anchor.diff:  
   (defclass configuration-option-type ()
     ((default :initarg :default
  +     :initform nil
        :accessor default
        :documentation "The default value if there is one")))
   
  
positive.code: 
  (defmacro one-of (options &rest args)
    `(make-instance 'one-of-configuration-option-type
  		  :options (list (mapcar #'make-configuration-type-item ',options))
  		  ,@args))
  
  (defmacro some-of (options &rest args)
  
negative.code:   ((name :initarg :name
  	 :accessor name
  	 :initform (error "Provide the type-item name"))
     (title :initarg :title
  	  :accessor title
  	  :initform (error "Provide the type-item title"))
     (configuration :initarg :configuration
  