Data.Automaton.Trans.RWS

This module combines the wrapping and running functions for the Reader, Writer and State monad layers in a single layer.

It is based on the strict RWS 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 RWS or Lazy.

Documentation

rwsS :: (Functor m, Monad m, Monoid w) => Automaton m (r, s, a) (w, s, b) -> Automaton (RWST r w s m) a b

Wrap an Automaton with explicit state variables in RWST monad transformer.

runRWSS :: (Functor m, Monad m, Monoid w) => Automaton (RWST r w s m) a b -> Automaton m (r, s, a) (w, s, b)

Run the RWST layer by making the state variables explicit.

newtype RWST r w s (m :: Type -> Type) a

A monad transformer adding reading an environment of type r, collecting an output of type w and updating a state of type s to an inner monad m.

Constructors

RWST

Fields

• runRWST :: r -> s -> m (a, s, w)

Instances

MFunctor (RWST r w s :: (Type -> Type) -> Type -> Type)

Defined in Control.Monad.Morph

Methods

hoist :: forall m n (b :: k). Monad m => (forall a. m a -> n a) -> RWST r w s m b -> RWST r w s n b

(Monoid w, MonadSplit g m) => MonadSplit g (RWST r w s m)

Defined in Control.Monad.Random.Class

Methods

getSplit :: RWST r w s m g

Monoid w => MonadTrans (RWST r w s)

Defined in Control.Monad.Trans.RWS.Strict

Methods

lift :: Monad m => m a -> RWST r w s m a

(Monoid w, MonadInterleave m) => MonadInterleave (RWST r w s m)

Defined in Control.Monad.Random.Class

Methods

interleave :: RWST r w s m a -> RWST r w s m a

(Monoid w, MonadRandom m) => MonadRandom (RWST r w s m)

Defined in Control.Monad.Random.Class

Methods

getRandomR :: Random a => (a, a) -> RWST r w s m a

getRandom :: Random a => RWST r w s m a

getRandomRs :: Random a => (a, a) -> RWST r w s m [a]

getRandoms :: Random a => RWST r w s m [a]

(Monoid w, MonadFail m) => MonadFail (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

fail :: String -> RWST r w s m a

(Monoid w, MonadFix m) => MonadFix (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

mfix :: (a -> RWST r w s m a) -> RWST r w s m a

(Monoid w, MonadIO m) => MonadIO (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

liftIO :: IO a -> RWST r w s m a

Contravariant m => Contravariant (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

contramap :: (a' -> a) -> RWST r w s m a -> RWST r w s m a'

(>$) :: b -> RWST r w s m b -> RWST r w s m a

(Monoid w, Functor m, MonadPlus m) => Alternative (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

empty :: RWST r w s m a

(<|>) :: RWST r w s m a -> RWST r w s m a -> RWST r w s m a

some :: RWST r w s m a -> RWST r w s m [a]

many :: RWST r w s m a -> RWST r w s m [a]

(Monoid w, Functor m, Monad m) => Applicative (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

pure :: a -> RWST r w s m a

(<*>) :: RWST r w s m (a -> b) -> RWST r w s m a -> RWST r w s m b

liftA2 :: (a -> b -> c) -> RWST r w s m a -> RWST r w s m b -> RWST r w s m c

(*>) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m b

(<*) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m a

Functor m => Functor (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

fmap :: (a -> b) -> RWST r w s m a -> RWST r w s m b

(<$) :: a -> RWST r w s m b -> RWST r w s m a

(Monoid w, Monad m) => Monad (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

(>>=) :: RWST r w s m a -> (a -> RWST r w s m b) -> RWST r w s m b

(>>) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m b

return :: a -> RWST r w s m a

(Monoid w, MonadPlus m) => MonadPlus (RWST r w s m)

Defined in Control.Monad.Trans.RWS.Strict

Methods

mzero :: RWST r w s m a

mplus :: RWST r w s m a -> RWST r w s m a -> RWST r w s m a

(Monoid w, PrimMonad m) => PrimMonad (RWST r w s m)

Defined in Control.Monad.Primitive

Associated Types

type PrimState (RWST r w s m)

Methods

primitive :: (State# (PrimState (RWST r w s m)) -> (# State# (PrimState (RWST r w s m)), a #)) -> RWST r w s m a

(Monoid w, Monad m) => Selective (RWST r w s m)

Defined in Control.Selective

Methods

select :: RWST r w s m (Either a b) -> RWST r w s m (a -> b) -> RWST r w s m b

Generic (RWST r w s m a)

Defined in Control.Monad.Trans.RWS.Strict

Associated Types

type Rep (RWST r w s m a) :: Type -> Type

Methods

from :: RWST r w s m a -> Rep (RWST r w s m a) x

to :: Rep (RWST r w s m a) x -> RWST r w s m a

type PrimState (RWST r w s m)

Defined in Control.Monad.Primitive

type PrimState (RWST r w s m) = PrimState m

type Rep (RWST r w s m a)

Defined in Control.Monad.Trans.RWS.Strict

type Rep (RWST r w s m a) = D1 ('MetaData "RWST" "Control.Monad.Trans.RWS.Strict" "transformers-0.6.1.0" 'True) (C1 ('MetaCons "RWST" 'PrefixI 'True) (S1 ('MetaSel ('Just "runRWST") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (r -> s -> m (a, s, w)))))

type RWS r w s = RWST r w s Identity

A monad containing an environment of type r, output of type w and an updatable state of type s.

