(48G 49G 50G) Runge-Kutta Diff Eqn solver

[Werner]

(06-11-2021 11:23 PM)rcthacker Wrote:  Equations are stored as programs?

Yes. Equations are 'compiled' into programs, and turned into equations again for stack display. On my 49G, doing
'(A+B)*(C+D)' \->S2
results in

Code:

SYMBOL
 ID A
 ID B
 x*
 ID C
 ID D
 x*
 x+
;
@

which is the way the equation is stored, with SysRPL commands. (anything starting with a small 'x' is a user command, ID is a global name, SYMBOL defines an equation and ; ends it).

Quote:How or where did you learn that a procedure could be substituted for the RHS of the DE?

As I said, I just tried it out. The ODE solver just needs an 'object' to return f(x,y), it does not manipulate the equation. All equations have program equivalents, but not all programs can be turned into equations, so I would have been very surprised if the input had been limited to equations only.

Quote:Was this characteristic also in the 48G and 49G firmware?

I only have a 48 and a 49. They both have the ODE solver, and I tried out things on the 49.

Quote:The work-around or its need does not seem consistent with a straight-forward Runge-Kutta formulation. Somewhat troubling.

I don't understand what you mean here.

Cheers, Werner