Since that time I have made a few changes which make it trivial to switch to mpl::plus etc. I agree that that would be a good thing.
It would be good, but, ultimately, this is an implementation detail that should have no impact on the library's end users...probably not something that needs to be a top priority...
I think that I can speed up compiliation a bit (maybe 2x but probably not more than that), but it would make the code very very ugly (much worse than it is alreay) so I didn't think that it was worth while.
I would rather not make the code totally incomprehensible unless there is a very clear and compelling reason to. It takes less than 30 seconds for me to recompile all 22 example programs on my machine, which is quite acceptable... Matthias