Control.Carrier.Writer.Church

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

Writer carrier

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

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

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

Since: 1.1.0.0

Constructors

WriterC (StateC w m a)

Instances

MonadTrans (WriterC w)

Defined in Control.Carrier.Writer.Church

Methods

lift :: Monad m => m a -> WriterC w m a

MonadFail m => MonadFail (WriterC w m)

Defined in Control.Carrier.Writer.Church

Methods

fail :: String -> WriterC w m a

MonadFix m => MonadFix (WriterC w m)

Defined in Control.Carrier.Writer.Church

Methods

mfix :: (a -> WriterC w m a) -> WriterC w m a

MonadIO m => MonadIO (WriterC w m)

Defined in Control.Carrier.Writer.Church

Methods

liftIO :: IO a -> WriterC w m a

Alternative m => Alternative (WriterC w m)

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]

Applicative (WriterC w m)

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

Functor (WriterC w m)

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

Monad (WriterC w m)

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

(Alternative m, Monad m) => MonadPlus (WriterC w m)

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)

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)

Writer effect

module Control.Effect.Writer