Language.Souffle.Marshal

This module exposes a uniform interface to marshal values to and from Souffle Datalog. This is done via the Marshal typeclass and MarshalT monad transformer. Also, a mechanism is exposed for generically deriving marshalling and unmarshalling code for simple product types.

Documentation

data MarshalT m a

A monad transformer, used solely for marshalling and unmarshalling between Haskell and Souffle Datalog.

Instances

MonadTrans MarshalT

Defined in Language.Souffle.Marshal

Methods

lift :: Monad m => m a -> MarshalT m a

MonadWriter w m => MonadWriter w (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

writer :: (a, w) -> MarshalT m a

tell :: w -> MarshalT m ()

listen :: MarshalT m a -> MarshalT m (a, w)

pass :: MarshalT m (a, w -> w) -> MarshalT m a

MonadState s m => MonadState s (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

get :: MarshalT m s

put :: s -> MarshalT m ()

state :: (s -> (a, s)) -> MarshalT m a

MonadError e m => MonadError e (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

throwError :: e -> MarshalT m a

catchError :: MarshalT m a -> (e -> MarshalT m a) -> MarshalT m a

Monad m => Monad (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

(>>=) :: MarshalT m a -> (a -> MarshalT m b) -> MarshalT m b

(>>) :: MarshalT m a -> MarshalT m b -> MarshalT m b

return :: a -> MarshalT m a

Functor m => Functor (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

fmap :: (a -> b) -> MarshalT m a -> MarshalT m b

(<$) :: a -> MarshalT m b -> MarshalT m a

Applicative m => Applicative (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

pure :: a -> MarshalT m a

(<*>) :: MarshalT m (a -> b) -> MarshalT m a -> MarshalT m b

liftA2 :: (a -> b -> c) -> MarshalT m a -> MarshalT m b -> MarshalT m c

(*>) :: MarshalT m a -> MarshalT m b -> MarshalT m b

(<*) :: MarshalT m a -> MarshalT m b -> MarshalT m a

MonadIO m => MonadIO (MarshalT m)

Defined in Language.Souffle.Marshal

Methods

liftIO :: IO a -> MarshalT m a

runMarshalT :: MarshalT m a -> Tuple -> m a

Execute the monad transformer and return the result. The tuple that is passed in will be used to marshal the data back and forth.

class Marshal a where

A typeclass for providing a uniform API to marshal/unmarshal values between Haskell and Souffle datalog.

The marshalling is done via a stack-based approach, where elements are pushed/popped one by one. The programmer needs to make sure that the marshalling values happens in the correct order or unexpected things might happen (including crashes). Pushing and popping of fields should happen in the same order (from left to right, as defined in Datalog).

Generic implementations for push and pop that perform the previously described behavior are available. This makes it possible to write very succinct code:

data Edge = Edge String String deriving Generic

instance Marshal Edge

Minimal complete definition

Nothing

Methods

push :: MonadIO m => a -> MarshalT m ()

Marshals a value to the datalog side.

default push :: (Generic a, SimpleProduct a (Rep a), GMarshal (Rep a), MonadIO m) => a -> MarshalT m ()

pop :: MonadIO m => MarshalT m a

Unmarshals a value from the datalog side.

default pop :: (Generic a, SimpleProduct a (Rep a), GMarshal (Rep a), MonadIO m) => MarshalT m a

Instances

Marshal Int32

Defined in Language.Souffle.Marshal

Methods

push :: forall (m :: Type -> Type). MonadIO m => Int32 -> MarshalT m ()

pop :: forall (m :: Type -> Type). MonadIO m => MarshalT m Int32

Marshal String

Defined in Language.Souffle.Marshal

Methods

push :: forall (m :: Type -> Type). MonadIO m => String -> MarshalT m ()

pop :: forall (m :: Type -> Type). MonadIO m => MarshalT m String

Marshal Text

Defined in Language.Souffle.Marshal

Methods

push :: forall (m :: Type -> Type). MonadIO m => Text -> MarshalT m ()

pop :: forall (m :: Type -> Type). MonadIO m => MarshalT m Text

Marshal Text

Defined in Language.Souffle.Marshal

Methods

push :: forall (m :: Type -> Type). MonadIO m => Text -> MarshalT m ()

pop :: forall (m :: Type -> Type). MonadIO m => MarshalT m Text