monads-tf-0.1.0.3: Monad classes, using type families

Copyright(c) Andy Gill 2001, (c) Oregon Graduate Institute of Science and Technology, 2001
LicenseBSD-style (see the file LICENSE)
Maintainerross@soi.city.ac.uk
Stabilityexperimental
Portabilitynon-portable (type families)
Safe HaskellSafe
LanguageHaskell98

Control.Monad.RWS.Lazy

Contents

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

The RWS monad

type RWS r w s = RWST r w s Identity #

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

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

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

evalRWS #

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.

execRWS #

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.

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

Map the return value, final state and output of a computation using the given function.

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

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

The RWST monad transformer

newtype RWST 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.

Constructors

RWST 

Fields

Instances

Monoid w => MonadTrans (RWST r w s) 

Methods

lift :: Monad m => m a -> RWST r w s m a #

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

Methods

(>>=) :: RWST r w s m a -> (a -> RWST r w s m b) -> RWST r w s m b #

(>>) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m b #

return :: a -> RWST r w s m a #

fail :: String -> RWST r w s m a #

Functor m => Functor (RWST r w s m) 

Methods

fmap :: (a -> b) -> RWST r w s m a -> RWST r w s m b #

(<$) :: a -> RWST r w s m b -> RWST r w s m a #

(Monoid w, MonadFix m) => MonadFix (RWST r w s m) 

Methods

mfix :: (a -> RWST r w s m a) -> RWST r w s m a #

(Monoid w, MonadFail m) => MonadFail (RWST r w s m) 

Methods

fail :: String -> RWST r w s m a #

(Monoid w, Functor m, Monad m) => Applicative (RWST r w s m) 

Methods

pure :: a -> RWST r w s m a #

(<*>) :: RWST r w s m (a -> b) -> RWST r w s m a -> RWST r w s m b #

(*>) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m b #

(<*) :: RWST r w s m a -> RWST r w s m b -> RWST r w s m a #

(Monoid w, MonadIO m) => MonadIO (RWST r w s m) 

Methods

liftIO :: IO a -> RWST r w s m a #

(Monoid w, Functor m, MonadPlus m) => Alternative (RWST r w s m) 

Methods

empty :: RWST r w s m a #

(<|>) :: RWST r w s m a -> RWST r w s m a -> RWST r w s m a #

some :: RWST r w s m a -> RWST r w s m [a] #

many :: RWST r w s m a -> RWST r w s m [a] #

(Monoid w, MonadPlus m) => MonadPlus (RWST r w s m) 

Methods

mzero :: RWST r w s m a #

mplus :: RWST r w s m a -> RWST r w s m a -> RWST r w s m a #

(Monoid w, MonadCont m) => MonadCont (RWST r w s m) Source # 

Methods

callCC :: ((a -> RWST r w s m b) -> RWST r w s m a) -> RWST r w s m a Source #

(Monoid w, MonadError m) => MonadError (RWST r w s m) Source # 

Associated Types

type ErrorType (RWST r w s m :: * -> *) :: * Source #

Methods

throwError :: ErrorType (RWST r w s m) -> RWST r w s m a Source #

catchError :: RWST r w s m a -> (ErrorType (RWST r w s m) -> RWST r w s m a) -> RWST r w s m a Source #

(Monoid w, Monad m) => MonadReader (RWST r w s m) Source # 

Associated Types

type EnvType (RWST r w s m :: * -> *) :: * Source #

Methods

ask :: RWST r w s m (EnvType (RWST r w s m)) Source #

local :: (EnvType (RWST r w s m) -> EnvType (RWST r w s m)) -> RWST r w s m a -> RWST r w s m a Source #

(Monad m, Monoid w) => MonadState (RWST r w s m) Source # 

Associated Types

type StateType (RWST r w s m :: * -> *) :: * Source #

Methods

get :: RWST r w s m (StateType (RWST r w s m)) Source #

put :: StateType (RWST r w s m) -> RWST r w s m () Source #

(Monoid w, Monad m) => MonadWriter (RWST r w s m) Source # 

Associated Types

type WriterType (RWST r w s m :: * -> *) :: * Source #

Methods

tell :: WriterType (RWST r w s m) -> RWST r w s m () Source #

listen :: RWST r w s m a -> RWST r w s m (a, WriterType (RWST r w s m)) Source #

pass :: RWST r w s m (a, WriterType (RWST r w s m) -> WriterType (RWST r w s m)) -> RWST r w s m a Source #

(Monoid w, Monad m) => MonadRWS (RWST r w s m) Source # 
type ErrorType (RWST r w s m) Source # 
type ErrorType (RWST r w s m) = ErrorType m
type EnvType (RWST r w s m) Source # 
type EnvType (RWST r w s m) = r
type StateType (RWST r w s m) Source # 
type StateType (RWST r w s m) = s
type WriterType (RWST r w s m) Source # 
type WriterType (RWST r w s m) = w

evalRWST #

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.

execRWST #

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.

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

Map the inner computation using the given function.

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

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

Lazy Reader-writer-state monads