Im having some issues with the rand function, i use it sometimes and i think that the result from it are very far from random, i get a lot of same number. Anyone got any idea whats going? Leo

Rand is a pseudo random number generator. It generates random numbers but it will generate the same numbers everytime you start it.

If you put: srand( (unsigned)time( NULL ) );
in your code the random number generator will be seeded with the current time so you get different values everytime you start it

try using this in your code.

#include <iostream>
#include <time.h>
#include <stdlib>
main()
{
int test;
bool go;

go = true;

if (go = true){
srand(time(NULL));
test = rand()%10;
std::cout << test;
}

return 0;
}
very basic C++ example, but should give you random numbers. I'm pretty sure this is the code, but I will have to check at home, for I am at office.


[edited by - ThomasSauder on November 4, 2002 3:16:55 PM]

rand() will give you the same numbers every time you execute your program. use srand( time( 0 ) ); instead, that way you get different results because the randomizer is seeded by the internal clock of the computer. or you can seed it manually by doing this:

// necessary includes
int main()
{
unsigned seed;
cout << "Enter seed: ";
cin >> seed;
srand( seed );
// rest of program and error checking.

return 0;
}

P.S dont forget to use #include <ctime> and #include <cstdlib> or you''ll get a syntax error.

Call srand only once at the beginning of the program, then call rand where you want the random number.

Can''t you also include windows.h and before randomizing the number, use srand(GetTickCount())?

For example:

#include <iostream.h>
#include <windows.h>

int main()
{
int number = 0;
srand(GetTickCount());
number = rand()%(rangevalue);
cout << number;
return 0;
}

Yes, but then you can only use the code in Windows.

thanks a lot guys, i will investigate that probleme further tomorow, because my tetris is going well, but i still think that my random is bugged, and i seeded it will see later

"The bible is probably the most genocidal book ever written!" Noam Chomsky

Question about this whole random number thing in C++.

I am coding a Battletech game and I need to call a function that simulates rolling 2 6-sided die. It sounds like I will be getting the same number each time I call the function. Is that true? I will only get a new number when I restart the program?
I know is BASIC they had a random number function that was seeded by the clock. Same deal here?

How does that work?

In c++ you also seed the random number generator with the time looks like

(other includes)
#include <ctime>

srand(time(0));

to get the number call the
rand()
function

Hmm learning OpenGL and C++ at the same time is like trying to learn french while in the middle of Paris