Small Solver Program

[Csaba Tizedes]

(02-14-2019 05:25 AM)Gamo Wrote:  a small but versatile solver program specifically for HP Voyager Series calculator.
Example for X^X = Y // X to the power of X equal to Y

Yes, the classic problem: which number you can power to itself to get the largest number on your calculator: x^x=10^100. Do LOG() of both sides: x×LOG(x)=100, then do the iteration: x_0:=50, then x_i+1:=100/log(x_i). The simple fixed point iteration and converges.

By the way, if you interested, here is my SOLVE(i) for HP-12C, which can solve any equation for ANY variable like on 15C, without rewriting the equation. Looks like indirect addressing without indirect addressing. 28 steps only.

Yes, my English is terrible, but more convenient than read the full material in Hungarian.
At the end of pdf you can find lots of applications which solved with this little solver (like ODE solve with EULER+SOLVE(i) on 12C (!!!), pressure vessel pneumatic conveying pipe sizing program, humidity and dew point solving, outer temperature calculation of a concrete silo wall or comparison of present values of educated and not educated people salaries with the little SOLVE combined with 12C's cash flow calculation capabilities - I guess this is shows clearly the power of this little routine possibilities and why I say everywhere, the SOLVER is MUST to implement ALL current calculators, I hope somebody read and understand what I want to say).

The small secant method in this paper for CASIO fx-50F meantime reduced to 13 steps, I guess the smallest solver for these blind machines. You can find attached.

Csaba