Object-oriented Software in Ada 95

322 A Text user interface
function State( The:in Board ) return Game_State is
subtype Position is Integer range 1 .. 9;
type Win_Line is array( 1 .. 3 ) of Position;
type All_Win_Lines is range 1 .. 8;
Cells: constant array ( All_Win_Lines ) of Win_Line :=
( (1,2,3), (4,5,6), (7,8,9), (1,4,7),
(2,5,8), (3,6,9), (1,5,9), (3,5,7) ); --All win lines
First : Character;
begin
for Pwl in All_Win_Lines loop --All Pos Win Lines
First := The.Sqrs( Cells(Pwl)(1) ); --First cell in line
if First /= ' ' then -- Looks promising
if First = The.Sqrs(Cells(Pwl)(2)) and then
First = The.Sqrs(Cells(Pwl)(3)) then return Win;
end if;
end if;
end loop;
if The.Moves >= 9 then --Check for draw
return Draw;
-- Board full
else
return Playable;
-- Still playable
end if;
end State;
The procedure Cell returns the contents of a cell on the playing board.
function Cell( The:in Board; Pos:in Integer ) return Character is
begin
return The.Sqrs( Pos );
end Cell;
The procedure reset resets the board to its initial empty state.
procedure Reset( The:in out Board ) is
begin
The.sqrs := ( others => ' '); --All spaces
The.moves := 0; --No of moves
end reset;
end Class_Board;
22.5.2 Package Pack_Program
The package Pack_Program contains the publicly visible procedure Play that will play the GUI based game
against two human opponents. In the private part of the package, the procedure Play is broken down into further
procedures and functions. The variables in the private part of the specification will be visible to all these
procedure and functions.
These variables define windows that are used in the playing of the game of noughts and crosses.
© M A Smith - May not be reproduced without permission