Syntax for Differential Equations Solver / desolve()???

[parisse]

(09-04-2015 11:10 PM)ewjax Wrote:  Items of note:
- near as I can tell, you cannot use the dy/dx template, you must enter the differential in y' form. Disappointing.

I think it's much more natural to use y'. I have nothing against the template as long as it is translated by the HP UI to diff(y,x) :-)

Quote:- you must explicitly put the multiplication star between x and e^x, otherwise it thinks you've created a new variable xe and won't implicitly insert the multiplication
- as mentioned, for some reason the variables x and y cannot have anything previously stored in them. I find this puzzling but it seems to be important, so...

It's very difficult to evaluate some variables but keep other variables unevaluated (the code to do that in solve or diff/int took months to mature), especially in a function like desolve that as a lot of possible syntaxes. Because if you desolve(y'+a*y) where a is assigned to say 2, you expect an answer with 2 not with a. I assume that users having to solve differential equations are more experienced users than those learning derivatives, so that I can spend more time coding math algorithms instead of bugprone user interaction code.