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#lang debug racket
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(require sugar/debug "hacs.rkt")
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(current-inference forward-check)
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(current-select-variable mrv)
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(current-order-values shuffle)
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(current-random #true)
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;; queens problem
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;; place queens on chessboard so they do not intersect
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(define board-size 8)
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(define queens (make-csp))
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(define qs (for/list ([q board-size]) (string->symbol (format "q~a" q))))
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(define rows (range (length qs)))
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(add-vars! queens qs rows)
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(define (q-col q) (string->number (string-trim (symbol->string q) "q")))
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(for* ([qs (in-combinations qs 2)])
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(match-define (list qa qb) qs)
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(match-define (list qa-col qb-col) (map q-col qs))
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(add-constraint! queens
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(λ (qa-row qb-row)
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(nor
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(= (abs (- qa-row qb-row)) (abs (- qa-col qb-col))) ; same diagonal?
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(= qa-row qb-row))) ; same row?
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(list qa qb)))
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(time-avg 10 (solve queens))
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(parameterize ([current-solver min-conflicts])
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(time-named (solve queens)))
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