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Clone Function in C++

class Dog { 
public:
   virtual Dog* clone() { return (new Dog(*this)); }  // co-variant return type
};

 class Yellowdog : public Dog { 
   virtual Yellowdog* clone() { return (new Yellowdog(*this)); }
};

 void foo(Dog* d) {      // d is a Yellowdog
   //Dog* c = new Dog(*d); // c is a Dog
   Dog* c = d->clone();    // c is a Yellowdog
   
//... 
   // 
}

 int main() {
   Yellowdog d;
   foo(&d);
}
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