Sieve of Eratosthenes

sieve.cc

class number_series {
    int number, factor;
public:
    number_series(int number) : 
      number(number), factor(0) { }

    int get(int n) {
        if (factor < n) {
            factor = (1+(n/number)) * number;
        }
        return factor;
    }
};

class prime_generator {
    std::vector<number_series> series;
    int prime;
public:
    prime_generator() : prime(2) {
        series.push_back(number_series(2));
    }

    int get() {
       for (int i = prime+1;;i++) {
            for (int j = 0; j < series.size(); j++) {
                if (series[j].get(i) == i)
                    goto irrelevant;
            }
            prime = i;
            series.push_back(number_series(i));
            return i;
irrelevant:; // C++ needs named breaks D:
        }
    }
};