gistfile1.txt

bool
is_prime(int num)
{
    int i, w;

    if (num <= 1)
        return false;

    if (num == 2 || num == 3)
        return true;

    if (num % 2 == 0)
        return false;

    if (num % 3 == 0)
        return false;

    if (bsearch(&num, primes, num_primes, sizeof(int), comp_prime))
        return true;

    i = primes[num_primes - 1];
    if (num < i)
        return false;

    w = 2;
    while (i * i <= num) {
        if (num % i == 0)
            return false;

        i += w;
        w = 6 - w;
    }

    return true;
}

int
comp_prime(const void *a, const void *b)
{
    if (*(int *)a > *(int *)b) return  1;
    if (*(int *)a < *(int *)b) return -1;

    return 0;
}