source: branches/streams/abcl/src/org/armedbear/lisp/print-unreadable-object.lisp

;;; print-unreadable-object.lisp
;;;
;;; Copyright (C) 2003-2005 Peter Graves
;;; $Id: print-unreadable-object.lisp 11391 2008-11-15 22:38:34Z vvoutilainen $
;;;
;;; This program is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License
;;; as published by the Free Software Foundation; either version 2
;;; of the License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program; if not, write to the Free Software
;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
;;;
;;; As a special exception, the copyright holders of this library give you
;;; permission to link this library with independent modules to produce an
;;; executable, regardless of the license terms of these independent
;;; modules, and to copy and distribute the resulting executable under
;;; terms of your choice, provided that you also meet, for each linked
;;; independent module, the terms and conditions of the license of that
;;; module.  An independent module is a module which is not derived from
;;; or based on this library.  If you modify this library, you may extend
;;; this exception to your version of the library, but you are not
;;; obligated to do so.  If you do not wish to do so, delete this
;;; exception statement from your version.

;;; Adapted from SBCL.

(in-package #:system)

(defun %print-unreadable-object (object stream type identity body)
  (setf stream (out-synonym-of stream))
  (when *print-readably*
    (error 'print-not-readable :object object))
  (format stream "#<")
  (when type
    (format stream "~S" (type-of object))
      (format stream " "))
  (when body
    (funcall body))
  (when identity
    (when (or body (not type))
      (format stream " "))
    (format stream "{~X}" (identity-hash-code object)))
  (format stream ">")
  nil)

(defmacro print-unreadable-object ((object stream &key type identity) &body body)
  `(%print-unreadable-object ,object ,stream ,type ,identity
           ,(if body
          `(lambda () ,@body)
          nil)))