On Sun, Feb 20, 2011 at 9:38 AM, tsuraan
I have a streaming network protocol where each message in the stream is prefixed by a 64-bit message length marker. Lazy ByteStrings seem to be an elegant way to wrap network communications, so I'm using them. I have one concern though: how can I prevent my program from hanging on to the beginning of the stream? My code looks roughly like this:
lazy <- getContents clientSock let (lenBS, rest1) = splitAt 8 lazy let length = runGet getWord64be lenBS let (msg, rest2) = splitAt (fromIntegral length) rest1 -- process msg
The program never uses that initial "lazy" again, but it's there, and it's been assigned, so I assume that reference to the head of the stream will always be around, and thus always consuming memory. Is there a way to indicate to haskell that I want to "forget" about that assignment, so the runtime doesn't need to keep the stream around? In this case, I think I could do the stream processing in a tail-recursive loop, and thus lose the previous references to the stream, but is there a more specific way to tell haskell that I'm done with some data?
One easy trick is to put the rest of the function body in a separate top-level function, so that the 'lazy' variable is no longer in scope. Antoine
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