21 lines
644 B
Plaintext
21 lines
644 B
Plaintext
; Each possible coordinate on the board.
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define output Coord Integer
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Coord 1.
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Coord a :- Coord b, b < 8, a = b + 1.
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; Each possible placement of a queen.
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define output decision Queen(Coord, Coord)
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Queen(row, col) :- Coord row, Coord col.
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; Exactly one queen goes on each row.
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:- For(row), @count Queen(row, _) = 1.
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; Exactly one queen goes on each column.
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:- For(col), @count Queen(_, col) = 1.
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; At most one queen can go along each main diagonal.
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:- For(diag), @count { Queen (row, col), diag = row + col } <= 1.
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; At most one queen can go along each orthogonal diagonal.
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:- For(diag), @count { Queen (row, col), diag = row - col } <= 1.
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