Control.Arrow.IOStateListArrow

Description

Version : $Id: IOStateListArrow.hs,v 1.7 20050902 17:09:39 hxml Exp $

Implementation of arrows with IO and a state

Synopsis

newtype IOSLA s a b = IOSLA {

runIOSLA :: (s -> a -> IO (s, [b]))

}

liftSt :: IOSLA s1 b c -> IOSLA (s1, s2) b c

runSt :: s2 -> IOSLA (s1, s2) b c -> IOSLA s1 b c

Documentation

newtype IOSLA s a b

list arrow combined with a state and the IO monad

Constructors

IOSLA

runIOSLA :: (s -> a -> IO (s, [b]))

Instances

liftSt :: IOSLA s1 b c -> IOSLA (s1, s2) b c

lift the state of an IOSLA arrow to a state with an additional component.

This is uesful, when running predefined IO arrows, e.g. for document input, in a context with a more complex state component.

runSt :: s2 -> IOSLA (s1, s2) b c -> IOSLA s1 b c

run an arrow with augmented state in the context of a simple state arrow. An initial value for the new state component is needed.

This is useful, when running an arrow with an extra environment component, e.g. for namespace handling in XML.

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