C++ comparator passing argument problem of complex situation

I have class A, in which there is a member variable of class B. And in B, there is a member variable of priority_queue "q" and I want to define a customized comparator class C for it. But for the comparator, the comparison needs a member variable "f_val" from A.

Since the original code is long, the basic idea is as follows:

class C
{
  map<Point,double> f_val;
  C(double f_val1)
  {
    f_val=f_val1;
  }
  bool operator () (const Point &pt1, const Point &pt2)
  {
    return f_val[pt1] > f_val[pt2];
  }

};



class A
{
    B b;
    map<Point,double> f_val;
}

class B
{
    B(map<Point,double> f_val1){f_val=f_val1;}
    priority_queue<Point,vector<Point>,C(f_val)> q;
    map<Point,double> f_val;
}