.. 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

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.

.. rst-class:: align-right

built-in method

.. index:: pair: this/1; Built-in method .. _methods_this_1:

this/1

Description

::

this(This)

Unifies its argument with the identifier of the object for which the predicate clause whose body is being executed is defined (or the object importing the category that contains the predicate clause). This private method is implemented as a unification between its argument and the corresponding implicit execution-context argument in the predicate clause making the call. This unification occurs at the clause head when the argument is not bound at compile time (the most common case). This method is useful for avoiding hard-coding references to an object identifier or for retrieving all object parameters with a single call when using parametric objects.

Modes and number of proofs

::

this(?object_identifier) - zero_or_one

Errors

(none)

Examples

::

% after compilation, the write/1 call will % be the first goal on the clause body test :- this(This), write('Using a predicate clause contained in '), writeq(This), nl.

.. seealso::

:ref:methods_context_1, :ref:methods_parameter_2, :ref:methods_self_1, :ref:methods_sender_1