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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.

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This example illustrates how to use a complementing category to define what is often described as an "around method". It uses the experimental @/1 goal annotation that allows calling the original predicate definition (in the patched object) from its new definition in the category. This annotation allows the new definition to call some goals, followed by a call to the original definition, followed by calls to some more goals, hence the name "around method".