about non-virtual func. in derived class

I have a question about polymorphism.
This is code

Code:

---

#include <iostream>
using namespace std;

class Pet {
 public: virtual void speak() const ;
};
void Pet::speak() const { cout << "Hi" << endl; }

class Dog : public Pet {
public: void speak() const { cout<<"hi too";}
void eat() const { cout<<"eat"; }
 };

int main() {
Dog simba; Pet* p=&simba; p->speak();//I can call dog::speak by pet pointer
//p->eat(); but I can not call dog::eat() by pet.
}

---

here how can i solve the problem.I mean i want to enhance my derived class and call my functions from base class pointer?

Is there a solution?
Thanks...

No. Change your pointer type or do a cast from Pet* to Dog* before accessing the function.

...or you can make your eat function virtual in your pet class.

That might be an even better solution, but I'm not sure what OP is trying to do.

Given the topic, I'd guess my solution is something he considered. In any event, I haven't seen many polymorphism examples with a single derived class.

just a question , why do you put const on a void function ,
dont see the point in this but someone tell me if i am wrong

Quote:

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Originally Posted by Anddos

just a question , why do you put const on a void function ,
dont see the point in this but someone tell me if i am wrong

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So it can operate on a const object. There are no members changed in it, so it's valid.

Just to expand on SlyMaelstrom's reply - the const qualifier has nothing to do with the return type of the function, be it "void", "int" or some other type. You can also have a const function which returns a const int, then you'd use the const keyword twice in the function declaration.

this example might be a good illustration (this deliberately won't compile.)

Code:

---

#include <iostream>
using namespace std;

class MyClass
{
  int i;
public:
  MyClass() : i(5) {}
  int geti() { return i;  }
      // geti() isn't const, it is free to modify the object.

};

int main()
{
  const MyClass MyObj;
  int x = MyObj.geti(); // ERROR!!  geti() may potentially modify MyObj.
  cout << x;
}

---

the compiler needs "const" after geti() as a promise that you are not going to modify MyObj.