Object-oriented Software in Ada 95

A Text user interface 321
package Class_Board is
type Board is private;
type Game_State is ( Win, Playable, Draw );
procedure Add( The:in out Board; Pos:in Integer;
Piece:in Character );
function Valid( The:in Board; Pos:in Integer ) return Boolean;
function State( The:in Board ) return Game_State;
function Cell( The:in Board; Pos:in Integer ) return Character;
procedure Reset( The:in out Board );
private
subtype Board_Index is Integer range 1 .. 9;
type Board_Array is array( Board_Index ) of Character;
type Board is record
Sqrs : Board_Array := ( others => ' '); --Initialize
Moves : Natural := 0;
end record;
end Class_Board;
Note:
It would have been elegant to re-use the previous noughts and crosses class for Board but the
functionality is too dissimilar to make this a practical proposition. Code re-use is not always possible!
In the implementation of the class the function Valid returns True if the suggested noughts and crosses
move is valid.
package body Class_Board is
function Valid(The:in Board; Pos:in Integer) return Boolean is
begin
return Pos in Board_Array'Range and then
The.Sqrs( Pos ) = ' ';
end Valid;
The procedure Add is responsible for adding a new piece onto the board..
procedure Add( The:in out Board; Pos:in Integer;
Piece:in Character ) is
begin
The.Sqrs( Pos ) := Piece;
end Add;
The function State returns the enumeration Win, Draw or Playable depending on the current state of the
game. The constant array cells holds all possible win lines and the main body of the code uses the values held
in this array to determine the current state of the game.
© M A Smith - May not be reproduced without permission