316 lines
9.2 KiB
Plaintext
316 lines
9.2 KiB
Plaintext
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(* Logitech Modula-2 version of proving you can't win at tic-tac-toe if the opponent is competent
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To build from the Modula-2 install directory:
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ntvdm m2 comp %1
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ntvdm m2 link %1
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ntvdm m2 %1
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*)
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(*$S-*)
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(*$R-*)
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(*$T-*)
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MODULE ttt;
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FROM SYSTEM IMPORT WORD, BYTE, ADDRESS;
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FROM NumberConversion IMPORT StringToCard;
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FROM Strings IMPORT Assign;
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FROM InOut IMPORT WriteLn, WriteInt, WriteCard, WriteString;
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CONST
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scoreWin = 6;
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scoreTie = 5;
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scoreLose = 4;
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scoreMax = 9;
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scoreMin = 2;
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scoreInvalid = 0;
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pieceBlank = 0;
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pieceX = 1;
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pieceO = 2;
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defaultIterations = 10;
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TYPE
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boardType = ARRAY[ 0..8 ] OF CARDINAL;
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scoreProc = PROCEDURE() : CARDINAL;
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VAR
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evaluated: CARDINAL; (* # of board positions evaluated *)
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board: boardType;
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procs : ARRAY[ 0..8 ] OF scoreProc;
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PROCEDURE lookForWinner() : CARDINAL;
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VAR t : CARDINAL;
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BEGIN
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t := board[ 0 ];
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IF pieceBlank <> t THEN
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IF ( ( ( t = board[1] ) AND ( t = board[2] ) ) OR
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( ( t = board[3] ) AND ( t = board[6] ) ) ) THEN
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RETURN t;
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END;
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END;
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t := board[1];
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IF ( t = board[4] ) AND ( t = board[7] ) THEN RETURN t; END;
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t := board[2];
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IF ( t = board[5] ) AND ( t = board[8] ) THEN RETURN t; END;
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t := board[3];
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IF ( t = board[4] ) AND ( t = board[5] ) THEN RETURN t; END;
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t := board[6];
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IF ( t = board[7] ) AND ( t = board[8] ) THEN RETURN t; END;
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t := board[4];
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IF pieceBlank <> t THEN
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IF ( ( ( t = board[0] ) AND ( t = board[8] ) ) OR
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( ( t = board[2] ) AND ( t = board[6] ) ) ) THEN
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RETURN t;
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END;
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END;
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RETURN pieceBlank;
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END lookForWinner;
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PROCEDURE proc0() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[0];
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IF ( ( ( x = board[1] ) AND ( x = board[2] ) ) OR
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( ( x = board[3] ) AND ( x = board[6] ) ) OR
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( ( x = board[4] ) AND ( x = board[8] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc0;
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PROCEDURE proc1() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[1];
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IF ( ( ( x = board[0] ) AND ( x = board[2] ) ) OR
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( ( x = board[4] ) AND ( x = board[7] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc1;
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PROCEDURE proc2() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[2];
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IF ( ( ( x = board[0] ) AND ( x = board[1] ) ) OR
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( ( x = board[5] ) AND ( x = board[8] ) ) OR
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( ( x = board[4] ) AND ( x = board[6] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc2;
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PROCEDURE proc3() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[3];
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IF ( ( ( x = board[4] ) AND ( x = board[5] ) ) OR
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( ( x = board[0] ) AND ( x = board[6] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc3;
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PROCEDURE proc4() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[4];
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IF ( ( ( x = board[0] ) AND ( x = board[8] ) ) OR
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( ( x = board[2] ) AND ( x = board[6] ) ) OR
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( ( x = board[1] ) AND ( x = board[7] ) ) OR
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( ( x = board[3] ) AND ( x = board[5] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc4;
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PROCEDURE proc5() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[5];
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IF ( ( ( x = board[3] ) AND ( x = board[4] ) ) OR
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( ( x = board[2] ) AND ( x = board[8] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc5;
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PROCEDURE proc6() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[6];
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IF ( ( ( x = board[7] ) AND ( x = board[8] ) ) OR
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( ( x = board[0] ) AND ( x = board[3] ) ) OR
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( ( x = board[4] ) AND ( x = board[2] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc6;
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PROCEDURE proc7() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[7];
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IF ( ( ( x = board[6] ) AND ( x = board[8] ) ) OR
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( ( x = board[1] ) AND ( x = board[4] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc7;
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PROCEDURE proc8() : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[8];
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IF ( ( ( x = board[6] ) AND ( x = board[7] ) ) OR
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( ( x = board[2] ) AND ( x = board[5] ) ) OR
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( ( x = board[0] ) AND ( x = board[4] ) ) )
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THEN RETURN x; END;
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RETURN pieceBlank;
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END proc8;
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PROCEDURE winner2( move: CARDINAL ) : CARDINAL;
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VAR x : CARDINAL;
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BEGIN
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x := board[ move ];
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CASE move OF
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0: IF NOT ( ( ( x = board[1] ) AND ( x = board[2] ) ) OR
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( ( x = board[3] ) AND ( x = board[6] ) ) OR
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( ( x = board[4] ) AND ( x = board[8] ) ) )
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THEN RETURN pieceBlank; END; |
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1: IF NOT ( ( ( x = board[0] ) AND ( x = board[2] ) ) OR
