| Copyright |
(c) Andy Gill 2001
(c) Oregon Graduate Institute of Science and Technology 2001 |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | libraries@haskell.org |
| Stability | experimental |
| Portability | non-portable (multi-param classes, functional dependencies) |
| Safe Haskell | Safe |
| Language | Haskell2010 |
Control.Monad.RWS.Lazy
Description
Lazy RWS monad.
Inspired by the paper Functional Programming with Overloading and Higher-Order Polymorphism , Mark P Jones ( http://web.cecs.pdx.edu/~mpj/ ) Advanced School of Functional Programming, 1995.
Synopsis
- 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 :: Type -> Type ) a = RWST (r -> s -> m (a, s, w))
- runRWST :: RWST r w s m a -> 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 :: 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
- module Control.Monad.RWS.Class
- module Control.Monad
- module Control.Monad.Fix
- module Control.Monad.Trans
- module Data.Monoid
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 :: Type -> Type ) 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
.
Constructors
| RWST (r -> s -> m (a, s, w)) |
Instances
| ( Monoid w, Monad m) => MonadRWS r w s ( RWST r w s m) Source # | |
|
Defined in Control.Monad.RWS.Class |
|
| ( Monoid w, MonadError e m) => MonadError e ( RWST r w s m) Source # | |
|
Defined in Control.Monad.Error.Class Methods throwError :: e -> RWST r w s m a Source # catchError :: RWST r w s m a -> (e -> RWST r w s m a) -> RWST r w s m a Source # |
|
| ( Monad m, Monoid w) => MonadReader r ( RWST r w s m) Source # | |
| ( Monad m, Monoid w) => MonadState s ( RWST r w s m) Source # | |
| ( Monoid w, Monad m) => MonadWriter w ( RWST r w s m) Source # | |
| 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) | |
|
Defined in Control.Monad.Trans.RWS.Lazy 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 # |
|
| Contravariant m => Contravariant ( 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) | |
| ( Monoid w, MonadCont m) => MonadCont ( RWST r w s m) Source # | |
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.
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 Source #
Lazy Reader-writer-state monads
module Control.Monad.RWS.Class
module Control.Monad
module Control.Monad.Fix
module Control.Monad.Trans
module Data.Monoid