Dev handling state refactor

essence-of-live-coding/essence-of-live-coding.cabal

@@ -79,17 +79,20 @@ library
     , LiveCoding.Preliminary.LiveProgram.HotCodeSwap
     , LiveCoding.Preliminary.LiveProgram.LiveProgram2
     , LiveCoding.Preliminary.LiveProgram.LiveProgramPreliminary
+    , LiveCoding.HandlingState.AccumTOrphan
 
   other-extensions:    DeriveDataTypeable
   build-depends:
       base >= 4.11 && < 5
     , transformers >= 0.5
+    , mtl >= 2.3
     , containers >= 0.6
     , syb >= 0.7
     , vector-sized >= 1.2
     , foreign-store >= 0.2
     , time >= 1.9
     , mmorph >= 1.1
+    , has-transformers
   hs-source-dirs:      src
   default-language:    Haskell2010
   default-extensions: StrictData
@@ -105,6 +108,7 @@ test-suite test
     , Feedback
     , Handle
     , Handle.LiveProgram
+    , HandlingState
     , Monad
     , Monad.Trans
     , RuntimeIO.Launch
@@ -119,6 +123,7 @@ test-suite test
     , transformers >= 0.5
     , containers >= 0.6
     , mtl >= 2.2
+    , mmorph >= 1.1
     , essence-of-live-coding
     , test-framework >= 0.8
     , test-framework-quickcheck2 >= 0.3

essence-of-live-coding/src/LiveCoding/Cell/Monad/Trans.hs

@@ -52,6 +52,23 @@ data State stateT stateInternal = State
   }
   deriving (Data, Eq, Show)
 
+-- runAccumC
+--   :: (Data accumT, Monad m)
+--   => Cell (AccumT accumT m) a  b
+--   -- ^ A cell with an accum state effect
+--   -> accumT
+--   -- ^ The initial state
+--   -> Cell                m  a (b, accumT)
+--   -- ^ The cell, returning its current state
+-- runAccumC cell stateT = _
+
+-- | The internal state of a cell to which 'runAccumC' or 'runAccumL' has been applied.
+data Accum accumT accumInternal = Accum
+  { accumT :: accumT
+  , accumInternal :: accumInternal
+  }
+  deriving (Data, Eq, Show)
+
 -- | Supply a 'ReaderT' environment before running the cell
 runReaderC ::
   r ->

essence-of-live-coding/src/LiveCoding/Cell/Util.hs

@@ -131,6 +131,15 @@ edge = proc b -> do
   bLast <- delay False -< b
   returnA -< b && not bLast
 
+changeInit :: (Monad m, Data a, Eq a) => a -> Cell m a (Maybe a)
+changeInit a0 = proc a -> do
+  aLast <- delay a0 -< a
+  returnA -< guard (a /= aLast) >> Just a
+
+change :: (Monad m, Data a, Eq a) => Cell m a (Maybe a)
+change = arr Just >>> changeInit Nothing >>> arr join
+
+
 -- * Debugging utilities
 
 -- | Print the current UTC time, prepended with the first 8 characters of the given message.