HP17BII+ - L() & G() Revisited


To avoid such erroneous results like described here:


After executing the steps described below, everything worked fine on my unit - S/N: CNA42903649 produced on a Monday !!! 2004 Week 29 ...

1. Initialize ALL <variable-name> first before you use L(<variable-name>:...)

Example: INIT-L: 0*A*B* ... *Z=0


(WARNING - BE CAREFUL HERE! EXIT IMMEDIATELY, TO NOT TO DELETE YOUR STORED EQUATIONS by incidently pressing function key two as well!)

3. Multiply each instance of L(<variable-name>:...) by ZERO to avoid side-effects within your equation.

Best regards,

Peter A. Gebhardt

Edited: 17 Sept 2006, 2:21 p.m.


Because of the contribution of Tom Sears made on comp.sys.hp48


I finally was able to emulate L() & G() on my HP49G+ ...

To test for yourself, take this example from Edition 2 of the HP17BII+ User Guide available here:


On page 170 look for the description of L(x:expr):

(1+i)^N x PV +((1–(1+i)^N)/(1–(1+i))) x PMT+FV

It can be written as:

L(NP:1+i) x 0 + L(NPN:G(NP)^N) x PV + ((1-G(NPN)) / (1-G(NP))) x PMT + FV

On the HP49G+ change the last equation to:

<< 'NP x 0 + NPN x PV + ((1-NPN) / (1-NP)) x PMT + FV'
{'NPN = NP^N' 'NP = 1 + i' }
+ <<

(18-Sep-2006, 9:48 GMT) Please be aware, that in { ... } order matters - "substitute" most complex first .... most simple last!

(18-Sep-2006, 16:46 GMT) Please be also aware, that the example TVM equation listed in the HP17BII+ User Guide, doesn't work the same as the Financial Solver! If you encounter differences in i then it might be due to limits in the solver. Set initial values for i to .0001 before you solve for i. Look here under Problem 2.


In my opinion, it's comparably easy to identify the respective L() & G() parts of the HP17 equation and put them into the list to be worked on by SUBST & STREAM.

Because I only tested with this readily available example, pls. comment once you have used the "algorithm" on your own HP17/19/200LX to HP49 migrations.

Best regards,

Peter A. Gebhardt

Edited: 18 Sept 2006, 12:25 p.m.

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