struct virt_z {
    double x;
    double y;
    struct z_wrap {
        virt_z &parent;
 
        operator double() { return parent.x * parent.y; }
        z_wrap &operator=( double in ) {
            parent.x = in;
            parent.y = 1;
            return *this;
        }
        z_wrap( virt_z &in ) : parent( in ) {}
    } z;
 
    virt_z() : z( *this ) {}
    virt_z( virt_z const &o ) : x( o.x ), y( o.y ), z( *this ) {}
};
 
#include <iostream>
 
int main() {
    virt_z xyz;
    xyz.x = 5;
    xyz.y = 2;
    std::cout << xyz.z << '\n';
    xyz.z = 8;
    std::cout << xyz.x << ' ' << xyz.y << ' ' << xyz.z << '\n';
}
 

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