And you could do it...

The poor man’s approach:

class body {

public:

inline virtual char* identify() const =0;

inline virtual float GetVolume() const =0;

inline virtual float GetSurface() const =0;

virtual int commit(const char * filename) const = 0;

};

#include "body.h"

class cylinder : public body {

public:

cylinder (float,float);

virtual char* identify() const;

virtual float GetVolume() const;

virtual float GetSurface() const;

virtual int commit(const char * filename) const;

cylinder(const char * filename);

protected:

// a cylinder is described by

// its radius and height

float radius;

float height;

};

#include "body.h"

class cube : public body {

public:

cube (float);

virtual char* identify() const;

virtual float GetVolume() const;

virtual float GetSurface() const;

virtual int commit(const char * filename) const;

cylinder(const char * filename);

protected:

// a cube has just one length to

// fully describe it...

float length;

};

We save the data on a file…

…and have a way of reconstructing the objects…

in this way, they become (simple) persistent objects!