On Thu, Mar 29, 2012 at 6:39 AM, Rob Desbois <rob.desbois@gmail.com> wrote:

I'm unable to use the reentrant macros for iteration currently..I
think I'm probably misunderstanding their usage, and a push in the
right direction would be much appreciated.

My need is to iterate through a sequence, then iterate through a
sequence nested within each element.
As I understand, I should be able to call (e.g.):
* BOOST_PP_SEQ_FOR_EACH(OP, data, seq) to iterate through the outer sequence
* then in OP(r, data, elem) call BOOST_PP_SEQ_FOR_EACH_R(r, OP2, data, elem)

[...]

Just to add to Paul's reply, no, this isn't going to work, as you've discovered, due to your attempt to expand SEQ_FOR_EACH_R within an expansion of SEQ_FOR_EACH_R. I ran into this inconvenience at some point, too, and simply wrote up a script to define a collection of macros similar to SEQ_FOR_EACH and SEQ_TRANSFORM that were reentrant (so they used token-pasting with an pp integral constant). It's fun exercise, but if you're not into writing it yourself, I'd be happy to point you to the code.

- Jeff