liftCallCC' :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b

In-situ lifting of a callCC operation to the new monad. This version uses the current state on entering the continuation.

get :: forall w (m :: Type -> Type) r s. (Monoid w, Monad m) => RWST r w s m s

Fetch the current value of the state within the monad.

tell :: forall (m :: Type -> Type) w r s. Monad m => w -> RWST r w s m ()

tell w is an action that produces the output w.

put :: forall w (m :: Type -> Type) s r. (Monoid w, Monad m) => s -> RWST r w s m ()

put s sets the state within the monad to s.

ask :: forall w (m :: Type -> Type) r s. (Monoid w, Monad m) => RWST r w s m r

Fetch the value of the environment.

asks :: forall w (m :: Type -> Type) r a s. (Monoid w, Monad m) => (r -> a) -> RWST r w s m a

Retrieve a function of the current environment.

• asks f = liftM f ask

local :: forall r w s (m :: Type -> Type) a. (r -> r) -> RWST r w s m a -> RWST r w s m a

Execute a computation in a modified environment

• runRWST (local f m) r s = runRWST m (f r) s

listen :: forall (m :: Type -> Type) r w s a. Monad m => RWST r w s m a -> RWST r w s m (a, w)

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

• runRWST (listen m) r s = liftM (\ (a, w) -> ((a, w), w)) (runRWST m r s)

listens :: forall (m :: Type -> Type) w b r s a. Monad m => (w -> b) -> RWST r w s m a -> RWST r w s 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)

• runRWST (listens f m) r s = liftM (\ (a, w) -> ((a, f w), w)) (runRWST m r s)

censor :: forall (m :: Type -> Type) w r s a. Monad m => (w -> w) -> RWST r w s m a -> RWST r w s 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)

• runRWST (censor f m) r s = liftM (\ (a, w) -> (a, f w)) (runRWST m r s)

rws :: (r -> s -> (a, s, w)) -> RWS r w s a

Construct an RWS computation from a function. (The inverse of runRWS.)

runRWS :: RWS r w s a -> r -> s -> (a, s, w)

Unwrap an RWS computation as a function. (The inverse of rws.)

evalRWS

Arguments

:: RWS r w s a

RWS computation to execute

-> r

initial environment

-> s

initial value

-> (a, w)

final value and output

Evaluate a computation with the given initial state and environment, returning the final value and output, discarding the final state.

execRWS

Arguments

:: RWS r w s a

RWS computation to execute

-> r

initial environment

-> s

initial value

-> (s, w)

final state and output

Evaluate a computation with the given initial state and environment, returning the final state and output, discarding the final value.

mapRWS :: ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b

Map the return value, final state and output of a computation using the given function.

• runRWS (mapRWS f m) r s = f (runRWS m r s)

withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a

withRWS f m executes action m with an initial environment and state modified by applying f.

• runRWS (withRWS f m) r s = uncurry (runRWS m) (f r s)

evalRWST

Arguments

:: Monad m

=> RWST r w s m a

computation to execute

-> r

initial environment

-> s

initial value

-> m (a, w)

computation yielding final value and output

Evaluate a computation with the given initial state and environment, returning the final value and output, discarding the final state.

execRWST

Arguments

:: Monad m

=> RWST r w s m a

computation to execute

-> r

initial environment

-> s

initial value

-> m (s, w)

computation yielding final state and output

Evaluate a computation with the given initial state and environment, returning the final state and output, discarding the final value.

mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b

Map the inner computation using the given function.

• runRWST (mapRWST f m) r s = f (runRWST m r s)

withRWST :: forall r' s r w (m :: Type -> Type) a. (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a

withRWST f m executes action m with an initial environment and state modified by applying f.

• runRWST (withRWST f m) r s = uncurry (runRWST m) (f r s)

reader :: forall w (m :: Type -> Type) r a s. (Monoid w, Monad m) => (r -> a) -> RWST r w s m a

Constructor for computations in the reader monad (equivalent to asks).

state :: forall w (m :: Type -> Type) s a r. (Monoid w, Monad m) => (s -> (a, s)) -> RWST r w s m a

Construct a state monad computation from a state transformer function.

modify :: forall w (m :: Type -> Type) s r. (Monoid w, Monad m) => (s -> s) -> RWST r w s m ()

modify f is an action that updates the state to the result of applying f to the current state.

• modify f = get >>= (put . f)

gets :: forall w (m :: Type -> Type) s a r. (Monoid w, Monad m) => (s -> a) -> RWST r w s m a

Get a specific component of the state, using a projection function supplied.

• gets f = liftM f get

writer :: forall (m :: Type -> Type) a w r s. Monad m => (a, w) -> RWST r w s m a

Construct a writer computation from a (result, output) pair.

pass :: forall (m :: Type -> Type) r w s a. Monad m => RWST r w s m (a, w -> w) -> RWST r w s 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.

• runRWST (pass m) r s = liftM (\ ((a, f), w) -> (a, f w)) (runRWST m r s)