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.
<lang c> /* 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; }</lang>