anchor.diff:    (declare (type (or null ucons) cdr)
              (type ucar car))
     (let ((alist (and cdr
  -                    (listp (ucons-table cdr))
  -                    (ucons-table cdr))))
  +                    (listp (utable cdr))
  +                    (utable cdr))))
       (the ucons
            (or
             (loop for cons of-type (cons ucar ulist) in alist
  
positive.code:         (t
           (write-string "[" stream)
           (loop while ulist do
             (write (ucons-car ulist) :stream stream)
             (when (ucons-cdr ulist)
               (write-string " " stream))
             (setf ulist (ucons-cdr ulist)))
           (write-string "]" stream))))
  
negative.code: (uiop:define-package :petalisp/utilities/ucons
    (:use :closer-common-lisp :alexandria)
    (:export
     #:ucons
     #:ucar
     #:ucdr
     #:ulist
     #:ulist*
     #:ulength
     #:ulist-shallow-copy
     #:ulist-deep-copy
     #:map-ulist
     #:do-ulist))
  
  