#include <iostream>

using namespace std;

template< typename T > void foo( T fun )
{
fun();
}

void bar()
{
  cout << "hello from bar" << endl;
}

struct functor
{
  void operator()() {
    cout << "hello from functor" << endl;
  }
};

main()
{
  foo(bar); // pass pointer to function
  foo(functor()); // pass functor instance
}