Control.Monad.Ology.Specific.WriterT

Documentation

execWriter :: Writer w a -> w

Extract the output from a writer computation.

• execWriter m = snd (runWriter m)

execWriterT :: Monad m => WriterT w m a -> m w

Extract the output from a writer computation.

• execWriterT m = liftM snd (runWriterT m)

mapWriter :: ((a, w) -> (b, w')) -> Writer w a -> Writer w' b

Map both the return value and output of a computation using the given function.

• runWriter (mapWriter f m) = f (runWriter m)

mapWriterT :: (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n b

Map both the return value and output of a computation using the given function.

• runWriterT (mapWriterT f m) = f (runWriterT m)

runWriter :: Writer w a -> (a, w)

Unwrap a writer computation as a (result, output) pair. (The inverse of writer.)

type Writer w = WriterT w Identity

A writer monad parameterized by the type w of output to accumulate.

The return function produces the output mempty, while >>= combines the outputs of the subcomputations using mappend.

newtype WriterT w (m :: Type -> Type) a

A writer monad parameterized by:

• w - the output to accumulate.
• m - The inner monad.

The return function produces the output mempty, while >>= combines the outputs of the subcomputations using mappend.

Constructors

WriterT

Fields

• runWriterT :: m (a, w)

Instances

Monoid w => TransConstraint MonadFail (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadFail m => Dict (MonadFail (WriterT w m))

Monoid w => TransConstraint MonadFix (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadFix m => Dict (MonadFix (WriterT w m))

Monoid w => TransConstraint MonadIO (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadIO m => Dict (MonadIO (WriterT w m))

Monoid w => TransConstraint Applicative (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). Applicative m => Dict (Applicative (WriterT w m))

Monoid w => TransConstraint Functor (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). Functor m => Dict (Functor (WriterT w m))

Monoid w => TransConstraint Monad (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). Monad m => Dict (Monad (WriterT w m))

Monoid w => TransConstraint MonadPlus (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadPlus m => Dict (MonadPlus (WriterT w m))

Monoid w => TransConstraint MonadException (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadException m => Dict (MonadException (WriterT w m))

Monoid w => TransConstraint MonadExtract (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadExtract m => Dict (MonadExtract (WriterT w m))

Monoid w => TransConstraint MonadInner (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadInner m => Dict (MonadInner (WriterT w m))

(MonadCatch e m, Monoid w) => MonadCatch e (WriterT w m)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

catch :: WriterT w m a -> (e -> WriterT w m a) -> WriterT w m a

(MonadThrow e m, Monoid w) => MonadThrow e (WriterT w m)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

throw :: e -> WriterT w m a

Monoid w => MonadTransCoerce (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

transCoerce :: forall (m1 :: Type -> Type) (m2 :: Type -> Type). Coercible m1 m2 => Dict (Coercible (WriterT w m1) (WriterT w m2))

Monoid w => MonadTransHoist (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hoist :: forall (m1 :: Type -> Type) (m2 :: Type -> Type). (Monad m1, Monad m2) => (m1 --> m2) -> WriterT w m1 --> WriterT w m2

Monoid w => MonadTransTunnel (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Associated Types

type Tunnel (WriterT w) :: Type -> Type

Methods

tunnel :: Monad m => ((forall (m1 :: Type -> Type) a. Monad m1 => WriterT w m1 a -> m1 (Tunnel (WriterT w) a)) -> m (Tunnel (WriterT w) r)) -> WriterT w m r

Monoid w => MonadTransUnlift (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

liftWithUnlift :: MonadIO m => (Unlift MonadTunnelIOInner (WriterT w) -> m r) -> WriterT w m r

getDiscardingUnlift :: forall (m :: Type -> Type). Monad m => WriterT w m (WUnlift MonadTunnelIOInner (WriterT w))

Monoid w => MonadTrans (WriterT w)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

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

Monoid w => TransConstraint (MonadCatch e) (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadCatch e m => Dict (MonadCatch e (WriterT w m))

Monoid w => TransConstraint (MonadThrow e) (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadThrow e m => Dict (MonadThrow e (WriterT w m))

