Safe Haskell | None |
---|---|

Language | Haskell2010 |

## Synopsis

- data State s m a where
- get :: forall a r. MemberWithError (State a) r => Sem r a
- gets :: forall s a r. Member (State s) r => (s -> a) -> Sem r a
- put :: forall s r. MemberWithError (State s) r => s -> Sem r ()
- modify :: Member (State s) r => (s -> s) -> Sem r ()
- runState :: s -> Sem (State s ': r) a -> Sem r (s, a)
- runLazyState :: s -> Sem (State s ': r) a -> Sem r (s, a)
- runStateInIORef :: forall s r a. Member (Lift IO) r => IORef s -> Sem (State s ': r) a -> Sem r a
- hoistStateIntoStateT :: Sem (State s ': r) a -> StateT s (Sem r) a

# Effect

data State s m a where Source #

An effect for providing statefulness. Note that unlike mtl's
`StateT`

, there is no restriction that the `State`

effect corresponds necessarily to *local* state. It could could just as well
be interrpeted in terms of HTTP requests or database access.

Interpreters which require statefulness can `reinterpret`

themselves in terms of `State`

, and subsequently call `runState`

.

## Instances

type DefiningModule (State :: Type -> k -> Type -> Type) Source # | |

Defined in Polysemy.State |

# Actions

# Interpretations

runLazyState :: s -> Sem (State s ': r) a -> Sem r (s, a) Source #

Run a `State`

effect with local state, lazily.

runStateInIORef :: forall s r a. Member (Lift IO) r => IORef s -> Sem (State s ': r) a -> Sem r a Source #