..
   This file is part of Logtalk <https://logtalk.org/>  
   Copyright 1998-2023 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 predicate**

.. index:: pair: set_logtalk_flag/2; Built-in predicate
.. _predicates_set_logtalk_flag_2:

``set_logtalk_flag/2``
======================

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

::

   set_logtalk_flag(Flag, Value)

Sets global, default, flag values. For local flag scope, use the
corresponding :ref:`directives_set_logtalk_flag_2` directive. To set a
global flag value when compiling and loading a source file, wrap the calls
to this built-in predicate with an :ref:`directives_initialization_1`
directive. For a description of the predefined compiler flags, please see
the :ref:`programming_flags` section in the User Manual.

Modes and number of proofs
--------------------------

::

   set_logtalk_flag(+atom, +nonvar) - one

Errors
------

| ``Flag`` is a variable:
|     ``instantiation_error``
| ``Value`` is a variable:
|     ``instantiation_error``
| ``Flag`` is neither a variable nor an atom:
|     ``type_error(atom, Flag)``
| ``Flag`` is an atom but an invalid flag:
|     ``domain_error(flag, Flag)``
| ``Value`` is not a valid value for flag ``Flag``:
|     ``domain_error(flag_value, Flag + Value)``
| ``Flag`` is a read-only flag:
|     ``permission_error(modify, flag, Flag)``

Examples
--------

::

   % turn off globally and by default the compiler
   % unknown entities warnings:
   | ?- set_logtalk_flag(unknown_entities, silent).

.. seealso::

   :ref:`predicates_create_logtalk_flag_3`,
   :ref:`predicates_current_logtalk_flag_2`
