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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2023 Paulo Moura <pmoura@logtalk.org> SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

To load this example and for sample queries, please see the SCRIPT.txt file.

This folder contains an example that shows how to implement class variables as defined in Smalltalk. The name shared instance variables is however much more accurate. In systems like Logtalk, which enables the use of explicit metaclasses, true class variables are just the class (as an object) own instance variables!

This example defines a root class, root and three instances, instance1, instance2, and instance3. The root class defines a shared instance variable (using a dynamic predicate) and the setter and getter methods which implement the variable sharing behavior.