PC-1211, PC-1250, etc. TVM

[robve]

I flipped the test lines 35 and 36 to avoid an issue when retrying. The point is really about picking a better rate when reasonably possible:

34 IF SGN Y=SGN W IF ABS Y<ABS W GOTO 33
35 IF Y<>0 IF W<>0 IF G LET G=0 : GOTO 33
36 IF ABS Y>ABS W LET I=V
37 RETURN

I actually also played a bit with the idea of a weighted average, something like:

35 IF Y<>0 IF W<>0 IF G LET G=0 GOTO 33
36 IF Y<>0 OR W<>0 IF SGN Y<>SGN W LET I=(I*ABS Y+V*ABS W)/(ABS Y+ABS W)
37 RETURN

But it's not working as well as I had expected.

Note that SHARP IF ... IF ... LET is more efficient and faster than IF ... AND ... LET.

EDIT: OK, just after writing this I see right away why it's not working well: if Y=0 then I=V when I should be picked. Duh... So it should be:
36 IF SGN Y<>SGN W LET I=(I*ABS W+V*ABS Y)/(ABS Y+ABS W) and maybe get rid of the extra iteration, although I get better results for some cases with it, such as I%=80 for PMT=-400 which is spot on.

- Rob