anchor.diff:  
     (statements
      (statements statement)
  -   nil)
  +   expression)
   
     (statement
  -   ())
  +   while-statement
  +   iteration-statement
  +   )
   
     (expression
      (expression + expression #'infix-to-prefix)
  
positive.code: (in-package :jsimple-parser)
  
  (defvar *lexer-position* 0)
  
negative.code: 	       (values 'id (copy-seq buffer)))
  	   (incf *lexer-position*)
             (vector-push-extend c buffer))))
        ;; TODO: Handle string!
        ()
        (t (error 'lexer-error c *lexer-position*)))))
  
  ;;; Since Lisp is written with prefix operators, we have to convert it into
  