Safe Haskell	None
Language	Haskell2010

Control.Carrier.Writer.Church

Contents

Writer carrier
Writer effect

Description

A high-performance, strict, church-encoded carrier for Writer.

This carrier issues left-associated mappends, meaning that Monoids such as [] with poor performance for left-associated mappends are ill-suited for use with this carrier. Alternatives such as Endo, Seq, or DList may be preferred.

Since: 1.1.0.0

Synopsis

runWriter :: Monoid w => (w -> a -> m b) -> WriterC w m a -> m b
execWriter :: (Monoid w, Applicative m) => WriterC w m a -> m w
newtype WriterC w m a = WriterC (StateC w m a)
module Control.Effect.Writer

Writer carrier

runWriter :: Monoid w => (w -> a -> m b) -> WriterC w m a -> m b Source #

Run a Writer effect with a Monoidal log, applying a continuation to the final log and result.

runWriter k (pure a) = k mempty a

runWriter k (tell w) = k w ()

runWriter k (listen (tell w)) = k w (w, ())

runWriter k (censor f (tell w)) = k (f w) ()

Since: 1.1.0.0

execWriter :: (Monoid w, Applicative m) => WriterC w m a -> m w Source #

Run a Writer effect with a Monoidal log, producing the final log and discarding the result value.

execWriter = runWriter (const . pure)

Since: 1.1.0.0

newtype WriterC w m a Source #

Since: 1.1.0.0

Constructors

WriterC (StateC w m a)

Instances

Instances details

MonadTrans (WriterC w) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods lift :: Monad m => m a -> WriterC w m a #
Monad (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods (>>=) :: WriterC w m a -> (a -> WriterC w m b) -> WriterC w m b # (>>) :: WriterC w m a -> WriterC w m b -> WriterC w m b # return :: a -> WriterC w m a #
Functor (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods fmap :: (a -> b) -> WriterC w m a -> WriterC w m b # (<$) :: a -> WriterC w m b -> WriterC w m a #
MonadFix m => MonadFix (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods mfix :: (a -> WriterC w m a) -> WriterC w m a #
MonadFail m => MonadFail (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods fail :: String -> WriterC w m a #
Applicative (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods pure :: a -> WriterC w m a # (<>) :: WriterC w m (a -> b) -> WriterC w m a -> WriterC w m b # liftA2 :: (a -> b -> c) -> WriterC w m a -> WriterC w m b -> WriterC w m c # (>) :: WriterC w m a -> WriterC w m b -> WriterC w m b # (<*) :: WriterC w m a -> WriterC w m b -> WriterC w m a #
MonadIO m => MonadIO (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods liftIO :: IO a -> WriterC w m a #
Alternative m => Alternative (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods empty :: WriterC w m a # (<\|>) :: WriterC w m a -> WriterC w m a -> WriterC w m a # some :: WriterC w m a -> WriterC w m [a] # many :: WriterC w m a -> WriterC w m [a] #
(Alternative m, Monad m) => MonadPlus (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods mzero :: WriterC w m a # mplus :: WriterC w m a -> WriterC w m a -> WriterC w m a #
(Algebra sig m, Monoid w) => Algebra (Writer w :+: sig) (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Church Methods alg :: forall ctx (n :: Type -> Type) a. Functor ctx => Handler ctx n (WriterC w m) -> (Writer w :+: sig) n a -> ctx () -> WriterC w m (ctx a) Source #

Writer effect

module Control.Effect.Writer