Re: transversal sum

[Jack Applegame via Digitalmars-d-learn]

void popFront() { foreach (ref r; rr) r.popFront(); }

I think it should be
void popFront() { foreach (ref r; rr.save) r.popFront(); }

but I think OP wanted a ready-made phobos solution, w/o all the
range boilerplate...

exactly.