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Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

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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