数独の問題を生成したい

sudoku_gen.lisp

(defun generate-numseq (size)
  "指定したサイズの数列を作る"
  (let ((gen-list '()))
    (labels ((gen (current num-list)
               (if (< current size)
                   (loop for x from 1 to size
                      if (not (member x num-list))
                         do (gen (1+ current) (cons x num-list)))
                   (push num-list gen-list))))
      (loop for x from 1 to size
           do (gen 1 (list x))))
    gen-list))

(defun numseq-sort (seq)
  "数列をソートする"
  (sort seq #'(lambda (a b)
                (loop for a1 in a
                      for b1 in b
                     if (< a1 b1)
                        do (return t)
                     if (> a1 b1)
                        do (return nil)
                     finally
                        (return t)))))

(defun duplicatep (seq)
  "数列に重複があるかを判定する"
  (loop for x in seq
       if (member x (cdr (member x seq)))
          do (return t)
       finally
          (return nil)))

(defun column-uniqp (seq)
  "列がユニークになっているかを判定する
seq: ((1 2 3) (2 3 1)) みたいなものを想定"
  (labels ((generate-seq (n)
             (loop for numseq in seq
                  collect (nth n numseq))))
    (loop for x from 0 to (1- (length (car seq)))
         if (duplicatep (generate-seq x))
            do (return nil)
         finally
            (return t))))