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This file is part of Logtalk <https://logtalk.org/>  
Copyright 1998-2022 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.
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    http://www.apache.org/licenses/LICENSE-2.0

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Design pattern:
	Abstract Factory

Description:
	"Provide an interface for creating families of related or dependent
	objects without specifying their concrete classes."

This pattern can be used with both classes and prototypes.

The sample implementation uses prototypes for simplicity with categories
playing a similar role to abstract classes.
