Polymorphism/C

This is a programming example for the Polymorphism programming task. If the task description is not listed here, refer back to that page.

Compiler: GCC, MSVC, BCC, Watcom

Libraries: Standard

 /* After reading this you may understand */ 
 /* why Bjarne Stroustrup's invented C++  */
 #if defined( _WIN32 ) || defined( MSC_VER )
 #define FN_PTR(x) (& x)
 #else
 #define FN_PTR(x) (x)
 #endif

 typedef struct Point
 {
   int x;
   int y;
   void (*dtor)();   /* virtual */
   void (*print)();  /* virtual */
 } Point;

 Point* Point_new0()
 {
   Point* pthis = (Point*) malloc( sizeof( Point ) );
   memset(pthis, 0, sizeof( Point ) );
   pthis->dtor  = FN_PTR(Point_dtor);
   pthis->print = FN_PTR(Point_print);
 }

 Point* Point_new1(int x0)
 {
   Point* pthis = (Point*) malloc( sizeof( Point ) );
   pthis->x = x0;
   pthis->y = 0;
   pthis->dtor  = FN_PTR(Point_dtor);
   pthis->print = FN_PTR(Point_print);
 }

 Point* Point_new2(int x0, int y0)
 {
   Point* pthis = (Point*) malloc( sizeof( Point ) );
   pthis->x = x0;
   pthis->y = y0;
   pthis->dtor  = FN_PTR(Point_dtor);
   pthis->print = FN_PTR(Point_print);
 }

 void Point_delete(Point** pthis)
 {
   if(pthis && *pthis)
   {
     (*pthis)->dtor();
     free(*pthis); *pthis = NULL;
   }
 }

 Point* Point_copy(Point* p)
 {
   Point* pthis = (Point*) malloc( sizeof( Point ) );
   memcpy(pthis, p, sizeof( Point ) );
   pthis->dtor  = FN_PTR(Point_dtor);
   pthis->print = FN_PTR(Point_print);
   return pthis;
 }

 int Point_getX(Point* pthis) { return pthis->x; }
 int Point_getY(Point* pthis) { return pthis->y; }
 int Point_setX(Point* pthis, int x0) { pthis->x = x0; }
 int Point_setY(Point* pthis, int y0) { pthis->y = y0; }
 void Point_print() { printf("Point\n"); }
 void Point_dtor() {}

 // Trick: This way Circle.x, Circle.y, Circle.r are available
 typedef union Circle
 {
   Point point;
   struct _Circle
   {
     Point point;
     int r;
   };
 } Circle;

 Circle* Circle_new0()
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   memset(pthis, 0, sizeof( Circle ) );
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
 }

 Circle* Circle_new1(int x0)
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   pthis->x = x0;
   pthis->y = 0;
   pthis->r = 0;
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
 }

 Circle* Circle_new2(int x0, int y0)
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   pthis->x = x0;
   pthis->y = y0;
   pthis->r = 0;
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
 }

 Circle* Circle_new3(int x0, int y0, int r0)
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   pthis->x = x0;
   pthis->y = y0;
   pthis->r = r0;
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
 }

 Circle* Circle_newP0(Point* p)
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   pthis->x = p->x;
   pthis->y = p->y;
   pthis->r = 0;
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
 }

 Circle* Circle_newP1(Point* p, int r0)
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   pthis->x = p->x;
   pthis->y = p->y;
   pthis->r = r0;
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
 }

 void Circle_delete(Circle** pthis)
 {
   if(pthis && *pthis)
   {
     (*pthis)->dtor();
     free(*pthis); *pthis = NULL;
   }
 }

 Circle* Circle_copy(Circle* c)
 {
   Circle* pthis = (Circle*) malloc( sizeof( Circle ) );
   memcpy(pthis, c, sizeof( Circle ) );
   pthis->dtor  = FN_PTR(Circle_dtor);
   pthis->print = FN_PTR(Circle_print);
   return pthis;
 }

 int Circle_getX(Circle* pthis) { return pthis->x; }
 int Circle_getY(Circle* pthis) { return pthis->y; }
 int Circle_getR(Circle* pthis) { return pthis->r; }
 int Circle_setX(Circle* pthis, int x0) { pthis->x = x0; }
 int Circle_setY(Circle* pthis, int y0) { pthis->y = y0; }
 int Circle_setR(Circle* pthis, int r0) { pthis->r = r0; }
 void Circle_print() { printf("Circle\n"); }
 void Circle_dtor() {}

 int main()
 {
    Point* p = Point_new0();
    Point* c = (Point*)Circle_new0();
    p->print();
    c->print();     
    return 0;
 }