Add 2 integers without using + operator

int sum(int a, int b) {
    int s = a ^ b;        // partial sum
    int c = (a & b) << 1; // carry
    
    // carry? 
    while( c != 0 ) {
        // yes -> sum it, recalc carry
        int newc = (s & c) << 1;
        s = s ^ c;
        c = newc;
    }
    
    return s;
}

Other entries:

• isPrime: Naive version 
• isPrime, Optimization 1: Iterate only until the square root of the number
• isPrime, Optimization 2: Only divide by odd numbers, until the square root of the number
• isPrime, Optimization 3: Skip the divisors that are multiple of 2 or 3
• Keep the previosly generated primes and use them to test the following numbers.
• isPrime, Recursive.