Control.Distributed.Closure

Serializable closures for distributed programming. This package builds a "remotable closure" abstraction on top of static pointers. See this blog post for a longer introduction.

Documentation

type Serializable a = (Binary a, Typeable a)

Values that can be sent across the network.

Closures

data Closure a

Type of serializable closures. Abstractly speaking, a closure is a code reference paired together with an environment. A serializable closure includes a shareable code reference (i.e. a StaticPtr). Closures can be serialized only if all expressions captured in the environment are serializable.

Instances

IsStatic Closure

Methods

fromStaticPtr :: StaticPtr a -> Closure a

Typeable * a => Binary (Closure a)

Methods

put :: Closure a -> Put

get :: Get (Closure a)

putList :: [Closure a] -> Put

closure :: StaticPtr a -> Closure a

Lift a Static pointer to a closure with an empty environment.

unclosure :: Closure a -> a

Resolve a Closure to the value that it represents. Calling unclosure multiple times on the same closure is efficient: for most argument values the result is memoized.

cpure :: Closure (Dict (Serializable a)) -> a -> Closure a

A closure can be created from any serializable value. cpure corresponds to Control.Applicative's pure, but restricted to lifting serializable values only.

cap :: Typeable a => Closure (a -> b) -> Closure a -> Closure b

Closure application. Note that Closure is not a functor, let alone an applicative functor, even if it too has a meaningful notion of application.

cmap :: Typeable a => StaticPtr (a -> b) -> Closure a -> Closure b

Closure is not a Functor, in that we cannot map arbitrary functions over it. That is, we cannot define fmap. However, we can map a static pointer to a function over a Closure.

Closure dictionaries

A Dict reifies a constraint in the form of a first class value. The Dict type is not serializable: how do you serialize the constraint that values of this type carry? Whereas, for any constraint c, a value of type Closure (Dict c) can be serialized and sent over the wire, just like any Closure. A static dictionary for some constraint c is a value of type Closure (Dict c).

data Dict a :: Constraint -> * where

Values of type Dict p capture a dictionary for a constraint of type p.

e.g.

Dict :: Dict (Eq Int)

captures a dictionary that proves we have an:

instance Eq 'Int

Pattern matching on the Dict constructor will bring this instance into scope.

Constructors

Dict :: Dict a

Instances

a :=> (Read (Dict a))

Methods

ins :: a :- Read (Dict a)

a :=> (Monoid (Dict a))

Methods

ins :: a :- Monoid (Dict a)

a :=> (Enum (Dict a))

Methods

ins :: a :- Enum (Dict a)

a :=> (Bounded (Dict a))

Methods

ins :: a :- Bounded (Dict a)

() :=> (Eq (Dict a))

Methods

ins :: () :- Eq (Dict a)

() :=> (Ord (Dict a))

Methods

ins :: () :- Ord (Dict a)

() :=> (Show (Dict a))

Methods

ins :: () :- Show (Dict a)

a => Bounded (Dict a)

Methods

minBound :: Dict a

maxBound :: Dict a

a => Enum (Dict a)

Methods

succ :: Dict a -> Dict a

pred :: Dict a -> Dict a

toEnum :: Int -> Dict a

fromEnum :: Dict a -> Int

enumFrom :: Dict a -> [Dict a]

enumFromThen :: Dict a -> Dict a -> [Dict a]

enumFromTo :: Dict a -> Dict a -> [Dict a]

enumFromThenTo :: Dict a -> Dict a -> Dict a -> [Dict a]

Eq (Dict a)

Methods

(==) :: Dict a -> Dict a -> Bool

(/=) :: Dict a -> Dict a -> Bool

(Typeable Constraint p, p) => Data (Dict p)

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Dict p -> c (Dict p)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Dict p)

toConstr :: Dict p -> Constr

dataTypeOf :: Dict p -> DataType

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c (Dict p))

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Dict p))

gmapT :: (forall b. Data b => b -> b) -> Dict p -> Dict p

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Dict p -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Dict p -> r

gmapQ :: (forall d. Data d => d -> u) -> Dict p -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Dict p -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Dict p -> m (Dict p)

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Dict p -> m (Dict p)

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Dict p -> m (Dict p)

Ord (Dict a)

Methods

compare :: Dict a -> Dict a -> Ordering

(<) :: Dict a -> Dict a -> Bool

(<=) :: Dict a -> Dict a -> Bool

(>) :: Dict a -> Dict a -> Bool

(>=) :: Dict a -> Dict a -> Bool

max :: Dict a -> Dict a -> Dict a

min :: Dict a -> Dict a -> Dict a

a => Read (Dict a)

Methods

readsPrec :: Int -> ReadS (Dict a)

readList :: ReadS [Dict a]

readPrec :: ReadPrec (Dict a)

readListPrec :: ReadPrec [Dict a]

Show (Dict a)

Methods

showsPrec :: Int -> Dict a -> ShowS

show :: Dict a -> String

showList :: [Dict a] -> ShowS

a => Monoid (Dict a)

Methods

mempty :: Dict a

mappend :: Dict a -> Dict a -> Dict a

mconcat :: [Dict a] -> Dict a

class c => Static c where

It's often useful to create a static dictionary on-the-fly given any constraint. Morally, all type class constraints have associated static dictionaries, since these are either global values or simple combinations thereof. But GHC doesn't yet know how to invent a static dictionary on-demand yet given any type class constraint, so we'll have to do it manually for the time being. By defining instances of this type class manually, or via withStatic if it becomes too tedious.

Minimal complete definition

closureDict

Methods

closureDict :: Closure (Dict c)