rem: return 0;
add: return true;
context: append_char_class (struct Spec_list *list,		   const unsigned char *char_class_str, size_t len){  enum Char_class char_class;  struct List_element *new;  char_class = look_up_char_class (char_class_str, len);  if (char_class == CC_NO_CLASS)    return 1;  new = (struct List_element *) xmalloc (sizeof (struct List_element));  new->next = NULL;  new->type = RE_CHAR_CLASS;  new->u.char_class = char_class;  assert (list->tail);  list->tail->next = new;  list->tail = new;  return 0;}