Re: WP 34s manual error Message #16 Posted by Paul Dale on 25 June 2011, 8:02 a.m., in response to message #15 by fhub
If you want a financial calculator, don't re-flash the 30b. I am never going to do as good a job on the financial functions as HP has done. I don't want to and I've little interest in doing so as a hobby.
The TVM program has been included because Walter thought it would be worthwhile even in this primitive state. I tend to agree and occasionally have to estimate loan repayments and durations. The command as implemented occupies a total of forty bytes of flash. I can live with that much to provide this service. I wouldn't want to dedicate too much more to what is not and never will be a core function for a scientific calculator.
If you're reworking this, then the best solution would be to use the explicit formulas for the unknowns whenever possible and to resort to the solver only when absolutely required. Also there are some numeric stability and accuracy concerns -- there was an article by Willam Kahan discussing the 12C (?) financial functions in some depth. These are difficult to get accurate everywhere.
In case it helps, the xrom code for this one is:
81fe: 1054 4d56 LBL'TVM'
8200: 8b50 RCL 80
8201: 8b51 RCL 81
8202: 8c52 RCL+ 82
8203: 0006 1
8204: 8c53 RCL+ 83
8205: 8b54 RCL 84
8206: 0300 y[^x]
8207: b964 DEC X
8208: 0304 /
8209: 8c51 RCL+ 81
820a: 8e53 RCL[times] 83
820b: ce50 FC? 80
820c: b303 SKIP 03
820d: 8b53 RCL 83
820e: ba64 INC X
820f: 0304 /
8210: 0301 +
8211: 013a RTN
Anyway, I doubt we'd include any augmented functions in the flash image, however adding them to the growing software library would be worthwhile.
- Pauli
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