(C++)Any way to limit the number of digits in a variable?

[FakezZ]

So I made a program to generate "random" numbers, but the numbers generated are friggin big! Is there any way to limit the number of digits (I don't wanna use rand(), because I want to do it myself )?

 

 

code:

 

#include <iostream>

#include <cmath>

int main()

{

int a = 32840;

int b = 299792458;

int d = 32677;

int s;

for (int x =1; x<=165400; x++)

{

s = (a*b + d) % 65689;

d=s;

std::cout << s << std::endl;

}

int n;

system ("PAUSE");

}

[Willson94]

well show us what you got..

[FakezZ]

well show us what you got..

lol yeah I copied the code, but forgot to paste it

[WanderingFool]

Well assuming your random number generator creates evenly distributed number, you could always just do %[maxnumber] to get values between 0 and [maxnumber]-1

 

Based on your formula, I am guessing you won't get too random of a number...but that is the concept behind getting the random numbers below a certain number.

[FakezZ]

Well assuming your random number generator creates evenly distributed number, you could always just do %[maxnumber] to get values between 0 and [maxnumber]-1

 

Based on your formula, I am guessing you won't get too random of a number...but that is the concept behind getting the random numbers below a certain number.

Excuse me if I didn't understand correctly, but you are suggesting to do a cyclic division with the max number I want? If that is the case, then I would prefer generating huge numbers, but only use the first lets say 10 digits and leave the rest. Is there any way to do that?

[WanderingFool]

Well I mean using module (%) to get the range of numbers.

 

e.g. if you are generating numbers "randomly" between 0 and 4,294,967,295 (size of unsigned int), but you only want 0 to 999 you would simply go

int newValue = oldValue % 1000;

 

range 0 - 24

int newValue = oldValue % 25;

[FakezZ]

Well I mean using module (%) to get the range of numbers.

 

e.g. if you are generating numbers "randomly" between 0 and 4,294,967,295 (size of unsigned int), but you only want 0 to 999 you would simply go

int newValue = oldValue % 1000;

 

range 0 - 24

int newValue = oldValue % 25;

Okay now I get it, but when i multiply a number by a really big one I get negative values for some reason

[WanderingFool]

Okay now I get it, but when i multiply a number by a really big one I get negative values for some reason

That is because you are using int type instead of unsigned int type.

 

e.g.

unsigned int s = (unsigned int)-1; //Will produce a very large number

[FakezZ]

That is because you are using int type instead of unsigned int type.

 

e.g.

unsigned int s = (unsigned int)-1; //Will produce a very large number

Thank you soo much man! You have solved many questions I have been having pretty much since I started programming

[FakezZ]

That is because you are using int type instead of unsigned int type.

 

e.g.

unsigned int s = (unsigned int)-1; //Will produce a very large number

So I have been experimenting with what you tought me and I end up with this code in order to output the numbers to a txt file :

 

 

#include <iostream>

#include <cmath>

#include <fstream>

using namespace std;

int main()

{

unsigned _int64 a = 32840;

unsigned _int64 b = 299792458;

unsigned _int64 d = 32677;

unsigned _int64 s;

for (int x =1; x<=165; x++)

{

s = (a*b + d) % 5477522378482473;

a=sqrt(s);

s=s % 937692130485;

//cout << s << std::endl;

ofstream file;

    file.open ("C:\\x\\serial.txt");

file << s << endl;

file.close();

}

return 0;

 

 

}

 

 

But, it only outputs the first number. What am I doing wrong

[MrSuperb]

Okay now I get it, but when i multiply a number by a really big one I get negative values for some reason

 

try to understand how data types work

[FakezZ]

try to understand how data types work

What do you mean? The problem is that the file only contains the first generated number, but it "should" contain them all

[WanderingFool]

The lines

ofstream file;    file.open ("C:\\x\\serial.txt");file.close();

should not be inside the for loop...every time you start the program this is what happens.  Initialize the variables, enter your for loop, open file, write to file, close file.  Opening the file overwrites your file...so put those lines outside of the for loop....ie you want your program to initialize the variables, open file, enter for loop, write to file, after the for loop has ended close the file.

