anchor.diff:  (defun compute-all-lookaheads (kernels grammar)
     "Compute the LR(1) lookaheads for all the collections in KERNELS."
     (declare (list kernels) (type grammar grammar))
  -  (setf (item-lookaheads (kernel-item (car kernels))) (list 'eof))
  +  (setf (item-lookaheads (kernel-item (car kernels))) (list 'yacc-eof-symbol))
     (let ((previously-changed kernels) (changed '())
           (propagate-only nil))
       (declare (optimize (speed 3) (space 0)))
  
positive.code: (defpackage #:yacc
    (:use #:common-lisp)
    (:export #:make-production #:make-grammar #:make-parser #:parse-with-lexer
             #:define-grammar #:define-parser
             #:yacc-parse-error #:yacc-parse-error-terminal
             #:yacc-parse-error-value #:yacc-parse-error-expected-terminals)
    #+CMU
  
negative.code:       (let ((stack (list 0)) symbol value)
          (flet ((next-symbol ()
                   (multiple-value-bind (s v) (funcall lexer)
                     (setq symbol (or s 'yacc-eof-symbol) value v))))
            (next-symbol)
            (loop
             (let* ((state (car stack))
  