anchor.diff:                 ((a1 a2 . rest) `(/ (%div ,a1 ,a2) ,@rest))))))
   
   (defun built-in-macro-expander (name)
  -  (or (getf +built-in-macroes+ name)
  +  (or (getf +built-in-macros+ name)
         (error "invalid macro name: ~A" name)))
   
   
  
positive.code:       (error (format nil "invalid operator: ~A" op))))
  
  
  ;;; built-in macroes
  ;;;   <built-in-macroes> ::= plist { <macro-name> => <macro-expander> }
  
  (defvar +built-in-macroes+
    (list '+ (lambda (args)
               (match args
                 (() 0)
  
negative.code: 
  (defun built-in-macro-p (form)
    (match form
      ((op . _) (and (getf +built-in-macros+ op) t))
      (_ nil)))
  
  (defun user-macro-p (form def)
  