In my application, I have the following pattern occurring at many places:

loop_over_i(i)
{
   do_something(i); // common for all loops
   do_remaining_things(i);
}

The do_something part is common for most loops and so I am trying to extract it out with a class. However, the loop no longer vectorizes. A sample code is given below:

#include <iostream>
using namespace std;

class Loop
{
public:
    Loop(int max) : max_(max), count_(0), sqr_(0)
    { }
    void more()
    { 
      ++count_ ;
      sqr_ = count_ * count_;
    }
    bool done() const
    {
      return count_ >= max_;
    }
    operator int() const
    {
      return count_;
    }
    int sqr() const
    {
      return sqr_;
    }
private:
    int count_, max_, sqr_;
};

int main()
{
    int square[50];
    // this loop vectorizes
    for (int i = 0; i < 50; ++i)
      {
        square[i] = i*i;
      }
    // this loop doesn't vectorize
    for (Loop loop(50); !loop.done(); loop.more())
    {
      square[loop] = loop.sqr();
    }
}

How can I implement what I need in a way that the loop vectorizes?