(define concat
  (lambda (a b)
    (if (null? a)
	b
	(cons (car a) (concat (cdr a) b)))))

(define inverte
  (lambda (a)
    (if (null? a)
	a
	(concat (inverte (cdr a)) (cons (car a) '())))))

(define p
  (lambda (l i)
    (if (= (length l) 8)
	   (begin (display l) (newline))
	   (if (<= i 8)
	       (if (testa l i 1)
		   (begin (p (inverte (cons i (inverte l))) 1) (p l (+ i 1)))
		   (p l (+ i 1)))))))
		   
(define pode?
  (lambda (x1 y1 x2 y2)
    (if (= (+ x1 y1) (+ x2 y2))
	#f
	(if (= (- x1 y1) (- x2 y2))
	    #f
	    (if (= y1 y2)
		#f
		#t)))))

(define testa
  (lambda (l i pos)
    (if (null? l)
	#t
	(if (= (length l) 1)
	    (pode? 1 (car l) (+ pos 1) i)
	    (if (pode? (length l) (car (inverte l)) (+ (length l) pos) i)
		(testa (inverte (cdr (inverte l))) i (+ pos 1))
		#f)))))