| Copyright | (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.Lazy
Contents
Description
A monad transformer that combines ReaderT, WriterT and StateT.
This version is lazy; for a strict version with the same interface,
see Control.Monad.Trans.RWS.Strict.
- type RWS r w s = RWST r w s Identity
- rws :: (r -> s -> (a, s, w)) -> RWS r w s a
- runRWS :: RWS r w s a -> r -> s -> (a, s, w)
- evalRWS :: RWS r w s a -> r -> s -> (a, w)
- execRWS :: RWS r w s a -> r -> s -> (s, w)
- mapRWS :: ((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 {
- runRWST :: r -> s -> m (a, s, w)
- evalRWST :: Monad m => RWST r w s m a -> r -> s -> m (a, w)
- execRWST :: Monad m => RWST r w s m a -> r -> s -> m (s, w)
- mapRWST :: (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 :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a
- ask :: (Monoid w, Monad m) => RWST r w s m r
- local :: (r -> r) -> RWST r w s m a -> RWST r w s m a
- asks :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a
- writer :: Monad m => (a, w) -> RWST r w s m a
- tell :: Monad m => w -> RWST r w s m ()
- listen :: Monad m => RWST r w s m a -> RWST r w s m (a, w)
- listens :: Monad m => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b)
- pass :: Monad m => RWST r w s m (a, w -> w) -> RWST r w s m a
- censor :: Monad m => (w -> w) -> RWST r w s m a -> RWST r w s m a
- state :: (Monoid w, Monad m) => (s -> (a, s)) -> RWST r w s m a
- get :: (Monoid w, Monad m) => RWST r w s m s
- put :: (Monoid w, Monad m) => s -> RWST r w s m ()
- modify :: (Monoid w, Monad m) => (s -> s) -> RWST r w s m ()
- gets :: (Monoid w, Monad m) => (s -> a) -> RWST r w s m a
- liftCallCC :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b
- liftCallCC' :: Monoid w => 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 :: (r -> s -> (a, s, w)) -> RWS r w s a Source #
Construct an RWS computation from a function.
(The inverse of runRWS.)
runRWS :: RWS r w s a -> r -> s -> (a, s, w) Source #
Unwrap an RWS computation as a function.
(The inverse of rws.)
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.
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.
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.
Instances
| Monoid w => MonadTrans (RWST r w s) # | |
| (Monoid w, Monad m) => Monad (RWST r w s m) # | |
| Functor m => Functor (RWST r w s m) # | |
| (Monoid w, MonadFix m) => MonadFix (RWST r w s m) # | |
| (Monoid w, MonadFail m) => MonadFail (RWST r w s m) # | |
| (Monoid w, Functor m, Monad m) => Applicative (RWST r w s m) # | |
| (Monoid w, MonadIO m) => MonadIO (RWST r w s m) # | |
| (Monoid w, Functor m, MonadPlus m) => Alternative (RWST r w s m) # | |
| (Monoid w, MonadPlus m) => MonadPlus (RWST r w s m) # | |
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.
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.
Reader operations
reader :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a Source #
Constructor for computations in the reader monad (equivalent to asks).
Writer operations
writer :: Monad m => (a, w) -> RWST r w s m a Source #
Construct a writer computation from a (result, output) pair.
State operations
state :: (Monoid w, Monad m) => (s -> (a, s)) -> RWST r w s m a Source #
Construct a state monad computation from a state transformer function.
get :: (Monoid w, Monad m) => RWST r w s m s Source #
Fetch the current value of the state within the monad.
put :: (Monoid w, Monad m) => s -> RWST r w s m () Source #
put ss.
Lifting other operations
liftCallCC :: Monoid w => 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.