anchor.diff:                       (open-list))   ; start the first eqnarray element
   
                  (rule (seq begin-env-open (opt "tabular" "array") "}"
  -                          (opt POS-TAB-ARG) (opt OPT_TAB_ARG) (rep* WHITESPACE))
  +                          (opt POS-TAB-ARG) (opt OPT-TAB-ARG) (rep* WHITESPACE))
                        (clean-up-quotes)
                        (let ((op (intern (string-trim "*" (latex-env-name token-text)))))
                          (if (eq op 'tabular)
  
positive.code: 
                 (rule (seq begin-env-open "displaymath" begin-env-close)
                       (clean-up-quotes)
                       (setd display-math-flag t)
                       (open-list 'display-math)
                       (goto :math))
  
  
negative.code: (defun set     (chars)          `(set     ,chars))
  (defun set-not (chars)          `(set-not ,chars))
  (defun alt     (&rest options)  `(alt     ,@options))
  (defun opt     (&rest options)  `(opt     ,@options))
  (defun rep+    (re)             `(rep+    ,re))
  (defun rep*    (re)             `(rep*    ,re))
  (defun seq     (&rest res)      `(seq     ,@res))
  (defun any     ()               `(any))
  
  (defun reject () (error "Failure reading the file."))
  
  (defmacro scan-rules ((token-variable stream-variable)
                        &body rules)
  