I am having great troubles with my HP-50g. It seems that there is a big clash between the way I am used to working with math, and the way the 50g is able to help me. Let me tell you what I need to do, and in what ways the 50g fails me. I am hoping that my frustration is simply due to inexperience (and bad documentation)... so any help would be very much appreciated.

A typical flow for me is this. I define a few expressions, for instance (not in HP notation, does not matter),

Quote:I then compute p1 * p2, and store it in another variable, say, p.

p1 = q / (m * (m + q^2))

p2 = q (m + 1) / m

At this point, p contains a function of m and q, which are two variable that are meaningful in the problem I am studying.

I then want to simplify this expression: nothing is easier: I go into the equation editor, hit simplify, then re-store the result in p. So far, so good.

**Then I hit the first bump.** I would like to evaluate p, and I would like to do it in a way that resembles the equation mode of the good ol' 32SII: I would like the calculator to prompt me for values for m and q, showing me any previous value held by the variables, and then evaluate the expression p based on the new values. I don't see any quick way of doing this. The only way seems to be to create variables m and q, store values in them, then retrieve p, and hit EVAL. Is it really necessary to go through this? Is there a better way?

Once I play with p (and m and q) for a little while, I change something in the problem I am analyzing (maybe I make a change in the algorithm I am analyzing, whatever), and I get a new p2, for instance,

Quote:Great, I recompute p1 * p2, and store the result in p. So far so good.

p2 = (m+1) (m-1) (m-q) / (m^2 + q)

**But now I hit the second, and bigger, bump.** When I try to simplify p, the calculator simplifies it all the way down to a real number! Just the presence of variables m and q in the directory caused the simplify algorithm to behave not only as simplify, but also as numerical substitute and evaluation!

This is absurd. If I have an equation on the stack, and call a command on that, the result should depend only on that -- not also on side factors like what other variables I have defined in that moment!!

This is also incredibly inconvenient. I want to have a simpler form of p first, so I can stare at it (and, e.g., infer by eye its asymptotic behavior, or whatnot). Only when I choose, I want to substitute the values of m and q into p and get a number!

Am I missing something?

Can I make the HP-50g work with my flow of playing with math?

Many thanks!

Luca