.. 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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.. rst-class:: align-right

built-in predicate

.. index:: pair: implements_protocol/2-3; Built-in predicate .. _predicates_implements_protocol_2_3:

implements_protocol/2-3

Description

::

implements_protocol(Object, Protocol) implements_protocol(Category, Protocol)

implements_protocol(Object, Protocol, Scope) implements_protocol(Category, Protocol, Scope)

Enumerates, by backtracking, all pairs of entities such that an object or a category implements a protocol. The relation scope is represented by the atoms public, protected, and private. This predicate only returns direct implementation relations. For a transitive closure, see the :ref:predicates_conforms_to_protocol_2_3 predicate.

Modes and number of proofs

::

implements_protocol(?object_identifier, ?protocol_identifier) - zero_or_more implements_protocol(?category_identifier, ?protocol_identifier) - zero_or_more

implements_protocol(?object_identifier, ?protocol_identifier, ?scope) - zero_or_more implements_protocol(?category_identifier, ?protocol_identifier, ?scope) - zero_or_more

Errors

| Object is neither a variable nor a valid object identifier: | type_error(object_identifier, Object) | Category is neither a variable nor a valid category identifier: | type_error(category_identifier, Category) | Protocol is neither a variable nor a valid protocol identifier: | type_error(protocol_identifier, Protocol) | Scope is neither a variable nor an atom: | type_error(atom, Scope) | Scope is an atom but an invalid entity scope: | domain_error(scope, Scope)

Examples

::

% check that the list object implements the listp protocol: | ?- implements_protocol(list, listp).

% check that the list object publicly implements the listp protocol: | ?- implements_protocol(list, listp, public).

% enumerate only objects that implement the listp protocol: | ?- current_object(Object), implements_protocol(Object, listp).

% enumerate only categories that implement the serialization protocol: | ?- current_category(Category), implements_protocol(Category, serialization).

.. seealso::

:ref:predicates_current_object_1, :ref:predicates_current_protocol_1, :ref:predicates_current_category_1, :ref:predicates_conforms_to_protocol_2_3