WIP Clock erasure should happen at compile time, but can't achieve it…

… through strictness

* Maybe through simplifying initClock (#304)
* Looking at the Core it turns out that erased clock isn't completely simplified,
  and it's somehow obvious because it can't be inlined since it's recursive
* I was hoping that if the automaton is evaluated strictly enough, it would be reduced to WHNF before reactimation starts
  but it's unclear whether this would even be visible in Core

rhine/src/Data/Automaton.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE ApplicativeDo #-}
+{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE ImportQualifiedPost #-}
@@ -258,7 +259,7 @@ stepAutomaton (Automaton automatonT) a =
 {-# INLINE stepAutomaton #-}
 
 reactimate :: (Monad m) => Automaton m () () -> m void
-reactimate (Automaton automaton) = StreamOptimized.reactimate $ hoist (`runReaderT` ()) automaton
+reactimate (Automaton !automaton) = StreamOptimized.reactimate $ hoist (`runReaderT` ()) automaton
 {-# INLINE reactimate #-}
 
 -- FIXME rename to mapAutomaton? if yes change in document

rhine/src/Data/Stream/Optimized.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DerivingVia #-}
 {-# LANGUAGE RankNTypes #-}
@@ -160,8 +161,8 @@ handleOptimized f stream = Stateful $ f $ toStreamT stream
 See 'Data.Stream.reactimate'.
 -}
 reactimate :: (Monad m) => OptimizedStreamT m () -> m void
-reactimate (Stateful stream) = StreamT.reactimate stream
-reactimate (Stateless f) = go
+reactimate (Stateful !stream) = StreamT.reactimate stream
+reactimate (Stateless !f) = go
   where
     go = f *> go
 {-# INLINE reactimate #-}
@@ -173,7 +174,6 @@ since the optimized version doesn't create a state type.
 -}
 constM :: m a -> OptimizedStreamT m a
 constM = Stateless
-{-# INLINE constM #-}
 
 -- | Perform one step of a stream, resulting in an updated stream and an output value.
 stepOptimizedStream :: (Functor m) => OptimizedStreamT m a -> m (Result (OptimizedStreamT m a) a)

rhine/src/FRP/Rhine/Reactimation.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE GADTs #-}
 
 {- |
@@ -55,7 +56,7 @@ flow ::
   Rhine m cl () () ->
   m void
 flow rhine = do
-  msf <- eraseClock rhine
+  !msf <- eraseClock rhine
   reactimate $ msf >>> arr (const ())
 {-# INLINE flow #-}