field ‘’ declared as a function
struct stack {
char x[LIMIT][10];
int top;
void (*push)(struct stack *, char *);
char *(*pop)(struct stack *self);
void (*init)(struct stack *self);
bool (*is_empty)(struct stack *self);
};
struct stack object;
object.push = push_function; // function defined elsewhere
object.pop = pop_function; // function defined elsewhere
// ...