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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 77a8662 · 2026-10-31

Moduleextensible-effects-5.0.0.1Haskell2010

Control.Eff.Writer.Strict

Strict write-only state

Synopsis

data Writer
value withWriter
value tell
value censor
value runWriter
value runFirstWriter
value runLastWriter
value runListWriter
value runMonoidWriter
value execWriter
value execFirstWriter
value execLastWriter
value execListWriter
value execMonoidWriter

Packageextensible-effects-5.0.0.1
Exports14
LanguageHaskell2010
LicenceMIT
SourceStrict.hs

datadata 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 ()

Instances3MonadBaseControl, Handle, StM

(MonadBase m m, LiftedBase m r) => MonadBaseControl m (Eff (Writer w ': r))Defined in extensible-effects-5.0.0.1 · Control.Eff.Writer.Strict
Monad m => Handle (Writer w) r a (b -> (w -> b -> b) -> m (a, b))Defined in extensible-effects-5.0.0.1 · Control.Eff.Writer.Strict
Given a value to write, and a callback (which includes empty and append), respond to requests.
type StM (Eff (Writer w ': r)) a = StM (Eff r) (a, [w])Defined in extensible-effects-5.0.0.1 · Control.Eff.Writer.Strict

valuewithWriter :: 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.

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

Write a new value.

valuecensor :: Member (Writer w) r => (w -> w) -> Eff r a -> Eff r a

Transform the state being produced.

valuerunWriter :: (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.

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

Handle Writer requests by taking the first value provided.

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

Handle Writer requests by overwriting previous values.

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

Handle Writer requests, using a List to accumulate values.

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

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

valueexecWriter :: (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.

valueexecFirstWriter :: 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.

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

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

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

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

valueexecMonoidWriter :: 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.