Limitations of SOLVE Application

[Michael Lopez]

Hi all,

Have been meaning to share this experience for a while (see my previous post below) but only just got around to it :-(.

In my quest to set-up my HP Prime to perform similar tasks to what I have previously programmed into my HP48 & HP50G's, I have now created numerous custom applications, mainly using the built-in SOLVE application. This has generally been quite successful & am very happy with the performance & flexibility of the HP Prime except for one apparent limitation that I haven't previously seen any reference to.

This limitation occurs when I try to solve a combination of equations & simple conditional expressions such as: "P1=IFTE(X>0,ExpressionA,ExpressionB)" & results in the solver not being able to find a solution. I've tried everything I can think of, such as changing the order of equations & expressions, but can't seem to overcome what may be an intentional limitation with this version of the firmware.

It is interesting though, that if all the equations are simple conditional expressions (I've only tried up to 2 or 3 at once) then the SOLVE application works & converges into a correct solution. Hence the problem seems to arise when I try to solve a mix of equations & other types of expressions.

As some of you will already be aware, this is not a limitation within the older Multiple-Equation Solver (using HP Solve) as implemented on the HP48G series & HP50G.

Have any others noticed this limitation or have I misunderstood something?

If it is a limitation within the HP Prime, it would be great if this can be overcome in a future firmware release.

Thanks,

Michael

Previous Post:

RE: User Defined Variables within SOLVE Application

Hi Terje & Carl,

Thank you very much for your comprehensive suggestions/examples & sorry to take a while to respond.

The fundamental (some might even say basic problem :-( ) I experienced at the beginning with the SOLVE application was that despite creating the multi-letter user variables before hand, when I typed them into SOLVE they were treated as separate variables. It did however dawn on me the day after I wrote the original post that the way to insert multi-letter (or letter-number) variables in equations within SOLVE was to press the VARS key & insert them from there instead of typing them in. This has worked fine & I've since used it many times.

Have now created quite a number of customised SOLVE applications with multiple equations & am still astonished by the speed of the PRIME which seems to be many times faster than my HP 50Gs. However, I have discovered some limitations in the SOLVE algorithm that I've never experienced in the HP 48 or HP50 series before (using their multiple equation solvers). I'll write a separate post on this as there are many things to like about the SOLVE implementation on the PRIME & it would be great if we can keep improving it.

In the meantime I hope this basic information on how to insert user defined variables helps others.

Cheers,

Michael