janni2

There are programs for tensor calculus, which state, that this is totally different from usual calculus, see - https://en.wikipedia.org/wiki/Tensor_software or especially - http://cadabra.science And even there you still don't get...

I got this too. The reason is actually that returning 0 in the getCurrentItem leads to this case and because this implementation does the modulo-thing also at getCurrentItem this happens....