Modulefused-effects-1.1.2.7Haskell2010

Control.Carrier.State.Lazy

A carrier for the State effect that refrains from evaluating its state until necessary. This is less efficient than Control.Carrier.State.Strict but allows some cyclic computations to terminate that would loop infinitely in a strict state carrier.

Note that the parameter order in runState, evalState, and execState is reversed compared the equivalent functions provided by transformers. This is an intentional decision made to enable the composition of effect handlers with . without invoking flip.

1 type
3 values

Packagefused-effects-1.1.2.7
Exports4
LanguageHaskell2010
LicenceBSD-3-Clause
SourceLazy.hs

Lazy state carrier

4 declarations

valuerunState :: s -> StateC s m a -> m (s, a)

Run a lazy State effect, yielding the result value and the final state. More programs terminate with lazy state than strict state, but injudicious use of lazy state may lead to thunk buildup.

runState s (pure a) = pure (s, a)

runState s get = pure (s, s)

runState s (put t) = pure (t, ())

valueevalState :: Functor m => s -> StateC s m a -> m a

Run a lazy State effect, yielding the result value and discarding the final state.

evalState s m = fmap snd (runState s m)

valueexecState :: Functor m => s -> StateC s m a -> m s

Run a lazy State effect, yielding the final state and discarding the return value.

execState s m = fmap fst (runState s m)

newtypenewtype StateC s (m :: Type -> Type) a

Constructors

StateC (s -> m (s, a))

Instances10MonadTrans, Monad, Functor, MonadFix, MonadFail, Applicative, …

MonadTrans (StateC s)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
Monad m => Monad (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
Functor m => Functor (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
MonadFix m => MonadFix (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
MonadFail m => MonadFail (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
Monad m => Applicative (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
(Alternative m, Monad m) => Alternative (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
(Alternative m, Monad m) => MonadPlus (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
MonadIO m => MonadIO (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy
Algebra sig m => Algebra (State s :+: sig) (StateC s m)Defined in fused-effects-1.1.2.7 · Control.Carrier.State.Lazy

State effect

0 declarations

module Control.Effect.State