Question with rand()

hey guys, im still working on that little turn based game and im trying to add random damage to it. but i think im using rand() wrong.

this is how i am calling it...

i have this function built to take arguements for the random number

Code:

int randomNum(int x,int y)
{
    srand(time(0));
    int random = rand();
    int number = (random % y)+x;
    return number;
}

and then when i call to it i use

Code:

int damage = randomNum(20,40);

in that spot im trying to get a random number between 20-40. but when i run my program i know i am getting a number higher than 40 sometimes...so i must be using rand() wrong. any help would be awesome! Thanks

First, you should only call srand() once, at the beginning of your program, not every time you need a random number. Your actual problem is where you put x and y in that code. Follow the calculations by hand and you will see where you went wrong.

Code:

int random = rand() % rangenumber (+startnumber);

example:

Code:

rand() % 20 +20;

will give 20-40

Edit: Oops

I really think you should leave out the parentheses around startnumber, Ideswa.

Code:

    int number = (random % (y - x))+x;

Think a bit and you'll understand why.

thanks guys, I was looking over the tutorial on this site for it and it gave the example

Code:

random = (rand() % (max - min + 1) + min)

and im getting all that except why we add +1. my math is not so hot, you guys know why thats needed? or is it?

Stick some values in there instead and you will see why.

Say we want to generate random numbers betwean 5 and 10:
random = (rand() % (10-5) + 5)
vs.
random = (rand() % (10-5+1) + 5)

First one will become this:
random = (rand() % 5 + 5)
which will generate numbers betwean (0 to 4) + 5 or 5 to 9
but we didnt want 5 to 9, we wanted 5 to 10 so...
random = (rand() % 6 + 5)
which will generate numbers betwean (0 to 5) + 5 or 5 to 10....YAY!

Ah I see whats going on now, Thanks alot!