;;; lib/obj/id.lisp --- IDs

 (in-package :obj/id)

 (defclass id ()

   ((id :initarg :id :initform 0 :accessor id :type fixnum)))

 (defgeneric reset-id (obj)

   (:documentation "Reset the id slot of SELF to 0.")

   (:method ((obj standard-object)) (setf (id obj) 0))

   (:method ((obj t)) 0))

 (defgeneric update-id (obj)

   (:documentation "Update the id slot of SELF.")

   (:method ((obj standard-object)) (setf (id obj) (hash-object obj)))

   (:method ((obj t)) (hash-object obj)))

 (defgeneric make-id (kind)

   (:documentation "Allocate a new ID object of a specified KIND.")

   (:method ((kind (eql nil)))

     (declare (ignore kind))

     (make-instance 'id))

   (:method ((kind (eql t)))

     (declare (ignore kind))

     (make-instance 'id :id most-positive-fixnum)))

 (defmethod print-object ((obj id) stream)

   (print-unreadable-object (obj stream :type "ID")

     (format stream "~A" (id obj))))

 (defclass id-factory () ())