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struct B { // default access modifier inside struct is public void set_n(int v) { n = v; } void f() { cout << "B::f" << endl; } protected: int m, n; // B::m, B::n are protected private: int x; };

struct D: B { using B::m; // D::m is public int get_n() { return n; } // B::n is accessible here, but not outside // int get_x() { return x; } // ERROR, B::x is inaccessible here private: using B::f; // D::f is private };

int main() { D d;

// d.x = 2; // ERROR, private // d.n = 2; // ERROR, protected d.m = 2; // protected B::m is accessible as D::m

d.set_n(2); // calls B::set_n(int)
cout << d.get_n() << endl; // output: 2

// d.f(); // ERROR, B::f is inaccessible as D::f

B& b = d; // b references d and "views" it as being type B

// b.x = 3; // ERROR, private // b.n = 3; // ERROR, protected // b.m = 3; // ERROR, B::m is protected

b.set_n(3); // calls B::set_n(int)

// cout << b.get_n(); // ERROR, 'struct B' has no member named 'get_n'

b.f();   // calls B::f()
return 0;

}