Простые числа, используем циклы - C++

#include <string>
#include <iostream>
#include <stdexcept>
#include <cmath>
 
 
class Primes {
 public:
  Primes(unsigned int maximumValue) : maximumValue(maximumValue),
    primes(new char[maximumValue / 8 + 1]) {
    fillPrimesUsingSieve();
  }
  virtual ~Primes() {
    delete [] primes;
  }
  bool isPrime(unsigned int n) {
    if (n <= maximumValue) {
      return primes[n / 8] & (1 << (n % 8));
    }
    return false;
  }
 private:
  void clearPrimes() {
    for (unsigned int i = 0; i < maximumValue / 8; ++i) {
      primes[i] = 255;
    }
  }
  void unsetPrime(unsigned int n) {
    primes[n / 8] &= ~(1 << (n % 8));
  }
  void fillPrimesUsingSieve() {
    clearPrimes();
    unsetPrime(0);
    unsetPrime(1);
    for (unsigned int i = 2; i <= sqrt(maximumValue); ++i) {
      for (unsigned int j = i + i; j <= maximumValue; j += i) {
        unsetPrime(j);
      }
    }
  }
  unsigned int maximumValue;
  char *primes;
};
 
int main(int argc, char *argv[]) {
  static const unsigned short int MAXIMUM_VALUE = -1;
  
  Primes primes(MAXIMUM_VALUE);
  
  int counter = 0;
  for (int i = 0; i < MAXIMUM_VALUE; ++i) {
    if (primes.isPrime(i)) {
      std::cout << "Prime #" << ++counter << " = " << i << std::endl;
    }
  }
  std::cout << "Total number of primes up to " << MAXIMUM_VALUE <<
    " is " << counter << "." << std::endl;
 
  return 0;
};