anchor.diff:      (rest (rec seq (list -1)))))
   
   ;;; POSITINO-IF-LIST function;{{{
  -;;; This function makes the list constructs from the position of elements in "lst" which sufferes "pred".
  +;;; This function makes the list constructs from the position of
  +;;; elements in "lst" which satisfies "pred".
   ;;; 16th Nov, 2010
  -;;; This function must be implemented based on POSITION-IF.
  -;;; Thus I change the order of "pred" and "lst". (I've already been familiar with this order, in any way);}}}
  +;;; This function must be implemented based on POSITION-IF.  Thus I
  +;;; change the order of "pred" and "lst". (I've already been familiar
  +;;; with this order, in any way);}}}
   (defun position-if-list (pred seq &key (key #'identity))
     (if (eql (type-of seq) 'cons)
       (let ((dummy (gensym)))
  
positive.code: ;;; This function behaves same as GROUP, but works for any sequence.
  (defun seqgroup (seq n)
    (labels ((rec (s a)
                  (if (/= 0 (length s))
                    (rec (subseq s (min n (length s))) (cons (subseq s 0 (min n (length s))) a))
                    (nreverse a))))
      (rec seq nil)))
  
  ;;; COMPOSE function;{{{
  
negative.code: ;;;    (remove nil (mapcar (lambda (x idx) (if (pred (funcall key x)) idx nil)) lst (iota (length lst))))))
  ;;;
  ;;; 22 Dec, 2010 chiku
  ;;; I revised the definition. This version works not only for list but
  ;;; also for general sequence.
  (defun position-list (item seq &key (key #'identity) (test #'eql))
    (labels ((rec (s acc)
                  (let ((pos (position item s :key key :test test)))
  