Yes, I think I'll reuse the framework, even though it is much more advanced than my usual standard.

Another feature I will need to add is to accumulate subtotals. Do you know of any issues with that? I'd like to allow the following:

acc a, b, c; // three identical accumulators
a(1); // 1
a(2); // 1 + 2

b(3); // 3
b(4); // 3 + 4

c(a); // 1 + 2
c(b); // 1 + 2 + 3 + 4 c(5); // 1 + 2 + 3 + 4 + 5