A few questions 42S Global Labels

[Egan Ford]

First, are there "hidden" global labels? I.e. a way to create a global label that can be called from a program, but does not appear with XEQ?

Second, is there a way to organize global labels in the XEQ list?

The challenge I face with a program I am writing is that my program front-ends the solver and PGMSLV requires a global label. Now I have many global labels that have limited use outside of this program.

Thanks.

[Thomas Okken]

Quote:

---

First, are there "hidden" global labels? I.e. a way to create a global label that can be called from a program, but does not appear with XEQ?

---

No.

Quote:

---

Second, is there a way to organize global labels in the XEQ list?

---

No, the global labels appear in the catalog in the order in which they appear in program memory, from last to first. There is no control over this, no grouping or reordering like on the RPL machines.

Quote:

---

The challenge I face with a program I am writing is that my program front-ends the solver and PGMSLV requires a global label. Now I have many global labels that have limited use outside of this program.

---

That's life on the HP-42S... There are ways to ameliorate the problem, though. You can use one global label for multiple functions; if you combine all the functions you want to be able to solve into one program, using a variable to select between them, then you can use one single global label as the entry point for all of them, thus reducing global label clutter at the expense of some obfuscation in your program:

    LBL "FCNS"

    MVAR "X"

    GTO IND "SEL" <-- selects which function to execute

    LBL 00

    1

    RCL "X"

    RCL/ "C"

    X^2

    -

    SQRT

    1/X

    RCL- "D"

    RTN

    LBL 01

    ...

    RTN

    LBL 02

    ...

    END

Using only one global label has the disadvantage that you're stuck with the same set of MVARs for all the sub-functions, but since you were talking about running the solver under program control, I'm guessing that's not a problem.

- Thomas

[Egan Ford]

Thanks. Great idea. Worked out perfect. Since I use VARMENU in the calling program there is no need for MVAR in the Solver global.

[Karl Schneider]

Thomas --

Good workaround. It's very similar in concept to my solution when someone asked how to be able to select which variable to SOLVE or INTEGrate using a pre-Pioneer model.

An excerpt from my article #556:

f(x, y, z) = 2*x - ln y + 1/z

x in R1; y in R2; z in R3

indirect in R00 (HP-41 only)

HP-15C/HP-34C program:      HP-41C/CV/CX program:

LBL A                       LBL "AA"

STO (i)                     STO IND 00

RCL 1                       RCL 01

2                           2

*                           *

RCL 2                       RCL 02

LN                          LN

-                           -

RCL 3                       RCL 03

1/x                         1/x

+                           +

RTN                         RTN

-- KS

Edited: 4 May 2009, 10:47 p.m.

[Egan Ford]

Karl,

Great article. Thanks.