+rule_t* rule_copy (rule_t* rule)
+{
+ rule_t* new_rule;
+ GList* r;
+ new_rule = rule_new ();
+ r = rule->right;
+ while (r != NULL)
+ {
+ rule_append (new_rule, symbol_copy (r->data));
+ r = g_list_next (r);
+ }
+ return new_rule;
+}
+
+symbol_t* rule_pop (rule_t* rule)
+{
+ GList* r;
+ if ((r = g_list_first (rule->right)) == NULL)
+ return NULL;
+ rule->right = g_list_remove_link (r, r);
+ g_free (r->data);
+ g_list_free (r);
+ if (rule->right == NULL)
+ return NULL;
+ return rule->right->data;
+}
+