Missing function on HP 42S

[lrdheat]

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…

[Allen]

(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.

[Werner]

(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

[lrdheat]

I also find that assigning a function of interest to the custom menu is a good option!

[Allen]

(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