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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 example illustrates how to define object constructors for a simple hierarchy of objects representing persons, students, and teachers. For simplicity, prototypes are used instead of classes. Logtalk provides a low-level, built-in predicate, create_object/4, for dynamically creating new objects. This predicate can be used to define object constructors, similar to those used in other OOP languages.

This example also illustrates how to efficiently represent objects with immutable state using parametric objects and object proxies (Prolog facts; see also the proxies example). This alternative is often a good choice when dealing with a very large number of objects due to its compact representation and/or connecting Prolog data tables with a Logtalk object hierarchies.