----------------------------------------------------------------------------------------------------------------------------------------------------- Enumerators are an efficient, predictable, and safe alternative to lazy I/O. Discovered by Oleg Kiselyov, they allow large datasets to be processed in near–constant space by pure code. Although somewhat more complex to write, using enumerators instead of lazy I/O produces more correct programs. http://hackage.haskell.org/package/enumerator http://john-millikin.com/software/enumerator/ ----------------------------------------------------------------------------------------------------------------------------------------------------- Hello -cafe, It's been a while since the last point release of enumerator. This one is sufficiently large that I think folks might want to know about it, and since I try not to spam too many announcements, I'll give a quick rundown on major changes in other 0.4.x versions as well. First, most of what I call "list analogues" -- enumerator-based versions of 'head', 'take', 'map', etc -- have been separated into three modules (Data.Enumerator.List, .Binary, and .Text) depending on what sorts of data they operate on. This separation has been an ongoing process throughout 0.4.x releases, and I think it's now complete. The old names in Data.Enumerator will continue to exist in 0.4.x versions, but will be removed in 0.5. Second, Gregory Collins and Ertugrul Soeylemez found a space leak in Iteratee's (>>=), which could cause eventual space exhaustion in some circumstances. If you use enumerators to process very large or infinite streams, you probably want to upgrade to version 0.4.7 or higher. Third, the source code PDF has seen some substantial improvement -- if you're interested in how the library is implemented, or have insomnia, read it at < http://john-millikin.com/software/enumerator/enumerator_0.4.8.pdf
Finally, there is a known issue in the current encoding of iteratees -- if an iteratee yields extra data but never consumed anything, that iteratee will violate the monad law of associativity. Oleg has updated his implementations to fix this problem, but since it would break a *lot* of dependent libraries, I'm holding off until the vague future of version 0.5. Since iteratees that yield extra data they didn't consume are invalid anyway, I hope this problem will not cause too much inconvenience. New features ----------------- * Range-limited binary file enumeration (requested + initial patch by Bardur Arantsson). * splitWhen , based on the "split" package < http://hackage.haskell.org/package/split > * 0.4.6: Typeable instances for most types (requested by Michael Snoyman) * 0.4.5: joinE , which simplifies enumerator/enumeratee composition (requested by Michael Snoyman)