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 | mail@daniel-mendler.de |
Stability | experimental |
Portability | portable |
Safe Haskell | Safe |
Language | Haskell2010 |
A monad transformer that combines ReaderT
, WriterT
and StateT
.
This version uses continuation-passing-style for the writer part
to achieve constant space usage. This transformer can be used as a
drop-in replacement for Control.Monad.Trans.RWS.Strict.
- type RWS r w s = RWST r w s Identity
- rws :: Monoid w => (r -> s -> (a, s, w)) -> RWS r w s a
- runRWS :: Monoid w => RWS r w s a -> r -> s -> (a, s, w)
- evalRWS :: Monoid w => RWS r w s a -> r -> s -> (a, w)
- execRWS :: Monoid w => RWS r w s a -> r -> s -> (s, w)
- mapRWS :: (Monoid w, Monoid w') => ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b
- withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a
- newtype RWST r w s m a = RWST {
- unRWST :: r -> s -> w -> m (a, s, w)
- rwsT :: (Functor m, Monoid w) => (r -> s -> m (a, s, w)) -> RWST r w s m a
- runRWST :: Monoid w => RWST r w s m a -> r -> s -> m (a, s, w)
- evalRWST :: (Monad m, Monoid w) => RWST r w s m a -> r -> s -> m (a, w)
- execRWST :: (Monad m, Monoid w) => RWST r w s m a -> r -> s -> m (s, w)
- 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
- withRWST :: (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a
- reader :: Monad m => (r -> a) -> RWST r w s m a
- ask :: Monad m => RWST r w s m r
- local :: (r -> r) -> RWST r w s m a -> RWST r w s m a
- asks :: Monad m => (r -> a) -> RWST r w s m a
- writer :: (Monoid w, Monad m) => (a, w) -> RWST r w s m a
- tell :: (Monoid w, Monad m) => w -> RWST r w s m ()
- listen :: (Monoid w, Monad m) => RWST r w s m a -> RWST r w s m (a, w)
- listens :: (Monoid w, Monad m) => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b)
- pass :: (Monoid w, Monoid w', Monad m) => RWST r w s m (a, w -> w') -> RWST r w' s m a
- censor :: (Monoid w, Monad m) => (w -> w) -> RWST r w s m a -> RWST r w s m a
- state :: Monad m => (s -> (a, s)) -> RWST r w s m a
- get :: Monad m => RWST r w s m s
- put :: Monad m => s -> RWST r w s m ()
- modify :: Monad m => (s -> s) -> RWST r w s m ()
- gets :: Monad m => (s -> a) -> RWST r w s m a
- liftCallCC :: CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b
- liftCallCC' :: CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b
- liftCatch :: Catch e m (a, s, w) -> Catch e (RWST r w s m) a
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
.)
:: 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 #
The RWST monad transformer
newtype 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
.
MonadTrans (RWST r w s) Source # | |
Monad m => Monad (RWST r w s m) Source # | |
Functor m => Functor (RWST r w s m) Source # | |
MonadFix m => MonadFix (RWST r w s m) Source # | |
MonadFail m => MonadFail (RWST r w s m) Source # | |
(Functor m, Monad m) => Applicative (RWST r w s m) Source # | |
MonadIO m => MonadIO (RWST r w s m) Source # | |
(Functor m, MonadPlus m) => Alternative (RWST r w s m) Source # | |
(Functor m, MonadPlus m) => MonadPlus (RWST r w s m) Source # | |
rwsT :: (Functor m, Monoid w) => (r -> s -> m (a, s, w)) -> RWST r w s m a Source #
The RWST constructor is deliberately not exported in the CPS module to avoid exposing the hidden state w. rwsT provides a safe way to construct a RWST with the same api as the original RWST.
runRWST :: Monoid w => RWST r w s m a -> r -> s -> m (a, s, w) Source #
Unwrap an RWST computation as a function.
:: (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 #
Reader operations
reader :: Monad m => (r -> a) -> RWST r w s m a Source #
Constructor for computations in the reader monad (equivalent to asks
).
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 #
is an action that produces the output tell
ww
.
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.
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.