anchor.diff:  
   Without initialization.
   
  +Convenient copier.
  +
  +    (defun birthday (person)
  +      (copy-person person :age (1+ (person-age person))))
  +
  +    (birthday *)
  +    => #.(PERSON \"Common Lisp\" 34)
  +
  +Load form.
  +
   Printer.
   
       (defconstructor person
  
positive.code: some or all of its slots." type-name)
           (,type-name ,@slot-names))
  
         (defmethod constructor-len ((x ,type-name))
           ,(length readers))
  
  
negative.code: 
      (person \"Common Lisp\" 33)
      => #.(PERSON \"Common Lisp\" 33)
  
  Pattern matching.
  
  