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   Copyright 1998-2019 Paulo Moura <pmoura@logtalk.org>

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   you may not use this file except in compliance with the License.
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.. index:: pair: category_property/2; Built-in predicate
.. _predicates_category_property_2:

category_property/2
===================

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

::

   category_property(Category, Property)

Enumerates, by backtracking, the properties associated with the defined
categories. The valid properties are listed in the language grammar section
on :ref:`entity properties <grammar_entity_properties>` and described in
the User Manual section on :ref:`category properties <categories_properties>`.

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

::

   category_property(?category_identifier, ?category_property) - zero_or_more

Errors
------

| Category is neither a variable nor a valid category identifier:
|     ``type_error(category_identifier, Category)``
| Property is neither a variable nor a callable term:
|     ``type_error(callable, Property)``
| Property is a callable term but not a valid category property:
|     ``domain_error(category_property, Property)``

Examples
--------

::

   % enumerate the properties of the core_messages built-in category:
   | ?- category_property(core_messages, Property).

   Property = source_data ;
   Property = static ;
   Property = built_in ;
   ...

.. seealso::

   :ref:`predicates_abolish_category_1`,
   :ref:`predicates_create_category_4`,
   :ref:`predicates_current_category_1`,
   :ref:`predicates_complements_object_2`,
   :ref:`predicates_extends_category_2_3`,
   :ref:`predicates_imports_category_2_3`
