source: branches/f4grobner/copy.lisp@ 3451

;;; -*-  mode: lisp; package: maxima; syntax: common-lisp; base: 10 -*- 
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;;;  copyright (c) 1999, 2002, 2009, 2015 marek rychlik <rychlik@u.arizona.edu>          
;;;                                                                              
;;;  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.                                         
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;;;  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.                                
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;;;  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.  
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(defpackage "COPY"
  (:use :cl)
  (:export "COPY-INSTANCE")
  (:shadowing-import-from 
   #+openmcl-native-threads #:ccl 
   #+cmu #:pcl
   #+sbcl #:sb-pcl 
   #+lispworks #:hcl 
   #+allegro #:mop 
   #+clisp #:clos
   #:class-slots #:slot-definition-name)
  (:documentation
   "Implements ring operations.  These are all operations that are
performed on the coefficients by the package, and thus the coefficient
ring can be changed by merely redefining these operations."))

(in-package :copy)


;; Source: http://stackoverflow.com/questions/11067899/is-there-a-generic-method-for-cloning-clos-objects
;; NOTE: This is a shallow copy. Add an around method for classes which need deep copy of the slots.
(defgeneric copy-instance (object &rest initargs &key &allow-other-keys)
  (:method ((object cons) &rest initargs &key &allow-other-keys) 
    (declare (ignore initargs))
    (copy-seq object))
  (:documentation "Makes and returns a shallow copy of OBJECT.

  An uninitialized object of the same class as OBJECT is allocated by
  calling ALLOCATE-INSTANCE.  For all slots returned by
  CLASS-SLOTS, the returned object has the
  same slot values and slot-unbound status as OBJECT.

  REINITIALIZE-INSTANCE is called to update the copy with INITARGS.")
  (:method ((object standard-object) &rest initargs &key &allow-other-keys)
    (let* ((class (class-of object))
           (copy (allocate-instance class)))
      (dolist (slot-name (mapcar #'slot-definition-name (class-slots class)))
        (when (slot-boundp object slot-name)
          (setf (slot-value copy slot-name)
                (slot-value object slot-name))))
      (apply #'reinitialize-instance copy initargs))))