At Fri, 1 Jul 2011 09:39:32 +0400, Eugene Kirpichov wrote:
Hi,
I'm rewriting timeplot to avoid holding the whole input in memory, and naturally a problem arises:
How to represent large but finite streams and functions that process them, returning other streams or some kinds of aggregate values?
Examples: * Adjacent differences of a stream of numbers * Given a stream of numbers with times, split it into buckets by time of given width and produce a stream of (bucket, 50%,75% and 90% quantiles in this bucket) * Sum a stream of numbers
Is this, perhaps, what comonads are for? Or iteratees?
Sounds like a good job for iteratees. Summing a stream of numbers is just an Iteratee. Transcoding a stream into another stream is a job for an Inum (Iteratee-enumerator) or enumeratee, depending on which package's nomenclature you use. You have three implementations to choose from: - http://hackage.haskell.org/package/iteratee (original) - http://hackage.haskell.org/package/enumerator (John Milikin's re-write) - http://hackage.haskell.org/package/iterIO (my 3rd-generation attempt) David