X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/lisp/blobdiff_plain/f4df6cf47a48e12e3e18d3d2a6285147f6f1c147..4b6a6387f82f1bb2058d642dcbd7040ce2578cea:/mdw-mop.lisp

diff --git a/mdw-mop.lisp b/mdw-mop.lisp
index e88ff12..a669490 100644
--- a/mdw-mop.lisp
+++ b/mdw-mop.lisp
@@ -29,6 +29,7 @@
 (defpackage #:mdw.mop
   (:use #:common-lisp #:mdw.base #+cmu #:pcl)
   (:export #:compatible-class
+	   #:copy-instance #:copy-instance-using-class
 	   #:initargs-for-effective-slot #:make-effective-slot
 	   #:filtered-slot-class-mixin
 	     #:filtered-direct-slot-definition
@@ -62,6 +63,27 @@ (defmethod validate-superclass
     ((sub standard-class) (super compatible-class))
   (eq (class-of sub) (find-class 'standard-class)))
 
+;;;--------------------------------------------------------------------------
+;;; Copying instances.
+
+(defgeneric copy-instance-using-class (class object &rest initargs)
+  (:documentation
+   "Does the donkey-work behind copy-instance."))
+
+(defmethod copy-instance-using-class
+    ((class standard-class) object &rest initargs)
+  (let ((new (apply #'allocate-instance class initargs)))
+    (dolist (slot (class-slots class))
+      (setf (slot-value-using-class class new slot)
+	    (slot-value-using-class class object slot)))
+    (apply #'shared-initialize new nil initargs)
+    new))
+
+(defun copy-instance (object &rest initargs)
+  "Make a copy of OBJECT, modifying it by setting slots as requested by
+   INITARGS."
+  (apply #'copy-instance-using-class (class-of object) object initargs))
+
 ;;;--------------------------------------------------------------------------
 ;;; Utilities for messing with slot options.