acid-state-0.16.0.1: Add ACID guarantees to any serializable Haskell data structure.

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

Data.Acid.Memory.Pure

Description

AcidState container without a transaction log. Mostly used for testing.

Synopsis

- class IsAcidic st where
  - acidEvents :: [Event st]
- data AcidState st
- data Event st where
  - 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)
- type EventResult ev = MethodResult ev
- type EventState ev = MethodState ev
- class Method ev => UpdateEvent ev
- class Method ev => QueryEvent ev
- data Update st a
- data Query st a
- openAcidState :: IsAcidic st => st -> AcidState st
- update :: UpdateEvent event => AcidState (EventState event) -> event -> (AcidState (EventState event), EventResult event)
- update_ :: UpdateEvent event => AcidState (EventState event) -> event -> AcidState (EventState event)
- query :: QueryEvent event => AcidState (EventState event) -> event -> EventResult event
- liftQuery :: Query st a -> Update st a
- runUpdate :: Update s r -> s -> (r, s)
- runQuery :: Query s r -> s -> r

# Documentation

class IsAcidic st where Source #

Methods

acidEvents Source #

Arguments

:: [Event st] | List of events capable of updating or querying the state.

data AcidState st Source #

State container offering full ACID (Atomicity, Consistency, Isolation and Durability) guarantees.

`Atomicity`
  State changes are all-or-nothing. This is what you'd expect of any state variable in Haskell and AcidState doesn't change that.
`Consistency`
  No event or set of events will break your data invariants.
`Isolation`
  Transactions cannot interfere with each other even when issued in parallel.
`Durability`
  Successful transaction are guaranteed to survive system failure (both hardware and software).

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) |

type EventResult ev = MethodResult ev Source #

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

type EventState ev = MethodState ev Source #

class Method ev => UpdateEvent ev Source #

All UpdateEvents are also Methods.

class Method ev => QueryEvent ev Source #

All QueryEvents are also Methods.

data Update st a Source #

Context monad for Update events.

#### Instances

Instances details

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
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

data Query st a Source #

Context monad for Query events.

#### Instances

Instances details

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
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

openAcidState Source #

Arguments

:: IsAcidic st |
=> st | Initial state value.
-> AcidState st |

Create an AcidState given an initial value.

update :: UpdateEvent event => AcidState (EventState event) -> event -> (AcidState (EventState event), EventResult event) Source #

Issue an Update event and wait for its result. Once this call returns, you are guaranteed that the changes to the state are durable. Events may be issued in parallel.

It's a run-time error to issue events that aren't supported by the AcidState.

update_ :: UpdateEvent event => AcidState (EventState event) -> event -> AcidState (EventState event) Source #

Same as `update` but ignoring the event result.

query :: QueryEvent event => AcidState (EventState event) -> event -> EventResult event Source #

Issue a Query event and wait for its result.

liftQuery :: Query st a -> Update st a Source #

Run a query in the Update Monad.

runUpdate :: Update s r -> s -> (r, s) Source #

Execute the `Update` monad in a pure environment.

runQuery :: Query s r -> s -> r Source #

Execute the `Query` monad in a pure environment.