Modulo?

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

Thanks

···

--
Posted via http://www.ruby-forum.com/.

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.

···

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Posted via http://www.ruby-forum.com/\.

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' :wink:

···

--
Brian Adkins
http://lojic.com/

http://lmgtfy.com/?q=modulo

···

On 19.03.2009 06:50, Zayd Connor wrote:

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

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 :wink:

-Rob

Rob Biedenharn http://agileconsultingllc.com
Rob@AgileConsultingLLC.com

···

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

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.

--
Brian Adkins
http://lojic.com/

I did.

  robert

···

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?

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 :wink:

-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 :slight_smile:

Thanks

--
Posted via http://www.ruby-forum.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 :slight_smile:

Thanks

Though there is one thing I would like to point out: 0 % 7 = 0
So 'remainder' is not strictly true

Michael

···

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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

Sebastian Hungerecker wrote:

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

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

···

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[I hope this survives email formatting...]

        __0_r_0_
      7 ) 0
0*7 => -0

···

On Mar 19, 2009, at 5:07 PM, Michael Malone wrote:

Sebastian Hungerecker wrote:

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

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

         ==
          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

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

Sebastian Hungerecker wrote:

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

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

···

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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 3/19/09 6:03 PM, Sebastian Hungerecker wrote:

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?

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.

···

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.

--
-yossef