Copyright	(c) Ivan Perez and Manuel Baerenz 2016
License	BSD3
Maintainer	ivan.perez@keera.co.uk
Safe Haskell	Safe-Inferred
Language	Haskell2010

Control.Monad.Trans.MSF.RWS

Description

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.

Synopsis

rwsS :: (Functor m, Monad m, Monoid w) => MSF m (r, s, a) (w, s, b) -> MSF (RWST r w s m) a b
runRWSS :: (Functor m, Monad m, Monoid w) => MSF (RWST r w s m) a b -> MSF m (r, s, a) (w, s, b)
evalRWS :: RWS r w s a -> r -> s -> (a, w)
evalRWST :: Monad m => RWST r w s m a -> r -> s -> m (a, w)
execRWS :: RWS r w s a -> r -> s -> (s, w)
execRWST :: Monad m => RWST r w s m a -> r -> s -> m (s, w)
mapRWS :: ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b
mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b
runRWS :: RWS r w s a -> r -> s -> (a, s, w)
rws :: (r -> s -> (a, s, w)) -> RWS r w s a
withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a
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
type RWS r w s = RWST r w s Identity
newtype RWST r w s (m :: Type -> Type) a = RWST {
- runRWST :: r -> s -> m (a, s, w)
}
writer :: forall (m :: Type -> Type) a w r s. Monad m => (a, w) -> RWST r w s m a
tell :: forall (m :: Type -> Type) w r s. Monad m => w -> RWST r w s m ()
state :: forall w (m :: Type -> Type) s a r. (Monoid w, Monad m) => (s -> (a, s)) -> RWST r w s m a
reader :: forall w (m :: Type -> Type) r a s. (Monoid w, Monad m) => (r -> a) -> RWST r w s m a
put :: forall w (m :: Type -> Type) s r. (Monoid w, Monad m) => s -> RWST r w s m ()
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
modify :: forall w (m :: Type -> Type) s r. (Monoid w, Monad m) => (s -> s) -> RWST r w s m ()
local :: forall r w s (m :: Type -> Type) a. (r -> r) -> RWST r w s m a -> RWST r w s m a
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)
listen :: forall (m :: Type -> Type) r w s a. Monad m => RWST r w s m a -> RWST r w s m (a, w)
liftCallCC' :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b
gets :: forall w (m :: Type -> Type) s a r. (Monoid w, Monad m) => (s -> a) -> RWST r w s m a
get :: forall w (m :: Type -> Type) r s. (Monoid w, Monad m) => RWST r w s m 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
asks :: forall w (m :: Type -> Type) r a s. (Monoid w, Monad m) => (r -> a) -> RWST r w s m a
ask :: forall w (m :: Type -> Type) r s. (Monoid w, Monad m) => RWST r w s m r

Documentation

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

Wrap an MSF with explicit state variables in RWST monad.

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

Run the RWST layer by making the state variables explicit.

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.

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.

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.

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.

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)

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)

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

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

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

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

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)

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)

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.

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

Instances details

(Monoid w, MonadSplit g m) => MonadSplit g (RWST r w s m)
Instance details Defined in Control.Monad.Random.Class Methods getSplit :: RWST r w s m g #
(Monoid w, MonadBase b m) => MonadBase b (RWST r w s m)
Instance details Defined in Control.Monad.Base Methods liftBase :: b α -> RWST r w s m α #
Monoid w => MonadTrans (RWST r w s)
Instance details 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)
Instance details 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)
Instance details 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)
Instance details 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)
Instance details 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)
Instance details 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)
Instance details Defined in Control.Monad.Trans.RWS.Strict Methods contramap :: (a' -> a) -> RWST r w s m a -> RWST r w s m a' # (>$) :: b -> RWST r w s m b -> RWST r w s m a #
(Monoid w, Functor m, MonadPlus m) => Alternative (RWST r w s m)
Instance details Defined in Control.Monad.Trans.RWS.Strict Methods empty :: RWST r w s m a # (<\|>) :: RWST r w s m a -> RWST r w s m a -> RWST r w s m a # some :: RWST r w s m a -> RWST r w s m [a] # many :: RWST r w s m a -> RWST r w s m [a] #
(Monoid w, Functor m, Monad m) => Applicative (RWST r w s m)
Instance details Defined in Control.Monad.Trans.RWS.Strict Methods pure :: a -> RWST r w s m a # (<>) :: RWST r w s m (a -> b) -> RWST r w s m a -> RWST r w s m b # liftA2 :: (a -> b -> c) -> RWST r w s m a -> RWST r w s m b -> RWST r w s m c # (>) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m b # (<*) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m a #
Functor m => Functor (RWST r w s m)
Instance details Defined in Control.Monad.Trans.RWS.Strict Methods fmap :: (a -> b) -> RWST r w s m a -> RWST r w s m b # (<$) :: a -> RWST r w s m b -> RWST r w s m a #
(Monoid w, Monad m) => Monad (RWST r w s m)
Instance details 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)
Instance details 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 #

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.

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.

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.

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).

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.

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)

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)
```

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

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)

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)

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.

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
```

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.

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)

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
```

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

Fetch the value of the environment.