Control.Object

Stateful effect transducer: The Mealy machine for effects.

Construction

newtype Object e m

The type 'Object e m' represents objects which can handle messages e, perform actions in the environment m. It can be thought of as an automaton that converts effects. Objects can be composed just like functions using .>>.; the identity element is echo.

Constructors

Object

Fields

runObject :: forall x. e x -> m (x, Object e m)

Instances

Typeable ((* -> *) -> (* -> *) -> *) Object

liftO :: Functor f => (forall x. e x -> f x) -> Object e f

Lift a natural transformation into an object.

echo :: Functor e => Object e e

Parrots messages given.

oneshot :: (Functor e, Monad m) => (forall a. e (m a) -> m a) -> Object e m

Build an object using continuation passing style.

stateful :: Monad m => (forall a. e a -> StateT s m a) -> s -> Object e m

Build a stateful object.

variable :: Applicative f => s -> Object (State s) f

A mutable variable.

Composition

(.>>.) :: Functor n => Object e m -> Object m n -> Object e n infixr 4

Compose two objects (aka Dependency Injection).

transObject :: Functor g => (forall x. f x -> g x) -> Object e f -> Object e g

Change the workspace of the object.

adaptObject :: Functor m => (forall x. e x -> f x) -> Object f m -> Object e m

Apply a function to the messages coming into the object.

Extensible objects

loner :: Functor m => Object Nil m

An object that won't accept any messages.

(.|>.) :: Functor m => Object f m -> Object (Union s) m -> Object (f |> Union s) m infixr 3

Extend an object by adding another independent object.

sharing :: Monad m => (forall a. e a -> StateT s m a) -> s -> Object (State s |> (e |> Nil)) m

Build a stateful object, sharing out the state.