on Wed Sep 03 2008, "Phil Endecott" <spam_from_boost_dev-AT-chezphil.org> wrote:
I just noticed this in the "lifetime of ranges vs. iterators" thread (which I've not really been following):
Arno Sch?dl wrote:
rng | filtered( funcA ) | filtered( funcB ) | filtered( funcC ) | filtered( funcD ) | filtered( funcE )
I thought it worth pointing out the similarity, and also the difference, between this and the proposed dataflow notation. Here, operator| is being used like a shell pipe operator. In dataflow, operator| has a quite different meaning: it's a vertical line, distributing the output of "rng" to the inputs of the funcs in parallel.
Very interesting.
Confusing, perhaps?
Perhaps
Anyway you could presumably write something like
rng >>= funcA >>= funcB ....
For which library are you suggesting that notation?
and I would be interested to hear how the two implementations compare. Is it true to say that stacked iterators implement a "data pull" style, while dataflow implements "data push"?
I believe that's correct.
I also note that Arno wants to use stacked iterators because this alternative:
result = fn1( fn2( fn3( fn4( huge_document ) ) ) );
creates large intermediates and requires dynamic allocation.
Yes, that's one of the classic reasons for using iterator adaptors.
Again, a framework that allowed buffering of "sensible size" chunks and potentially distributed the work between threads could be a good solution.
Yes, parallelizing operations on such structures is an interesting problem. I think it may require the imposition of a segmented view over even nonsegmented structures. -- Dave Abrahams BoostPro Computing http://www.boostpro.com