..
   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

   Unless required by applicable law or agreed to in writing, software
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   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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.. 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`
