Polysemy.RevState

Effect

newtype RevState s m a where

A State effect for threading state backwards instead of forwards through a computation.

Constructors

RevState :: (s -> (s, a)) -> RevState s m a

Actions

revState :: forall s a r. Member (RevState s) r => (s -> (s, a)) -> Sem r a

Gets the state as sent from the next call to revState / revPut / revModify, use it, and send a new state into the past.

revGet :: forall s r. Member (RevState s) r => Sem r s

Gets the state as sent from the next call to revState / revPut / revModify.

revPut :: forall s r. Member (RevState s) r => s -> Sem r ()

Sends a new state into the past.

revModify :: forall s r. Member (RevState s) r => (s -> s) -> Sem r ()

Gets the state as sent from the next call to revState / revModify / revPut, modify it, and return it into the past.

Interpretations

runRevState :: Member Fixpoint r => s -> Sem (RevState s ': r) a -> Sem r (s, a)

Run a RevState effect with local state that is propagated backwards through the computation, from last action to first.

runLazyRevState :: Member Fixpoint r => s -> Sem (RevState s ': r) a -> Sem r (s, a)

Run a RevState effect with local state that is lazily propagated backwards through the computation, from last action to first.