In article <f04d2210909252208k4fd66540u54a5d280613bb043 / mail.gmail.com>,
  Charles Oliver Nutter <headius / headius.com> writes:

> Yes, this is definitely a step in the right direction. But I wonder if
> allowing people to do arbitrarily complex external iteration is worth
> it? It's going to be slow as long as switching stacks is slow, and
> it's always going to be a heavy operation on platforms where
> stack-juggling isn't permitted (or is too hard to bother trying).

In general, internal iterator is easier to implement.  This
is why Ruby uses internal iterator long time.  Although
Fiber based external iterator is slower than ideal, it makes
many internal iterators usable as external iterator without
effort.
-- 
Tanaka Akira