Re: Control.Concurrent.Chan: how do i close a channel?

On 2007-07-17, David Menendez wrote:

On 7/16/07, Claus Reinke wrote:

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I often use Chan (Maybe a), with Nothing to tell the reader thread that EOF is reached -- perhaps something like that is what you're looking for?

yes. but that would add another slight indirection, and it still doesn't make getChanContents itself any more useable. if you "often" have to modify/expand the API when you use it, perhaps there is something missing in that API? the "much like hGetContents" comment does seem to suggest that as well.

If STM is available, you could use a TChan for content and a TVar for signalling.

That seems excessive. STM has nice composable properties but if you're not composing it with other STM usages, there's not much reason to buy those properties.

getClosableChanContents :: Chan (Maybe a) -> IO [a] getClosableChanContents ch = unsafeInterleaveIO $ do x <- readChan ch case x of Nothing -> return [] Just y -> do ys <- getClosableChanContents ch return (y : ys)

Untested of course. With the corresponding

writeList2CChan :: Chan (Maybe a) -> [a] -> IO () writeList2CChan ch ls = do sequence_ (map (writeChan ch) . (Just)) ls) writeChan ch Nothing

Am I missing something that makes this "not lazy enough"? -- Aaron Denney -><-