Functor

#include <iostream>
#include <math.h>
using namespace std;

class Pow
{
   public:
      double operator()(double x, int y)
      {
　　　　　double xx = x;
         for (int i = 0; i < y-1; i++)
            x *=xx;
         return x;
      }
};

int main()
{
   int a = 5;
   cout << pow(a, 2) << endl;
   Pow mypow;
   cout << "mypow:" << mypow(a, 2);
   return 0;
}

   for (auto itr = vi.begin(); itr != vi.end(); ++itr)
   {
      cout << *itr << endl;
   }

for (auto i:vi)
{
   cout << i << endl;   
}