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+;;; installed-scm-file
+
+;;;; Copyright (C) 1999, 2001, 2006, 2009, 2015 Free Software Foundation, Inc.
+;;;; Copyright (C) 1993-1998 Erick Gallesio - I3S-CNRS/ESSI <eg@unice.fr>
+;;;;
+;;;; This library is free software; you can redistribute it and/or
+;;;; modify it under the terms of the GNU Lesser General Public
+;;;; License as published by the Free Software Foundation; either
+;;;; version 3 of the License, or (at your option) any later version.
+;;;;
+;;;; This library 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
+;;;; Lesser General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU Lesser General Public
+;;;; License along with this library; if not, write to the Free Software
+;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+;;;;
+
+
+;;;;
+;;;; This file was based upon active-slot.stklos from the STk distribution
+;;;; version 4.0.1 by Erick Gallesio <eg@unice.fr>.
+;;;;
+
+(define-module (oop goops active-slot)
+ :use-module (oop goops internal)
+ :export (<active-class>))
+
+(define-class <active-class> (<class>))
+
+(define-method (compute-get-n-set (class <active-class>) slot)
+ (if (eq? (slot-definition-allocation slot) #:active)
+ (let* ((index (slot-ref class 'nfields))
+ (s (slot-definition-options slot))
+ (before-ref (get-keyword #:before-slot-ref s #f))
+ (after-ref (get-keyword #:after-slot-ref s #f))
+ (before-set! (get-keyword #:before-slot-set! s #f))
+ (after-set! (get-keyword #:after-slot-set! s #f))
+ (unbound *unbound*))
+ (slot-set! class 'nfields (+ index 1))
+ (list (lambda (o)
+ (if before-ref
+ (if (before-ref o)
+ (let ((res (struct-ref o index)))
+ (and after-ref (not (eqv? res unbound)) (after-ref o))
+ res)
+ *unbound*)
+ (let ((res (struct-ref o index)))
+ (and after-ref (not (eqv? res unbound)) (after-ref o))
+ res)))
+
+ (lambda (o v)
+ (if before-set!
+ (if (before-set! o v)
+ (begin
+ (struct-set! o index v)
+ (and after-set! (after-set! o v))))
+ (begin
+ (struct-set! o index v)
+ (and after-set! (after-set! o v)))))))
+ (next-method)))