/** Sets the transaction Number and/or split Action based on book option:
  * if the book option is TRUE (split action is to be used for NUM) then 'num'
  * sets split-action and, if 'tran' and 'action' are provided, 'action'
  * sets transaction-num; if book option is FALSE (tran-num is to be used for NUM)
  * then 'num' sets transaction-num and, if 'split' and 'action' are
  * provided, 'action' sets 'split-action'. If any arguments are NULL,
  * no change is made to the field that would otherwise be
  * affected. If 'tran' and 'num' are passed with 'split and 'action' set to
  * NULL, it is xaccTransSetNum (trans, num). Likewise, if 'split and 'action'
  * are passed with 'tran' and 'num' set to NULL, it is xaccSplitSetAction (split,
  * action). */
void
gnc_set_num_action (Transaction *trans, Split *split,
                    const char *num, const char *action)
{
    gboolean num_action = qof_book_use_split_action_for_num_field
                           (qof_session_get_book(gnc_get_current_session ()));

    if (trans && num && !split && !action)
    {
        xaccTransSetNum (trans, num);
        return;
    }

    if (!trans && !num && split && action)
    {
        xaccSplitSetAction (split, action);
        return;
    }

    if (trans)
    {
        if (!num_action && num)
            xaccTransSetNum (trans, num);
        if (num_action && action)
            xaccTransSetNum (trans, action);
    }

    if (split)
    {
        if (!num_action && action)
            xaccSplitSetAction (split, action);
        if (num_action && num)
           xaccSplitSetAction (split, num);
    }
}