Moduleacid-state-0.16.1.4Haskell2010

Data.Acid.Common

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

classclass IsAcidic st where

newtypenewtype Update st a

Context monad for Update events.

Instances4MonadState, Monad, Functor, Applicative

newtypenewtype Query st a

Context monad for Query events.

Instances4MonadReader, Monad, Functor, Applicative

valueliftQuery :: Query st a -> Update st a

Run a query in the Update Monad.

typetype EventResult ev = MethodResult ev

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

typetype EventState ev = MethodState ev

datadata 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.

classclass Method ev => UpdateEvent ev

All UpdateEvents are also Methods.

classclass Method ev => QueryEvent ev

All QueryEvents are also Methods.

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