Missing function on HP 42S
11-17-2021, 06:51 PM
Post: #1
 lrdheat Senior Member Posts: 735 Joined: Feb 2014
Missing function on HP 42S
I used to think that the lack of an Nroot key on the HP 42S was a bit of a shortcoming, especially if one wanted to integrate an equation that had fractional powers involved where negative numbers were involved. It would be a convenience to have such a key on the HP 42S, but it is not a hard work around…it is easy to break such an integral into 2 integrals. In the case of the negative part of the integral’s domain in an odd numbered root, to make that part of the integral produce a negative number, integrate it from the absolute value of the lower end of the domain as lower limit, and use 0 as the upper limit. Store the result. The domain from 0 on up can be integrated in normal fashion. This can then be added to the stored result for the answer to the full domain integral.

Carry on…
11-21-2021, 11:20 PM
Post: #2
 Allen Member Posts: 151 Joined: Aug 2014
RE: Missing function on HP 42S
(11-17-2021 06:51 PM)lrdheat Wrote:  ... it is not a hard work around…it is easy to break such an integral into 2 integrals.

I think you have said very elegantly exactly why there is NOT an built-in function that does this, especially for something that does not come up very frequently.

I would say the same about my own desires for a PMOD- Modular exponentiation function. It's fairly easy to write a program that does this, and probably most people wouldn't use it anyway, hence there is no need to include it. (Never mind that ternary operators are tricky with a 4-level RPN stack.)

More functions == more opportunity for bugs, more development expense, more ROM, longer manual, longer time to market, etc.

99.999% of the time I like the 42s exactly how it is. Though, I do wish the CATalog function of the 42S was sticky and opened where you last exited. For example, having to enter MOD twice near each other in a program requires many keystrokes.

17bii | 32s | 32sii | 41c | 41cv | 41cx | 42s | 48g | 48g+ | 48gx | 50g | 30b

11-22-2021, 08:01 AM
Post: #3
 Werner Senior Member Posts: 703 Joined: Dec 2013
RE: Missing function on HP 42S
(11-21-2021 11:20 PM)Allen Wrote:  I would say the same about my own desires for a PMOD- Modular exponentiation function.

Here's my 41-compatible, stack-only version: Z^YMOD.

Quote:Though, I do wish the CATalog function of the 42S was sticky and opened where you last exited. For example, having to enter MOD twice near each other in a program requires many keystrokes.

You can make any built-in menu 'sticky' selecting it twice.
To enter MOD twice, do
SHIFT-CONVERT
SHIFT-CONVERT again
V (down)
MOD (the menu doesn't go away)
MOD

Cheers, Werner
11-22-2021, 03:20 PM
Post: #4
 lrdheat Senior Member Posts: 735 Joined: Feb 2014
RE: Missing function on HP 42S
I also find that assigning a function of interest to the custom menu is a good option!
11-23-2021, 03:27 AM
Post: #5
 Allen Member Posts: 151 Joined: Aug 2014
RE: Missing function on HP 42S
(11-22-2021 08:01 AM)Werner Wrote:
(11-21-2021 11:20 PM)Allen Wrote:  I would say the same about my own desires for a PMOD- Modular exponentiation function.
Here's my 41-compatible, stack-only version: Z^YMOD.

Warner,
Thank you for the menu tip!

I did write my own 39 byte program (with 4 char label), but use storage registers:
Code:
 00 { 39-Byte Prgm } 01>LBL "PMOD" 02 STO 03 03 SIGN 04 X<>Y 05>LBL 01 06 STO 02 07 1 08 AND 09 RCL× ST Z 10 X=0? 11 SIGN 12 × 13 RCL 03 14 MOD 15 X<>Y 16 X^2 17 RCL 03 18 MOD 19 X<>Y 20 RCL 02 21 2 22 BASE÷ 23 X!=0? 24 GTO 01 25 Rv 26 END

17bii | 32s | 32sii | 41c | 41cv | 41cx | 42s | 48g | 48g+ | 48gx | 50g | 30b

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