A Haskell library that adds ACID (Atomicity, Consistency, Isolation and Durability) guarantees to any serializable Haskell data structure.
See
Questions tagged [acid-state]
24 questions
58
votes
1 answer
How to handle changing the implementation of Events when using Data.Acid
I have a moderately sized application that uses Data.Acid for persistence and I've encountered a situation where I need to update the implementation of one of my Update events for the next version of the server. I.e. I have something like
myUpdate…
shang
- 24,642
- 3
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- 86
7
votes
1 answer
Use acid-state like event log in Haskell
I'm using acid-state in a project and I quite like it. I like how easy it is to add persistence to plain Haskell datatypes without much boilerplate.
As far as I understand, acid-state keeps a log of events, instead of writing out the entire new…
xnyhps
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6
votes
1 answer
How to zoom in acid-state?
data Foo = Foo {
_bar :: Map String Integer
} deriving (Eq, Ord, Read, Show, Data, Typeable)
$(deriveSafeCopy 0 'base 'Foo)
$(makeLenses ''Foo)
Given the above code I am under the impression that it should be possible to do this:
addEntry ::…
fho
- 6,787
- 26
- 71
5
votes
1 answer
How to use Network.WebSockets.Snap in a snaplet?
It would be nice to be able to use the Network.WebSockets module from inside a snaplet, but I can't figure out how to actually do it.
Using the runWebSocketsSnap :: MonadSnap m => ServerApp -> m () function from Network.WebSockets.Snap it is easy to…
dermoritz
- 187
- 8
5
votes
1 answer
Acid-state: MonadState instance for Update
I'm trying acid-state. The documentation states that Update st is an instance of MonadState st. I tried different things, but my compiler doesn't want to see that :( I tried the HelloWorld.hs from examples, but got the same…
Yuras
- 13,856
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4
votes
2 answers
Avoiding Errors caused by IO when talking to a database inside of a WAI handler
I am writing a web service in haskell using warp, wai, and acid-state. As of now, I have two handler functions that require database interaction, the latter of which is giving me trouble.
The first, is registration:
registerUser :: AcidState…
user3594595
4
votes
1 answer
How can a monadic/sequential migration be implemented for data in acid-state?
Current state
I have two data types.
data Foo = Foo
{ fooId :: RecordId Foo
, bars :: [RecordId Bar]
...
}
data Bar = Bar
{ barId :: RecordId Bar
...
}
This schema allows for each Foo to refer to an arbitrary list of Bars.…
matchwood
- 257
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4
votes
1 answer
Running template haskell in template haskell
insertST :: StateDecoder -> SomeState -> Update SomeState SomeThing
insertST stDecoder st = ...
the stuff in StateDecoder can't be used in
$(makeAcidic ''SomeState ['insertST])
but if I declare a state and wrap it like this ...
myDecoder ::…
TallerGhostWalt
- 464
- 3
- 11
4
votes
1 answer
Unexpected return type of Acid State query (Happstack)
I'm trying to extend Happstack crash course blog with some additional functionality: displaying a list of all tags on home page.
My blog record looks like this:
data Blog = Blog
{ nextPostId :: PostId
, posts :: IxSet Post
, allTags…
eugenia
- 43
- 5
3
votes
1 answer
Haskell: acid-state over multiple files?
I have a file structure like this:
--- Database.hs ---
data Database = ...
...
--- User.hs ---
import Database
addUser :: Update Database ()
...
--- Post.hs
import Database
addPost :: Update Database ()
...
The problem is that I need to called…
sqd
- 1,485
- 13
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3
votes
1 answer
How can I get cabal to install acid-state?
I'm a newbie to Haskell, and wanted to try the acid-state library, but I get the following output when trying to install it:
>cabal install acid-state
Resolving dependencies...
Configuring acid-state-0.7.5...
Building…
Diego Saa
- 1,426
- 1
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- 23
2
votes
1 answer
Making sequences of events atomic in acid-state
I am strugging with grouping sequences of events into one atomic transaction.
Consider a Map stored in acid-state, and imagine you want to implement Data.Map.alter. The function that takes a maybe-value and returns one cannot be stored in the…
user2645074
- 107
- 8
2
votes
1 answer
Ambiguous Type Variable in AcidState functions
I've got a situation in a Haskell web project where I'm getting the error Ambiguous type variable.
The relevant code is
--- Other import statements
import qualified Model as Model
---------- HTTP Handlers
needItem db user itemName = do
…
Inaimathi
- 13,853
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2
votes
1 answer
acid-state convenience wrapper without template haskell?
In acid-state tutorial all the examples use Template Haskell. However, due to some reasons I am not very keen on using it.
I know one can use acid-state without template haskell, as shown…
Andriy Drozdyuk
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1
vote
1 answer
Testing Acid-State with hspec
i'm a haskell noob and have problems with testing functions with acid-states.This ist my Datastructure
data UserState = UserState { name :: String }
deriving (Eq, Ord, Read, Show, Data, Typeable)
and this is the function i want to test:
setName…
alex.b
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