On 09/23/09 14:47, Christopher Schmidt wrote:
Larry Evans schrieb:
Thanks for all the work.
However, I was wondering why you couldn't eliminate some of the extensive BOOST_PP magic in:
https://svn.boost.org/trac/boost/browser/sandbox/SOC/2009/fusion/boost/fusio...
by using the "tagged multiple inheritance"(TMI) method shown around here:
https://svn.boost.org/trac/boost/browser/sandbox/variadic_templates/libs/mpl...
...
The only other objection might be to limit the number of instantiations because the more template instantiations, the slower the compile time; however, Doug Gregor suggested he wasn't too worried about that at the bottom of:
http://groups.google.com/group/comp.std.c++/msg/6449d909fd3d5cdc
-regards, Larry
Thank you very much for your feedback.
Your'e very welcome.
I did consider that specific method. I decided against using it due to the enormous amount of template instantiations and the expensive type_at.
I'm not sure there would be more template instantiations. It would really help my understanding if maybe you could explain ( with maybe a few examples and concrete numbers for number of instantiations), why there would be more instantiations with the TMI method. I know that would be a lot of work, but it certainly would make your case a lot stronger.
The current implementation is 4-unrolled recursive. I am pretty certain that it is faster - there are about 4 to 8 times less template instantiations.
Yeah, I saw that 4 a lot of places. I think other libraries use some macro to set such a number. For example, BOOST_MPL_LIMIT_UNROLLING here: https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/aux_/iter_fold_if_i... Are there plans to add a similar macro to variadic fusion vector?