Object-oriented Software in Ada 95

The specification for the class Cell which holds a counter is as follows:
Case study: Design of a game 137
with Class_Counter;
use Class_Counter;
package Class_Cell is
type Cell is private;
type Cell_Holds is ( C_White, C_Black, Empty );
procedure Initialize( The:in out Cell );
function Holds( The:in Cell ) return Cell_Holds;
procedure Add( The:in out Cell; Players_Counter:in Counter );
procedure Display( The:in Cell );
procedure Flip( The:in out Cell );
function To_Colour( C:in Cell_Holds ) return Counter_Colour;
private
type Cell_Is is ( Empty_Cell, Not_Empty_Cell );
type Cell is record
Contents: Cell_Is := Empty_Cell;
Item : Counter; --The counter
end record;
end Class_Cell;
In the implementation of the package the procedure Initialize sets the contents of the cell to empty.
package body Class_Cell is
procedure Initialize( The:in out Cell ) is
begin
The.Contents := Empty_Cell; --Initialize cell to empty
end Initialize;
The procedure Holds returns the contents of the cell which is defined by the enumeration type
Cell_Holds.
function Holds( The:in Cell ) return Cell_Holds is
begin
case The.Contents is
when Empty_Cell => --Empty
return Empty;
-- No counter
when Not_Empty_Cell => --Counter
case Rep( The.Item ) is
when White => return C_White; -- white counter
when Black => return C_Black; -- black counter
end case;
end case;
end Holds;
The next three procedures implement:
• Adding of a new counter into a cell.
• Displaying the contents of a cell.
• Flipping the counter in the cell to the other colour.
procedure Add(The:in out Cell; Players_Counter:in Counter) is
begin
The := (Not_Empty_Cell,Players_Counter);
end Add;
© M A Smith - May not be reproduced without permission