sieve(int max) {
  // Arrays are indexed starting with 0
  primes = dynamic array of int, initial length 0;
  checked = array of bool, length max-1, initially false;
  for x from 2 to max {
    if checked[x-2] // the number 2 is the 0th element of checked
       then next;
       else {append x to primes;
             for y from x to max step 2 { // goes through x, 2x, 3x, etc.
               checked[y-2] = true;}
            }
  return primes;
}