The next code, it's about the problem Eight Queens, i found it in internet,
but i'm new in LISP and i don´t know how to compile it...
Can you help me?
(defun find-queen (arr p d)
(destructuring-bind ((px py) (dx dy)) (list p d)
(do ((x px (+ x dx))
(y py (+ y dy)))
((not (array-in-bounds-p arr x y)))
(when (= (aref arr x y) 1) (return t)))))
(defun queen-in-row (board row)
(find-queen board (list row 0) '(0 1)))
(defun queen-in-col (board col)
(find-queen board (list 0 col) '(1 0) ))
(defun queen-in-diags (board x y)
(member t (mapcar (lambda (p)
(find-queen board (list x y) p))
'((1 1) (-1 -1) (1 -1) (-1 1)))))
(defun queen-in-range (board x y)
(or (queen-in-row board x)
(queen-in-col board y)
(queen-in-diags board x y)))
(defun backtracking (pred explore node)
(if (funcall pred node) (list node)
(mapcan (lambda (n) (backtracking pred explore n))
(funcall explore node))))
(defun count-queens (board)
(loop for i below (array-total-size board)
for box = (row-major-aref board i)
count (> box 0)))
(defun solutionp (board)
(and board (= 8 (count-queens board))))
(defun put-queens (board)
(loop for i below 8
when (not (queen-in-row board i))
return
(loop for j below 8
for b = (copy-array board)
when (not (queen-in-range board i j))
do (setf (aref b i j) 1)
and collect b)))
(defun 8-queens ()
(backtracking #'solutionp #'put-queens board))
(defvar board (make-array '(8 8) :initial-element 0))
--
Victor Manuel Grijalva Altamirano
Universidad Tecnologica de La Mixteca
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