Acessing protected members of composition class - c++

Question

I have the below class that has two custom objects as member variables. I get errors with the bold section. What is the proper way to access protected members of the composition classes? I get 'within this context' errors the f, gleft, and gright functions and when I try to resize u.
class C
{
protected:
A x;
B y;
double a;
double b;
Eigen::MatrixXd u;
public:
double f(double x)
{
return x;
}
double gleft(double tau)
{
return tau
}
double gright(double tau)
{
return 0;
}
FD_Euro_Put(): x(), y(), a(0), b(0){}
FD_Euro_Put(char y1, double y2, double y3, double y4, double x2,
double x3, double x4, double x5, double x6, double x7):
x(x1, x2, x3, x4, x5, x6, x7)
{
double Xleft = x1*x2;
double Xright = x1*x3;
double Tauf = x1*x1;
double NN = floor((x1/x2);
a = x1*x2 - 0.5;
b = x1*x2 + 0.5;
pde = HeatPDE(y1, NN, Xleft, Xright, Tauf, Alpha); //begin problem area
u.resize(pde.N+1, pde.M+1);
if(fdtype == 'f')
u = pde.Forward_Euler(&f, &gleft, &gright);
else if(fdtype == 'b')
u = pde.Backward_Euler(&f, &gleft, &gright);
else if(fdtype == 'c')
u = pde.Crank_Nicolson(&f, &gleft, &gright); //end problem area
else
cout << "Incorrect choice for finite difference type!" << endl;
}

Answer 1

You can't access protected members of a class unless it explicitly lists you as a friend or you inherit from that class.
A hack would be to wrap that class in your own class which gives getters for those members.
But from a logical standpoint, if those members aren't public, you probably shouldn't need access to them anyway.