exp-no-recursion.c

#define EXP_STACKSIZE 1000
static void push_elist(E_list *s[], int *i, E_list *e)
{
	assert(*i < EXP_STACKSIZE);
	s[(*i)++] = e;
}
static E_list *pop_elist(E_list *s[], int *i)
{
	return s[--(*i)];
}

static E_list *next_E_list(E_list *s[], int *si)
{
	E_list *p = pop_elist(s, si);
	Exp *t = p->e;

	if (t->type != CONNECTOR_type)
	{
		for (E_list *l = t->u.l; l != NULL; l = l->next)
			push_elist(s, si, l);
	}

	return p;
}

void free_Exp(Exp *e)
{
	if (e == NULL) return;
	int si;
	E_list *s[EXP_STACKSIZE];

	/* Make the expression look like E_list. */
	s[0] = &(E_list){ NULL, e };
	si = 1;

	while (si > 0)
	{
		E_list *p = next_E_list(s, &si);

		free(p->e);
		if (e != p->e) free(p);
	}
}

void free_E_list(E_list *l)
{
	if (l == NULL) return;
	int si;
	E_list *s[EXP_STACKSIZE];

	s[0] = l;
	si = 1;

	while (si > 0)
	{
		E_list *p = next_E_list(s, &si);

		free(p->e);
		free(p);
	}
}

int size_of_expression(Exp * e)
{
	if (e == NULL) return 0;
	E_list *s[1000];
	int si;
	int size = 0;

	/* Make the expression look like E_list. */
	s[0] = &(E_list){ NULL, e };
	si = 1;

	while (si > 0)
	{
		E_list *p = next_E_list(s, &si);
		if (p->e->type == CONNECTOR_type) size++;
	}

	return size;
}