Hey, What is the proper way to use the rand() command??

To generate a random number between 0 and 99:
int number = rand() % 100;
To generate a random float between 0 and 1:
float number = (float)rand() / RAND_MAX;

~~~~~~~~~~
Martee
http://www.csc.uvic.ca/~mdill

To generate numbers greater than randmax:


#define BigRand(x) ((rand ()*((x)/RANDMAX) + rand ())%(x))

Martee: rand() returns an interger value between 0 and RAND_MAX. To get a (pseudo) random value between 0 and 1 (both inclusive) you should write

float fNumber = ((float)rand() / (float)(RAND_MAX + 1));

Moreover, computing a random integer number between 0 and N as

int nNumber = rand() % N;

it somewhat wrong, since there are changes you are modifing the equi-probabilities of the resulting value. You should do something like

float fNumber = ((float)rand() / (float)(RAND_MAX + 1));int nNumber = (int)(fNumber * (float)N);

Slower but more accurate.



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or better yet, staying with integers

#define RAND(__range) ((((long)rand ()) * (__range)) / (RAND_MAX+1))

How about negative numbers?