On Mon, Dec 10, 2018 at 3:15 PM Michael Powell via Boost-users <boost-users@lists.boost.org> wrote:

And so on... Which also guarantees that I am also walking both tree's
at the same moment and in like fashion.

For comparison, you might consider the use of Boost.Coroutine to allow you to interleave recursive steps through your two trees:
https://www.youtube.com/watch?v=3SvkWY7JSeY
(originally discussed here:)
https://groups.google.com/forum/#!msg/boost-list/AZQgtk6jMho/fIFowJ72AgAJ