(Monoid w, MonadFail m) => MonadFail (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

fail :: String -> WriterT w m a

(Monoid w, MonadFix m) => MonadFix (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

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

(Monoid w, MonadIO m) => MonadIO (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

liftIO :: IO a -> WriterT w m a

(Monoid w, MonadZip m) => MonadZip (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

mzip :: WriterT w m a -> WriterT w m b -> WriterT w m (a, b)

mzipWith :: (a -> b -> c) -> WriterT w m a -> WriterT w m b -> WriterT w m c

munzip :: WriterT w m (a, b) -> (WriterT w m a, WriterT w m b)

Foldable f => Foldable (WriterT w f)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

fold :: Monoid m => WriterT w f m -> m

foldMap :: Monoid m => (a -> m) -> WriterT w f a -> m

foldMap' :: Monoid m => (a -> m) -> WriterT w f a -> m

foldr :: (a -> b -> b) -> b -> WriterT w f a -> b

foldr' :: (a -> b -> b) -> b -> WriterT w f a -> b

foldl :: (b -> a -> b) -> b -> WriterT w f a -> b

foldl' :: (b -> a -> b) -> b -> WriterT w f a -> b

foldr1 :: (a -> a -> a) -> WriterT w f a -> a

foldl1 :: (a -> a -> a) -> WriterT w f a -> a

toList :: WriterT w f a -> [a]

null :: WriterT w f a -> Bool

length :: WriterT w f a -> Int

elem :: Eq a => a -> WriterT w f a -> Bool

maximum :: Ord a => WriterT w f a -> a

minimum :: Ord a => WriterT w f a -> a

sum :: Num a => WriterT w f a -> a

product :: Num a => WriterT w f a -> a

(Eq w, Eq1 m) => Eq1 (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

liftEq :: (a -> b -> Bool) -> WriterT w m a -> WriterT w m b -> Bool

(Ord w, Ord1 m) => Ord1 (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

liftCompare :: (a -> b -> Ordering) -> WriterT w m a -> WriterT w m b -> Ordering

(Read w, Read1 m) => Read1 (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (WriterT w m a)

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [WriterT w m a]

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (WriterT w m a)

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [WriterT w m a]

(Show w, Show1 m) => Show1 (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> WriterT w m a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [WriterT w m a] -> ShowS

Contravariant m => Contravariant (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

contramap :: (a' -> a) -> WriterT w m a -> WriterT w m a'

(>$) :: b -> WriterT w m b -> WriterT w m a

Traversable f => Traversable (WriterT w f)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

traverse :: Applicative f0 => (a -> f0 b) -> WriterT w f a -> f0 (WriterT w f b)

sequenceA :: Applicative f0 => WriterT w f (f0 a) -> f0 (WriterT w f a)

mapM :: Monad m => (a -> m b) -> WriterT w f a -> m (WriterT w f b)

sequence :: Monad m => WriterT w f (m a) -> m (WriterT w f a)

(Monoid w, Alternative m) => Alternative (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

empty :: WriterT w m a

(<|>) :: WriterT w m a -> WriterT w m a -> WriterT w m a

some :: WriterT w m a -> WriterT w m [a]

many :: WriterT w m a -> WriterT w m [a]

(Monoid w, Applicative m) => Applicative (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

pure :: a -> WriterT w m a

(<*>) :: WriterT w m (a -> b) -> WriterT w m a -> WriterT w m b

liftA2 :: (a -> b -> c) -> WriterT w m a -> WriterT w m b -> WriterT w m c

(*>) :: WriterT w m a -> WriterT w m b -> WriterT w m b

(<*) :: WriterT w m a -> WriterT w m b -> WriterT w m a

Functor m => Functor (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

fmap :: (a -> b) -> WriterT w m a -> WriterT w m b

(<$) :: a -> WriterT w m b -> WriterT w m a

(Monoid w, Monad m) => Monad (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

