Data.Acid.Common

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

Documentation

runGetLazyFix :: Get a -> ByteString -> Either String a

class SafeCopy st => IsAcidic st where

Methods

acidEvents

Arguments

:: [Event st]

List of events capable of updating or querying the state.

newtype Update st a

Context monad for Update events.

Constructors

Update

Fields

• unUpdate :: State st a

Instances

MonadState st (Update st)

Defined in Data.Acid.Common

Methods

get :: Update st st

put :: st -> Update st ()

state :: (st -> (a, st)) -> Update st a

Monad (Update st)

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)

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)

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

Context monad for Query events.

Constructors

Query

Fields

• unQuery :: Reader st a

Instances

MonadReader st (Query st)

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)

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)

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)

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

liftQuery :: Query st a -> Update st a

Run a query in the Update Monad.

type EventResult ev = MethodResult ev

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

type EventState ev = MethodState ev

data Event st where

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)) -> Event (EventState ev)

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

class Method ev => UpdateEvent ev

All UpdateEvents are also Methods.

class Method ev => QueryEvent ev

All QueryEvents are also Methods.

eventsToMethods :: [Event st] -> [MethodContainer st]