c plus plus code fragments

#include <iostream>
#include <functional>
#include <algorithm>
#include <vector>

using namespace std;

struct A {
  A(int a) : _a(a)     {};
  void g ()            { cout << "void f(), " << _a << endl;};
  void f (int i) const { cout << "int A::f (" << i << "), " << _a << endl; }
  int _a;
};

int main(int argc, char* argv[]) {

  vector <A> v;

  v.push_back (A (1));
  v.push_back (A (1));
  v.push_back (A (2));
  v.push_back (A (3));
  v.push_back (A (5));
  v.push_back (A (8));


  for_each (v.begin (), v.end (), mem_fun_ref(&A::g));
  
  for_each (v.begin (), v.end (), 
                 bind2nd (mem_fun_ref(&A::f), 10));

 


  return 0;
}

template <class T> class F;

template <class T>
void g(F<T>*);

struct G {
  int i_;
};


template <class T> class F {
  public:
    T t_;
};

int main() {
  F<G> f;

  f.t_.i_=42;

  g(&f);
}

template <class T>
void g(F<T>* f) {

}