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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2024 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

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% start by loading the example:

| ?- logtalk_load(self_vs_super(loader)). ...

% illustrate the differences between sending a message to "self" % and making a "super" call to call an inherited meta-predicate

% "user" defines a foo/1 predicate:

| ?- foo(X).

X = 1 ? ; X = 2 ? ; X = 3 yes

% "super" calls preserve "sender" and therefore the foo/1 predicate % is called by the meta-predicate in the context of "user":

| ?- proto::meta_super(foo, X). Execution context for the parent object meta/2 meta-predicate: self: proto this: parent sender: user

X = 1 ? ; X = 2 ? ; X = 3 yes

% messages to "self" reset "sender" and therefore the foo/1 predicate % is called in the context of "proto", hence the existence error:

| ?- proto::meta_self(foo, X). Execution context for the parent object meta/2 meta-predicate: self: proto this: parent sender: proto

uncaught exception: error(existence_error(procedure,foo/1),logtalk(call(foo(_307)),c(proto,proto,r(user,proto,c(user,user,r(user,proto,[],[])),[]))))