#include <stdio.h>
#include <stdlib.h>

struct foo {
  void (*print)(struct foo *, FILE *);
};

void
print_foo(struct foo *obj, FILE *f)
{
  obj->print(obj, f);
}

struct bar {
  struct foo vtable;
  int n;
};

void print_bar(struct foo *obj, FILE *f)
{
  struct bar *b = (struct bar *)obj;
  fprintf(f, "bar: %d\n", b->n);
}

struct foo *
make_bar(int n) {
  struct bar *b;
  b = malloc(sizeof *b);
  b->vtable.print = print_bar;
  b->n = n;
  return (struct foo *)b;
}

struct baz {
  struct foo vtable;
  double d;
};

void print_baz(struct foo *obj, FILE *f)
{
  struct baz *b = (struct baz *)obj;
  fprintf(f, "baz: %f\n", b->d);

}

struct foo *
make_baz(double d) {
  struct baz *b;
  b = malloc(sizeof *b);
  b->vtable.print = print_baz;
  b->d = d;
  return (struct foo *)b;
}

int
main(void)
{
  struct foo *objects[2];

  objects[0] = make_bar(1);
  objects[1] = make_baz(2.0);

  print_foo(objects[0], stdout);
  print_foo(objects[1], stdout);

  return 0;
}