Copyright	PublicDomain
Maintainer	lemmih@gmail.com
Portability	non-portable (uses GHC extensions)
Safe Haskell	None
Language	Haskell2010

Data.Acid.Common

Description

Common structures used by the various backends (local, memory).

Synopsis

Documentation

class IsAcidic st where Source #

Methods

Arguments

:: [Event st]

List of events capable of updating or querying the state.

newtype Update st a Source #

Context monad for Update events.

Constructors

Update
Fields unUpdate :: State st a

Instances

MonadState st (Update st) Source #
Instance details Defined in Data.Acid.Common Methods get :: Update st st # put :: st -> Update st () # state :: (st -> (a, st)) -> Update st a #
Monad (Update st) Source #
Instance details Defined in Data.Acid.Common Methods (>>=) :: Update st a -> (a -> Update st b) -> Update st b # (>>) :: Update st a -> Update st b -> Update st b # return :: a -> Update st a # fail :: String -> Update st a #
Functor (Update st) Source #
Instance details Defined in Data.Acid.Common Methods fmap :: (a -> b) -> Update st a -> Update st b # (<$) :: a -> Update st b -> Update st a #
Applicative (Update st) Source #
Instance details Defined in Data.Acid.Common Methods pure :: a -> Update st a # (<>) :: Update st (a -> b) -> Update st a -> Update st b # liftA2 :: (a -> b -> c) -> Update st a -> Update st b -> Update st c # (>) :: Update st a -> Update st b -> Update st b # (<*) :: Update st a -> Update st b -> Update st a #

newtype Query st a Source #

Context monad for Query events.

Constructors

Query
Fields unQuery :: Reader st a

Instances

MonadReader st (Query st) Source #
Instance details Defined in Data.Acid.Common Methods ask :: Query st st # local :: (st -> st) -> Query st a -> Query st a # reader :: (st -> a) -> Query st a #
Monad (Query st) Source #
Instance details Defined in Data.Acid.Common Methods (>>=) :: Query st a -> (a -> Query st b) -> Query st b # (>>) :: Query st a -> Query st b -> Query st b # return :: a -> Query st a # fail :: String -> Query st a #
Functor (Query st) Source #
Instance details Defined in Data.Acid.Common Methods fmap :: (a -> b) -> Query st a -> Query st b # (<$) :: a -> Query st b -> Query st a #
Applicative (Query st) Source #
Instance details Defined in Data.Acid.Common Methods pure :: a -> Query st a # (<>) :: Query st (a -> b) -> Query st a -> Query st b # liftA2 :: (a -> b -> c) -> Query st a -> Query st b -> Query st c # (>) :: Query st a -> Query st b -> Query st b # (<*) :: Query st a -> Query st b -> Query st a #

Run a query in the Update Monad.

Events return the same thing as Methods. The exact type of EventResult depends on the event.

data Event st where Source #

We distinguish between events that modify the state and those that do not.

UpdateEvents are executed in a MonadState context and have to be serialized to disk before they are considered durable.

QueryEvents are executed in a MonadReader context and obviously do not have to be serialized to disk.

Constructors

UpdateEvent :: UpdateEvent ev => (ev -> Update (EventState ev) (EventResult ev)) -> MethodSerialiser ev -> Event (EventState ev)
QueryEvent :: QueryEvent ev => (ev -> Query (EventState ev) (EventResult ev)) -> MethodSerialiser ev -> Event (EventState ev)

All UpdateEvents are also Methods.

All QueryEvents are also Methods.