Control.Comonad.Trans.Store.Lazy

The lazy store (state-in-context/costate) comonad transformer is subject to the laws:

 x = put (get x) x
 y = get (put y x)
 put y x = put y (put z x)

Thanks go to Russell O'Connor and Daniel Peebles for their help formulating and proving the laws for this comonad transformer.

The Store comonad

type Store s = StoreT s Identity

store :: (s -> a) -> s -> Store s a

runStore :: Store s a -> (s -> a, s)

The Store comonad transformer

data StoreT s w a

Constructors

StoreT (w (s -> a)) s

Instances

ComonadTrans (StoreT s)

ComonadHoist (StoreT s)

Functor w => Functor (StoreT s w)

Comonad w => Comonad (StoreT s w)

runStoreT :: StoreT s w a -> (w (s -> a), s)

Operations

get :: StoreT s w a -> s

put :: Comonad w => s -> StoreT s w a -> a

modify :: Comonad w => (s -> s) -> StoreT s w a -> a

experiment :: (Comonad w, Functor f) => f (s -> s) -> StoreT s w a -> f a