Apply hlint suggestions

.hlint.yaml

@@ -0,0 +1,66 @@
+# HLint configuration file
+# https://github.com/ndmitchell/hlint
+##########################
+
+# This file contains a template configuration file, which is typically
+# placed as .hlint.yaml in the root of your project
+
+
+# Specify additional command line arguments
+#
+# - arguments: [--color, --cpp-simple, -XQuasiQuotes]
+- arguments: [-XArrows]
+
+# Control which extensions/flags/modules/functions can be used
+#
+# - extensions:
+#   - default: false # all extension are banned by default
+#   - name: [PatternGuards, ViewPatterns] # only these listed extensions can be used
+#   - {name: CPP, within: CrossPlatform} # CPP can only be used in a given module
+#
+# - flags:
+#   - {name: -w, within: []} # -w is allowed nowhere
+#
+# - modules:
+#   - {name: [Data.Set, Data.HashSet], as: Set} # if you import Data.Set qualified, it must be as 'Set'
+#   - {name: Control.Arrow, within: []} # Certain modules are banned entirely
+#
+# - functions:
+#   - {name: unsafePerformIO, within: []} # unsafePerformIO can only appear in no modules
+
+
+# Add custom hints for this project
+#
+# Will suggest replacing "wibbleMany [myvar]" with "wibbleOne myvar"
+# - error: {lhs: "wibbleMany [x]", rhs: wibbleOne x}
+
+# The hints are named by the string they display in warning messages.
+# For example, if you see a warning starting like
+#
+# Main.hs:116:51: Warning: Redundant ==
+#
+# You can refer to that hint with `{name: Redundant ==}` (see below).
+
+# Turn on hints that are off by default
+#
+# Ban "module X(module X) where", to require a real export list
+# - warn: {name: Use explicit module export list}
+#
+# Replace a $ b $ c with a . b $ c
+# - group: {name: dollar, enabled: true}
+#
+# Generalise map to fmap, ++ to <>
+# - group: {name: generalise, enabled: true}
+
+
+# Ignore some builtin hints
+# - ignore: {name: Use let}
+# - ignore: {name: Use const, within: SpecialModule} # Only within certain modules
+
+
+# Define some custom infix operators
+# - fixity: infixr 3 ~^#^~
+
+
+# To generate a suitable file for HLint do:
+# $ hlint --default > .hlint.yaml

rhine-examples/src/ADSR.hs

@@ -142,6 +142,7 @@ decay
   -> Behaviour (ExceptT (Diff time) m) time amplitude
 decay d = linearly d 1
 
+{- HLINT ignore sustain "Eta reduce" -} -- Doesn't compile on GHC 9.0 otherwise
 -- | A period in which a given amplitude is sustained indefinitely.
 sustain :: Monad m => amplitude -> Behaviour m time amplitude
 sustain amplitude = arr_ amplitude

rhine-examples/src/EventClock.hs

@@ -76,7 +76,7 @@ responsive = timeInfo >>> proc TimeInfo {..} -> do
 randomsExample :: IO ()
 randomsExample = runEventChanT $ flow wholeSystem
   where
-    busy = (liftClock Busy :: HoistClock IO EventIO Busy) -- TODO Can't remove brackets. GHC parser bug?
+    busy = liftClock Busy :: HoistClock IO EventIO Busy
     emitEventSystem   = randomNumbers >-> emitS @@ busy
     handleEventSystem = handleEvents            @@ EventClock
     eventSystem = emitEventSystem ||@ concurrentlyWithEvents @|| handleEventSystem
@@ -93,8 +93,8 @@ threadsRandomsExample = do
   let
     eventClock = eventClockOn chan :: HoistClock EventIO IO (EventClock String)
     eventSystem = handleEvents @@ eventClock ||@ concurrently @|| responsive @@ waitClock
-    busy = (liftClock Busy :: HoistClock IO EventIO Busy) -- TODO Can't remove brackets. GHC parser bug?
-  void $ forkIO $ flow $ eventSystem
+    busy = liftClock Busy :: HoistClock IO EventIO Busy
+  void $ forkIO $ flow eventSystem
   withChan chan $ flow $ randomNumbers >-> emitS' @@ busy
 
