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

newtype StateArrow s a b c = StateArrow (a (b, s) (c, s))
runState :: Arrow a => StateArrow s a e b -> a (e, s) (b, s)
class (ArrowState s a, Arrow a') => ArrowAddState s a a' | a -> a' where
- liftState :: a' e b -> a e b
- elimState :: a e b -> a' (e, s) (b, s)

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

Instances details

ArrowError ex a => ArrowError ex (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State Methods fetch :: StateArrow s a e s Source # store :: StateArrow s a s () Source #
ArrowReader r a => ArrowReader r (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.State Methods lift :: a b c -> StateArrow s a b c Source #
Category a => Category (StateArrow s a :: Type -> Type -> Type) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods id :: forall (a0 :: k). StateArrow s a a0 a0 (.) :: forall (b :: k) (c :: k) (a0 :: k). StateArrow s a b c -> StateArrow s a a0 b -> StateArrow s a a0 c
Arrow a => Arrow (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State 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')
ArrowApply a => ArrowApply (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods app :: StateArrow s a (StateArrow s a b c, b) c
ArrowChoice a => ArrowChoice (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State 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
ArrowLoop a => ArrowLoop (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods loop :: StateArrow s a (b, d) (c, d) -> StateArrow s a b c
ArrowPlus a => ArrowPlus (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods (<+>) :: StateArrow s a b c -> StateArrow s a b c -> StateArrow s a b c
ArrowZero a => ArrowZero (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods zeroArrow :: StateArrow s a b c
ArrowCircuit a => ArrowCircuit (StateArrow s a) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods delay :: b -> StateArrow s a b b Source #
Arrow a => Functor (StateArrow s a b) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods fmap :: (a0 -> b0) -> StateArrow s a b a0 -> StateArrow s a b b0 (<$) :: a0 -> StateArrow s a b b0 -> StateArrow s a b a0
Arrow a => Applicative (StateArrow s a b) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods pure :: a0 -> StateArrow s a b a0 (<>) :: StateArrow s a b (a0 -> b0) -> StateArrow s a b a0 -> StateArrow s a b b0 liftA2 :: (a0 -> b0 -> c) -> StateArrow s a b a0 -> StateArrow s a b b0 -> StateArrow s a b c (>) :: StateArrow s a b a0 -> StateArrow s a b b0 -> StateArrow s a b b0 (<*) :: StateArrow s a b a0 -> StateArrow s a b b0 -> StateArrow s a b a0
ArrowPlus a => Alternative (StateArrow s a b) Source #
Instance details Defined in Control.Arrow.Transformer.State Methods empty :: StateArrow s a b a0 (<\|>) :: StateArrow s a b a0 -> StateArrow s a b a0 -> StateArrow s a b a0 some :: StateArrow s a b a0 -> StateArrow s a b [a0] many :: StateArrow s a b a0 -> StateArrow s a b [a0]
ArrowPlus a => Semigroup (StateArrow s a b c) Source #
Instance details Defined in Control.Arrow.Transformer.State 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 b0 => b0 -> StateArrow s a b c -> StateArrow s a b c
ArrowPlus a => Monoid (StateArrow s a b c) Source #
Instance details Defined in Control.Arrow.Transformer.State 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')

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

Instances details

ArrowAddState r a a' => ArrowAddState r (Automaton a) (Automaton a') Source #
Instance details Defined in Control.Arrow.Transformer.Automaton 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 #
Instance details Defined in Control.Arrow.Transformer.State 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 #
Instance details Defined in Control.Arrow.Transformer.Error 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 #
Instance details Defined in Control.Arrow.Transformer.Reader 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 #
Instance details Defined in Control.Arrow.Transformer.Static 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 #
Instance details Defined in Control.Arrow.Transformer.Writer 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 #