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  1. #include <stdio.h>
  2.  
  3. struct point;
  4. struct point3d;
  5. struct point_it_vtbl;
  6.  
  7. int point_calc(struct point*);
  8. int point3d_calc(struct point*);
  9. void point_init(struct point*, int, int);
  10. void point3d_init(struct point3d*, int, int, int);
  11. void point_print(struct point*);
  12. void point3d_print(struct point*);
  13.  
  14.  
  15. struct point_it_vtbl {
  16.     int (*calc)(struct point*);
  17.     void (*print)(struct point*);
  18. }
  19. 	point_vtbl = { &point_calc, &point_print },
  20. 	point3d_vtbl = { &point3d_calc, &point3d_print }
  21. ;
  22.  
  23. struct point {
  24.     struct point_it_vtbl* vtbl;
  25.     int x, y;
  26. };
  27.  
  28. struct point3d {
  29.     struct point base;
  30.     int z;
  31. };
  32.  
  33.  
  34. int point_calc(struct point* this) {
  35.     return this->x * this->y;
  36. }
  37.  
  38. int point3d_calc(struct point* this) {
  39.     return point_calc(this) * (*(struct point3d*)this).z;
  40. }
  41.  
  42. void point_print(struct point* this) {
  43.     printf("%i, %i", this->x, this->y);
  44. }
  45.  
  46. void point3d_print(struct point* this) {
  47.     point_print(this);
  48.     printf(", %i", (*(struct point3d*)this).z);
  49. }
  50.  
  51. void test(struct point* p) {
  52.     p->vtbl->print(p);
  53. }
  54.  
  55. int main(void) {
  56.     struct point3d t = { { &point3d_vtbl, 6, 3 } , 9 };
  57.     test((struct point*)&t);
  58.     printf(" %i", t.base.vtbl->calc(&t.base));
  59.     return 0;
  60. }
Success #stdin #stdout 0s 9416KB
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Standard input is empty
stdout
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6, 3, 9 162
https://ideone.com/f76mhk
language:
C99 (gcc 8.3)
created:
9 years ago
visibility:
public

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