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 | [email protected] |
Stability | experimental |
Portability | portable |
Safe Haskell | Safe |
Language | Haskell98 |
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.
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
.)
:: 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.
:: 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
.
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
.
MonadTrans (RWST r w s) | |
Defined in Control.Monad.Trans.RWS.CPS | |
Monad m => Monad (RWST r w s m) | |
Functor m => Functor (RWST r w s m) | |
MonadFix m => MonadFix (RWST r w s m) | |
Defined in Control.Monad.Trans.RWS.CPS | |
MonadFail m => MonadFail (RWST r w s m) | |
Defined in Control.Monad.Trans.RWS.CPS | |
(Functor m, Monad m) => Applicative (RWST r w s m) | |
Defined in Control.Monad.Trans.RWS.CPS Methodspure :: 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) | |
Defined in Control.Monad.Trans.RWS.CPS | |
(Functor m, MonadPlus m) => Alternative (RWST r w s m) | |
(Functor m, MonadPlus m) => MonadPlus (RWST r w s m) | |
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
.)
:: (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.
:: (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.
runRWST (mapRWST f m) r s = f (runRWST m r s)
mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n bwithRWST :: (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 :: 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 :: (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.
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)
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.
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)
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.
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.
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.8.3/docs/html/libraries/transformers-0.5.6.2/Control-Monad-Trans-RWS-CPS.html