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Pack logtalk -- logtalk-3.85.0/manuals/_sources/refman/methods/existence_error_2.rst.txt

.. This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2024 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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.. rst-class:: align-right

built-in method

.. index:: pair: existence_error/2; Built-in method .. _methods_existence_error_2:

existence_error/2

Description

::

existence_error(Thing, Culprit)

Throws an existence error. Used when the subject of an operation does not exist. This built-in method is declared private and thus cannot be used as a message to an object. Calling this predicate is equivalent to the following sequence of goals:

::

..., context(Context), throw(error(existence_error(Thing,Culprit), Context)).

This allows the user to generate errors in the same format used by the runtime.

Possible values for Thing include:

  • predicate
  • non_terminal
  • predicate_declaration
  • procedure
  • source_sink
  • stream
  • object
  • protocol
  • category
  • module
  • ancestor
  • library
  • file
  • directive
  • engine
  • thread
  • goal_thread The value of Culprit is the argument or one of its sub-terms that caused the error.

Modes and number of proofs

::

existence_error(@nonvar, @nonvar) - error

Errors

| When called: | existence_error(Thing, Culprit)

Examples

::

..., \+ current_object(payroll), existence_error(object, payroll).

.. seealso::

:ref:methods_catch_3, :ref:methods_throw_1, :ref:methods_context_1, :ref:methods_instantiation_error_0, :ref:methods_uninstantiation_error_1, :ref:methods_type_error_2, :ref:methods_domain_error_2, :ref:methods_consistency_error_3, :ref:methods_evaluation_error_1, :ref:methods_permission_error_3, :ref:methods_representation_error_1, :ref:methods_resource_error_1, :ref:methods_syntax_error_1, :ref:methods_system_error_0