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/MSF.hs

@@ -6,6 +6,7 @@
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE BangPatterns #-}
 
 module Data.Automaton.MSF where
 
@@ -244,7 +245,7 @@ stepMSF (MSF automatonT) a =
 {-# INLINE stepMSF #-}
 
 reactimate :: (Monad m) => MSF m () () -> m void
-reactimate (MSF automaton) = AutomatonOptimized.reactimate $ hoist (`runReaderT` ()) automaton
+reactimate (MSF !automaton) = AutomatonOptimized.reactimate $ hoist (`runReaderT` ()) automaton
 {-# INLINE reactimate #-}
 
 -- FIXME rename to mapMSF? if yes change in document

rhine/src/Data/Automaton/Optimized.hs

@@ -3,6 +3,7 @@
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE BangPatterns #-}
 
 module Data.Automaton.Optimized where
 
@@ -112,8 +113,8 @@ handleS :: (Functor m) => (AutomatonT m a -> AutomatonT n b) -> OptimizedAutomat
 handleS f automaton = Stateful $ f $ toAutomatonT automaton
 
 reactimate :: (Monad m) => OptimizedAutomatonT m () -> m void
-reactimate (Stateful automaton) = AutomatonT.reactimate automaton
-reactimate (Stateless f) = go
+reactimate (Stateful !automaton) = AutomatonT.reactimate automaton
+reactimate (Stateless !f) = go
   where
     go = f *> go
 {-# INLINE reactimate #-}

rhine/src/FRP/Rhine/Reactimation.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE GADTs #-}
+{-# LANGUAGE BangPatterns #-}
 
 {- |
 Run closed 'Rhine's (which are signal functions together with matching clocks)
@@ -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 #-}