node-op.cc

template<class T>
class Node {
  protected:
    T val;
  virtual T getVal() { return this.val; }
  virtual void setVal(T val) { this.val = val; }
  
  template <typename R, typename V>
  virtual Node<R> operator+(Node<V> rhs);
}

class DoubleNode: public Node<double> {
  virtual DoubleNode operator+(DoubleNode n){
    return new DoubleNode( this.getVal() + n.getVal() ); // handle double + double
  }
  virtual DoubleNode operator+(IntNode n){
    return new DoubleNode( this.getVal() + n.getVal() ); // handle double + int
  }
}

class IntNode: public Node<int> {
  virtual DoubleNode operator+(DoubleNode n) {
    // implementation 
  }
  virtual IntNode operator+(IntNode n) {
    // implementation
  }
}