declare
  v_b1 boolean;
  v_b2 boolean;
begin

  v_b2 := sys.diutil.int_to_bool(1);
  --  select sys.diutil.int_to_bool(0) into v_b1 from dual;
  if v_b1 = TRUE then
    dbms_output.put_line('TRUE');
  else
    dbms_output.put_line('FALSE');
  end if;

  if v_b2 = TRUE then
    dbms_output.put_line('TRUE');
  else
    dbms_output.put_line('FALSE');
  end if;
end;