Re: Fusion-ifying proto parse trees

"Eric Niebler" <eric@xxxxxxxxxxxxxxxxxxxx> writes:

> Every time you increment a joint view iterator, you're checking to see
> if you've reached the end of the first sequence, so you know when to
> start the second. And if Iterator::first_type is itself a joint view
> iterator, it *also* must check to see if it's at the end of *its*
> first sequence to know if it should start its second. And so on. If
> you do a bunch of push_backs and end up with a joint_view of a
> joint_view of a joint_view, iterating it will be far from
> trivial. This sort of flattening-on-the-fly is *exactly* the problem
> that non-segmented proto has, and is the problem that segmented
> iterators solve.

Just to be clear, this is all compile-time cost.  There's no reason
*that* has to be slow at runtime.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com



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