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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 shows the use of meta-predicates in Logtalk. Meta-predicates are predicates whose head includes arguments that will be called as goals in the body of the predicate definition.

This example defines the following objects:

• company usage example of the map_reduce/5 meta-predicate
• fibonacci example of calculating Fibonacci numbers using the fold_left/4 meta-predicate
• sort(_) this is a parametric object containing a method that implements the quicksort sorting algorithm; the parameter is interpreted as the type of the elements being sorted
• tracer this object implements a meta-predicate that is used by sort(_) to trace the sorting algorithm steps
• metapreds, descendant, and test objects used for illustrating the use of closures as meta-arguments
• predicates object defining some predicates for testing meta-predicates defined in the Logtalk library
• grammar object illustrating using phrase/2 as a meta-predicate meta-argument