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.. rst-class:: align-right

**built-in method**

.. index:: pair: predicate_property/2; Built-in method
.. _methods_predicate_property_2:

``predicate_property/2``
========================

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

::

   predicate_property(Predicate, Property)

Enumerates, by backtracking, the properties of a visible object predicate.
Properties for predicates not declared using a scope directive are not
enumerated. The valid predicate properties are listed in the language
grammar section on :ref:`predicate properties <grammar_predicate_properties>`
and described in the User Manual section on
:ref:`predicate properties <predicates_properties>`.

When ``Predicate`` is listed in a :ref:`directives_uses_2` or
:ref:`directives_use_module_2` directive, properties are enumerated for
the referenced object or module predicate.

When ``Predicate`` is bound at compile-time to a ``(:)/2`` term, this
predicate enumerates properties for module predicates (assuming that
the :term:`backend Prolog compiler` supports modules).

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

::

   predicate_property(+callable, ?predicate_property) - zero_or_more

Errors
------

| ``Predicate`` is a variable:
|     ``instantiation_error``
| ``Predicate`` is neither a variable nor a callable term:
|     ``type_error(callable, Predicate)``
| ``Property`` is neither a variable nor a valid predicate property:
|     ``domain_error(predicate_property, Property)``

Examples
--------

| To enumerate, by backtracking, the properties of a locally visible user predicate or a user predicate visible in :term:`this`:
|     ``predicate_property(Predicate, Property)``
| To enumerate, by backtracking, the properties of a public or protected predicate visible in :term:`self`:
|     ``::predicate_property(Predicate, Property)``
| To enumerate, by backtracking, the properties of a public predicate visible in an explicit object:
|     ``Object::predicate_property(Predicate, Property)``

An example of enumerating properties for locally visible object predicates.
These include predicates listed using :ref:`directives_uses_2` and
:ref:`directives_use_module_2` directives:

::

   :- object(foo).

       :- uses(bar, [
           baz/1, quux/2
       ]).

       :- public(pred/1).
       pred_prop(Pred, Prop) :-
          predicate_property(Pred, Prop).

   :- end_object.

::

   | ?- foo::pred(baz(_), Prop).
   Prop = logtalk ;
   Prop = scope(public) ;
   Prop = public ;
   Prop = declared_in(bar) ;
   ...

.. seealso::

   :ref:`methods_current_op_3`,
   :ref:`methods_current_predicate_1`,
   :ref:`directives_uses_2`,
   :ref:`directives_use_module_2`
