transformers-0.5.6.2: Concrete functor and monad transformers
Copyright (c) Daniel Mendler 2016
(c) Andy Gill 2001
(c) Oregon Graduate Institute of Science and Technology 2001
License BSD-style (see the file LICENSE)
Maintainer R.Paterson@city.ac.uk
Stability experimental
Portability portable
Safe Haskell Safe
Language Haskell98

Control.Monad.Trans.RWS.CPS

Description

A monad transformer that combines ReaderT , WriterT and StateT . This version uses continuation-passing-style for the writer part to achieve constant space usage. For a lazy version with the same interface, see Control.Monad.Trans.RWS.Lazy .

Synopsis

The RWS monad

type RWS r w s = RWST r w s Identity Source #

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

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

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

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

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

evalRWS Source #

Arguments

:: Monoid w
=> 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 Source #

Arguments

:: Monoid w
=> 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 :: ( Monoid w, Monoid w') => ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b Source #

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

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

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

The RWST monad transformer

data RWST r w s m a Source #

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 .

Instances

Instances details
MonadTrans ( RWST r w s) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

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

Monad m => Monad ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

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

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

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

Functor m => Functor ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

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

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

MonadFix m => MonadFix ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

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

MonadFail m => MonadFail ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

( Functor m, Monad m) => Applicative ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

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

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

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

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

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

MonadIO m => MonadIO ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

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

( Functor m, MonadPlus m) => Alternative ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

empty :: RWST r w s m a Source #

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

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

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

( Functor m, MonadPlus m) => MonadPlus ( RWST r w s m) Source #
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

mzero :: RWST r w s m a Source #

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

rwsT :: ( Functor m, Monoid w) => (r -> s -> m (a, s, w)) -> RWST r w s m a Source #

Construct an RWST computation from a function. (The inverse of runRWST .)

runRWST :: Monoid w => RWST r w s m a -> r -> s -> m (a, s, w) Source #

Unwrap an RWST computation as a function. (The inverse of rwsT .)

evalRWST Source #

Arguments

:: ( Monad m, Monoid w)
=> 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 Source #

Arguments

:: ( Monad m, Monoid w)
=> 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 :: ( Monad n, Monoid w, Monoid w') => (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b Source #

Map the inner computation using the given function.

withRWST :: (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a Source #

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

Reader operations

reader :: Monad m => (r -> a) -> RWST r w s m a Source #

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

ask :: Monad m => RWST r w s m r Source #

Fetch the value of the environment.

local :: (r -> r) -> RWST r w s m a -> RWST r w s m a Source #

Execute a computation in a modified environment

asks :: Monad m => (r -> a) -> RWST r w s m a Source #

Retrieve a function of the current environment.

Writer operations

writer :: ( Monoid w, Monad m) => (a, w) -> RWST r w s m a Source #

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

tell :: ( Monoid w, Monad m) => w -> RWST r w s m () Source #

tell w is an action that produces the output w .

listen :: ( Monoid w, Monad m) => RWST r w s m a -> RWST r w s m (a, w) Source #

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

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

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.

pass :: ( Monoid w, Monoid w', Monad m) => RWST r w s m (a, w -> w') -> RWST r w' s m a Source #

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.

censor :: ( Monoid w, Monad m) => (w -> w) -> RWST r w s m a -> RWST r w s m a Source #

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

State operations

state :: Monad m => (s -> (a, s)) -> RWST r w s m a Source #

Construct a state monad computation from a state transformer function.

get :: Monad m => RWST r w s m s Source #

Fetch the current value of the state within the monad.

put :: Monad m => s -> RWST r w s m () Source #

put s sets the state within the monad to s .

modify :: Monad m => (s -> s) -> RWST r w s m () Source #

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

gets :: Monad m => (s -> a) -> RWST r w s m a Source #

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

Lifting other operations

liftCallCC :: CallCC m (a, s, w) (b, s, w) -> CallCC ( RWST r w s m) a b Source #

Uniform lifting of a callCC operation to the new monad. This version rolls back to the original state on entering the continuation.

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

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

liftCatch :: Catch e m (a, s, w) -> Catch e ( RWST r w s m) a Source #

Lift a catchE operation to the new monad.