transformers-0.1.0.0: Concrete monad transformers

Portabilityportable
Stabilityexperimental
Maintainerlibraries@haskell.org

Control.Monad.Trans.RWS.Strict

Contents

Description

Strict 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

The RWS monad

type RWS r w s = RWST r w s IdentitySource

rws :: (r -> s -> (a, s, w)) -> RWS r w s aSource

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

evalRWS :: RWS r w s a -> r -> s -> (a, w)Source

execRWS :: RWS r w s a -> r -> s -> (s, w)Source

mapRWS :: ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s bSource

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

The RWST monad transformer

newtype RWST r w s m a Source

Constructors

RWST 

Fields

runRWST :: r -> s -> m (a, s, w)
 

Instances

Monoid w => MonadTrans (RWST r w s) 
(Monoid w, Monad m) => Monad (RWST r w s m) 
Monad m => Functor (RWST r w s m) 
(Monoid w, MonadFix m) => MonadFix (RWST r w s m) 
(Monoid w, MonadPlus m) => MonadPlus (RWST r w s m) 
(Monoid w, Monad m) => Applicative (RWST r w s m) 
(Monoid w, MonadPlus m) => Alternative (RWST r w s m) 
(Monoid w, MonadIO m) => MonadIO (RWST r w s m) 

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

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

mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n bSource

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

Reader operations

ask :: (Monoid w, Monad m) => RWST r w s m rSource

local :: (Monoid w, Monad m) => (r -> r) -> RWST r w s m a -> RWST r w s m aSource

asks :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m aSource

Writer operations

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

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

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

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

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

State operations

get :: (Monoid w, Monad m) => RWST r w s m sSource

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

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

Monadic state transformer.

Maps an old state to a new state inside a state monad. The old state is thrown away.

gets :: (Monoid w, Monad m) => (s -> a) -> RWST r w s m aSource

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

Lifting other operations

liftCallCC :: Monoid w => ((((a, s, w) -> m (b, s, w)) -> m (a, s, w)) -> m (a, s, w)) -> ((a -> RWST r w s m b) -> RWST r w s m a) -> RWST r w s m aSource

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

liftCallCC' :: Monoid w => ((((a, s, w) -> m (b, s, w)) -> m (a, s, w)) -> m (a, s, w)) -> ((a -> RWST r w s m b) -> RWST r w s m a) -> RWST r w s m aSource

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

liftCatch :: (m (a, s, w) -> (e -> m (a, s, w)) -> m (a, s, w)) -> RWST l w s m a -> (e -> RWST l w s m a) -> RWST l w s m aSource

Lift a catchError operation to the new monad.