Re: [Haskell-beginners] Hints on how to remove unsafePerformIO from my function?

19 Jul 2010

      Okay, I figured this out on my own.  This isn't as elegant but it definitely
works:

fetchUDPSIP :: TChan a -> TChan B.ByteString -> IO ()
fetchUDPSIP commands chan = do
  sock <- getUDPSocket 5060
  loop sock
  where
    loop sock = do
      result <- getUDP sock
      (atomically . writeTChan chan) result
      loop sock

fetchLine = do
  loop
  where
    loop = do
      result <- Prelude.getLine
      Prelude.putStrLn result
      loop

On Mon, Jul 19, 2010 at 11:09 AM, David McBride wrote:
...
I tried this:
fetchUDPSIP :: TChan a -> TChan B.ByteString -> IO ()
fetchUDPSIP commands chan = do
  sock <- getUDPSocket 5060
  results <- (mapM unsafeInterleaveIO . repeat . getUDP) sock
mapM_ (atomically . writeTChan chan) results
fetchLine = do
  results <- (mapM unsafeInterleaveIO . repeat) Prelude.getLine
  mapM_ Prelude.putStrLn results
But it seems to have become strict again in that neither version will
return any results until it has gotten everything it can.
Also I'm not sure, but I'm pretty sure any "unsafe" function is still going
to have the original problem where it causes all other threads to stop while
it performs, so I don't think I can use unsafe anything at all and have my
program work properly.
On Mon, Jul 19, 2010 at 10:41 AM, Stephen Tetley 
...
wrote:
...
How about unsafeInterleaveIO? - You might have to experiment where to
put it, but you shouldn't need the local unstrict definition.
Because it doesn't violate type safety it is considered less heinous
than unsafePerformIO.
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