Some extra kit for Chans
|LTS Haskell 20.24:||0.0.4.1|
|Stackage Nightly 2023-06-08:||0.0.4.1|
|Latest on Hackage:||0.0.4.1|
Maintained by firstname.lastname@example.org
This version can be pinned in stack with:
Module documentation for 0.0.4.1
This is just some extra
TChan kit that might help the average user. It relies on
spawning threads with
async and either canceling (debouncing) or waiting (throttling) messages.
Unfortunately, the current design is slightly untyped in the sense that the channel which you supply is the output channel, and the returned channel is the one you would write to. I’m not sure how this should be fixed. There’s a series of “typed” alternatives to each underlying channel type, that allows users to restrict them to “read-only”, “write-only”, or “Writable a => …” etc.
An example might be the following:
import Control.Concurrent.Chan (readChan) import Control.Concurrent.Chan.Scope (Scope (..)) import Control.Concurrent.Chan.Typed (ChanRW) import Control.Concurrent.Chan.Extra (allowReading, throttleStatic, intersperseStatic) -- For example, some websockets: data SomeMessage = Ping | Foo -- | ... throttleLayer :: ChanRW 'Read SomeMessage -> IO (ChanRW 'Write SomeMessage) throttleLayer output = do (x,_) <- throttleStatic output 1000000 -- nanoseconds, = 1 second pure x pingLayer :: ChanRW 'Read SomeMessage -> IO (ChanRW 'Write SomeMessage) pingLayer output = do (x,_,_) <- intersperseStatic output (pure Ping) 1000000 pure x performWebsocket :: ChanRW 'Read SomeMessage -> IO () performWebsocket output = do sendable <- pingLayer . allowReading =<< throttleLayer output emittingThread <- async $ forever $ do -- the thread that actually facilitates the sending of messages queued in the chans msg <- readChanRW output send msg -- something like that - it'll include Ping messages for us, -- and throttle the outgoing messages at the same time. writeChanRW sendable Foo