..
   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.
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       http://www.apache.org/licenses/LICENSE-2.0

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.. 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 a default 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.

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

::

   context(--callable) - one

Errors
------

| ``Context`` is not a variable:
|     ``type_error(var, Context)``

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`
