Hi, I'm currently working on a program that parses a large binary file and produces various textual outputs extracted from it. Simple enough. But: since we're talking large amounts of data, I'd like to have reasonable performance. Reading the binary file is very efficient thanks to Data.Binary. However, output is a different matter. Currently, my code looks something like: summarize :: Foo -> ByteString summarize f = let f1 = accessor f f2 = expression f : in B.concat [f1,pack "\t",pack (show f2),...] which isn't particularly elegant, and builds a temporary ByteString that usually only get passed to B.putStrLn. I can suffer the inelegance were it only fast - but this ends up taking the better part of the execution time. I tried to use lazy ByteStrings, the theory being that the components that already are (strict) ByteStrings could be recycled as chunks. I also tried to push the output down into the function (summarize :: Foo -> IO ()), but both of these were actuall slower. Since I surely can't be the first person that needs to output tab-separated text, I'd be grateful if somebody could point me in the right direction. -k -- If I haven't seen further, it is by standing in the footprints of giants