[FakezZ]

The lines

ofstream file;    file.open ("C:\\x\\serial.txt");file.close();

should not be inside the for loop...every time you start the program this is what happens.  Initialize the variables, enter your for loop, open file, write to file, close file.  Opening the file overwrites your file...so put those lines outside of the for loop....ie you want your program to initialize the variables, open file, enter for loop, write to file, after the for loop has ended close the file.

Ok thanks

[FakezZ]

The lines

ofstream file;    file.open ("C:\\x\\serial.txt");file.close();

should not be inside the for loop...every time you start the program this is what happens.  Initialize the variables, enter your for loop, open file, write to file, close file.  Opening the file overwrites your file...so put those lines outside of the for loop....ie you want your program to initialize the variables, open file, enter for loop, write to file, after the for loop has ended close the file.

aghhh did it and now the text file is empty This is confusing...

[MrSuperb]

What do you mean? The problem is that the file only contains the first generated number, but it "should" contain them all

 

well if you don't know why the number flips to negative, you clearly have a lack of knowledge about how primitive data types work. no offense intended.

[thereau]

#include <iostream>

#include <cmath>

int main()

{

unsigned long long a = 32840;

unsigned long long b = 299792458;

unsigned long long d = 32677;

unsigned long long s;

for (int x =1; x<=165400; x++)

{

s = (a*b + d) % 65689;

while(s>max value that you want s to be)s%=10;

d=s;

std::cout << s << std::endl;

}

int n;//

system ("PAUSE");

return 0;

}

If you want to make a simple "number generator" you cand use the date and time, so the number will be different every time you use it.

[FakezZ]

 

#include <iostream>

#include <cmath>

int main()

{

unsigned long long a = 32840;

unsigned long long b = 299792458;

unsigned long long d = 32677;

unsigned long long s;

for (int x =1; x<=165400; x++)

{

s = (a*b + d) % 65689;

while(s>max value that you want s to be)s%=10;

d=s;

std::cout << s << std::endl;

}

int n;//

system ("PAUSE");

return 0;

}

If you want to make a simple "number generator" you cand use the date and time, so the number will be different every time you use it.

 

Yeah I solved this problem, however now I want to try to output these numbers to a text file to save them

[WanderingFool]

btw meant to say...code tags when the code is longer people

 

Anyways this is just a quick example of how I would format this thing

 #include <iostream>#include <cmath>#include <fstream>using namespace std;int main(){	unsigned _int64 a = 32840;	unsigned _int64 b = 299792458;	unsigned _int64 d = 32677;	unsigned _int64 s;	ofstream file;	file.open("C:\\x\\serial.txt");	for (int x =1; x<=165; x++)	{		s = (a*b + d) % 5477522378482473;		a=sqrt(s);		s=s % 937692130485;		file << s << endl;	}	file.close();	return 0;}

[Mauri]

Check this out: http://media.ch9.ms/ch9/9fb9/5f4cd3b3-4569-4651-987a-46dcc2739fb9/GN13STLrandConsideredHarmful_mid.mp4

[FakezZ]

Check this out: http://media.ch9.ms/ch9/9fb9/5f4cd3b3-4569-4651-987a-46dcc2739fb9/GN13STLrandConsideredHarmful_mid.mp4

Yeah I figured out how to do it. Thanks anyways

[ehsanawan]

use the printf function and use %(limit)d specifier

[ShadRS]

The main topic seems to have been answered, but I thought I'd point this out.

 

You called:

ofstream file;file.open("C:\\x\\serial.txt");

Which, as someone said, wipes the file out every time you open it.  If you wanted to open the file to append to it, use the following:

ofstream file;file.open("C:\\x\\serial.txt", std::ios::app);

But moving it outside the for loop was the best option in this case.