Object-oriented Software in Ada 95

140 Case study: Design of a game
The procedure Now_Playing records the colour of the current player. This information is used by
subsequent methods add and Check_Move.
procedure Now_Playing(The:in out Board; C:in Counter_Colour) is
begin
The.Player := C;
--Player
case C is
--Opponent
when White => The.Opponent := Black;
when Black => The.Opponent := White;
end case;
end Now_Playing;
The procedure Display displays a representation of the reversi board on the output device. For this
implementation of the game, the output device is an ANSI text-based terminal.
procedure Display( The:in Board ) is
Dashes: String( 1 .. The.Sqrs'Length*4+1 ) := (others=>'-');
begin
Screen_Clear;
--Clear screen
Put( Dashes ); New_Line; --Top
for X in The.Sqrs'range(1) loop
Put("|");
--Cells on line
for Y in The.Sqrs'range(2) loop
Put(" "); Display( The.Sqrs(X,Y) ); Put(" |");
end loop;
New_Line; Put( Dashes ); New_Line; --Bottom lines
end loop;
New_Line;
Put( "Player X has " );
Put( Integer(The.Score(Black)), Width=>2 );
Put( " counters" ); New_Line;
Put( "Player O has " );
Put( Integer(The.Score(White)), Width=>2 );
Put( " counters" ); New_Line;
end Display;
The function Check_Move checks the validity of a proposed move on the board. This function is decomposed
into the function Find_Turned which calculates the number of pieces that will be turned if a move is made into
the specified square.
function Check_Move( The:in Board; X,Y:in Integer )
return Move_Status is
begin
if X = 0 and then Y = 0 then
return Pass;
elsif X in Board_Index and then Y in Board_Index then
if Holds( The.Sqrs( X, Y ) ) = Empty then
if Find_Turned(The, X, Y) > 0 then
return Ok;
end if;
end if;
end if;
return Invalid;
end Check_Move;
© M A Smith - May not be reproduced without permission