Eric Niebler
Disclaimer: I haven't looked. But knowing the forward-only nature of parameter packs, I wonder how you can implement a random-access sequence like vector without (a) instantiating O(N) templates, like tuple, or (b) using the preprocessor and living with arbitrary limits.
I fear that the mpl simply cannot be implemented with variadics without radically changing the compile-time complexity of things.
I think there's a way to do it in O(1), but it's not implemented in the library right now. See [1]. In my opinion, this is only a tiny part of the MPL and even if it can't be improved, there are other areas where we benefit from C++11 in the MPL. Do you feel like that would be a deal breaker if O(1) access was impossible? Regards, Louis Dionne [1]: github.com/dabrahams/mpl11/blob/master/standalone/O1_variadics.cpp