Question

i have got this code:

class father{
public:
    virtual void f() { cout<<1;}
};

class son:public father{
public:
    void f() {cout<<2;}
};

void test (father x){x.f();}

int main(){
    son s;
    test(s);
}

the question says:

1. the output is ‘1’, what is the rule about polymorphism that the programmer forgot and how can i fix it so the output would be ‘2’?

2. there is another rule that the programmer forgot when he wrote the father class, and he need to add an empty function to avoid problems from other sons of the father class. what is the rule and what is the missing function?

---

another question
write the g function so the next code would run with no crashes

int x=11; g(x)=22;

Answer 1

When you pass the son object to the test function by value, it will be converted to a father object because test takes a father, not a son. If you want to accept instances of subclass without conversion, you need to accept the argument by reference or pointer.

So if you change the signature of test to void test (father& x), it will work as you want.