anchor.diff:               generalized boolean.
       key --- a designator for a function of one parameter.
   
  -   It first removes all the objects that is equal to OBJ in PLACE and then
  -   PUSHes the OBJ into PLACE. Equality of objects are checked with the value
  -   that is acquired by applying the function specified to KEY keyword parameter
  -   and tested by the function specified to TEST keyword parameter. Defaults for
  -   KEY and TEST are #'IDENTITY and #'EQL, respectively.
  -    The KEY function, if supplied, is applied to OBJ too and the result object
  -   is used to the equality check, likewise PUSHNEW and ADJOIN.
  +   It first removes all the objects that is equal to OBJ in PLACE and
  +   then PUSHes the OBJ into PLACE. Equality of objects are checked with
  +   the value that is acquired by applying the function specified to KEY
  +   keyword parameter and tested by the function specified to TEST
  +   keyword parameter. Defaults for KEY and TEST are #'IDENTITY and
  +   #'EQL, respectively.  The KEY function, if supplied, is applied to
  +   OBJ too and the result object is used to the equality check, likewise
  +   PUSHNEW and ADJOIN.
      "
     (once-only (obj)
       `(progn
  
positive.code: ;;; I was wrong. It seems convinient to have the default method.
  (defmacro dlambda (&body keyword-args-body)
    (with-gensyms (args)
    `(lambda (&rest ,args)
         (case (car ,args)
           ,@(mapcar
               (lambda (x)
                   `(,(if (eq (car x) t)
                        t
                        (list (car x)))
                      (apply (lambda ,@(cdr x))
                             ,(if (eq (car x) t)
                                args
                                `(cdr ,args)))))
               keyword-args-body)))))
  
  ;;; LREC function and ALREC macro
  
negative.code:   (labels ((rec (lst)
               (if lst
                 (mapcan (lambda (x)
                           (let ((head (car lst)))
                             (if (funcall forkp head)
                               (list (cons head x) x)
                               (list (cons head x)))))
                         (rec (cdr lst)))
                 (list ()))))
      (rec lst)))
  