Apply some hlint suggestions

app/Main.hs

@@ -4,7 +4,7 @@ module Main where
 
 import           Control.Monad
 import qualified Data.ByteString     as BS
-import           Data.Maybe          (catMaybes)
+import           Data.Maybe          (mapMaybe)
 import           Data.Set            as Set hiding (foldl)
 import qualified Data.Text           as T
 import           Emulator            (reset, stepFrame)
@@ -65,7 +65,7 @@ render renderer = do
   pure texture
 
 eventsToIntents :: [SDL.Event] -> Set Intent
-eventsToIntents events = Set.fromList $ catMaybes $ eventToIntent . SDL.eventPayload <$> events
+eventsToIntents events = Set.fromList $ mapMaybe (eventToIntent . SDL.eventPayload) events
   where
     eventToIntent :: SDL.EventPayload -> Maybe Intent
     eventToIntent SDL.QuitEvent = Just Exit

src/Emulator/Mapper/Mapper2.hs

@@ -44,7 +44,7 @@ read (Mapper2 Cartridge {..} _ prgBank1 prgBank2) addr
 write :: Mapper2 -> Word16 -> Word8 -> IO ()
 write (Mapper2 Cartridge {..} prgBanks prgBank1 _) addr v
   | addr' < 0x2000 = VUM.write chrRom addr' v
-  | addr' >= 0x8000 = modifyIORef prgBank1 (const $ toInt v `rem` prgBanks)
+  | addr' >= 0x8000 = writeIORef prgBank1 (toInt v `rem` prgBanks)
   | addr' >= 0x6000 = VUM.write sram (addr' - 0x6000) v
   | otherwise = error $ "Erroneous cart write detected!" ++ prettifyWord16 addr
   where addr' = fromIntegral addr

src/Emulator/Mapper/Mapper3.hs

@@ -46,7 +46,7 @@ write (Mapper3 Cartridge {..} chrBank _ _) addr v
   | addr' < 0x2000 = do
     chrBankV <- readIORef chrBank
     VUM.write chrRom ((chrBankV * 0x2000) + addr') v
-  | addr' >= 0x8000 = modifyIORef chrBank (const $ toInt v .&. 3)
+  | addr' >= 0x8000 = writeIORef chrBank (toInt v .&. 3)
   | addr' >= 0x6000 = VUM.write sram (addr' - 0x6000) v
   | otherwise = error $ "Erroneous cart write detected!" ++ prettifyWord16 addr
   where addr' = fromIntegral addr

src/Emulator/Mapper/Mapper7.hs

@@ -43,7 +43,7 @@ write (Mapper7 Cartridge {..} prgBank) addr v
     let m = case v .&. 0x10 of
           0x00 -> MirrorSingle0
           0x10 -> MirrorSingle1
-    modifyIORef mirror (const m)
+    writeIORef mirror m
   | addr' >= 0x6000 = VUM.write sram (addr' - 0x6000) v
   | otherwise = error $ "Erroneous cart write detected!" ++ prettifyWord16 addr
   where addr' = fromIntegral addr

src/Emulator/Opcode.hs

@@ -5,7 +5,6 @@ module Emulator.Opcode (
   , decodeOpcode
 ) where
 
-import           Data.List              (intersperse)
 import           Data.Word
 import           Emulator.Util
 
@@ -55,7 +54,7 @@ data Opcode = Opcode {
 
 instance Show Opcode where
   show (Opcode raw mn mode len cyc pageCrossCy) =
-    concat . intersperse " "
+    unwords
       $ "Opcode:" : prettifyWord8 raw
       : show mn : show mode
       : map show [len, cyc, pageCrossCy]

test/Nestest/Parsing.hs

@@ -33,7 +33,7 @@ parseTrace = do
   _ <- space
   cyc <- string "CYC:" >> cyclesP
   _ <- space
-  _ <- string "SL:" >> (many $ noneOf "\n")
+  _ <- string "SL:" >> many (noneOf "\n")
   let opcode = decodeOpcode a0r
   pure $ Trace pcv spv av xv yv pv opcode a0r a1r a2r cyc