anchor.diff:  (define-rule alphanumeric (alphanumericp character))
   
   (define-rule simple-name (and alpha-char (* (or alphanumeric #\_ )))
  -  (:concat t))
  +  (:text t))
     
   (define-rule dotref (or (and #\. simple-name)
                       (and "['" simple-name "']"))
  
positive.code:     result))
  
  (defun simplify-code (code)
    (concat-neighboring-strings
     (replace-substition
      (trim-whitespace
       code))))
  
negative.code:                     #\. (* (digit-char-p character))
                      (? (and (or "e" "E" ) (? (or "-" "+")) (* (digit-char-p character)))))
    (:lambda (list)
      (parse-number:parse-number (text list))))
  
  (define-rule number (or float integer))
  
  