text: #ifndef PARENT_H
  #define PARENT_H
  
  // Forward declaration to reduce precompile time.
  class Child;
  
  class Parent {
  public:
    /** Construct a Parent particle with an Id and mass. */
    Parent(int id, double mass);
  
    /** Destructor to clean up the particle pointer */
    ~Parent(void);
  
    /** A member function to call a member function in the Child class */
    void run(void);
  
    /** Get the Id */
    int getId(void);
    
    /** Get the mass */
    double getMass(void);
  
    /** Get the child pointer */
    Child* getChild(void);
  
  private:
    /** A data member to store a pointer to the Child class */
    Child *m_child;
  
    /** A data member to store the Id */
    int m_id;
  
    /** A data member to store the mass */
    double m_mass;
  };
  
  #endif
  
  