Copyright	(c) Ross Paterson 2003
License	BSD-style (see the LICENSE file in the distribution)
Maintainer	R.Paterson@city.ac.uk
Stability	experimental
Portability	non-portable (multi-parameter type classes)
Safe Haskell	Safe
Language	Haskell98

Control.Arrow.Transformer.State

Description

An arrow transformer that adds a modifiable state, based of section 9 of Generalising Monads to Arrows, by John Hughes, Science of Computer Programming 37:67-111, May 2000.

Synopsis

Documentation

newtype StateArrow s a b c Source #

An arrow type that augments an existing arrow with a modifiable state. The ArrowState class contains the operations on this state.

Constructors

StateArrow (a (b, s) (c, s))

Instances

ArrowError ex a => ArrowError ex (StateArrow s a) Source #
Methods raise :: StateArrow s a ex b Source # handle :: StateArrow s a e b -> StateArrow s a (e, ex) b -> StateArrow s a e b Source # tryInUnless :: StateArrow s a e b -> StateArrow s a (e, b) c -> StateArrow s a (e, ex) c -> StateArrow s a e c Source # newError :: StateArrow s a e b -> StateArrow s a e (Either ex b) Source #
ArrowWriter w a => ArrowWriter w (StateArrow s a) Source #
Methods write :: StateArrow s a w () Source # newWriter :: StateArrow s a e b -> StateArrow s a e (b, w) Source #
Arrow a => ArrowState s (StateArrow s a) Source #
Methods fetch :: StateArrow s a e s Source # store :: StateArrow s a s () Source #
ArrowReader r a => ArrowReader r (StateArrow s a) Source #
Methods readState :: StateArrow s a b r Source # newReader :: StateArrow s a e b -> StateArrow s a (e, r) b Source #
Arrow a => ArrowAddState s (StateArrow s a) a Source #
Methods liftState :: a e b -> StateArrow s a e b Source # elimState :: StateArrow s a e b -> a (e, s) (b, s) Source #
ArrowAddError ex a a' => ArrowAddError ex (StateArrow s a) (StateArrow s a') Source #
Methods liftError :: StateArrow s a' e b -> StateArrow s a e b Source # elimError :: StateArrow s a e b -> StateArrow s a' (e, ex) b -> StateArrow s a' e b Source #
ArrowAddWriter w a a' => ArrowAddWriter w (StateArrow s a) (StateArrow s a') Source #
Methods liftWriter :: StateArrow s a' e b -> StateArrow s a e b Source # elimWriter :: StateArrow s a e b -> StateArrow s a' e (b, w) Source #
ArrowAddReader r a a' => ArrowAddReader r (StateArrow s a) (StateArrow s a') Source #
Methods liftReader :: StateArrow s a' e b -> StateArrow s a e b Source # elimReader :: StateArrow s a e b -> StateArrow s a' (e, r) b Source #
Arrow a => ArrowTransformer (StateArrow s) a Source #
Methods lift :: a b c -> StateArrow s a b c Source #
Category * a => Category * (StateArrow s a) Source #
Methods id :: cat a a # (.) :: cat b c -> cat a b -> cat a c #
Arrow a => Arrow (StateArrow s a) Source #
Methods arr :: (b -> c) -> StateArrow s a b c # first :: StateArrow s a b c -> StateArrow s a (b, d) (c, d) # second :: StateArrow s a b c -> StateArrow s a (d, b) (d, c) # (***) :: StateArrow s a b c -> StateArrow s a b' c' -> StateArrow s a (b, b') (c, c') # (&&&) :: StateArrow s a b c -> StateArrow s a b c' -> StateArrow s a b (c, c') #
ArrowZero a => ArrowZero (StateArrow s a) Source #
Methods zeroArrow :: StateArrow s a b c #
ArrowPlus a => ArrowPlus (StateArrow s a) Source #
Methods (<+>) :: StateArrow s a b c -> StateArrow s a b c -> StateArrow s a b c #
ArrowChoice a => ArrowChoice (StateArrow s a) Source #
Methods left :: StateArrow s a b c -> StateArrow s a (Either b d) (Either c d) # right :: StateArrow s a b c -> StateArrow s a (Either d b) (Either d c) # (+++) :: StateArrow s a b c -> StateArrow s a b' c' -> StateArrow s a (Either b b') (Either c c') # (\|\|\|) :: StateArrow s a b d -> StateArrow s a c d -> StateArrow s a (Either b c) d #
ArrowApply a => ArrowApply (StateArrow s a) Source #
Methods app :: StateArrow s a (StateArrow s a b c, b) c #
ArrowLoop a => ArrowLoop (StateArrow s a) Source #
Methods loop :: StateArrow s a (b, d) (c, d) -> StateArrow s a b c #
ArrowCircuit a => ArrowCircuit (StateArrow s a) Source #
Methods delay :: b -> StateArrow s a b b Source #
Arrow a => Functor (StateArrow s a b) Source #
Methods fmap :: (a -> b) -> StateArrow s a b a -> StateArrow s a b b # (<$) :: a -> StateArrow s a b b -> StateArrow s a b a #
Arrow a => Applicative (StateArrow s a b) Source #
Methods pure :: a -> StateArrow s a b a # (<>) :: StateArrow s a b (a -> b) -> StateArrow s a b a -> StateArrow s a b b # liftA2 :: (a -> b -> c) -> StateArrow s a b a -> StateArrow s a b b -> StateArrow s a b c # (>) :: StateArrow s a b a -> StateArrow s a b b -> StateArrow s a b b # (<*) :: StateArrow s a b a -> StateArrow s a b b -> StateArrow s a b a #
ArrowPlus a => Alternative (StateArrow s a b) Source #
Methods empty :: StateArrow s a b a # (<\|>) :: StateArrow s a b a -> StateArrow s a b a -> StateArrow s a b a # some :: StateArrow s a b a -> StateArrow s a b [a] # many :: StateArrow s a b a -> StateArrow s a b [a] #
ArrowPlus a => Semigroup (StateArrow s a b c) Source #
Methods (<>) :: StateArrow s a b c -> StateArrow s a b c -> StateArrow s a b c # sconcat :: NonEmpty (StateArrow s a b c) -> StateArrow s a b c # stimes :: Integral b => b -> StateArrow s a b c -> StateArrow s a b c #
ArrowPlus a => Monoid (StateArrow s a b c) Source #
Methods mempty :: StateArrow s a b c # mappend :: StateArrow s a b c -> StateArrow s a b c -> StateArrow s a b c # mconcat :: [StateArrow s a b c] -> StateArrow s a b c #

