type vrec( disc : t := 8 ) is record
   case disc is
   when sn
      | s1 range 1 .. 0
      | s2 range c5 + 2 .. c5 + 1
      | 3 .. 2 => null;
   when  s1 range 4 .. c5
   | s1 range c5 - 4 .. c5 / 2
   | 3 .. 1 + c5 mod 3
   | sn
   | s1 range 5 .. c5 - 1
   | 6 .. 7
   | s10
   | 9
   | s10 range 10 .. 9 => null;
   when c5 + c5 - 2 .. 8 => null;
   end case;
end record;
