Pass a member function as argument before knowing which instance of class to use.

Consider the following artificial example which illustrates what I'm
trying to :

using namespace std;

class Foo
{
public:
   void f1();
   void f2();
}

class Bar
{
public:
   void g1(vector<token> toks);
   void g2(vector<token> toks);
private:
   int get_key(token t);
   map<int,Foo> m_foomap;
}

void Bar::g1(vector<token> toks)
{
    for(token t : toks)
    {
       int key = get_key(t);
       Foo curfoo = m_foomap[key];
       curfoo.f1();
    }
}

void Bar::g1(vector<token> toks)
{
    for(token t : toks)
    {
       int key = get_key(t);
       Foo curfoo = m_foomap[key];
       curfoo.f2();
    }
}

.... same thing for n different functions.

What I'd like to do is make a function that would work like this:

void Bar::g(vector<token> toks, function<void(int) > fun_to_use)
{
    for(token t : toks)
    {
       int key = get_key(t);
       Foo curfoo = m_foomap[key];
       curfoo.fun_to_use();
    }
}

that does the loop and calls the appropriate function. How do I go about
specifying this so that I can bind the correct function to the correct
instance? Is this possible?

Cheers,
--
Human Being