I'm not there yet, but I know enough about the problem now that I wouldn't "buy" a partial solution.
Before I start playing around with the problem, is my throwing increment_and_dereference optimization fair game? I believe I can't > do without.
Since dereference does not need to end-check, throwing increment() is probably the basic building block. Fair game?
Sorry, I really don't know what you're asking.
A basic multiple-filter loop is this: filter_increment { for(;;) { ++i; if( empty() || predA( dereference() && predB( dereference ) && predC( dereference ) && predD( dereference ) ) break; // <--- towards base_range *** function stack *** towards outermost filter_iterator ----> } } If empty() evaluates to true, all pred* are skipped. This "skipping" in recursion needs exceptions. Exceptions are the only means C++ gives us to "jump" in a recursive environment. At least in Win32, exceptions are slow, probably too slow to be practical. I heard that table-based exceptions are much faster, but I have no practical experience. Before spending time working on the problem you posed, I want to make sure than my solution does not get trashed because I use exceptions. If we want to avoid them, I would say that there is no way to get optimal performance with stacked iterators, and I would not even try. Arno -- Dr. Arno Schoedl · aschoedl@think-cell.com Technical Director think-cell Software GmbH · Invalidenstr. 34 · 10115 Berlin, Germany http://www.think-cell.com · phone +49-30-666473-10 · toll-free (US) +1-800-891-8091 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl · Amtsgericht Charlottenburg, HRB 85229