anchor.diff:  (defun ulength (ulist)
     "Return the length of the given ulist."
     (declare (ulist ulist) (optimize speed))
  -  (iterate (for elt in-ulist ulist)
  -           (counting t)))
  +  (loop counting t
  +        while (setf ulist (ucdr ulist))))
   
   (defun ulist-shallow-copy (ulist)
     "Return a list of the elements of ULIST."
  
positive.code: ;;; © 2016-2018 Marco Heisig - licensed under AGPLv3, see the file COPYING
  
  (uiop:define-package :petalisp/utilities/ucons
    (:use :closer-common-lisp :alexandria :iterate)
    (:export
     #:ucons #:ucar #:ucdr #:ucaar #:ucadr #:ucdar #:ucddr
     #:ulist #:ulist* #:ulength
  
negative.code:              (declare (ignorable ,var))
               ,result))))))
  
  (declaim (inline map-ulist))
  (defun map-ulist (function &rest sequences)
    (declare (function function))
  