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.Reader

Description

Arrow transformer that adds a read-only state (i.e. an environment).

Synopsis

Documentation

newtype ReaderArrow r a b c Source #

An arrow type that augments an existing arrow with a read-only state (or environment). The ArrowReader class contains the operations on this state.

Constructors

ReaderArrow (a (b, r) c)

Instances

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

runReader :: Arrow a => ReaderArrow r a e b -> a (e, r) b Source #

Encapsulation of a state-reading computation, taking a value for the state.

Typical usage in arrow notation:

   proc p -> ...
       (|runReader cmd|) env

class (ArrowReader r a, Arrow a') => ArrowAddReader r a a' | a -> a' where Source #

Adding a ReaderArrow 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 runReader encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance

   instance Arrow a => ArrowAddReader r (ArrowReader r a) a

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

   instance ArrowAddReader r a a' =>
       ArrowAddReader r (FooArrow a) (FooArrow a')

Minimal complete definition

liftReader, elimReader

Methods

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

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

Typical usage in arrow notation:

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

elimReader :: a e b -> a' (e, r) b Source #

Elimination of a state reader from a computation, taking a value for the state.

Typical usage in arrow notation:

   proc p -> ...
       (|elimReader cmd|) env

Instances

ArrowAddReader r a a' => ArrowAddReader r (Automaton a) (Automaton a') Source #
Methods liftReader :: Automaton a' e b -> Automaton a e b Source # elimReader :: Automaton a e b -> Automaton a' (e, r) b Source #
Arrow a => ArrowAddReader r (ReaderArrow r a) a Source #
Methods liftReader :: a e b -> ReaderArrow r a e b Source # elimReader :: ReaderArrow r a e b -> a (e, r) b Source #
(ArrowAddReader r a a', ArrowChoice a, ArrowChoice a') => ArrowAddReader r (ErrorArrow ex a) (ErrorArrow ex a') Source #
Methods liftReader :: ErrorArrow ex a' e b -> ErrorArrow ex a e b Source # elimReader :: ErrorArrow ex a e b -> ErrorArrow ex a' (e, r) b 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 #
(ArrowAddReader r a a', Applicative f) => ArrowAddReader r (StaticArrow f a) (StaticArrow f a') Source #
Methods liftReader :: StaticArrow f a' e b -> StaticArrow f a e b Source # elimReader :: StaticArrow f a e b -> StaticArrow f a' (e, r) b Source #
(ArrowAddReader r a a', Monoid w) => ArrowAddReader r (WriterArrow w a) (WriterArrow w a') Source #
Methods liftReader :: WriterArrow w a' e b -> WriterArrow w a e b Source # elimReader :: WriterArrow w a e b -> WriterArrow w a' (e, r) b Source #