I use my nonblocking library:

eg for IRC bot:

   let myCallbacks = defaultCallbacks {
                                done_connected = binded,
                                done_reading = response_get tm ref stdgen gsref,
                                done_writing = response_written,
                                done_closed = \pl s -> do
                                    putStrLn "peer closed, reconnecting"
                                    s <- socket myCallbacks
                                    connect pl s "83.140.172.212:6667"
                                    return 1,
                                handle_error = \pl s buf len-> do
                                    str <- peekCStringLen (buf,fromIntegral len)
                                    putStrLn $ "error "++str++", reconnecting"
                                    s <- socket myCallbacks
                                    connect pl s "83.140.172.212:6667"
                                    return 1,
                                tick = binded_tick tm
                              }
    s <- socket myCallbacks

    pl <- epoll 1000
    connect pl s "83.140.172.212:6667"
    run_loop pl (-1)

Hi Niklas and Patrick,

Thankyou both for the comments -- this is what I am looking for. 

I have a follow-on question, if I have code like

getPages :: IO()
getPages = do (page1, page2, page3)
     <- runConcurrently $ (,,)
     <$> Concurrently (getURL "url1")
     <*> Concurrently (getURL "url2")
     <*> Concurrently (getURL "url3")

main :: IO()

main = do 

    f <- async getPages

    cancel f

Am I guaranteed the the getURL() calls will definitely have either finished, or cancel? (I looked through the source (https://hackage.haskell.org/package/async-2.2.2/docs/src/Control.Concurrent.Async.html#Concurrently), and I think so, because runConcurrently is implemented in terms of race, which is implemented using withAsync, but I'm not confident with interpreting Haskell!)

Many thanks,

Mike

On Wed, 18 Mar 2020 at 03:15, Niklas Hambüchen <mail@nh2.me> wrote:

I've you're new to async, also check out my recent rework of the docs that talk about this topic specifically:

https://github.com/simonmar/async/pull/105/files

(To be available in the next release of async.)

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