(06-14-2021 10:24 PM)rcthacker Wrote: "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." I doubt the firmware writers designed the input arguments to allow for this.

If all they wanted to allow were equations, it would have been very easy to restrict the inputs to equations only, but they didn't.

Quote:In a straight-forward Runge-Kutta code all of the function inputs and outputs would be accessible variables. It's a mystery to me that the firmware writers decided to represent 2nd order DEs with a matrix of coefficients and a vector of dependent variables: neither representable in an algebraic expression/object in the RPL OS/User language. Maybe an academic feature.

The firmware writers didn't decide that; it's a common way of representing higher-order ODEs as first-order ones.

Cheers, Werner