Control.Eff.Writer.Lazy

Lazy write-only state

Documentation

data Writer w v where

The Writer monad

In MTL's Writer monad, the told value must have a |Monoid| type. Our writer has no such constraints. If we write a |Writer|-like interpreter to accumulate the told values in a monoid, it will have the |Monoid w| constraint then

Constructors

Tell :: w -> Writer w ()

Instances

(MonadBase m m, LiftedBase m r) => MonadBaseControl m (Eff (Writer w ': r))

Defined in Control.Eff.Writer.Lazy

Associated Types

type StM (Eff (Writer w ': r)) a :: Type

Methods

liftBaseWith :: (RunInBase (Eff (Writer w ': r)) m -> m a) -> Eff (Writer w ': r) a

restoreM :: StM (Eff (Writer w ': r)) a -> Eff (Writer w ': r) a

Monad m => Handle (Writer w) r a (b -> (w -> b -> b) -> m (a, b))

Given a value to write, and a callback (which includes empty and append), respond to requests.

Defined in Control.Eff.Writer.Lazy

Methods

handle :: (Eff r a -> b -> (w -> b -> b) -> m (a, b)) -> Arrs r v a -> Writer w v -> b -> (w -> b -> b) -> m (a, b)

handle_relay :: (r ~ (Writer w ': r'), Relay (b -> (w -> b -> b) -> m (a, b)) r') => (a -> b -> (w -> b -> b) -> m (a, b)) -> (Eff r a -> b -> (w -> b -> b) -> m (a, b)) -> Eff r a -> b -> (w -> b -> b) -> m (a, b)

respond_relay :: (a -> b -> (w -> b -> b) -> m (a, b)) -> (Eff r a -> b -> (w -> b -> b) -> m (a, b)) -> Eff r a -> b -> (w -> b -> b) -> m (a, b)

type StM (Eff (Writer w ': r)) a

Defined in Control.Eff.Writer.Lazy

type StM (Eff (Writer w ': r)) a = StM (Eff r) (a, [w])

withWriter :: Monad m => a -> b -> (w -> b -> b) -> m (a, b)

How to interpret a pure value in a writer context, given the value for mempty.

tell :: Member (Writer w) r => w -> Eff r ()

Write a new value.

censor :: forall w a r. Member (Writer w) r => (w -> w) -> Eff r a -> Eff r a

Transform the state being produced.

runWriter :: (w -> b -> b) -> b -> Eff (Writer w ': r) a -> Eff r (a, b)

Handle Writer requests, using a user-provided function to accumulate values, hence no Monoid constraints.

runFirstWriter :: Eff (Writer w ': r) a -> Eff r (a, Maybe w)

Handle Writer requests by taking the first value provided.

runLastWriter :: Eff (Writer w ': r) a -> Eff r (a, Maybe w)

Handle Writer requests by overwriting previous values.

runListWriter :: Eff (Writer w ': r) a -> Eff r (a, [w])

Handle Writer requests, using a List to accumulate values.

runMonoidWriter :: Monoid w => Eff (Writer w ': r) a -> Eff r (a, w)

Handle Writer requests, using a Monoid instance to accumulate values.

execWriter :: (w -> b -> b) -> b -> Eff (Writer w ': r) a -> Eff r b

Handle Writer requests, using a user-provided function to accumulate values and returning the final accumulated values.

execFirstWriter :: Eff (Writer w ': r) a -> Eff r (Maybe w)

Handle Writer requests by taking the first value provided and and returning the final accumulated values.

execLastWriter :: Eff (Writer w ': r) a -> Eff r (Maybe w)

Handle Writer requests by overwriting previous values and returning the final accumulated values.

execListWriter :: Eff (Writer w ': r) a -> Eff r [w]

Handle Writer requests, using a List to accumulate values and returning the final accumulated values.

execMonoidWriter :: Monoid w => Eff (Writer w ': r) a -> Eff r w

Handle Writer requests, using a Monoid instance to accumulate values and returning the final accumulated values.