Safe Haskell	Safe
Language	Haskell2010

Control.Monad.RSS.Lazy

Contents

The RSS monad
The RSST monad transformer
Lazy Reader-writer-state monads

Description

Lazy RSS monad.

This is a variant of the classic "Control.Monad..RWS.Lazy" transformer, where the Writer part rides with the State part.

Synopsis

The RSS monad

type RSS r w s = RSST r w s Identity #

A monad containing an environment of type r, output of type w and an updatable state of type s.

rss :: Monoid w => (r -> s -> (a, s, w)) -> RSS r w s a #

Construct an RSS computation from a function. (The inverse of runRSS.)

runRSS :: Monoid w => RSS r w s a -> r -> s -> (a, s, w) #

Unwrap an RSS computation as a function. (The inverse of rws.)

evalRSS #

Arguments

:: Monoid w
=> RSS 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.

execRSS #

Arguments

:: Monoid w
=> RSS 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.

withRSS :: (r' -> s -> (r, s)) -> RSS r w s a -> RSS r' w s a #

The RSST monad transformer

data RSST r w s m a #

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, Monad m) => MonadRWS r w s (RSST r w s m) #

Monad m => MonadReader r (RSST r w s m) #
Methods ask :: RSST r w s m r # local :: (r -> r) -> RSST r w s m a -> RSST r w s m a # reader :: (r -> a) -> RSST r w s m a #
Monad m => MonadState s (RSST r w s m) #
Methods get :: RSST r w s m s # put :: s -> RSST r w s m () # state :: (s -> (a, s)) -> RSST r w s m a #
(Monoid w, Monad m) => MonadWriter w (RSST r w s m) #
Methods writer :: (a, w) -> RSST r w s m a # tell :: w -> RSST r w s m () # listen :: RSST r w s m a -> RSST r w s m (a, w) # pass :: RSST r w s m (a, w -> w) -> RSST r w s m a #
MonadTrans (RSST r w s) #
Methods lift :: Monad m => m a -> RSST r w s m a #
Monad m => Monad (RSST r w s m) #
Methods (>>=) :: RSST r w s m a -> (a -> RSST r w s m b) -> RSST r w s m b # (>>) :: RSST r w s m a -> RSST r w s m b -> RSST r w s m b # return :: a -> RSST r w s m a # fail :: String -> RSST r w s m a #
Functor m => Functor (RSST r w s m) #
Methods fmap :: (a -> b) -> RSST r w s m a -> RSST r w s m b # (<$) :: a -> RSST r w s m b -> RSST r w s m a #
MonadFix m => MonadFix (RSST r w s m) #
Methods mfix :: (a -> RSST r w s m a) -> RSST r w s m a #
(Functor m, Monad m) => Applicative (RSST r w s m) #
Methods pure :: a -> RSST r w s m a # (<>) :: RSST r w s m (a -> b) -> RSST r w s m a -> RSST r w s m b # (>) :: RSST r w s m a -> RSST r w s m b -> RSST r w s m b # (<*) :: RSST r w s m a -> RSST r w s m b -> RSST r w s m a #
MonadIO m => MonadIO (RSST r w s m) #
Methods liftIO :: IO a -> RSST r w s m a #
(Functor m, MonadPlus m) => Alternative (RSST r w s m) #
Methods empty :: RSST r w s m a # (<\|>) :: RSST r w s m a -> RSST r w s m a -> RSST r w s m a # some :: RSST r w s m a -> RSST r w s m [a] # many :: RSST r w s m a -> RSST r w s m [a] #
MonadPlus m => MonadPlus (RSST r w s m) #
Methods mzero :: RSST r w s m a # mplus :: RSST r w s m a -> RSST r w s m a -> RSST r w s m a #

evalRSST #

Arguments

:: (Monad m, Monoid w)
=> RSST 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.

execRSST #

Arguments

:: (Monad m, Monoid w)
=> RSST 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.

withRSST :: (r' -> s -> (r, s)) -> RSST r w s m a -> RSST r' w s m a #

withRSST f m executes action m with an initial environment and state modified by applying f.

runRSST (withRSST f m) r s = uncurry (runRSST m) (f r s)

Lazy Reader-writer-state monads

module Control.Monad.RWS.Class

module Control.Monad

module Control.Monad.Fix

module Control.Monad.Trans

module Data.Monoid