 

rhine-gloss/src/FRP/Rhine/Gloss/Pure.hs

@@ -118,6 +118,6 @@ flowGlossWithWorldMSF GlossSettings { .. } clock msf
         (time, tag) <- fst $ fst $ runWriter $ flip runReaderT (0, Nothing) $ unGlossM $ initClock clock -< ()
         msf -< (time, tag)
       getPic (_, pic) = pic
-      stepWith (diff, maybeEvent) (msf, _) = snd *** id $ runWriter $ unMSF msf ((diff, maybeEvent), ())
+      stepWith (diff, maybeEvent) (msf, _) = first snd $ runWriter $ unMSF msf ((diff, maybeEvent), ())
       handleEvent event = stepWith (0, Just event)
       simStep diff = stepWith (diff, Nothing)

rhine/src/FRP/Rhine/ClSF/Random.hs

@@ -35,7 +35,7 @@ runRandS
   => ClSF (RandT g m) cl a     b
   -> g -- ^ The initial random seed
   -> ClSF          m  cl a (g, b)
-runRandS clsf g = MSF.runRandS (morphS commuteReaderRand clsf) g
+runRandS clsf = MSF.runRandS (morphS commuteReaderRand clsf)
 
 -- | Updates the generator every step but discards the generator.
 evalRandS
@@ -59,9 +59,7 @@ evalRandIOS
   :: Monad m
   =>     ClSF (RandT StdGen m) cl a b
   -> IO (ClSF               m  cl a b)
-evalRandIOS clsf = do
-  g <- newStdGen
-  return $ evalRandS clsf g
+evalRandIOS clsf = evalRandS clsf <$> newStdGen
 
 -- | Evaluates the random computation by using the global random generator on the first tick.
 evalRandIOS'

rhine/src/FRP/Rhine/ClSF/Reader.hs

@@ -40,7 +40,7 @@ runReaderS
   :: Monad m
   => ClSF (ReaderT r m) cl a b -> ClSF m cl (a, r) b
 runReaderS behaviour
-  = arr swap >>> (MSF.runReaderS $ morphS commuteReaders behaviour)
+  = arr swap >>> MSF.runReaderS (morphS commuteReaders behaviour)
 
 -- | Remove a 'ReaderT' layer by passing the readonly environment explicitly.
 runReaderS_

rhine/src/FRP/Rhine/Clock/FixedStep.hs

@@ -10,7 +10,7 @@ and a deterministic schedule for such clocks.
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeOperators #-}
+
 module FRP.Rhine.Clock.FixedStep where
 
 

rhine/src/FRP/Rhine/Clock/Realtime/Millisecond.hs

@@ -5,7 +5,7 @@ Provides a clock that ticks at every multiple of a fixed number of milliseconds.
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeOperators #-}
+
 module FRP.Rhine.Clock.Realtime.Millisecond where
 
 -- base

rhine/src/FRP/Rhine/ResamplingBuffer/Interpolation.hs

@@ -52,8 +52,8 @@ which should be chosen much larger than the average time between @cl1@'s ticks.
 sinc
   :: ( Monad m, Clock m cl1, Clock m cl2
      , VectorSpace v s
-     , Ord (s)
-     , Floating (s)
+     , Ord s
+     , Floating s
      , s ~ Diff (Time cl1)
      , s ~ Diff (Time cl2)
      )

rhine/src/FRP/Rhine/ResamplingBuffer/KeepLast.hs

@@ -15,5 +15,5 @@ import FRP.Rhine.ResamplingBuffer.Timeless
 keepLast :: Monad m => a -> ResamplingBuffer m cl1 cl2 a a
 keepLast = timelessResamplingBuffer AsyncMealy {..}
   where
-    amPut _ a = return a
-    amGet   a = return (a, a)
+    amGet a = return (a, a)
+    amPut _ = return

rhine/src/FRP/Rhine/Schedule/Concurrently.hs

@@ -129,7 +129,7 @@ concurrentlyExcept = Schedule $ \cl1 cl2 -> do
           putMVar mvar $ Left e -- Either throw own exception or acknowledge the exception from the other clock
         Left e -> void $ putMVar iMVar $ Left e
     catchAndDrain mvar initScheduleAction = catchE initScheduleAction $ \e -> do
-      _ <- reactimate $ (constM $ ExceptT $ takeMVar mvar) >>> arr (const ()) -- Drain the mvar until the other clock acknowledges the exception
+      _ <- reactimate $ constM (ExceptT $ takeMVar mvar) >>> arr (const ()) -- Drain the mvar until the other clock acknowledges the exception
       throwE e
 
 -- | As 'concurrentlyExcept', with a single possible exception value.