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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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.. rst-class:: align-right

built-in predicate

.. index:: pair: create_logtalk_flag/3; Built-in predicate .. _predicates_create_logtalk_flag_3:

create_logtalk_flag/3

Description

::

create_logtalk_flag(Flag, Value, Options)

Creates a new Logtalk flag and sets its default value. User-defined flags can be queried and set in the same way as predefined flags by using, respectively, the :ref:predicates_current_logtalk_flag_2 and :ref:predicates_set_logtalk_flag_2 built-in predicates. For a description of the predefined compiler flags, please see the :ref:programming_flags section in the User Manual.

This predicate is based on the specification of the SWI-Prolog create_prolog_flag/3 built-in predicate and supports the same options: access(Access), where Access can be either read_write (the default) or read_only; keep(Keep), where Keep can be either false (the default) or true, for deciding if an existing definition of the flag should be kept or replaced by the new one; and type(Type) for specifying the type of the flag, which can be boolean, atom, integer, float, or term (which only restricts the flag value to ground terms). When the type/1 option is not specified, the type of the flag is inferred from its initial value.

Modes and number of proofs

::

create_logtalk_flag(+atom, +ground, +list(ground)) - one

Errors

| Flag is a variable: | instantiation_error | Value is not a ground term: | instantiation_error | Options is not a ground term: | instantiation_error | Flag is neither a variable nor an atom: | type_error(atom, Flag) | Options is neither a variable nor a list: | type_error(atom, Flag) | Value is not a valid value for flag Flag: | domain_error(flag_value, Flag + Value) | Flag is a system-defined flag: | permission_error(modify, flag, Flag) | An element Option of the list Options is not a valid option | domain_error(flag_option,Option) | The list Options contains a type(Type) option and Value is not of type Type | type_error(Type, Value)

Examples

::

% create a new boolean flag with default value set to false: | ?- create_logtalk_flag(pretty_print_blobs, false, []).

.. seealso::

:ref:predicates_current_logtalk_flag_2, :ref:predicates_set_logtalk_flag_2