Polymorphism/C: Difference between revisions

<syntaxhighlight 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)->dtor();

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

structint _Circler;

{};

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)->dtor();

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;