Safe Haskell	Safe-Inferred
Language	Haskell2010

Data.Automaton.Trans.Writer

Description

An Automaton with a WriterT layer outputs an extra monoid value on every step.

It is based on the strict writer monad Strict, so when combining it with other modules such as mtl's, the strict version has to be included, i.e. Strict instead of Writer or Lazy.

Synopsis

newtype WriterT w (m :: Type -> Type) a = WriterT {
- runWriterT :: m (a, w)
}
type Writer w = WriterT w Identity
tell :: forall (m :: Type -> Type) w. Monad m => w -> WriterT w m ()
listen :: forall (m :: Type -> Type) w a. Monad m => WriterT w m a -> WriterT w m (a, w)
listens :: forall (m :: Type -> Type) w b a. Monad m => (w -> b) -> WriterT w m a -> WriterT w m (a, b)
censor :: forall (m :: Type -> Type) w a. Monad m => (w -> w) -> WriterT w m a -> WriterT w m a
runWriter :: Writer w a -> (a, w)
execWriter :: Writer w a -> w
mapWriter :: ((a, w) -> (b, w')) -> Writer w a -> Writer w' b
execWriterT :: Monad m => WriterT w m a -> m w
mapWriterT :: (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n b
writer :: forall (m :: Type -> Type) a w. Monad m => (a, w) -> WriterT w m a
writerS :: (Functor m, Monad m, Monoid w) => Automaton m a (w, b) -> Automaton (WriterT w m) a b
runWriterS :: (Functor m, Monad m) => Automaton (WriterT w m) a b -> Automaton m a (w, b)

Documentation

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

Instances details

MFunctor (WriterT w :: (Type -> Type) -> Type -> Type)
Instance details Defined in Control.Monad.Morph Methods hoist :: forall m n (b :: k). Monad m => (forall a. m a -> n a) -> WriterT w m b -> WriterT w n b #
(Monoid w, MonadSplit g m) => MonadSplit g (WriterT w m)
Instance details Defined in Control.Monad.Random.Class Methods getSplit :: WriterT w m g #
Monoid w => MMonad (WriterT w)
Instance details Defined in Control.Monad.Morph Methods embed :: forall (n :: Type -> Type) m b. Monad n => (forall a. m a -> WriterT w n a) -> WriterT w m b -> WriterT w n b #
Monoid w => MonadTrans (WriterT w)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods lift :: Monad m => m a -> WriterT w m a #
(Monoid w, MonadInterleave m) => MonadInterleave (WriterT w m)
Instance details Defined in Control.Monad.Random.Class Methods interleave :: WriterT w m a -> WriterT w m a #
(MonadRandom m, Monoid w) => MonadRandom (WriterT w m)
Instance details Defined in Control.Monad.Random.Class Methods getRandomR :: Random a => (a, a) -> WriterT w m a # getRandom :: Random a => WriterT w m a # getRandomRs :: Random a => (a, a) -> WriterT w m [a] # getRandoms :: Random a => WriterT w m [a] #
(Monoid w, MonadFail m) => MonadFail (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods fail :: String -> WriterT w m a #
(Monoid w, MonadFix m) => MonadFix (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods mfix :: (a -> WriterT w m a) -> WriterT w m a #
(Monoid w, MonadIO m) => MonadIO (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods liftIO :: IO a -> WriterT w m a #
(Monoid w, MonadZip m) => MonadZip (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods liftEq :: (a -> b -> Bool) -> WriterT w m a -> WriterT w m b -> Bool #
(Ord w, Ord1 m) => Ord1 (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods liftCompare :: (a -> b -> Ordering) -> WriterT w m a -> WriterT w m b -> Ordering #
(Read w, Read1 m) => Read1 (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods contramap :: (a' -> a) -> WriterT w m a -> WriterT w m a' # (>$) :: b -> WriterT w m b -> WriterT w m a #
Traversable f => Traversable (WriterT w f)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods traverse :: Applicative f0 => (a -> f0 b) -> WriterT w f a -> f0 (WriterT w f b) # sequenceA :: Applicative f0 => WriterT w f (f0 a) -> f0 (WriterT w f a) # mapM :: Monad m => (a -> m b) -> WriterT w f a -> m (WriterT w f b) # sequence :: Monad m => WriterT w f (m a) -> m (WriterT w f a) #
(Monoid w, Alternative m) => Alternative (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods empty :: WriterT w m a # (<\|>) :: WriterT w m a -> WriterT w m a -> WriterT w m a # some :: WriterT w m a -> WriterT w m [a] # many :: WriterT w m a -> WriterT w m [a] #
(Monoid w, Applicative m) => Applicative (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods pure :: a -> WriterT w m a # (<>) :: WriterT w m (a -> b) -> WriterT w m a -> WriterT w m b # liftA2 :: (a -> b -> c) -> WriterT w m a -> WriterT w m b -> WriterT w m c # (>) :: WriterT w m a -> WriterT w m b -> WriterT w m b # (<*) :: WriterT w m a -> WriterT w m b -> WriterT w m a #
Functor m => Functor (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods fmap :: (a -> b) -> WriterT w m a -> WriterT w m b # (<$) :: a -> WriterT w m b -> WriterT w m a #
(Monoid w, Monad m) => Monad (WriterT w m)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods mzero :: WriterT w m a # mplus :: WriterT w m a -> WriterT w m a -> WriterT w m a #
(Monoid w, PrimMonad m) => PrimMonad (WriterT w m)
Instance details Defined in Control.Monad.Primitive Associated Types type PrimState (WriterT w m) # Methods primitive :: (State# (PrimState (WriterT w m)) -> (# State# (PrimState (WriterT w m)), a #)) -> WriterT w m a #
(Monoid w, Selective f) => Selective (WriterT w f)
Instance details Defined in Control.Selective Methods select :: WriterT w f (Either a b) -> WriterT w f (a -> b) -> WriterT w f b #
Generic (WriterT w m a)
Instance details Defined in Control.Monad.Trans.Writer.Strict Associated Types type Rep (WriterT w m a) :: Type -> Type # Methods from :: WriterT w m a -> Rep (WriterT w m a) x # to :: Rep (WriterT w m a) x -> WriterT w m a #
(Read w, Read1 m, Read a) => Read (WriterT w m a)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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)
Instance details Defined in Control.Monad.Trans.Writer.Strict 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 PrimState (WriterT w m)
Instance details Defined in Control.Monad.Primitive type PrimState (WriterT w m) = PrimState m
type Rep (WriterT w m a)
Instance details Defined in Control.Monad.Trans.Writer.Strict type Rep (WriterT w m a) = D1 ('MetaData "WriterT" "Control.Monad.Trans.Writer.Strict" "transformers-0.6.1.0" 'True) (C1 ('MetaCons "WriterT" 'PrefixI 'True) (S1 ('MetaSel ('Just "runWriterT") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (m (a, w)))))

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.

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

tell w is an action that produces the output w.

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)

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)

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)

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

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

execWriter :: Writer w a -> w #

Extract the output from a writer computation.

```
execWriter m = snd (runWriter 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)

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

Extract the output from a writer computation.

execWriterT m = liftM snd (runWriterT 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)

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.)

writerS :: (Functor m, Monad m, Monoid w) => Automaton m a (w, b) -> Automaton (WriterT w m) a b Source #

Convert an extra log output into a WriterT effect.

This is the opposite of runWriterS.

runWriterS :: (Functor m, Monad m) => Automaton (WriterT w m) a b -> Automaton m a (w, b) Source #

Convert a WriterT effect into an extra log output.

This is the opposite of writerS.