# HP Forums

Full Version: Fun with a 17bii
You're currently viewing a stripped down version of our content. View the full version with proper formatting.

I recently acquired a nice second-hand 17bii (the real deal, not the + model). My wife and I have been house shopping, so I've got an excuse to grab a financial model to complement my stack of scientifics.

So with that out of the way, let's (ab)use the solver a bit. Here's about 10 minutes of tinkering and familiarizing myself with the cooler features: the Fibonacci sequence.

`FIB:IF(S(NEXT):NEXT:INIT+L(A:0)+L(B:0)+-L(NEXT:1))=L(B:G(A))+L(A:G(NEXT))`

Solve for INIT to get the first term of the sequence, and solve for NEXT to fetch subsequent terms.

Anybody else have some interesting - and not necessarily useful - solver routines? I'm sure a chess-playing program is out of the question, but has anybody tried tic-tac-toe?

Oh, and it does a damn nice job of financial calculation too. :)

Dave, it works equally well with a 27S. (The unit has just arrived. Customs must have made some dents in it but it still works.)

Can you explain it a little. I do understand what happens if you solve for NEXT:

```NEXT=L(B:G(A))+L(A:G(NEXT))
```

This returns the sum of A and B and replaces B by A and A by NEXT. So far, so good. But the other case...

```INIT+L(A:0)+L(B:0)+-L(NEXT:1)=L(B:G(A))+L(A:G(NEXT))
```
What I can see is that you set A=B=0 and NEXT=1 on the left side of the equation and then B=0 and A=1 on the right side. This results in...
```INIT+-1=1
```
It looks to me that the "-" before L(NEXT:1) is superfluous.

Did I get it right?

Yeah, that should have just been something like "...L(B:0)-L(NEXT:1)...". That's what I get for figuring this stuff out so late at night. :) I'm sure it could be cleaned up a lot in other areas, too.

That's pretty much how it works. Solving for INIT resets A, B, and NEXT, and returns 1 (the first term of the sequence). Solving for NEXT gives you all the subsequent terms. It doesn't really matter what INIT gets set to, so I just fiddled with the equation so it gives you the first term (one).