1 ENTER 3 / 3 * 1 -
01-22-2016, 09:18 PM
Post: #1
 hank Junior Member Posts: 15 Joined: Nov 2014
1 ENTER 3 / 3 * 1 -
I've always wondered why this kind of calculation on HP calculators returns a tiny negative residual, but this is not the case with other brands like TI, which return 0. I assume HP sees some advantage in doing arithmetic this way. Any help with this would be greatly appreciated.
01-22-2016, 09:26 PM
Post: #2
 boniholmes Junior Member Posts: 17 Joined: Dec 2015
RE: 1 ENTER 3 / 3 * 1 -
My old Sharp EL-512 does the same, by giving -1. -11

HP-11, HP-41C, HP-41CV, HP-41CX, MATH/STAT, Surveying, X MEM, 82143A printer, 82104A card reader
01-22-2016, 09:33 PM
Post: #3
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
1/3 = 0.333...3 (the number of digits depends on the respective calculator). Take this and multiply by 3 and you'll get 0.999...9 instead of 1. Subtracting 1 will result in -1 ULP, e.g. -1x10^(-16) on the WP 34S. So far, everything is perfectly ok on this calculator as well as on every HP calc I know.

Others will know more about TI.

d:-)
01-22-2016, 09:34 PM
Post: #4
 hank Junior Member Posts: 15 Joined: Nov 2014
RE: 1 ENTER 3 / 3 * 1 -
Amazing! I thought that it was a peculiarity of HP calculators.
01-22-2016, 09:44 PM
Post: #5
 hank Junior Member Posts: 15 Joined: Nov 2014
RE: 1 ENTER 3 / 3 * 1 -
Thanks Walter. I knew that it is deliberate and understand how it arises, but wondered why HP chooses to do it this way while TI doesn't. Maybe someone here will know.
On some TV show years ago, maybe Nova, they has some college math or science teacher showing his desk drawer filled with calculators that "failed" that test, but obviously there must be a good reason for HP's approach.
01-22-2016, 10:08 PM
Post: #6
 Paul Dale Senior Member Posts: 1,412 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
HP calculators aren't lying to you about the result. The ones that give a perfect 1 are lying.

I don't trust calculators that lie.

- Pauli
01-22-2016, 10:15 PM
Post: #7
 hank Junior Member Posts: 15 Joined: Nov 2014
RE: 1 ENTER 3 / 3 * 1 -
Paul, I think that I get your meaning. HP is being transparent as to how a calculation is being done. Verswy interesting. Thank you!
01-22-2016, 10:57 PM
Post: #8
 quantalume Member Posts: 101 Joined: Dec 2015
RE: 1 ENTER 3 / 3 * 1 -
Considering a lot of great engineering work was done with slide rules, I'll take 10 significant digits any day without complaint. The best way to work 1/3*3-1 is in your head. :-P

David Brunell
Houston, Texas
01-22-2016, 11:12 PM
Post: #9
 hank Junior Member Posts: 15 Joined: Nov 2014
RE: 1 ENTER 3 / 3 * 1 -
No complaints here, David. However, I do wonder about HP's rationale.

Btw. I deeply regret having sold my Posft Versalog slide rule decades ago. What a beauty it was!
01-22-2016, 11:21 PM
Post: #10
 BobVA Member Posts: 209 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
My HP45, in default Fix 2 display mode, returns "-0.00" :-)
01-22-2016, 11:31 PM
Post: #11
 hank Junior Member Posts: 15 Joined: Nov 2014
RE: 1 ENTER 3 / 3 * 1 -
Interesting that it does that. Thanks!
01-22-2016, 11:46 PM
Post: #12
 Gerson W. Barbosa Senior Member Posts: 1,094 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
(01-22-2016 11:12 PM)hank Wrote:  However, I do wonder about HP's rationale.

Some enlightenment here and here, by Rodger Rosenbaum.
01-22-2016, 11:50 PM
Post: #13
 hank Junior Member Posts: 15 Joined: Nov 2014
RE: 1 ENTER 3 / 3 * 1 -
(01-22-2016 11:46 PM)Gerson W. Barbosa Wrote:
(01-22-2016 11:12 PM)hank Wrote:  However, I do wonder about HP's rationale.

Some enlightenment here and here, by Rodger Rosenbaum.

Thanks a lot Gerson. I'll check out the links.

Hank
01-23-2016, 12:33 AM
Post: #14
 TASP Senior Member Posts: 401 Joined: Mar 2015
RE: 1 ENTER 3 / 3 * 1 -
HPs don't handle bleen correctly either.

2speed HP41CX,int2XMEM+ZEN, HPIL+DEVEL, HPIL+X/IO, I/R, 82143, 82163, 82162 -25,35,45,55,65,67,70,80
Post: #15
 Paul Berger (Canada) Senior Member Posts: 409 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
(01-22-2016 09:18 PM)hank Wrote:  I've always wondered why this kind of calculation on HP calculators returns a tiny negative residual, but this is not the case with other brands like TI, which return 0. I assume HP sees some advantage in doing arithmetic this way. Any help with this would be greatly appreciated.

Well not all TI calculators TI-59 returns -1E-12, my Commodore PR100 returns a similar result as does any HP calculator I have handy.
01-23-2016, 06:29 AM
Post: #16
 quantalume Member Posts: 101 Joined: Dec 2015
RE: 1 ENTER 3 / 3 * 1 -
OK, I'll play along. TI-36X, -1E-12. I have a lot of other TI calcs I could try, but this one is solar, whereas the others need batteries which I'm too lazy to round up.

David Brunell
Houston, Texas
01-23-2016, 06:35 AM
Post: #17
 boniholmes Junior Member Posts: 17 Joined: Dec 2015
RE: 1 ENTER 3 / 3 * 1 -
TI-57: -1x10^(-10)

HP-11, HP-41C, HP-41CV, HP-41CX, MATH/STAT, Surveying, X MEM, 82143A printer, 82104A card reader
01-23-2016, 07:10 AM (This post was last modified: 01-23-2016 09:41 AM by Paul Dale.)
Post: #18
 Paul Dale Senior Member Posts: 1,412 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
For the Sinclair Scientific simulator: -1.0000-05

Pauli
01-23-2016, 09:22 AM
Post: #19
 Steve Simpkin Senior Member Posts: 360 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
-1.E-34
Free42 V1.5.5 (iPhone App)
01-23-2016, 09:48 AM
Post: #20
 Terje Vallestad Member Posts: 141 Joined: Dec 2013
RE: 1 ENTER 3 / 3 * 1 -
−1.00000000ᴇ−12
HP Prime (iPhone App)
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