.. 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: context/1; Built-in method .. _methods_context_1:

context/1

Description

::

context(Context)

Returns the execution context for a predicate clause using the term logtalk(Head,ExecutionContext) where Head is the head of the clause containing the call. This private predicate is mainly used for providing an error context when type-checking predicate arguments. The ExecutionContext term should be regarded as an opaque term, which can be decoded using the :ref:`logtalk::execution_context/7 apis:logtalk/0::execution_context/7` predicate. Calls to this predicate are inlined at compilation time.

.. warning::

As the execution context term includes the clause head, the head of the clause calling the context(Context) method cannot contain the Context variable as that would result in the creation of a cyclic term. The compiler detects and reports any offending clauses by throwing a representation_error(acyclic_term) error.

Modes and number of proofs

::

context(--callable) - one

Errors

(none)

Examples

::

foo(A, N) :- % type-check arguments context(Context), type::check(atom, A, Context), type::check(integer, N, Context), % arguments are fine; go ahead ... .

.. seealso::

:ref:methods_parameter_2, :ref:methods_self_1, :ref:methods_sender_1, :ref:methods_this_1