Is it possible(another one!) to 'define' an operator() from a function pointer?

I was wondering if the above was possible since it would reduce some layers of redirection in my code.

Code:

class Operator : public token
{
public:
    //Operator(std::string input);
    Operator(std::string input,int p,Assoc a);
    Operator(){};//DUMMY..remove later
    int prec;
    Assoc assoc;
    void operator()(std::vector<token*>& instack);
};

Constructor:

Code:

Operator::Operator(std::string input,int p,Assoc a)
{
    this->type=op;
    this->raw=input;
    this->prec = p;
    this->assoc = a;

    &operator() = opmap[input]; 
    //This is erroneous ..but illustrates what I'd like to do.(Note that there isn't any mismatch
 //in type of the functions. Also, opmap is map mapping strings to function pointers.)

}

What I have now for the operator()

Code:

void Operator::operator()(std::vector<token*>& instack)
{
    (opmap[this->raw])(instack);
}

Well a function pointer uses the operator () to execute its own code. You're not going to get away from that. I mean you could look at function pointers as a type that defines operator () and you aren't allowed to overload it for the same reason you can't overload operators on other built-in types.