(>>=) :: WriterT w m a -> (a -> WriterT w m b) -> WriterT w m b

(>>) :: WriterT w m a -> WriterT w m b -> WriterT w m b

return :: a -> WriterT w m a

(Monoid w, MonadPlus m) => MonadPlus (WriterT w m)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

mzero :: WriterT w m a

mplus :: WriterT w m a -> WriterT w m a -> WriterT w m a

Invariant m => Invariant (WriterT w m)

from the transformers package

Defined in Data.Functor.Invariant

Methods

invmap :: (a -> b) -> (b -> a) -> WriterT w m a -> WriterT w m b

(Monoid w, MonadException m) => MonadException (WriterT w m)

Defined in Control.Monad.Ology.Specific.WriterT

Associated Types

type Exc (WriterT w m)

Methods

throwExc :: Exc (WriterT w m) -> WriterT w m a

catchExc :: WriterT w m a -> (Exc (WriterT w m) -> WriterT w m a) -> WriterT w m a

(MonadExtract m, Monoid w) => MonadExtract (WriterT w m)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

mToValue :: Extract (WriterT w m)

(MonadInner m, Monoid w) => MonadInner (WriterT w m)

Defined in Control.Monad.Ology.Specific.WriterT

Methods

retrieveInner :: WriterT w m a -> Result (Exc (WriterT w m)) a

(Read w, Read1 m, Read a) => Read (WriterT w m a)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

readsPrec :: Int -> ReadS (WriterT w m a)

readList :: ReadS [WriterT w m a]

readPrec :: ReadPrec (WriterT w m a)

readListPrec :: ReadPrec [WriterT w m a]

(Show w, Show1 m, Show a) => Show (WriterT w m a)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

showsPrec :: Int -> WriterT w m a -> ShowS

show :: WriterT w m a -> String

showList :: [WriterT w m a] -> ShowS

(Eq w, Eq1 m, Eq a) => Eq (WriterT w m a)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

(==) :: WriterT w m a -> WriterT w m a -> Bool

(/=) :: WriterT w m a -> WriterT w m a -> Bool

(Ord w, Ord1 m, Ord a) => Ord (WriterT w m a)

Defined in Control.Monad.Trans.Writer.Lazy

Methods

compare :: WriterT w m a -> WriterT w m a -> Ordering

(<) :: WriterT w m a -> WriterT w m a -> Bool

(<=) :: WriterT w m a -> WriterT w m a -> Bool

(>) :: WriterT w m a -> WriterT w m a -> Bool

(>=) :: WriterT w m a -> WriterT w m a -> Bool

max :: WriterT w m a -> WriterT w m a -> WriterT w m a

min :: WriterT w m a -> WriterT w m a -> WriterT w m a

type Tunnel (WriterT w)

Defined in Control.Monad.Ology.Specific.WriterT

type Tunnel (WriterT w) = (,) w

type Exc (WriterT w m)

Defined in Control.Monad.Ology.Specific.WriterT

type Exc (WriterT w m) = Exc m

writer :: forall (m :: Type -> Type) a w. Monad m => (a, w) -> WriterT w m a

Construct a writer computation from a (result, output) pair. (The inverse of runWriter.)

tell :: forall (m :: Type -> Type) w. Monad m => w -> WriterT w m ()

tell w is an action that produces the output w.

pass :: forall (m :: Type -> Type) w a. Monad m => WriterT w m (a, w -> w) -> WriterT w m a

pass m is an action that executes the action m, which returns a value and a function, and returns the value, applying the function to the output.

• runWriterT (pass m) = liftM (\ ((a, f), w) -> (a, f w)) (runWriterT m)

listens :: forall (m :: Type -> Type) w b a. Monad m => (w -> b) -> WriterT w m a -> WriterT w m (a, b)

listens f m is an action that executes the action m and adds the result of applying f to the output to the value of the computation.

• listens f m = liftM (id *** f) (listen m)

• runWriterT (listens f m) = liftM (\ (a, w) -> ((a, f w), w)) (runWriterT m)

listen :: forall (m :: Type -> Type) w a. Monad m => WriterT w m a -> WriterT w m (a, w)

listen m is an action that executes the action m and adds its output to the value of the computation.

