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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.

This directory contains sample implementations of design patterns, originating from the OOP and AI communities. The OOP patterns are split between behavioral, creational, and structural patterns. Most of them are described in the book:

Design Patterns - Elements of Reusable Object-Oriented Software Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides Addison-Wesley Professional Computing Series ISBN 0-201-63361-2

If you don't have access to a copy of the book, see freely available Internet resources such as:

https://en.wikipedia.org/wiki/Design_Patterns

Note that the design patterns described in the book (aka the "Gang of Four" or "GoF" book) assume, in general, a class-based object-oriented language. Logtalk features, notably the support for prototypes, categories, parametric entities, and event-driven programming, allow alternative, and sometimes preferable, solutions for some of the design patterns. When applicable, the design patterns are generalized to apply to both classes and prototypes.

It is also important to note that basic Logtalk (and Prolog) features, for example, meta-predicates and multifile predicates, can complement or provide alternative solutions for the problems targeted by some of the patterns. Thus, these sample implementations of design patterns should be taken as examples to be mined for ideas rather than canonical advice on how to solve the described problems.

Given that Logtalk is a declarative language, the creational patterns are usually reinterpreted as structural patterns as objects, including those playing the role of instances, are often defined in source files instead of being forcefully dynamically created.

The descriptions of the design patterns are citations from the book when applicable.