = do
@@ -48,4 +41,4 @@ main = do
   result <- parseDocument <$> BS.readFile inputPath
   case result of
     Left parseError -> hPutStrLn stderr $ show parseError
-    Right doc -> Lazy.writeFile outputPath . render $ reveal doc
+    Right doc -> Lazy.writeFile outputPath . render =<< reveal doc