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.. rst-class:: align-right

**built-in predicate**

.. 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`
