> > type Piece_T(Color: Color_T) is
> > � record
> > � � case Color is
> > � � � when White =>
> > � � � � White_Piece: Piece_Type_T;
> > � � � when Black =>
> > � � � � Black_Piece: Piece_Type_T;
> > � � � when None =>
> > � � � � null;
> > � � end case;
> > � end record;
> 
> The problem with this is that you'd then need two code paths for
> Black_Piece and White_Piece, every time. 

Right. Actually, I anticipated that you would *want* two code paths for 
the black and for the white pieces. Else, your approach the approach 
below is better.

> To overcome this, here is solution 2a1:

> type Square_T (Color : Color_T := None) is record
>    case Color is
>       when None => null;
>       when Black | White => Piece_Type : Piece_Type_T;
>    end case;
> end record;

-- 
------ Stefan Lucks   --  Bauhaus-University Weimar  --   Germany  ------
               Stefan dot Lucks at uni minus weimar dot de
------  I  love  the  taste  of  Cryptanalysis  in  the  morning!  ------