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   Copyright 1998-2021 Paulo Moura <pmoura@logtalk.org>
   SPDX-License-Identifier: Apache-2.0

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.. index:: pair: threaded/0; Directive
.. _directives_threaded_0:

``threaded/0``
==============

Description
-----------

::

   threaded

Declares that an object supports threaded engines, concurrent calls,
and asynchronous messages. Any object containing calls to the built-in
multi-threading predicates (or importing a category that contains such
calls) must include this directive.

This directive results in the automatic creation and set up of an object
message queue when the object is loaded or created at runtime. Object
message queues are used for exchanging thread notifications and for
storing concurrent goal solutions and replies to the multi-threading
calls made within the object. The message queue for the
:ref:`user <objects_user>` pseudo-object is automatically created at
Logtalk startup (provided that multi-threading programming is supported
and enabled for the chosen :term:`backend Prolog compiler`).

Template and modes
------------------

::

   threaded

Examples
--------

::

   :- threaded.

.. seealso::

   :ref:`directives_synchronized_1`,
   :ref:`predicates_object_property_2`
