Maybe i need to get some sleep, but can someone explain how modulos work? Thanks

on 2009-03-19 06:51

on 2009-03-19 07:18

Zayd Connor wrote: > Maybe i need to get some sleep, but can someone explain how modulos > work? > > Thanks result = 7 % 3 puts result --output:-- 1 7 has two 3's in it, and after removing those two 3's from 7, the remainder is 1.

on 2009-03-19 14:50

Zayd Connor <devrubygem@gmail.com> writes: > Maybe i need to get some sleep, but can someone explain how modulos > work? From "Discrete Mathematics by Rosen": "Let a be an integer and m be a positive integer. We denote by a mod m the remainder when a is divided by m. It follows from the definition of remainder that a mod m is the integer r such that: a = q * m + r and 0 <= r < m " This is all assuming you didn't type an 'o' when you meant 'e' ;)

on 2009-03-19 15:26

On 19.03.2009 06:50, Zayd Connor wrote: > Maybe i need to get some sleep, but can someone explain how modulos > work? http://lmgtfy.com/?q=modulo

on 2009-03-19 15:43

On Mar 19, 2009, at 10:22 AM, Robert Klemme wrote: > On 19.03.2009 06:50, Zayd Connor wrote: >> Maybe i need to get some sleep, but can someone explain how modulos >> work? > > http://lmgtfy.com/?q=modulo > This seems completely unnecessary. There was already a great response from Brian who not only directly addressed the "modulos", but also picked up and pointed out (subtly) that the question might have been about "modules". Something that makes perfect sense, but I certainly didn't see that possibility. And did you Google modulo or module yourself to see how useful the result really is? If you're going to simply shout lmgtfy, at least put "ruby" in there, too (well, for module, not for modulo ;-) -Rob Rob Biedenharn http://agileconsultingllc.com Rob@AgileConsultingLLC.com

on 2009-03-19 16:05

On 19.03.2009 15:40, Rob Biedenharn wrote: > And did you Google modulo or module yourself to see how useful the > result really is? I did. robert

on 2009-03-19 16:15

Rob Biedenharn wrote: > On Mar 19, 2009, at 10:22 AM, Robert Klemme wrote: > >> On 19.03.2009 06:50, Zayd Connor wrote: >>> Maybe i need to get some sleep, but can someone explain how modulos >>> work? >> >> http://lmgtfy.com/?q=modulo >> > > > This seems completely unnecessary. There was already a great response > from Brian who not only directly addressed the "modulos", but also > picked up and pointed out (subtly) that the question might have been > about "modules". Something that makes perfect sense, but I certainly > didn't see that possibility. > > And did you Google modulo or module yourself to see how useful the > result really is? If you're going to simply shout lmgtfy, at least put > "ruby" in there, too (well, for module, not for modulo ;-) > > -Rob > > Rob Biedenharn http://agileconsultingllc.com > Rob@AgileConsultingLLC.com Thanks guys,(singing) I can see clearly now the rain is gone :). Maybe I should have been more clear and added the % sign when mentioning modulo, so I wouldn't confuse anyone thinking I meant modules :) Thanks

on 2009-03-19 21:02

> Thanks guys,(singing) I can see clearly now the rain is gone :). Maybe I > should have been more clear and added the % sign when mentioning modulo, > so I wouldn't confuse anyone thinking I meant modules :) > > Thanks > > Though there is one thing I would like to point out: 0 % 7 = 0 So 'remainder' is not strictly true Michael ======================================================================= This email, including any attachments, is only for the intended addressee. It is subject to copyright, is confidential and may be the subject of legal or other privilege, none of which is waived or lost by reason of this transmission. If the receiver is not the intended addressee, please accept our apologies, notify us by return, delete all copies and perform no other act on the email. Unfortunately, we cannot warrant that the email has not been altered or corrupted during transmission. =======================================================================

on 2009-03-19 21:53

Michael Malone wrote: > Though there is one thing I would like to point out: 0 % 7 = 0 > So 'remainder' is not strictly true Sorry I don't follow you. What's the remainder of 0/7 if not 0? 0-7*0 is 0, is it not? Confused, Sebastian

