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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.

% start by loading the design pattern sample implementations:

| ?- logtalk_load(design_patterns('behavioral/visitor/loader')). ...

% print all car components by calling the visitor/1 meta-predicate % with a closure (use a lambda expression so that we can print a % new-line after each component):

| ?- sedan::visitor([Component]>>(write(Component),nl)).

engine(diesel) wheel(front_left) wheel(front_right) wheel(rear_right) wheel(rear_left) wheel(left_door) wheel(right_door) body(station_wagon) yes

% use the visitor meta-predicate that is added using hot-patching:

| ?- sedan::alt_visitor([Component]>>(write(Component),nl)).

engine(diesel) wheel(front_left) wheel(front_right) wheel(rear_right) wheel(rear_left) wheel(left_door) wheel(right_door) body(station_wagon) yes

% use the standard setof/3 meta-predicate to construct a list of % all component types:

| ?- setof( Type, Component^Arity^(sedan::component(Component), functor(Component,Type,Arity)), Types ).

Types = [body, engine, wheel] yes