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   Copyright 1998-2021 Paulo Moura <pmoura@logtalk.org>
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.. index:: pair: complements_object/2; Built-in predicate
.. _predicates_complements_object_2:

``complements_object/2``
========================

Description
-----------

::

   complements_object(Category, Object)

Enumerates, by backtracking, all category–object pairs such that the
category explicitly complements the object.

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

::

   complements_object(?category_identifier, ?object_identifier) - zero_or_more

Errors
------

| ``Category`` is neither a variable nor a valid category identifier:
|     ``type_error(category_identifier, Prototype)``
| ``Object`` is neither a variable nor a valid object identifier:
|     ``type_error(object_identifier, Parent)``

Examples
--------

::

   % check that the logging category complements the employee object:
   | ?- complements_object(logging, employee).

.. seealso::

   :ref:`predicates_current_category_1`,
   :ref:`predicates_imports_category_2_3`
