random number generation into text file

[Sycrupol]

Hi all!

I need to create a random number generator which generates white noise (equally distributed random numbers) into a text file as output. I thought to use for cicle with rand() function, but i don't understand perfecly (after reading the function definition) how it works, and how can i write the generated numbers into a text file. Any help would be appreciated, thanks beforehand.

[PanGalactic]

What do you have so far? Folks here are not going to do your homework for you.

[Sycrupol]

Correct, as always, so far i have:

//white noise generator

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main() {
srand(time(NULL));
for(int i = 0; i < 1000; ++i) {
value = rand()%1;
}
return 0;
}

Which is perfect for my aims, as far as i've understood it generates random numbers up to 1, but i don't know how (reading the tutorials so far) to write those into a the text file (the randoms, and i values inside the cicle also).

[Bazzy]

If using C++ you need to #include<fstream> declare an ofstream eg: ofstream file ( "myfile.txt" ); and use the << operator: file << i << ' ' << value << '\n';

Anyway, in the code you posted 'value' isn't declared


Tutorial on C++ files: http://www.cplusplus.com/doc/tutorial/files/

[Sycrupol]

Thank you, I made some progress, I've got the .txt file after using the compiler but it seems empty (sized 0 kbytes, and empty when opened), and i can't figure it out why. Any suggestions where i went the wrong way?

The code so far:

//white noise generator

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <fstream>
using namespace std;

int main() {
    srand(time(NULL));
    float value=0.0;
    ofstream myfile ("feherzaj.txt");
    myfile.open ("feherzaj.txt", ios::out | ios::app );
    if (myfile.is_open())
    {
                         for (int i = 0; i < 1000; ++i) {
                             value = rand(); 
                             myfile << i << " " << value << "\n";
                             }
    myfile.close();
    }
    else cout << "Unable to open file";
    return 0;
}

The file also appears to be opened, because the code haven't triggered else option.

A sidewalk, but my curiosity is limitless, how you highlight your code on this page, to make it more readable?

[PanGalactic]

A sidewalk, but my curiosity is limitless, how you highlight your code on this page, to make it more readable?

http://www.cplusplus.com/forum/articles/1624/

[Hammurabi]

You don't want rand() % 1 as that will always be 0. rand() % 100 will give numbers between 0 and 99, inclusive. (Be forewarned, however, that the first few lowest numbers are somewhat overrepresented.)

[Sycrupol]

Thank you I've made the code more readable, but still haven't soluted that I got an empty file after compiling it, instead of a file with random numbers...

I've figured it out with help, thank you all for helping!