..
   This file is part of Logtalk <https://logtalk.org/>  
   Copyright 1998-2021 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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   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
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.. index:: pair: dynamic/1; Directive
.. _directives_dynamic_1:

``dynamic/1``
=============

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

::

   dynamic(Name/Arity)
   dynamic((Name/Arity, ...))
   dynamic([Name/Arity, ...])

   dynamic(Entity::Name/Arity)
   dynamic((Entity::Name/Arity, ...))
   dynamic([Entity::Name/Arity, ...])

   dynamic(Module:Name/Arity)
   dynamic((Module:Name/Arity, ...))
   dynamic([Module:Name/Arity, ...])

   dynamic(Name//Arity)
   dynamic((Name//Arity, ...))
   dynamic([Name//Arity, ...])

   dynamic(Entity::Name//Arity)
   dynamic((Entity::Name//Arity, ...))
   dynamic([Entity::Name//Arity, ...])

   dynamic(Module:Name//Arity)
   dynamic((Module:Name//Arity, ...))
   dynamic([Module:Name//Arity, ...])

Declares dynamic predicates and dynamic grammar rule non-terminals. Note
that an object can be static and have both static and dynamic
predicates/non-terminals. When the dynamic predicates are local to an object,
declaring them also as :ref:`private predicates <directives_private_1>`
allows the Logtalk compiler to generate optimized code for asserting and
retracting predicate clauses. Categories can also contain dynamic predicate
directives but cannot contain clauses for dynamic predicates.

The predicate indicators (or non-terminal indicators) can be explicitly
qualified with an object, category, or module identifier when the predicates
(or non-terminals) are also declared :ref:`multifile <directives_multifile_1>`.

Note that dynamic predicates cannot be declared synchronized (when
necessary, declare the predicates updating the dynamic predicates as
:ref:`synchronized <directives_synchronized_1>`).

.. warning::

   Some backend Prolog compilers declare ``dynamic`` as an operator
   for a lighter syntax. But this makes the code non-portable and is
   a practice best avoided.

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

::

   dynamic(+qualified_predicate_indicator_term)
   dynamic(+qualified_non_terminal_indicator_term)

Examples
--------

::

   :- dynamic(counter/1).

   :- dynamic((lives/2, works/2)).

   :- dynamic([db/4, key/2, file/3]).

.. seealso::

   :ref:`directives_dynamic_0`,
   :ref:`methods_predicate_property_2`
