[C++] 콜론 초기화

#include <iostream>
using namespace std;
 
class A {
    int a;
public :
    A(int a) {
        this->a = a;
    }
    void dispA() {
        cout << a << endl;
    }
};
class B : virtual public A{
    int b;
public :
    B(int a, int b) : A(a) {
        this->b = b;
    }
    void dispB() {
        cout << b << endl;
    }
};
class C : virtual public A {
    int c;
public :
    C(int a, int c) : A(a) {
        this->c = c;
    }
    void dispC() {
    cout << c << endl;
    }
};
class D : public B, public C {
    int d;
public :
    D(int a, int b, int c, int d) : B(a, b), C(a, c), A(a) {
        this->d = d;
    }
    void dispD() {
        cout << d << endl;
    }
};
void main() {
    D dd(1, 2, 3, 4);
    dd.dispD();
    dd.dispC();
    dd.dispB();
    dd.dispA();
}