on 2009-03-19 22:11

Sebastian Hungerecker wrote: > Sebastian > > Many people I know and work with simplify the modulo operator to themselves as remainder, so mentally (whether or not it is correct) assume 0/7 = 0 r 7 I am just making an explicit example of this not necessarily obvious case. It's totally fine when one knows the semantics of modulo, it's the simplification to remainder that many people make that causes problems here. Michael ======================================================================= This email, including any attachments, is only for the intended addressee. It is subject to copyright, is confidential and may be the subject of legal or other privilege, none of which is waived or lost by reason of this transmission. If the receiver is not the intended addressee, please accept our apologies, notify us by return, delete all copies and perform no other act on the email. Unfortunately, we cannot warrant that the email has not been altered or corrupted during transmission. =======================================================================

on 2009-03-19 22:45

On Mar 19, 2009, at 5:07 PM, Michael Malone wrote: >> Confused, > > Michael [I hope this survives email formatting...] __0_r_0_ 7 ) 0 0*7 => -0 == 0 Just because people can't understand division and remainders isn't enough to keep them away from technical discussions. The original response (which I deleted months ago [or was that yesterday?]) had an accurate definition. -Rob Rob Biedenharn http://agileconsultingllc.com Rob@AgileConsultingLLC.com

on 2009-03-19 23:06

Michael Malone wrote: > Many people I know and work with simplify the modulo operator to > themselves as remainder, so mentally (whether or not it is correct) > assume 0/7 = 0 r 7 Maybe I'm slow, but I don't get it. You're saying that many people assume that x % y is the same as the remainder of dividing x by y, right? I don't see anything wrong with that. If I understand you correctly, you're also saying that this assumption is wrong in the case of 0%7. I don't understand why that should be the case. The remainder of 0/7 is 0, right? And 0%7 is also 0, so where's the problem? Still confused, Sebastian

on 2009-03-19 23:18

Sebastian Hungerecker wrote: > If I understand you correctly, you're also saying that this assumption is > wrong in the case of 0%7. I don't understand why that should be the case. The > remainder of 0/7 is 0, right? And 0%7 is also 0, so where's the problem? > > Still confused, > Sebastian > > Sorry for confusing everyone here, I just know of a particular case where 0%7 = 7 was assumed. I was trying to stop this happening again, but I think I've caused more confusion than it's worth. Sorry folks. Ignore my post and you'll sleep more easily. Michael ======================================================================= This email, including any attachments, is only for the intended addressee. It is subject to copyright, is confidential and may be the subject of legal or other privilege, none of which is waived or lost by reason of this transmission. If the receiver is not the intended addressee, please accept our apologies, notify us by return, delete all copies and perform no other act on the email. Unfortunately, we cannot warrant that the email has not been altered or corrupted during transmission. =======================================================================

on 2009-03-19 23:25

Robert Klemme <shortcutter@googlemail.com> writes: > On 19.03.2009 06:50, Zayd Connor wrote: >> Maybe i need to get some sleep, but can someone explain how modulos >> work? > > http://lmgtfy.com/?q=modulo That is *awesome* ! Sponsored by "Backpack" - interesting.

on 2009-03-20 03:10

```
On 3/19/09 6:03 PM, Sebastian Hungerecker wrote:
> remainder of 0/7 is 0, right? And 0%7 is also 0, so where's the problem?
Going by the usual definition of "remainder", there is a difference
between modulo and remainder when negative numbers get involved.
remainder(a,b) = a - trunc(a/b) * b
modulo(a,b) = a - floor(a/b) * b
```

on 2009-03-20 03:58

On Mar 19, 5:15 pm, Michael Malone <michael.mal...@tait.co.nz> wrote: > Sorry for confusing everyone here, I just know of a particular case > where 0%7 = 7 was assumed. This is confusing. As in 0%7 = 7 is very confusing. A mod B shouldn't have a result that's equal to or greater than B. If that happens, you take a B out until you can't anymore. The remainder when A is divided by B is the same thing. If you end up with something greater than B, you stopped too soon. As John W. Kennedy pointed out, the difference between modulo and a simple remainder comes up when dealing with negative numbers.