| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Polysemy.State
Synopsis
- data State s m a where
- get :: forall s r. MemberWithError (State s) r => Sem r s
- 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 ()
- modify' :: Member (State s) r => (s -> s) -> Sem r ()
- runState :: s -> Sem (State s ': r) a -> Sem r (s, a)
- evalState :: s -> Sem (State s ': r) a -> Sem r a
- runLazyState :: s -> Sem (State s ': r) a -> Sem r (s, a)
- evalLazyState :: s -> Sem (State s ': r) a -> Sem r a
- runStateIORef :: forall s r a. Member (Embed 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
modify' :: Member (State s) r => (s -> s) -> Sem r () Source #
A variant of modify in which the computation is strict in the
new state.
Interpretations
evalState :: s -> Sem (State s ': r) a -> Sem r a Source #
Run a State effect with local state.
Since: 1.0.0.0
runLazyState :: s -> Sem (State s ': r) a -> Sem r (s, a) Source #
Run a State effect with local state, lazily.
evalLazyState :: s -> Sem (State s ': r) a -> Sem r a Source #
Run a State effect with local state, lazily.
Since: 1.0.0.0
runStateIORef :: forall s r a. Member (Embed IO) r => IORef s -> Sem (State s ': r) a -> Sem r a Source #
Run a State effect by transforming it into operations over an IORef.
Note: This is not safe in a concurrent setting, as modify isn't atomic.
If you need operations over the state to be atomic,
use runAtomicStateIORef or
runAtomicStateTVar instead.
Since: 1.0.0.0