• runWriterT (listen m) = liftM (\ (a, w) -> ((a, w), w)) (runWriterT m)

censor :: forall (m :: Type -> Type) w a. Monad m => (w -> w) -> WriterT w m a -> WriterT w m a

censor f m is an action that executes the action m and applies the function f to its output, leaving the return value unchanged.

• censor f m = pass (liftM (\ x -> (x,f)) m)

• runWriterT (censor f m) = liftM (\ (a, w) -> (a, f w)) (runWriterT m)

Orphan instances

Monoid w => TransConstraint MonadFail (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadFail m => Dict (MonadFail (WriterT w m))

Monoid w => TransConstraint MonadFix (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadFix m => Dict (MonadFix (WriterT w m))

Monoid w => TransConstraint MonadIO (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadIO m => Dict (MonadIO (WriterT w m))

Monoid w => TransConstraint Applicative (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). Applicative m => Dict (Applicative (WriterT w m))

Monoid w => TransConstraint Functor (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). Functor m => Dict (Functor (WriterT w m))

Monoid w => TransConstraint Monad (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). Monad m => Dict (Monad (WriterT w m))

Monoid w => TransConstraint MonadPlus (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadPlus m => Dict (MonadPlus (WriterT w m))

Monoid w => TransConstraint MonadException (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadException m => Dict (MonadException (WriterT w m))

Monoid w => TransConstraint MonadExtract (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadExtract m => Dict (MonadExtract (WriterT w m))

Monoid w => TransConstraint MonadInner (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadInner m => Dict (MonadInner (WriterT w m))

(MonadCatch e m, Monoid w) => MonadCatch e (WriterT w m)

Methods

catch :: WriterT w m a -> (e -> WriterT w m a) -> WriterT w m a

(MonadThrow e m, Monoid w) => MonadThrow e (WriterT w m)

Methods

throw :: e -> WriterT w m a

Monoid w => MonadTransCoerce (WriterT w)

Methods

transCoerce :: forall (m1 :: Type -> Type) (m2 :: Type -> Type). Coercible m1 m2 => Dict (Coercible (WriterT w m1) (WriterT w m2))

Monoid w => MonadTransHoist (WriterT w)

Methods

hoist :: forall (m1 :: Type -> Type) (m2 :: Type -> Type). (Monad m1, Monad m2) => (m1 --> m2) -> WriterT w m1 --> WriterT w m2

Monoid w => MonadTransTunnel (WriterT w)

Associated Types

type Tunnel (WriterT w) :: Type -> Type

Methods

tunnel :: Monad m => ((forall (m1 :: Type -> Type) a. Monad m1 => WriterT w m1 a -> m1 (Tunnel (WriterT w) a)) -> m (Tunnel (WriterT w) r)) -> WriterT w m r

Monoid w => MonadTransUnlift (WriterT w)

Methods

liftWithUnlift :: MonadIO m => (Unlift MonadTunnelIOInner (WriterT w) -> m r) -> WriterT w m r

getDiscardingUnlift :: forall (m :: Type -> Type). Monad m => WriterT w m (WUnlift MonadTunnelIOInner (WriterT w))

Monoid w => TransConstraint (MonadCatch e) (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadCatch e m => Dict (MonadCatch e (WriterT w m))

Monoid w => TransConstraint (MonadThrow e) (WriterT w)

Methods

hasTransConstraint :: forall (m :: Type -> Type). MonadThrow e m => Dict (MonadThrow e (WriterT w m))

(Monoid w, MonadException m) => MonadException (WriterT w m)

Associated Types

type Exc (WriterT w m)

Methods

throwExc :: Exc (WriterT w m) -> WriterT w m a

catchExc :: WriterT w m a -> (Exc (WriterT w m) -> WriterT w m a) -> WriterT w m a

(MonadExtract m, Monoid w) => MonadExtract (WriterT w m)

Methods

mToValue :: Extract (WriterT w m)

(MonadInner m, Monoid w) => MonadInner (WriterT w m)

Methods

retrieveInner :: WriterT w m a -> Result (Exc (WriterT w m)) a