anchor.diff:                     (form `(prog1 ,(car rgensyms)
                               (check-type ,(car rgensyms)
                                           (or ucons null)))))
  +              (declare (inline ucons))
                 (loop for gensym in (cdr rgensyms)
                       do (setf form `(ucons ,gensym ,form)))
                 form)))))
  
positive.code:            (declare (list alist))
             (or (cdr (assoc car alist))
                 (let ((ucons (%ucons car cdr)))
                   (cond
                     ((> (length alist) 5)
                      (setf (ucons-table cdr)
                            (alist-hash-table alist :test #'eql :size 16))
                      (setf (gethash car (ucons-table cdr)) ucons))
                     (t
                      (push (cons car ucons)
                            (ucons-table cdr))))
                   ucons))))
      (if (null cdr)
          (hash-table-lookup *ucons-root-table*)
          (let ((table (ucons-table cdr)))
            (etypecase table
              (list (alist-lookup table))
              (hash-table (hash-table-lookup table)))))))
  
  (defun ulist (&rest args)
    "Return the ulist associated with the supplied arguments."
    (declare (dynamic-extent args))
    (labels ((%list (first rest)
               (if (null rest)
                   (ucons first nil)
                   (ucons first (%list (car rest) (cdr rest))))))
      (%list (first args) (rest args))))
  
  (define-compiler-macro ulist (&whole whole &rest arg-forms)
    (if (> (length arg-forms) 15)
        whole
        (let ((gensyms
                (loop for arg-form in arg-forms
                      collect (gensym "ARG"))))
          `(let* ,(mapcar #'list gensyms arg-forms)
             ,(let (form)
                (loop for gensym in (reverse gensyms)
                      do (setf form `(ucons ,gensym ,form)))
  
negative.code:    all future and past invocation of this function with the same
     arguments."
    (declare (type (or null ucons) cdr)
             (type ucons-car car)
             (values ucons))
    (flet ((hash-table-lookup (hash-table)
             (declare (hash-table hash-table))
             (or (gethash car hash-table)
  