How to generate a boolean with p probability using C rand() function?

Question

How can I generate a random boolean with a probability of p (where 0 <= p <= 1.0) using the C standard library rand() function?

i.e.

bool nextBool(double probability)
{
    return ...
}

Answer 1

Do you mean generate a random variable so that p(1) = p and p(0) = (1-p)?

If so, compare the output of rand() to p*RAND_MAX.

Answer 2

bool nextBool(double probability)
{
    return (rand() / (double)RAND_MAX) < probability;
}

or (after seeing other responses)

bool nextBool(double probability)
{
    return rand() <  probability * RAND_MAX;
}