TVM formula error in programming manual?

[dm319]

I love this. But really puts my TVM contribution into perspective! I want to rewrite it with all these optimisations now. I wonder if we could have a series of 'TVM tests' (i.e. calculate I%YR given PV=10'000, PMT = -2000 etc etc). Like different classes of how difficult it is to calculate accurately and then we can see how our programs are fairing.