runState :: Arrow a => StateArrow s a e b -> a (e, s) (b, s) Source #

Encapsulation of a state-using computation, exposing the initial and final states.

Typical usage in arrow notation:

   proc p -> do
       ...
       (result, final_state) <- (|runState cmd|) init_state

class (ArrowState s a, Arrow a') => ArrowAddState s a a' | a -> a' where Source #

Adding a StateArrow to an arrow type, but not necessarily as the outer arrow transformer.

Typically a composite arrow type is built by applying a series of arrow transformer to a base arrow (usually either a function arrow or a Kleisli arrow. One can add a transformer to the top of this stack using the lift method of the ArrowTransformer class, or remove a state transformer from the top of the stack using the runState encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance

   instance Arrow a => ArrowAddState s (ArrowState s a) a

they are equivalent to lift and runState respectively. Instances are lifted through other transformers with

   instance ArrowAddState s a a' =>
       ArrowAddState s (FooArrow a) (FooArrow a')

Minimal complete definition

liftState, elimState

Methods

liftState :: a' e b -> a e b Source #

Lift a computation from an arrow to one with an added state.

Typical usage in arrow notation:

   proc p -> ...
       (|liftState cmd|)

elimState :: a e b -> a' (e, s) (b, s) Source #

Elimination of a state transformer from a computation, exposing the initial and final states.

Typical usage in arrow notation:

   proc p -> do
       ...
       (result, final_state) <- (|elimState cmd|) init_state

Instances

ArrowAddState r a a' => ArrowAddState r (Automaton a) (Automaton a') Source #
Methods liftState :: Automaton a' e b -> Automaton a e b Source # elimState :: Automaton a e b -> Automaton a' (e, r) (b, r) Source #
Arrow a => ArrowAddState s (StateArrow s a) a Source #
Methods liftState :: a e b -> StateArrow s a e b Source # elimState :: StateArrow s a e b -> a (e, s) (b, s) Source #
(ArrowAddState s a a', ArrowChoice a, ArrowChoice a') => ArrowAddState s (ErrorArrow ex a) (ErrorArrow ex a') Source #
Methods liftState :: ErrorArrow ex a' e b -> ErrorArrow ex a e b Source # elimState :: ErrorArrow ex a e b -> ErrorArrow ex a' (e, s) (b, s) Source #
ArrowAddState s a a' => ArrowAddState s (ReaderArrow r a) (ReaderArrow r a') Source #
Methods liftState :: ReaderArrow r a' e b -> ReaderArrow r a e b Source # elimState :: ReaderArrow r a e b -> ReaderArrow r a' (e, s) (b, s) Source #
(ArrowAddState s a a', Applicative f) => ArrowAddState s (StaticArrow f a) (StaticArrow f a') Source #
Methods liftState :: StaticArrow f a' e b -> StaticArrow f a e b Source # elimState :: StaticArrow f a e b -> StaticArrow f a' (e, s) (b, s) Source #
(ArrowAddState s a a', Monoid w) => ArrowAddState s (WriterArrow w a) (WriterArrow w a') Source #
Methods liftState :: WriterArrow w a' e b -> WriterArrow w a e b Source # elimState :: WriterArrow w a e b -> WriterArrow w a' (e, s) (b, s) Source #