I am writing a binary data parser and use `iteratee' package. The following pattern appears quite often in my code:
results <- map someConversion `liftM` replicateM nbytes Iter.head
The meaning is: take `nbytes' from stream, apply `someConversion' to every byte and return the list of `results'. But there's more than one way to do it[1]:
i1, i2, i3 :: Monad m => Int -> IterateeG [] Word8 m [String] i1 n = map conv `liftM` replicateM n Iter.head i2 n = map conv `liftM` joinI (Iter.take n stream2list) i3 n = joinI $ Iter.take n $ joinI $ mapStream conv stream2list
[1] http://en.wikipedia.org/wiki/There's_more_than_one_way_to_do_it If you try the program[2] I've hpasted, you will see that these three iteratees have equal results. [2] http://hpaste.org/fastcgi/hpaste.fcgi/view?id=12464#a12464 Of those i1, i2, i3 which one is "better" and why? Or is there another - preferable - way of applying iteratees to this task? My naïve guess is that i1 will have worse performance with big n's. It looks like `i1' is reading bytes one by one, while `i2' takes whole chunks of data... I'm not sure though. I would appreciate it a lot if you improve my understanding. -- vvv