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 MarshalM monad. Also, a mechanism is exposed for generically deriving marshalling and unmarshalling code for simple product types.

Documentation

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. You need to make sure that the marshalling of 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 :: a -> MarshalM PushF ()

Marshals a value to the datalog side.

default push :: (Generic a, SimpleProduct a (Rep a), GMarshal (Rep a)) => a -> MarshalM PushF ()

pop :: MarshalM PopF a

Unmarshals a value from the datalog side.

default pop :: (Generic a, SimpleProduct a (Rep a), GMarshal (Rep a)) => MarshalM PopF a

Instances

Marshal Int32

Defined in Language.Souffle.Marshal

Methods

push :: Int32 -> MarshalM PushF ()

pop :: MarshalM PopF Int32

Marshal String

Defined in Language.Souffle.Marshal

Methods

push :: String -> MarshalM PushF ()

pop :: MarshalM PopF String

Marshal Text

Defined in Language.Souffle.Marshal

Methods

push :: Text -> MarshalM PushF ()

pop :: MarshalM PopF Text

Marshal Text

Defined in Language.Souffle.Marshal

Methods

push :: Text -> MarshalM PushF ()

pop :: MarshalM PopF Text

data PushF a

A data type used for serializing a Marshal-able value from Haskell to Souffle, only used internally.

Constructors

PushInt Int32 a

PushStr String a

Instances

Functor PushF

Defined in Language.Souffle.Marshal

Methods

fmap :: (a -> b) -> PushF a -> PushF b

(<$) :: a -> PushF b -> PushF a

data PopF a

A data type used for deserializing a Marshal-able value from Souffle to Haskell, only used internally.

Constructors

PopInt (Int32 -> a)

PopStr (String -> a)

Instances

Functor PopF

Defined in Language.Souffle.Marshal

Methods

fmap :: (a -> b) -> PopF a -> PopF b

(<$) :: a -> PopF b -> PopF a

data MarshalM f a

The monad used for serializing and deserializing of values that implement the Marshal typeclass.

Instances

Functor f => Monad (MarshalM f)

Defined in Language.Souffle.Marshal

Methods

(>>=) :: MarshalM f a -> (a -> MarshalM f b) -> MarshalM f b

(>>) :: MarshalM f a -> MarshalM f b -> MarshalM f b

return :: a -> MarshalM f a

Functor f => Functor (MarshalM f)

Defined in Language.Souffle.Marshal

Methods

fmap :: (a -> b) -> MarshalM f a -> MarshalM f b

(<$) :: a -> MarshalM f b -> MarshalM f a

Functor f => Applicative (MarshalM f)

Defined in Language.Souffle.Marshal

Methods

pure :: a -> MarshalM f a

(<*>) :: MarshalM f (a -> b) -> MarshalM f a -> MarshalM f b

liftA2 :: (a -> b -> c) -> MarshalM f a -> MarshalM f b -> MarshalM f c

(*>) :: MarshalM f a -> MarshalM f b -> MarshalM f b

(<*) :: MarshalM f a -> MarshalM f b -> MarshalM f a

interpret :: Monad m => (forall x. f x -> m x) -> MarshalM f a -> m a

Helper function for interpreting the actual (de-)serialization of values. This allows both the compiled and interpreted variant to handle (de-)serialization in their own way.