Control.Eff.Concurrent.Api

This module contains a mechanisms to specify what kind of messages a process can receive and possible answer by sending a message back to the orginator.

A message can be either a blocking or a non-blocking request.

The type magic in the Api type familiy allows to define a related set of messages along with the corresponding responses.

A process can serve a specific Api instance by using the functions provided by the Control.Eff.Concurrent.Api.Server module.

To enable a process to use such a service, the functions provided by the Control.Eff.Concurrent.Api.Client should be used.

Documentation

data family Api (api :: Type) (reply :: Synchronicity)

This data family defines an API, a communication interface description between to processes, where one process acts as a server and the other(s) as client(s).

The first parameter is usually a user defined phantom type that identifies the Api instance.

The second parameter specifies if a specific constructor of an (GADT-like) Api instance is Synchronous, i.e. returns a result and blocks the caller or if it is Asynchronous

Example:

data BookShop deriving Typeable

data instance Api BookShop r where
  RentBook  :: BookId   -> Api BookShop ('Synchronous (Either RentalError RentalId))
  BringBack :: RentalId -> Api BookShop 'Asynchronous

type BookId = Int
type RentalId = Int
type RentalError = String

Instances

Show (Observation o) => Show (Api (CallbackObserver Type o) r)

Methods

showsPrec :: Int -> Api (CallbackObserver Type o) r -> ShowS

show :: Api (CallbackObserver Type o) r -> String

showList :: [Api (CallbackObserver Type o) r] -> ShowS

data Api (CallbackObserver k o)

data Api (CallbackObserver k o) where

• CbObserved :: Api (CallbackObserver Type o) Asynchronous

data Synchronicity

This data kind is used to indicate at the type level if a specific constructor of an Api instance has a result for which some caller has to wait, or if it is asynchronous.

Constructors

Synchronous Type

Blocking operation with a specific return type, e.g. ('Synchronous (Either RentalError RentalId))

Asynchronous

Non-blocking async operation

newtype Server api

This is a tag-type that wraps around a ProcessId and holds an Api index type.

Constructors

Server

Fields

• _fromServer :: ProcessId

Instances

Eq (Server k api)

Methods

(==) :: Server k api -> Server k api -> Bool

(/=) :: Server k api -> Server k api -> Bool

Ord (Server k api)

Methods

compare :: Server k api -> Server k api -> Ordering

(<) :: Server k api -> Server k api -> Bool

(<=) :: Server k api -> Server k api -> Bool

(>) :: Server k api -> Server k api -> Bool

(>=) :: Server k api -> Server k api -> Bool

max :: Server k api -> Server k api -> Server k api

min :: Server k api -> Server k api -> Server k api

Read (Server k api)

Methods

readsPrec :: Int -> ReadS (Server k api)

readList :: ReadS [Server k api]

readPrec :: ReadPrec (Server k api)

readListPrec :: ReadPrec [Server k api]

Typeable k api => Show (Server k api)

Methods

showsPrec :: Int -> Server k api -> ShowS

show :: Server k api -> String

showList :: [Server k api] -> ShowS

fromServer :: forall api api. Iso (Server api) (Server api) ProcessId ProcessId

proxyAsServer :: proxy api -> ProcessId -> Server api

Tag a ProcessId with an Api type index to mark it a Server process handling that API

asServer :: forall api. ProcessId -> Server api

Tag a ProcessId with an Api type index to mark it a Server process handling that API