Improving the solver experience on the 41C

[Jeff_Kearns]

(02-16-2016 03:41 AM)quantalume Wrote:  One of the features I like about later-model HP calculators is the use of named variables and the ability to solve for any one of the variables in an equation. The solver function available in the Advantage module is decent enough from a functional standpoint, but one generally needs to write multiple RPN functions for the same equation, depending on the variable being solved for.

Karl Schneider wrote an excellent article on how SOLVE and INTEG work in HP's RPN-based models. In it, he addresses the issue you raised about 'generally' needing to write multiple RPN functions in order to solve for different variables in a multi-variable equation by invoking a multiple-input, single-output (MISO) procedure. I have found this technique particularly useful in the HP-15C - especially for the TVM equation with 6 variables - and the use of the indirect storage register (e.g IND 00 in the HP-41C) allows for solving any variable.

While your program certainly has some interesting features in that it creates a menu of variables, why go to all the trouble to write a new solver routine rather than use the existing Advantage Pac program, if you have it already? Can the menu feature be combined with the ADV routine? I get the impression that Stefan Vorkoetter's approach was initially based on his HP-19C (29C) solver routine and was ported to the HP-41 because he didn't have an Advantage Pac. Please correct me if I am mistaken.

Jeff Kearns