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( ( x = board[4] ) AND ( x = board[7] ) ) )
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THEN x := pieceBlank; END; |
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2: IF NOT ( ( ( x = board[0] ) AND ( x = board[1] ) ) OR
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( ( x = board[5] ) AND ( x = board[8] ) ) OR
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( ( x = board[4] ) AND ( x = board[6] ) ) )
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THEN x := pieceBlank; END; |
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3: IF NOT ( ( ( x = board[4] ) AND ( x = board[5] ) ) OR
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( ( x = board[0] ) AND ( x = board[6] ) ) )
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THEN x := pieceBlank; END; |
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4: IF NOT ( ( ( x = board[0] ) AND ( x = board[8] ) ) OR
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( ( x = board[2] ) AND ( x = board[6] ) ) OR
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( ( x = board[1] ) AND ( x = board[7] ) ) OR
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( ( x = board[3] ) AND ( x = board[5] ) ) )
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THEN x := pieceBlank; END; |
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5: IF NOT ( ( ( x = board[3] ) AND ( x = board[4] ) ) OR
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( ( x = board[2] ) AND ( x = board[8] ) ) )
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THEN x := pieceBlank; END; |
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6: IF NOT ( ( ( x = board[7] ) AND ( x = board[8] ) ) OR
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( ( x = board[0] ) AND ( x = board[3] ) ) OR
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( ( x = board[4] ) AND ( x = board[2] ) ) )
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THEN x := pieceBlank; END; |
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7: IF NOT ( ( ( x = board[6] ) AND ( x = board[8] ) ) OR
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( ( x = board[1] ) AND ( x = board[4] ) ) )
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THEN x := pieceBlank; END; |
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8: IF NOT ( ( ( x = board[6] ) AND ( x = board[7] ) ) OR
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( ( x = board[2] ) AND ( x = board[5] ) ) OR
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( ( x = board[0] ) AND ( x = board[4] ) ) )
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THEN x := pieceBlank; END;
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END;
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RETURN x;
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END winner2;
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PROCEDURE minmax( alpha: CARDINAL; beta: CARDINAL; move: CARDINAL; depth: CARDINAL ): CARDINAL;
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VAR p, value, pieceMove, score : CARDINAL;
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BEGIN
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evaluated := evaluated + 1;
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value := scoreInvalid;
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IF depth >= 4 THEN
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(* lookForWinner is >14% slower than using scoring procs, unlike Turbo Modula-2 on CP/M *)
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(* p := lookForWinner(); *)
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(* p := winner2( move ); *)
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p := procs[ move ]();
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IF p <> pieceBlank THEN
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IF p = pieceX THEN
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RETURN scoreWin;
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ELSE
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RETURN scoreLose;
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END;
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ELSIF depth = 8 THEN
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RETURN scoreTie;
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END;
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END;
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IF ODD( depth ) THEN
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value := scoreMin;
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pieceMove := pieceX;
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ELSE
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value := scoreMax;
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pieceMove := pieceO;
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END;
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p := 0;
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REPEAT
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IF board[ p ] = pieceBlank THEN
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board[ p ] := pieceMove;
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score := minmax( alpha, beta, p, depth + 1 );
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board[ p ] := pieceBlank;
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IF ODD( depth ) THEN
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IF ( score = scoreWin ) THEN RETURN scoreWin; END;
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IF ( score > value ) THEN
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value := score;
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IF ( value >= beta ) THEN RETURN value; END;
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IF ( value > alpha ) THEN alpha := value; END;
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END;
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ELSE
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IF ( score = scoreLose ) THEN RETURN scoreLose; END;
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IF ( score < value ) THEN
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value := score;
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IF ( value <= alpha ) THEN RETURN value; END;
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IF ( value < beta ) THEN beta := value; END;
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END;
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END;
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END;
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p := p + 1
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UNTIL p > 8;
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RETURN value;
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END minmax;
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PROCEDURE runit( move : CARDINAL );
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VAR score : CARDINAL;
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BEGIN
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board[move] := pieceX;
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score := minmax( scoreMin, scoreMax, move, 0 );
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board[move] := pieceBlank;
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END runit;
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VAR
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i, loops, tsstart, tsend : CARDINAL;
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cmd : ARRAY[0..127] OF CHAR;
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done : BOOLEAN;
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BEGIN
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loops := 0;
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IF ( loops = 0 ) THEN loops := defaultIterations; END;
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procs[ 0 ] := proc0;
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procs[ 1 ] := proc1;
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procs[ 2 ] := proc2;
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procs[ 3 ] := proc3;
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procs[ 4 ] := proc4;
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procs[ 5 ] := proc5;
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procs[ 6 ] := proc6;
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procs[ 7 ] := proc7;
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procs[ 8 ] := proc8;
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FOR i := 0 TO 8 DO
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board[i] := pieceBlank;
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END;
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FOR i := 1 TO loops DO
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evaluated := 0; (* once per loop to prevent overflow *)
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runit( 0 );
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runit( 1 );
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runit( 4 );
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END;
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WriteString( "moves evaluated: " ); WriteInt( evaluated, 8 ); WriteLn;
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WriteString( "iterations: " ); WriteInt( loops, 8 ); WriteLn;
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END ttt.
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