Programming Forums > Application Development > C++

bl00dninja · Nov 30th, 2005, 3:17 AM

you can use integer division and modulus to break numbers apart. a classic example would be to convert decimal to binary. another example would be if you wanted to "make change". a solution rather easy for the human brain...how many coins of each type would you give to someone who needed 41 cents back in change? for those of us who've "worked a register" we all know it's one of each. one quarter, one dime, one nickel, and one penny. besides being the key to data encryption...modulus can help you divide numbers like you divide strings. in review...it's the REMAINDER after integer division. if you divide 1 by 2...2 goes into 1 zero times...leaving a remainder of two. it's a rather magical function. learn to use it.

as to "what can be evenly divided by what" let's restate, the syntax is: (for C/C++)

(Toggle Plain Text)

#include <iostream>
using namespace std;

int main(){
    
    int x, y;
    
    cout<<"enter 2 numbers"<<endl;
    cin>>x>>y;

    if (x % y ==0)
    {
        cout<<"yay!  this shit is true!!!"<<endl;
    }

     if (x % y != 0)
    {
        cout<<"crap!!! it's false!!!"<<endl;
    }
    
    system("pause");
}

kurifu · Nov 30th, 2005, 4:27 AM

Most easily said, modulus return the remainder after division. Remember how you used to do division in grade 3 and 4, they wouldn't make you calculate all those decimals, instead you just specific the remainder... so yup, it is that simple.

SittingDuck · Nov 30th, 2005, 5:03 AM

Quote:

Originally Posted by coldDeath

Kilo, my favourite usage for the modolus is when finding put if a number is even or odd.

Just do a quick divide by 2, then if it returns 0, its an even number

Division can take up to 44 ticks. And can take up to three. Just check the least significant bit, it's much quicker.

DaWei · Nov 30th, 2005, 9:10 AM

Let's see...post 12 repeats posts 2 and 5 and post 13 repeats post 9. Next?

nnxion · Nov 30th, 2005, 11:33 AM

Post 15 repeats post 14. HAH you didn't see that one coming, did you?

DaWei · Nov 30th, 2005, 12:29 PM

We finally introduced recursion into the thread

.

Munsta · Nov 30th, 2005, 2:57 PM

:p

Quote:

Today 12:29 PM
DaWei We finally introduced recursion into the thread .
Today 11:33 AM
nnxion Post 15 repeats post 14. HAH you didn't see that one coming, did you?
Today 09:10 AM
DaWei Let's see...post 12 repeats posts 2 and 5 and post 13 repeats post 9. Next?
Today 05:03 AM
SittingDuck
Quote:
Originally Posted by coldDeath
Kilo, my favourite usage for the modolus is when finding put if a number is even or odd.

Just do a quick divide by 2, then if it returns 0, its an even number

Division can take up to 44 ticks. And can take up to three. Just check the least significant bit, it's much quicker.
Today 04:27 AM
kurifu Most easily said, modulus return the remainder after division. Remember how you used to do division in grade 3 and 4, they wouldn't make you calculate all those decimals, instead you just specific the remainder... so yup, it is that simple.
Today 03:17 AM
bl00dninja you can use integer division and modulus to break numbers apart. a classic example would be to convert decimal to binary. another example would be if you wanted to "make change". a solution rather easy for the human brain...how many coins of each type would you give to someone who needed 41 cents back in change? for those of us who've "worked a register" we all know it's one of each. one quarter, one dime, one nickel, and one penny. besides being the key to data encryption...modulus can help you divide numbers like you divide strings. in review...it's the REMAINDER after integer division. if you divide 1 by 2...2 goes into 1 zero times...leaving a remainder of two. it's a rather magical function. learn to use it.

as to "what can be evenly divided by what" let's restate, the syntax is: (for C/C++)

Code:

#include <iostream> using namespace std; int main(){ int x, y; cout<<"enter 2 numbers"<<endl; cin>>x>>y; if (x % y ==0) { cout<<"yay! this shit is true!!!"<<endl; } if (x % y != 0) { cout<<"crap!!! it's false!!!"<<endl; } system("pause"); }

Today 02:32 AM
coldDeath Good point, lectricpharaoh, i forgot all about that.

But if i'm correct, the best what in Python is using the modolus. But maybe i'm wrong.
Today 02:21 AM
lectricpharaoh
Quote:
Originally Posted by coldDeath
Kilo, my favourite usage for the modolus is when finding put if a number is even or odd.

Just do a quick divide by 2, then if it returns 0, its an even number
I prefer value & 1 for this, especially in tight loops (for example, it is the test condition).

@Kilo: Remember that modulus is a component of integer division. When using numbers in floating-point form (actually, any number capable of representing fractional amounts), the idea of a remainder doesn't make sense. As such, using it for float and double values will cause a compile-time error.
Today 02:18 AM
coldDeath Kilo, my favourite usage for the modolus is when finding put if a number is even or odd.

Just do a quick divide by 2, then if it returns 0, its an even number
Yesterday 09:14 PM
DaWei Here is example usage from a recent thread.
Yesterday 08:33 PM
Kilo thanks man!
Yesterday 08:29 PM
Jessehk modulus is simply the remainder.

*C/C++ syntax for modulus used (%)*

eg:

Code:

4 % 2 = 0

that is because 4 is evenly divided by 2, which gives a remainder of 0

Code:

20 % 3 = 2

3 * 6 = 18

20 - 18 = 2

the remainder is 2.
hope that helps
Yesterday 06:26 PM
DaWei The term is "evenly divisible", but the answer is "yes".
Yesterday 06:24 PM
Kilo so i would test... and if the remainder is 0? then my constant was divisible by the given number?
Yesterday 05:49 PM
DaWei Modulus version division. Both, successively, often required.
Yesterday 05:38 PM
Kilo can someone please explain to me how to use a modulus operater properly?

lets i have a number... and i want to divide it by another number to test if it divisible. I was told modulus would do that for me?

EDIT: disregard "recursion" being used in the topic

MBirchmeier · Nov 30th, 2005, 3:37 PM

Quote: