anchor.diff:                                             (x x x x 6 x x x 1)
                                              (x 6 8 x x 9 x 5 7)))
   
  -
  -
  -
  -
  -
  -(dolist (sudoku (list
  -                 *royco-minut-soup*
  -                 *metrofrance/694/moyen*
  -                 *20-minutes/1499/facile*
  -                 *20-minutes/1501/difficile*
  -                 *20-minutes/1502/expert*
  -                 *metrofrance/696/facile*
  -                 *20-minutes/1505/moyen*
  -                 ))
  -  (multiple-value-bind (solutions tries) (sudoku-solver sudoku)
  -    (terpri)
  -    (sudoku-print sudoku)
  -    (format t "  has ~D solution~:*~P,~%  found in ~D tries.~2%" (length solutions) tries)
  +(defparameter *metrofrance/700/moyen* #2A ((1 9 x 8 3 7 x x x)
  +                                           (7 5 x x 2 x x x x)
  +                                           (4 x x x 9 x x x 7)
  +                                           (x 3 4 x x x x x 9)
  +                                           (9 x 7 x x x 6 x 2)
  +                                           (8 x x x x x 4 7 x)
  +                                           (3 x x x 1 x x x 6)
  +                                           (x x x x 6 x x 3 4)
  +                                           (x x x 9 4 3 x 2 8)))
  +
  +
  +
  +
  +
  +
  +(dolist (sudoku '(
  +                  *20-minutes/1499/facile*
  +                  *20-minutes/1501/difficile*
  +                  *20-minutes/1502/expert*
  +                  *20-minutes/1505/moyen*
  +                  *20-minutes/1506/facile*
  +                  *metrofrance/694/moyen*
  +                  *metrofrance/696/facile*
  +                  *metrofrance/700/moyen*
  +                  *royco-minut-soup*
  +                  ))
  +  (multiple-value-bind (solutions tries) (sudoku-solver (symbol-value sudoku))
  +    (terpri) (print sudoku) (terpri)
  +    
  +    (sudoku-print (symbol-value sudoku))
  +    (format t "  ~A (with ~D empty slots)~%  has ~D solution~:*~P,~%  found in ~D tries.~2%"
  +            sudoku (sudoku-count-empty-slots (symbol-value sudoku))
  +            (length solutions) tries)
       (map nil 'sudoku-print solutions)))
   
   
  
positive.code:   sudoku)
  
  
  ;;----------------------------------------------------------------------
  
  (defparameter *royco-minut-soup* #2A((x x x 8 x 4 2 x x)
  
negative.code:                                           (8 x x x x 2 x 9 x)
                                            (x x 4 5 7 x 3 x 2)))
  
  (defparameter *20-minutes/1506/facile* #2A((3 x 5 8 4 x x x 1)
                                             (7 x x x x x 5 x x)
                                             (4 x 1 6 3 x 8 x x)
                                             (8 x x x x x 3 5 7)
                                             (x x 3 x x x 9 x x)
                                             (6 1 9 x x x x x 8)
                                             (x x 8 x 6 2 4 x 5)
                                             (x x 7 x x x x x 2)
                                             (2 x x x 5 1 7 x 3)))
  
  (defparameter *metrofrance/694/moyen* #2A((x x 1 2 x x x x 8)
                                            (x x x x 5 1 x x 3)
                                            (x 7 x x x x 6 x 1)
  