Re: [Haskell-cafe] Problems with iteratees

From: wren ng thornton On 2/2/11 11:25 PM, Maciej Wos wrote:

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I think the problem is that the iteratee you give to I.convStream always returns Just [something] while you should return Nothing on EOF.

That makes sense for the hanging problem (which I only noticed during debugging). Though I still get the the same error message when running the whole program...

I don't have too much to add to Maciej and Oleg's reply, except that I'd recommend looking at the Wave codec over the Tiff reader in those versions of iteratee. I don't think that's the only problem, though, because then you'd be getting a "Divergent iteratee" error. The "endOfInput" error is suspicious, and I think you'll need to track it down to solve this problem. It doesn't appear to be from either iteratee or protocol-buffers. Could it be coming from your IO library? I wonder if the enumerator is trying to force a read after EOF has been reached for some reason? As an experiment, you could try using a custom convStream function like this: convStream2 :: Monad m => IterateeG s el m (Maybe (s' el')) -> EnumeratorN s el s' el' m aconvStream2 fi iter = fi >>= check where check (Just xs) = lift (runIter iter (Chunk xs)) >>= docase check (Nothing) = return iter docase (Done a _) = return . return $ a docase (Cont k Nothing) = convStream2 fi k docase (Cont k (Just "endOfInput")) = convStream2 (return Nothing) k docase (Cont _ (Just e)) = return $ throwErr e This may help determine if it's a problem with IO or with the message parsing. John

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When I put this all together, the process is killed with:

control message: Just (Err "endOfInput")

Data.Iteratee.Base.run is the origin of the "control message:" part of

On Thu, Feb 3, 2011 at 10:06 AM, wren ng thornton wrote: the

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error, but I don't know where (Err "endOfInput") is coming from since Data.Iteratee.Base only uses (Err "EOF") or (Err "Divergent Iteratee"). I believe runGetEnumeratee is where the problem is, though it could also be the use site or something in one of the libraries. Any help would be appreciated.

-- Live well, ~wren