objective 0.0 → 0.0.1

raw patch · 2 files changed

+19/−14 lines, 2 files

Files

• objective.cabal +2/−2
• src/Control/Object.hs +17/−12

@@ -2,9 +2,9 @@ -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                objective
-version:             0.0
+version:             0.0.1
 synopsis:            Extensible objects
--- description:         
+description:         Stateful effect transducer
 homepage:            https://github.com/fumieval/objective
 license:             BSD3
 license-file:        LICENSE

@@ -8,26 +8,30 @@ import Control.Monad
 import Data.Typeable
 
--- | The type 'Object e m' represents objects which can handle messages 'e', perform actions in the 'Monad' 'm'.
--- It can be thought of as a function where both domain and codomain are effects.
+-- | The type 'Object e m' represents objects which can handle messages 'e', perform actions in the environment 'm'.
+-- It can be thought of as a function between effects.
 -- Thus, it can be composed just like functions using '(.>>.)' (not often needed); the identity element is `echo`.
 newtype Object e m = Object { runObject :: forall x. e x -> m (x, Object e m) } deriving Typeable
 
+-- | Lift a natural transformation into an object.
+liftO :: Functor f => (forall x. e x -> f x) -> Object e f
+liftO f = Object $ fmap (\x -> (x, liftO f)) . f
+
 -- | Change the workspace of the object.
-transObject :: Monad n => (forall x. m x -> n x) -> Object e m -> Object e n
-transObject f (Object m) = Object $ liftM (fmap (transObject f)) . f . m
+transObject :: Functor g => (forall x. f x -> g x) -> Object e f -> Object e g
+transObject f (Object m) = Object $ fmap (fmap (transObject f)) . f . m
 
 -- | Apply a function to the messages coming into the object.
-adaptObject :: Monad m => (forall x. e x -> f x) -> Object f m -> Object e m
-adaptObject f (Object m) = Object $ liftM (fmap (adaptObject f)) . m . f
+adaptObject :: Functor f => (forall x. e x -> f x) -> Object f m -> Object e m
+adaptObject f (Object m) = Object $ fmap (fmap (adaptObject f)) . m . f
 
 -- | Parrots messages given.
 echo :: Functor e => Object e e
 echo = Object (fmap (\x -> (x, echo)))
 
 -- | Compose two objects (aka Dependency Injection).
-(.>>.) :: Monad n => Object e m -> Object m n -> Object e n
-Object m .>>. Object n = Object $ \e -> liftM (\((x, m'), n') -> (x, m' .>>. n')) $ n (m e)
+(.>>.) :: Functor n => Object e m -> Object m n -> Object e n
+Object m .>>. Object n = Object $ \e -> fmap (\((x, m'), n') -> (x, m' .>>. n')) $ n (m e)
 
 -- | Build an object.
 oneshot :: (Functor e, Monad m) => (forall a. e (m a) -> m a) -> Object e m
@@ -56,8 +60,9 @@   get_ = Get id
   put_ s = Put s ()
 
-variable :: Monad m => s -> Object (AccessT s Zero) m
+-- | A mutable variable.
+variable :: Applicative f => s -> Object (AccessT s Zero) f
 variable s = Object $ \x -> case x of
-  Get cont -> return (cont s, variable s)
-  Put s' cont -> return (cont, variable s')
-  LiftAccessT e -> return (extract e, variable s)+  Get cont -> pure (cont s, variable s)
+  Put s' cont -> pure (cont, variable s')
+  LiftAccessT e -> pure (extract e, variable s)